MDT FULL SUBJECT-1.pdf

PLASTICS
● Definition: A group of engineered materials characterized
by large molecules that are built up by the joining of
smaller molecules.
● They are natural or synthetics resins.

PROPERTIES OF PLASTICS
• Light weight
• Good resistance to corrosion
• Easy of fabrication into complex shapes
• Low electrical and thermal conductivity
• Good surface finish
• Good optical properties
• Good resistance to shock and vibration.

CLASSIFICATION – POLYMERS
● Classification based on their industrial usage:
(a) plastics and
(b) elastomers.
● Classification based on their temperature dependence:
(a) thermoplasts and
(b) thermosets

THERMOPLASTICS
● Plastics which softens up on heating and hardens up on cooling where the
softening and hardening are totally reversible processes.
● Hence thermoplasts can be recycled.
● They consist of linear molecular chains bonded together by weak secondary
bonds or by inter-winding.
● Cross-linking between molecular chains is absent in theromplasts.
● E.g.: Acrylics, PVC, Nylons, Perspex glass, etc.

THERMOPLASTICS
Acrylonitrile-butadiene-styrene (ABS)
Characteristics: Outstanding strength and toughness, resistance to heat distortion;
good electrical properties; flammable and soluble in some organic solvents.
Application: Refrigerator lining, lawn and garden equipment, toys, highway safety
devices.
Acrylics (poly-methyl-methacrylate) PMMA
Characteristics: Outstanding light transmission and resistance to weathering; only fair
mechanical properties.
Application: Lenses, transparent aircraft enclosures, drafting equipment, outdoor signs.

Fluorocarbons (PTFE or TFE,Teflon)
Characteristics: Chemically inert in almost all environments, excellent electrical
properties; low coefficient of friction; may be used to 260ooC; relatively weak
and poor cold-flow properties.
Application: Anticorrosive seals, chemical pipes and valves, bearings, anti
adhesive coatings, high temperature electronic parts.
Polyamides (nylons)
Characteristics: Good mechanical strength, abrasion resistance, and toughness;
low coefficient of friction; absorbs water and some other liquids.
Application: Bearings, gears, cams, bushings, handles, and jacketing for wires and
cables.
Contd…

Polycarbonates
Characteristics: Dimensionally stable: low water absorption; transparent; very
good impact resistance and ductility.
Application: Safety helmets, lenses light globes, base for photographic film
Polyethylene
Characteristics: Chemically resistant and electrically insulating; tough and
relatively low coefficient of friction; low strength and poor resistance to
weathering.
Application: Flexible bottles, toys, tumblers, battery parts, ice trays, film
wrapping materials.
Contd…

Polypropylene
Characteristics: Resistant to heat distortion; excellent electrical properties and
fatigue strength; chemically inert; relatively inexpensive; poor resistance to UV
light.
Application: Sterilizable bottles, packaging film, TV cabinets, luggage
Polystyrene
Characteristics: Excellent electrical properties and optical clarity; good thermal
and dimensional stability; relatively inexpensive
Application: Wall tile, battery cases, toys, indoor lighting panels, appliance
housings.
Contd…

THERMOSETS
● Plastics which are ‘set’ under the application of heat and/or pressure.
● This process is not reversible, hence thermosets can not be recycled.
● They consist of 3-D network structures based on strong covalent bonds to form
rigid solids. linear molecular chains bonded together by weak secondary bonds
or by inter-winding.
● Characterized by high modulus / rigidity /dimensional stability when compared
with thermoplasts.
● E.g.: Epoxies, Amino resins, some polyester resins, etc.

● Thermosets are strengthened by reinforcements .
● Different reinforcements are in use according to the necessity. Glass fibres are most
commonly used to form structural and moulding plastic compounds.
● Two most important types of glass fibres are E (electrical)- and S (high strength)-
glasses.
● E-glass (lime-aluminium-borosilicate glass with zero or low sodium and potassium
levels) is often used for continuous fibres.
● S-glass (65%SiO2, 25%Al2O3 and 10% MgO) has higher strength-to-weight ratio and is
more expansive thus primary applications include military and aerospace applications.
● Carbon fibre reinforced plastics are also often used in aerospace applications. However
they are very expansive.
● The other classes of reinforcements include aramid (aromatic polyamide) fibers.
● They are popularly known as Kevlar.

THERMOSETS
Epoxies
Characteristics: Excellent combination of mechanical properties and corrosion
resistance; dimensionally stable; good adhesion; relatively inexpensive; good
electrical properties.
Application: Electrical mouldings, sinks, adhesives, protective coatings, used with
fiberglass laminates.
Phenolics
Characteristics: Excellent thermal stability to over 150o C; may be compounded
with a large number of resins, fillers, etc.; inexpensive.
Application: Motor housing, telephones, auto distributors, electrical fixtures.
Contd…

Polyester (PET or PETE)
Characteristics: One of the toughest of plastic films; excellent fatigue and tear
strength, and resistance to humidity acids, greases, oils and solvents
Application: Magnetic recording tapes, clothing, automotive tire cords, beverage
containers.

Chemical classification Trade name characteristics Typical application
Epoxy Araldite oxiron Good toughness.
Resistant to;acids.
alkalies and solvents.
excellent adhesion to
metal, glass and wood.
Adhesive and coatings,
tools and
dies, filament wound
vessels,
laminates for aircraft,
patching
compound for metal and
plastics.
Melamine-formal-dehyde Good for application
requiring cycling between
wet and dry conditions.
Hard and abrasion
resistant. Good dielectric.
Tablc-ware, electric
insulation,
automotIve Ignition parts,
cutlery handles,jars and
bowls.

Phenol-
formaldehyde
Bakelite
Marblette Durez
Cataljn
Good dimensional stability
Excellent insulating qualities.
Inert
to most solvents and weak
acids.
Good strength around inserts.
Industrial electrical parts.
automotive electrical
components,
paper impregnated battery
separators.
Electrical insulation.
Phenol-furfural Durite Similar to Phenolfonnaldehyde. Electrical insulation. Mechanical
parts. Housings and containers.
Alkyd
(Modified
polyester)
Glyptal Duraplex
Beckosol Teglac
Rezly
Can be made flexible, resilient or
rigid. Can resist acids but not
alkalies, with glass fibre
reinforcement resists salt water
and fungus growth.
Boats, Tanks, Trailer and Tractor
components. Ducts, shrouds.
Vaulting poles.

ADDITIVES TO POLYMERS
● The properties of polymers can be further modified by the addition of agents
which are basically of two types.
● Those that enter the molecular structure are usually called "additives", whereas
those that form a clearly defined second phase are called "fillers".
…

1. PLASTICIZERS
● Plasticizers are liquids of high boiling point and low molecular weight, which are
added to improve the plastic behaviour of the polymer.
● They are essentially oily in nature. Organic solvents, resins and even water are
used as plasticizers.

2. FILLERS
● A filler is used to economize on the quantity of polymer required and/or to vary the properties
to some extent, for example, mechanical strength, electrical resistance etc.
● A filler, whose function is to increase mechanical strength, is termed a "reinforcing filler".
● A filler is commonly fibrous in nature and is chemically inert with respect to the polymer with
which it is to be used.
● Common fillers are wood flour, cellulose, cotton flock, and paper (for improving mechanical
strength); mica and asbestos (for heat resistance); talc (for acid resistance).Other filler
materials are : fabric, chipped-wood moulding compound, wood veneer, textile or glass fibres.
● The commonly used "reinforcing filler agents" with plastics are : fibres/filaments of glass,
graphite or boron.

3. Catalysts
● These are usually added to promote faster and more complete polymerization
and as such they are also called 'accelerators' and 'hardeners' e.g., ester is used
as a catalyst for Urea Formaldehyde.
4. Initiators
● As the name indicates, the initiators are used to initiate the reaction, that is, to
allow polymerization to begin. They stabilize the ends of the reaction sites of the
molecular chains. H2O2 is a common initiator.
5. Dyes and Pigments
● These are added, in many cases, to impart a desired colour to the material.

6. Lubricants
● Lubricants are added to the polymers for the following purposes : to reduce
friction during processing, to prevent parts from sticking to mould walls, to
prevent polymer films from sticking to each other and to impart an elegant
finish to the final product. Commonly used lubricants include : oils, soaps and
waxes.
7. Flame retardants
● Most plastics will ignite at sufficiently high temperatures. The non-
inflammability of the plastics can be enhanced either by producing them from
less inflammable raw materials or by adding "flame retardants". The common
flame retardants are : compounds of chlorine, bromine and phosphorous.

8. Solvents
● Solvents are useful for dissolving certain fillers or plasticizers and help in
manufacturing by allowing processing in the fluid state, For example, alcohol is
added in cellulose nitrate plastics to dissolve Camphor. However, subsequently,
the solvents must be removed by evaporation.
9. Stabilisers and anti-oxidants are added to retard the degradation of polymers
due to heat, light and oxidation.
10. Elastomers are added to plastics to enhance their elastic properties.

PLASTIC PROCESS
MOULDING
1. injection moulding
2. compression moulding
3. transfer moulding
4. blow moulding
FORMING
1. extrusion
2. thermoforming
3. rotational moulding, slush moulding, casting
4. calendaring
5. spinning
OTHERS : lamination, reinforcement and coating

INJECTION MOULDING MACHINE
Parts of Injection moulding machine
1. injection unit
2. clamping unit
3. controls unit
● INJECTION MOULDING MACHINE
● INJECTION MOULDING PROCESS
● WORKING VIDEO
● MOULD ASSEMBLY VIDEO 1
● MOULD ASSEMBLY VIDEO 2

INJECTION MOULDING
● The polymer is melted and than forced into a mould.
● Thermoplastic pellets melted and melt injected under high pressure (70MPa)
into a mold using a plunger
● Molten plastic takes the shape of the mold, cools, solidifies, shrinks and is
ejected.
● Molds usually made in two parts (internal and external part).
● Use of injection molding machine mainly used for thermoplastics (gears, cams,
pistons, rollers, valves, fan blades, rotors, washing machine agitators, knobs,
handles, camera cases, battery cases, sports helmets etc…)

INJECTION MOULDING
TYPES
● Hand injection moulding
● Hot runner moulding
● Gas injection moulding process
● Co-Injection moulding
● Multi component injection moulding process
● Multi colour injection moulding process
● Reaction injection moulding process

INJECTION MOULDING
ADVANTAGES
● Moulding are produced in the finished
● Moulded to the repeatable precision
● Metal inserts, threads and holes can be moulded
● High out put rate can be achieved
DISADVANTAGES
● Capital cost of the injection moulding machine can be high compared with other
● Mould costs can be high compared with other

SPECIFICATIONS
1. Shot capacity: the maximum amount of material the screw can displace from the barrel by a
single stoke of injection.(unit- mm3 )
2. Injection rate: it is maximum polymer displaced during injection stroke per unit volume (unit -
gram/sec)
3. Injection pressure: it is the maximum pressure the injection unit is capable of exerting on
plastic melt at screw tip (N/m2)
4. Plasticising capacity: the maximum quantity of a specified plastic material that can be raised
to a uniform and mouldable temperature in a unit time.

SPECIFICATIONS
5. Clamping tonnage: the maximum clamping force (tons) that is applied to the mould to keep
the mould platen when the moving mould platen is in fully open position.
6. Maximum day light: it is the maximum distance between fixed mould platen and moving
mould platen when the moving mould platen is in fully open position.
7. Minimum day light: it is the distance between fixed mould platen and moving mould platen
when the moving mould platen is in fully closed position.
8. Number of impressions: the number of mouldings that the machine will produce in an hour.

SHOT CAPACITY
● Shot capacity with material “B”

PLASTICIZING CAPACITY
● Plasticizing rate of material “B”

CLAMPING CAPACITY
● Clamping force is calculated by multiplying projected area with injection
pressure.
● Usually 33 to 50% injection pressure is considered for calculation and normally
63KN/m2 is considered as the cavity pressure and may be substituted in place of
injection pressure.
● Maximum injection pressure can be obtained from machine manufacturer’s data
sheet

CYCLE TIME
● Cycle time
Tc =
m x 3600
P
○ Tc = minimum cycle time obtainable
○ M = mass of the shot
○ P = Plasticizing capacity of the machine with the particular polymer being moulded (kg/h)

NUMBER OF CAVITY CALCULATION
Numbers of cavities in mould depend on
● Production requirement to meet target.
● Machine’s capacity
1. shot
2. Plasticizing
3. clamping
● Max. Size of component and the mould that can fit into the moulding machine
between tie rods.
● Max. Injection pressure required to flow and fills the particular plastic into mould

● It is determined by three ways
1. Determined by shot capacity
2. Determined by plasticizing capacity and
3. Determined by clamping capacity
● Once all the three are found, select the least number of cavities. If it is in
decimal, round of to minimum size

● Determined by clamping capacity based on 85% of rated capacity

FEED SYSTEM
● The flow way between nozzle to cavity or impression is termed as feed system. It
consists of
1. Sprue: carry material to runner
2. Runner: connects sprue with gate
3. Gate: connects runner with impression
Material → Sprue → Runner → Gate

SPRUE
● Sprue - during injection process, plastic material is delivered to the nozzle of
the machine as a melt. It is then transferred to the impression through a
passage. This passage is a tapered hole with in a bush. The material in this
passage is termed as the sprue, and the bush is called sprue bush

RUNNER
● This is a channel machined with the mould plate to connect the sprue with the
gate to the impression.
● Runner is positioned on the parting surface, while on more complex designs the
runner is positioned below the parting surface
● The wall of the runner channel must be smooth to prevent any restrictions of the
flow

RUNNER CROSS SECTION SHAPE
● Four forms of cross sectional shapes are
1. Fully round
2. Trapezoidal
3. Modified trapezoidal
4. hexagonal

RUNNER CROSS SECTION SHAPE
● The ratio of cross-sectional area to periphery will, therefore, give a direct
indication of the efficiency of the runner design, the the higher value the greater
the efficiency.
● The round and square types of runner are the two most satisfactory designs.
● The square runner difficult to eject, because this an angle 100 is incorporated on
the runner wall, thus modifying the square to the trapezoidal section.
● The hexagonal runner is basically a double trapezoidal runner.

RUNNER SIZE
● While deciding the size of runner following factors should be considered.
1. Volume of moulding
2. Types of plastic material to be used
3. Wall section of moulding
4. Distance of wall of impression from the main runner or sprue
● The runner should not be below 2mm diameter, nor above 10mm diameter.
● The calculated size should be increased to the next suitable cutter size.

RUNNER LAYOUT
● The layout of runner system depends upon the following factors
1. Number of impression
2. Shape of component
● Balanced runner: Runner should be balanced. Which means the distance plastic
material travels from sprue to gate should be same for each moulding in order to
ensure that all impressions will get filled up uniform.
● Runner length: Length should be get to a minimum to reduce pressure loss.

GATE
● A gate is a channel or orifice connecting the runner with the impression.
● It has a small cross sectional area when compared with the rest of the feed
system.
● The small cross-sectional area is necessary so that
1. The gate freezes soon after the impression is filled.so that the impression is
filled so that the injection plunger can be withdrawn without the probability
of void being created in moulding by suck back
2. It allows for simple degating and in some moulds this degating can be
automatic.
3. After degrading only a small witness mark remains.

GATE
4. Better control of the filling of multi impressions can
be achieved.
5. Packing the impression with material in excess of that required to compensate
for shrinkage is minimized

GATE SIZE
● The size of the gate can be considered in terms of gate cross-sectional area and
the gate length (gate land)
● Optimum size of the gate depends on the following factors
1. Flow characteristics of the material to be moulded.
2. Wall section of the moulding
3. Volume of the material to be injected in to the impression.
4. Temperature of the mould

BALANCED GATING
● It is often necessary to balance the gates of a multi-impression mould to ensure
that the impressions fills simultaneously.
● By adopting the method of balanced gating there are two ways varying the
restriction
1. By varying the land length
2. By varying the cross-sectional area of the gate.

TYPES OF GATE
1. SPRUE GATE(or) CENTRE GATE
2. RECTANGULAR EDGE GATE
3. OVERLAP GATE
4. FAN GATE
5. TAB GATE
6. DIPHRAM GATE
7. RING GATE
8. FILM GATE
9. PIN GATE
10. SUB SURFACE GATE

SPRUE GATE (OR) CENTRE GATE
● When the moulding is directly fed from a sprue, the feed section is termed a
sprue gate.
● The main disadvantages with this type of gate is that it leaves a large gate mark
on the moulding.
● The size of this mark depends on
1. The diameter at the small end of the sprue
2. The sprue angle
3. Sprue length

RECTANGULAR EDGE GATE
● This is a general purpose gate and in its simplest form is merely a rectangular
channel machined in one mould plate to connect the runner to the impression.
ADVANTAGES
● The cross-sectional form is simple and therefore, cheap to machine
● Close accuracy in the gate dimensions can be achieved
● The gate dimensions can be easily and quickly modified.
● All common moulding materials can be moulded through this type of gate.

RECTANGULAR EDGE GATE
○ For rectangular gate
h = depth
w = width
l = length of gate respectively. Then, depth h is given by
h=n x t
● Where, t= thickness of wall in mm
n= material constant (eg: 0.6 for polythene, 0.7 for poly acetate)
● The minimum depth of gate controls the time for which the gate remain open
● Width is given by 𝐰 =
𝐧 𝐀
𝟑𝟎
, where A is area of cavity

OVERLAP GATE
● The gate can be considered as a variation of the basic rectangular type gate.
● In certain types of moulding the melt jets into an impression if its does not
contact a restriction immediately.
● Therefore, for block type mouldings the rectangular gate is replaced by overlap
gate which, directs the melt flow against an opposite impression face.

FAN GATE
● This is another edge type gate but dimensions of the fan gate are not constant.
● Gate at the impression is relatively wide and , because of this large volume
material can be injected in a short time.
● This is used for large area , thin walled mouldings.

TAB GATE
● This is a gating technique for feeding solid type mouldings.
● The right angled turn which the melt must take prevents the undesirable jetting
which otherwise occur.
● The impression will fill uniformly. Thus the tab gate is an alternative to the
overlap type gate

DIAPHRAGM GATE
● This gate is used for single-impression tubular shaped mouldings on underfeed
and runner-less moulds

RING GATE
● The function of this gate is identical to diaphragm gate.
● The gate provides for a feed all around the external periphery of the moulding
and permits the use of a conventional runner system to connect the impressions.
● The runner, in the form of a trapezoidal annulus, is machined into the mould
plate. The trapezoidal runner is normally used.

FILM GATE
● The gate may be considered as a long rectangular type edge gate and it is used
for large, thin walled components to assist in the production of warpage free
products.
● The gate normally extends across the complete width of the moulding
● The gate depth may be somewhat less than for a corresponding rectangular gate

PIN GATE
● This is a circular gate used for feeding into the base at component and, because
its relatively small in diameter.
● However the pin gate may be used in three plate-
1. Under feed mould
2. Hot runner mould
3. Two plate mould

SUBSURFACE GATE
● The subsurface gate is a circular oval gate which submerged and ‘feeds’ into the
impression below the parting surface of the mould.

EJECTION SYSTEM
● Ejection video 1
● Ejection pin mark

EJECTION SYSTEM
● The ejector system consists of
1. THE EJECTOR GRID
2. THE EJECTOR PLATE ASSEMBLY
3. THE METHOD OF EJECTION

THE EJECTOR GRID
● The ejector grid is that part f the mould which supports the mould plate and
provides a space into which the ejector plate assembly can be fitted and
operated.
● The grid normally consists of a back plate on to which is mounted a number of
conveniently shaped support blocks
● The following types of ejector grid design is frequently used
1. The in-line ejector grid
2. The frame type ejector grid
3. The circular support block grid

EJECTOR PLATE ASSEMBLY
● The ejector plate assembly is that part of the mould to which the ejector
element is attached.
● The assembly is contained in a pocket, formed by ejector grid, directly behind
the mould plate.
● The assembly consists of
1. Ejector rod: Functions as an actuating member and also as a method guiding
the assembly.
2. Ejector plate: purpose is to transmit the ejector force from the actuating
system of the injection machine to the moulding via an ejector element
3. Retaining plate: Its purpose is to retain the ejector element

METHODS OF EJECTION
1. Pin ejection (video)
2. Sleeve ejection
3. Blade ejection
4. Valve ejection (video)
5. Stepped ejection
6. Air ejection (video)
7. Stripper plate ejection (video)
8. Stripper bar ejection

ASSIGNMENT
1. Pin ejection
2. Sleeve ejection
3. Blade ejection
4. Valve ejection
5. Stepped ejection
6. Air ejection
7. Stripper plate ejection
8. Stripper bar ejection

EJECTION FORCE CALCULATION
● Force required to ejecting moulding of a male core can be calculated
approximately from the following formula

PARTING SURFACE
● The parting surface of a mould are those portions of both mould plates adjacent
to the impression which butt together to form a seal and prevent the loss of
plastic material from the impression.
● Parting surfaces are classified as flat and non-flat.
● The non-flat parting surfaces include stepped, profiled, and angled surfaces.
● If the parting surfaces are not properly matched, the moulding material from the
impression will escape through the gap. This escaped melt is called the flash.
● The nature of parting surface depends entirely on the shape of the component.

TYPES OF PARTING SURFACES
1. Flat parting surface
2. Angled parting surfaces
3. Stepped parting surfaces
4. Profiled parting surfaces

FLAT PARTING SURFACE
● Consider the moulding shown in figure below. The cavity for this part can be cut
in to one mould plate.
● The position of the parting surface will therefore be at the top of the moulding.
● Parting surface itself being perfectly flat. For appearance, this is the ideal one as
the parting line is not noticeable unless flash develops

ANGLED PARTING SURFACE
● The designer is frequently get problem with a component which, while fairly
regular in form, cannot be ejected from the mould if a flat parting surface is
adopted.
● However, by adopting angled parting surface, all parts of the component are in
line of draw and it can be ejected.

STEPPED PARTING SURFACE
● It is frequently necessary to incorporate a stepped or profiled surface to cater for
one or two small irregularities in an otherwise regular form.
● Normally this is best achieved by localizing the change in parting surface to
permit the major portion of the surface to be kept flat.

PROFILED PARTING SURFACE
● An example is shown in the figure below.
● The component is given left side. It will be noted that while in cross-section, the
component form is constant, the general form incorporate curves.
● As the edge of the component is square with the face, the entire form can be
cut into one mould plate.
● Thus the general form of the parting surface will follow the inside surface of the
moulding.

VENTING
● When plastic material enters the impression, air is displaces. Normally the air can
escape between the two mould plates. But if the plates are matched perfectly,
the air may be trapped with in the impression resulting in discolouration, sinks,
incomplete filling etc.
● Vents are provided in the mould to allow such air to escape freely.
● The vent is a shallow slot not more than 0.05 mm deep and 3mm wide. If the
depth is more, the plastic material can pass through the slot and leave a flash
mark.

VENTING
● Positions where the vents are required are:
1. At the point furthermost from the gate on symmetrical moulding.
2. At the point where flow paths are likely to meet and
3. At the bottom of a projection

SHRINKAGE
● When a hot plastic cools inside a mould, it contracts by an amount depending on
the material being processed and the final product is smaller than the mould
size.
● This contraction is called shrinkage

VARIOUS FACTORS THAT AFFECT SHRINKAGE
● Basic plastic material
● Filler used and percentage
● Part wall thickness
● Melt temperature
● Mould temperature
● Injection pressure
● Injection time
● Hold on pressure
● Hold on time
● Gate area

VARIOUS FACTORS THAT AFFECT SHRINKAGE
Shrinkage increases with
● Increase of material temperature
● Increase of mould temperature
● Increase in wall thickness
● Low injection pressure
Shrinkage decreases with
● Low melt and mould temperature
● High injection pressure
● Long injection time
● Presence of filler material and its content

SHRINKAGE CALCULATION
● The shrinkage factor S calculating from the following equation ( unit of S - mm/mm )
Dc = Dp + (Dp × S ) + (Dp × S2 )
= Dp ( 1+ S+S2)
● Shrinkage factor is very small, so S2 can be avoid
Dc = Dp ( 1+ S )
● Dc – cavity and core steel dimension
Dp – product dimension

MOULD COOLING
● One fundamental principle on injection moulding is that hot material enters the
mould, where it cools rapidly to a temperature at which it solidifies sufficiently
to retain the shape of the impression.
● While the melt flows more freely in a hot mould, a greater cooling period is
required before the solidifies in a cold mould it may not reach the extremities of
the impression.
● The operating temperature for a mould will depend on a number of factors
which include the following, (a) type and grade of material to be moulded,
(b)length of flow within the impression, (c) wall section of the moulding; length
of the feed system, etc

SIDE CORE AND SIDE CAVITY
● A side core is a local which is normally mounted at right angles to the mould axis
for forming a hole or recess in the side face of a moulding.
● This side core prevents the in line removal of the moulding and some means
must be provided for withdrawing the side core prior to ejection.
● The side cavity performs a similar function to the side core.
● The side cavity is a segment of solid cavity insert or plate which can be
withdrawn to permit the moulding to be ejected in line.

MOULD WITH INTERNAL UNDERCUT
● An internal under cut is, any restriction which prevents a moulding from being
extracted from the core in line of draw.
● Various methods are used for relieving internal undercuts depends upon the
shape and position of the restriction.
● Video1
● Video 2

TWO PLATE MOULD
● A two plate mould consists of two plates with the cavity and core mounted in
either plate.
● The plates are fastened to the press platens, and moving half of the mould
usually contains the ejector mechanism and the runner system.
● A two plate mould is the most logical type of tool to use for parts that requires
large gates.

THREE PLATE MOULD
● The three plate mould is made up of three plates. They are,
1. Stationary plate which is attached to the stationary platen of the machine and usually
contains the sprue and half runner
2. The middle or cavity plate, which contains half of the runner and gate on one side and
the cavity on the other side and allowed to float when the mould opens,
3. A core plate which contains the moulded part and ejector system.

MULTI- DAYLIGHT MOULDS
● Fig (E)- this mould consists of three main parts; a feed plate, a floating cavity
plate and a moving mould plate.
● When the mould is opened there are again two daylights. fig(F).
● This design permits a particular feed technique known as underfeeding, and the
double daylight is necessary in this case to permit the feed system to be
removed from the mould.

TRIPPLE DAY LIGHT MOULD
● Moulds of this type results when the underfeed and stripper plate designs are
combined.
● There are 4 basic plates in the assembly of triple day light mould.
1. Core plate
2. Cavity plate
3. Feed plate
4. Stripper plate
● Here first opening- between core and feed plate
second opening- between core and cavity plate
third opening- between core and stripper plate
Hence the name triple day light.

RUNNER LESS MOULDS
● The term runner less mould may be applied to any mould in which a
conventional runner system is not incorporated.
● For, a simple two plate mould, a runner system to provide a flow path for
plastic material from the central sprue to each impression, the gate being
situated on the mould’s parting surface.
● The alternative underfeed design permits the gate to be located at the base
of the component, but a more complex multi-plate system is necessary.

PREVIOUS YEAR QUESTIONS
Part A
1. List any two types of thermo setting plastic material
2. List two examples of thermo plastics
3. Define term short capacity
4. State importance of venting
5. Identify properties of PVC
6. State the functions of gate in injection moulding
7. state the term mould cooling
8. State the term runner used in a mould

Part B & C
1. Resolve the functions of side core and side cavity
2. Illustrate the working principle of injection moulding process
3. Illustrate the working of mechanical clamping unit in an injection moulding machine
4. Explain stripper plate ejection technique used in injection mould with meat sketch
5. Explain the necessity of hot runner injection moulding
6. State the properties of thermoset polyurethane
7. Identify the necessity of cooling system in an injection moulding
8. Describe the advantages of additives in used in plastics
9. State the function of runner in injection moulding and discuss the factors to be considered for
designing a runner

Part B & C
10. Describe the triple day light mould with suitable sketch
11. Illustrate the method of forming internal undercut on a component with form pin
12. Demonstrate the diaphragm gate used in injection mould
13. Compare thermo plastic material with thermo setting plastic material
14. Formulate the importance of parting surface in a mould
15. Illustrate sleeve ejection method used in a mould
16. Construct a typical mould indicating sprue bush, register ring, guide pillar and guide bush
17. Define the functions of gate and list different types of gate
18. Discuss the purpose of following additives used in plastics : plasticizer, lubricants, colourants,
stabilizer,

COMPRESSION MOULDING
● The mould is held between the heated plates of a hydraulic press
● Moulding compound(powder or granule form) is placed in the mould
● Mould close and press
● The moulding compound softens and flows to shape as the mould temperature
high enough
● For thermo plastic material is held under pressure for specified period
● For thermosetting plastic material is held under pressure and temperature for
specified period

ADVANTAGES
● Both thermo plastic and thermosetting materials may be moulded
● Wastage of material is low. No runner or sprue
● With material having fibre reinforcement, this method gives products of
maximum impact strength
● For larger parts (>1.5kg) this method recommended as equipment cost of other
method is very high
● Lowest equipment cost

DISADVANTAGES
● Not suitable for complicated shape
● Less surface finish
● Articles which require very close dimensional tolerances are not suitable for
compression moulding

APPLICATION
● Manufacturing of electrical parts
● Manufacturing of gears
● Radio cases
● Large containers
● Diodes
● Fibre reinforcement plastic parts

TYPES OF COMPRESSION MOULD
1. flash moulds
2. Semi positive moulds
3. Positive moulds
4. Landed positive mould

1. FLASH MOULDS

1. FLASH MOULDS
● A flash mould is defined as the mould in which the parting line is at right angles
to the direction of force.
● It is designed in a manner that permits excess material to escape easily as
pressure is applied and forms a thin fin.
● This fin hardens first preventing the escapement of mould charge.
● Here the material lost through flashing is higher than other type of compression
moulds. Here the parts produced are not of high quality
● It produce horizontal flash, such flash must be removed after moulding
● The flash mould does not require accurate measuring of mould charge since
excess material cause the flash

2. POSITIVE MOULDS

2. POSITIVE MOULDS
● Positive mould produces a vertical flash in the direction of moulding pressure.
● The upper part of the mould is closely to the lower part of the mould
● Fully positive mould is the opposite of flash moulds
● Positive mould requires accurate measuring of charges
● This type of mould is suitable to plastics of high bulk factor

3. SEMI POSITIVE MOULDS

3. SEMI POSITIVE MOULDS
● Semi positive type combines factors of both flash type and positive type.
● External or internal lands maybe used
● Lands are the area of the plates of the mould that contact each other when
mould is closed
● Lands are incorporated to restrict the travel of the plunger, thus assures good
dimensional accuracy.

4. LANDED POSITIVE MOULD

4. LANDED POSITIVE MOULD
● Landed positive mould are similar to positive type but the telescope is made deep
to allowed more compression on the moulding
● Here land is incorporated in the design to stop the travel of the plunger at the
pre determined point. So that the thickness of the part is maintained.
● Landed positive moulds are two types
○ Internally landed mould
○ Externally landed mould

COMPARISON
Compression moulding Injection moulding
● Both material use, preferably
thermoset material
● Post mould operation required
● Wastage of material is less
● Complicated shapes cannot be mould
● Reinforcement is possible
● Recommended for larger products
● Low production rate
● Both material use, preferably
thermoplastic material
● Produced in the finished form. So no
post operation
● Wastage of material is high
● Complicated shapes can be mould
● Reinforcement is not possible
● Not recommended for larger products
● High production rate

TRANSFER MOULDING
● Usually used for thermosetting plastics
● Transfer moulding is very similar to compression moulding and is developed to
avoid the disadvantages found in that process.
● In this method, thermosetting charge is heated and compressed in a separate
chamber and then injected into the closed mould where it is allowed to cool and
solidify.
● Transfer moulding is capable of moulding part shapes that are more intricate
than compression moulding but not as intricate as injection moulding

TRANSFER MOULDING
ADVANTAGES
● Higher dimensional tolerance
● High cavity count
● Short production cycle for high weight parts
● Encapsulation is possible
● Inserts can be incorporated
● Finishing cost is reduced because less flash on parts
● It produces better uniformity

TRANSFER MOULDING
DISADVANTAGES
● More expensive cooling than compression moulding
● Slower production cycle than injection moulding
● Manual handling of piston can be a problem

TRANSFER MOULDING
APPLICATION
● Electronic apparatus and connections
● Coil
● Integrated circuits
● Plugs
● Connectors
● Utensils handle
● Electrical appliances parts

TRANSFER MOULDING
TYPES
1. pot transfer mould
2. plunger transfer mould

TRANSFER MOULDING
1. POT TRANSFER MOULD

TRANSFER MOULDING
1. POT TRANSFER MOULD
● Chamber is loaded with moulding material then heat it in the chamber and melts
● The melted material forced with the help of a plunger through the heated sprue
into the runner, gate and finally, the heated cavity.
● The ejector pin then push the moulded articles out.
● The cull with sprue go along with the plunger which sub sequentially cut-off.
● Wastage of material and operation time are high as compared to plunger
transfer moulding.

TRANSFER MOULDING
2. PLUNGER TRANSFER MOULD

TRANSFER MOULDING
2. PLUNGER TRANSFER MOULD
● Chamber is loaded with moulding material then heat it in the chamber and melts
● The melted material forced with the help of a plunger through the heated runner
and then to the heated cavity.
● The ejector pin then push the moulded articles out.
● There is no Sprue in plunger transfer moulding.
● The cull and runner go along with the mould which sub sequentially cut-off. But
they are small in size.
● Wastage of material and operation time are low as compared to pot transfer
moulding.

COMPARISON
Compression moulding Transfer moulding
● Breathing is required to remove gas
and cure time
● Cure time ranges to 30-300sec
● Mouldable size is limited by the
capacity of the press.
● Incorporation of insert is difficult
● Tolerance level is fair
● shrinkage is minimum
● venting is required to remove gas and
cure time
● Cure time ranges to 45-90 sec
● Mouldable size is limited by the
geometry of the parts
● Incorporation of insert is easy.
Complicated parts can also be
accommodated.
● Close tolerance are possible
● Shrinkage is high

Part A
1. List the different type of compression mould
2. State the function of plunger in compression moulding
Part B&C
1. Explain about plunger type transfer moulding process with sketch
2. Explain the advantages and disadvantages of transfer moulding process
3. Explain flash type compression mould with neat sketch
4. Differentiate between compression moulding and transfer moulding techniques
5. Identify different parts of pot transfer mould with neat sketch
6. Describe the landed positive mould with sketch

Part B&C
7. State the principle of transfer moulding with sketch
8. State the principle of compression moulding with sketch
9. Explain the advantages and disadvantages of compression moulding process
10. Describe the landed positive mould with sketch
11. Explain process of compression moulding and flash mould type with sketch

EXTRUSION
● Video 1
● Video 2

EXTRUSION
● Long plastic products with uniform cross sections are readily produced by the
extrusion process.
● Thermoplastic pellets & powders are fed through a hopper into the barrel
chamber of a screw extruder. A rotating screw propels the material through a
preheating section, where it is heated, homogenized, and compressed, and then
forces it through a heated die and onto a conveyor belt.
● As the plastic passes onto the belt, it is cooled by jets of air or sprays of water
which harden it sufficiently to preserve its newly imparted shape.
● It continues to cool as it passes along the belt and is then either cut into lengths
or coiled

EXTRUSION
ADVANTAGES
● Trimming of the runner from the part is eliminated
● Less material needs to be heated for each shot
● Material is not subjected to repeated heating
● Thin walled parts do not have to wait for the thicker sprues and runners to
solidify, and less material needs to be heated for each cycle
● The process is continuous and provides a cheap and rapid method of moulding.
● Common production shapes include a wide variety of solid forms, as well as
tubes, pipes, and even coated wires and cables

EXTRUSION
EXTRUDE SCREW
● It has 3 different zones
● Feed zone: preheat the plastic and convey it into the sub sequent zone. Screw
depth constant in this zone.
● Compression zone: this has decreasing channel depth. It expels air tapped
between the original granules.
● Metering zone: constant screw depth but less than feed zone. Main function is
homogenize the melt and quality.

EXTRUSION
PIPE EXTRUSION
● A typical pipeline consist of a single or a twin-screw extruder, a die, equipment
for inside and outside calibration, a cooling tank, a wall thickness measuring
device, haul off and a windup unit for self supporting pipe units.
● A small diameter tube(less than 10mm) is usually made with a free extrusion
process. Large diameter pipes are usually made with pipe extrusion.
● Which is done by the help of calibrating unit and pipe sizing device just below
the die.
● Calibrator solidifies the plastic and transfer the stress acting on the product.

BLOW MOULDING
● BLOW MOULDING VIDEO 1
● BLOW MOULDING VIDEO 2
● BLOW MOULDING PARISON MAKING VIDEO

BLOW MOULDING
● Blow moulding is the process of forming hollow articles from a softened plastic
tube.
● The process consists of forming a tube of melt called parison and introducing air
into the parison to expand it.
● The tube is extruded in a split cavity die.
● The split mould is closed around the tube. after moulding, the splits are opened
and the part is removed.
● Usually thermo plastic material are used for blow moulding

BLOW MOULDING
ADVANTAGES
● Low tool and die cost
● Fast production
● Ability to mould complex part
● Minimum weld line
LIMITATIONS
● Limited to hollow part
● strength of the products are low
● Capacity of the products are low

BLOW MOULDING
APPLICATION
● Typical parts made are bottles, toys, air ducts of automobiles, chemical and
gasoline tanks, and a number of households goods
TYPES
1. Extrusion blow moulding(75%) (VIDEO)
2. Injection blow moulding (VIDEO)
3. Stretch blow moulding (VIDEO)

BLOW MOULDING
EXTRUSION BLOW MOULDING

BLOW MOULDING
EXTRUSION BLOW MOULDING
● In this process, molten thermo plastic material from an extruder passes down
wards through a die and is formed into a tube.
● This is clamped between the mould halves, pinching the bottom end closed.
● A blow pin is inserted at the top or bottom to fill the parison with air and expand
it out to the cavity walls.
● This process is normally associated with the manufacture of small containers
such as those used for shampoos, washing liquids etc.

ROTATIONAL MOULDING
● VIDEO 1
● VIDEO 2

ROTATIONAL MOULDING
● It is the only operation in plastic industry by which relatively stress free, one piece,
hollow items of uniform wall thickness can be produced in a single operation.
● Four steps: 1. Loading 2. Heating 3. Cooling 4. Unloading
● In loading stage predetermined amount of plastic material , in the form of a powder
or a liquid is charged into a hollow mould
● Then the machine rotates and moves the mould into heating chamber. There plastic
melt and stick to the mould surface.
● In cooling stage mould is placed in cooling chamber in which a combination of air
and water is used to cool the mould slowly.
● Material: PE, PP, PVC, NYLON, PC .

ROTATIONAL MOULDING
APPLICATION
● Industrial products: Tanks, drums, containers, pump bodies, septic tank etc
● Transportation products: Tool boxes, fuel tanks, battery cases, motor cycle
bumpers etc

MULTI COLOUR MOULDING
 VIDEO
 VIDEO 2

MULTI COLOUR MOULDING
 Also called double shot moulding
 It is used for making two colour moulded parts by means of successive
moulding operations
 First moulding the basic case then moulding with the next shot in to the first
moulded part.
 These steps can be accomplished using two separate machines .

THERMOFORMING
 In this process, a thermoplastic sheet can be formed into a three- dimensional shape
by the application of heat and differential pressures.
 First, the plastic sheet is clamped to a frame and uniformly heated to make it soft
and flowable.
 Then a differential pressure (either vacuum or pressure or both) is applied to make
the sheet conform to the shape of a mould or die positioned below the frame.
 It is possible to use most of the thermoplastic materials. The starting material is a
plastic sheet of uniform thickness.
 It is a relatively simple process and is used for making such parts as covers, displays,
blister packaging, trays, drinking cups and food packaging

CALENDARING
 Sheets can be produced by calendaring process.
 The polymer is first mixed with the plasticizers and other additives such as
colouring agents
 The mix is then heated for a short time to produce a rough sheet, which is fed
through a series of rollers.
 The thickness is gradually reduced. The final sheet thickness is determined by the
setting of the gap between the last pair of rolls

FILAMENT WINDING
 It is a fabrication technic for manufacturing composite material.
 The process involves winding filaments under varying amounts of tension over a
male mould or mandrel.
 The mandrel rotates while the carriage moves horizontally laying down fibre desired
patterns.
 The most common fibre are carbon or glass fibre and they are coated with synthetic
resin as they wound.
 Once the mandrel is completely covered to the desired thickness, the mandrel is
placed in a chamber to solidify the resin.
 Finally the mandrel is removed leaving a hollow part

PREFORM MOULDING
 This technique is particularly suited for mass production and for more complex shapes
 There are two stages in this process.
First stage
 A perform is made by spraying chopped fibre on to a perforated metal screen which has
the shape of the article to be moulded.
 The fibre are held on the screen by suction applied by exhaust fan.
 A resin binder is then sprayed in the mat and resulting perform is taken and cured on
an oven about 1500C for several minutes.
Second stage
 The perform is then transferred to the lower half of the mould and then brought into
position to press the composite into shape.
 The curing in the mould depends on the temperature from 1 min at 1500C to 10 min at
800C.

MAT AND FABRIC MOULDING
 This is similar to preform moulding except that the material is placed in
the mould, is the chopped stand mat that have been tailored to the die.
 The resin may be poured separately.
 Epoxy to paper and asbestos to phenol laminations are made in this
method.
 Moulding of high strength lamination and structural components are
application of mat and fabric moulding.

PRE-MIX MOULDING
 The resin, reinforcement, the fillers, catalyst, pigments are mixed together
to a doughy mass that can be moulded by compression or transfer
moulding.
 The resin generally used polyesters, epoxies and phenolics.
 The common reinforcement are glass fibres and asbestos fibres.
 It is a high speed process.
 The part that are produced by this process have high strengths, uniform
appearance and good surface finish

CASTING
 Some thermo plastics( nylon, acrylics) and thermosetting plastics( epoxy,
polyurethane, polyester) can be cast into a variety of shapes.
 Typical parts cast are gears, bearings, wheels, thick sheets and components
required abrasive wear
TYPES
1. Conventional casting
2. Centrifugal casting
3. Potting and encapsulation

CASTING
CONVENTIONAL CASTING
 In the conventional casting of thermoplastics a mixture of monomer ,
catalyst, and various additives are heated and poured into the mould.
 The part forms after polymerization take place at ambient pressure.
CENTRIFUGAL CASTING
 This process is also used for plastics including reinforced plastics with short
fibres.
POTTING AND ENCAPSULATION
 This process casting the plastic around an electrical component to embed it
in the plastic
 Potting is done in a housing or case which is an integral part of the product.
 In encapsulation the component is coated with a layer of the solidified plastic.

DIFFERENCE b/w CASTING AND
MOULDING
 Both the processes involves pouring of molten plastic into a mould/die which
will take the shape of cavity mould or die on solidification.
 The basic difference between moulding and casting is the method by which
molten metal is poured. In moulding the metal is poured under pressure but
in casting it doesn't requires any external pressure because of low viscosity of
metal which facilitate it to move easily under gravitational force.
 Moulding also gives you the final product but in case of casting it may not be
true and you may obtain unfinished part depending on your final product
requirements. (requirement of machining after casting).
 Casting use a one time mould but moulding can use moulds on repetition too.
 Moulding is cost effective process.

JOINING OF PLASTICS
 Plastics can be joined by many methods especially heat and mechanical
fastening
 Different methods are
1. Mechanical fastening
2. Spin welding
3. Solvent bonding
4. Ultrasonic welding
5. Hot gas welding

JOINING OF PLASTICS
MECHANICAL FASTENING
 These are the commonly used joining methods.
 They require a plastic that is strong enough to with stand the strain.
 Threaded fasteners work best on thick sections.
 Push on lock and clips may be better for thinner sections

JOINING OF PLASTICS
SPIN WELDING
● In spin welding process, one part is held stationary, while the other is
attached to a spindle which is brought up to pre determined speed and
then forced against the stationary part. Parts thus fuse together under
heat generated by friction

JOINING OF PLASTICS
SOLVENT BONDING
● In this method of joining, plastics are joined by softening them by
solvent and then clamping or pressing together.
● In this way plastic molecule intermingle and the parts bond together
when the solvents evaporates

JOINING OF PLASTICS
ULTRASONIC WELDING
● In this method two parts are to be joined are placed together and the
pulses are transmitted from a generator to the parts by a vibrating tool,
causing them to be vibrate against each other at frequencies around
20kHz.
● The parts are heated and fused together.

JOINING OF PLASTICS
HOT GAS WELDING
● In this process the parts to be joined are heated by an hot inert gas until
the parts soften and can be pushed together.
● Inert gases used are- argon , krypton
● Dissolvers – benzene, toluene, acetone

PART A
1. State the basic difference between mould and casting
2. Define the term extrusion in extrusion moulding
3. Identify the process for make a plastic pipe
4. List the types of blow moulding
PART B & C
1. Illustrate the method of forming parison using die in blow moulding process
2. Summarize the method of welding plastic materials
3. Explain pipe extrusion with suitable figure

PART B & C
4. Summarize the blow moulding process
5. Describe principle of rotational blow moulding with sketch
6. Explain the calendaring process with sketch
7. Illustrate extrusion blow moulding process
8. Explain multi colour moulding with sketch
9. Explain filament welding with sketch
10. Describe the method of joining plastic material
11. Explain vacuum forming with sketch

DIE CASTING
● It is process in which molten metal is forced under high pressure into a
cavity in a metal die.
● This is done in a fraction of second.
● Then the metal is allowed to solidify.
● When the casting has solidified the die is opened and the casting is ejected

SAND CASTING v/s DIE CASTING
● In the case of the sand casting, a separate mould has to be made in each and
every case.
● If we want to make a sand casting, initially we have to make the pattern, then we
have to make the mould, then we pour the molten metal. Once we pour the
molten metal ,once the molten metal is solidified we break that sand mould, and
the mould is no more permanent.
● If we want to make another casting, again we have to make another mould and
we have to pour, likewise in each and every case we have to make a separate
mould.

SAND CASTING v/s DIE CASTING
● So, this involves lot of labour and also it increases the cost of production and
also productivity will be lesser.
● Now, to overcome these drawbacks, this what say metal die casting has been
developed.

DIE CASTING
ADVANTAGES
● It requires less floor space than other casting process.
● Die casting provides precision manufacture with close tolerances.
● Thin section of complex shapes are possible.
● Die casting provides greatly improved surface finish.
● Casting produced by die castings are less defective.

DIE CASTING
LIMITATIONS
● The cost of equipment is high
● The size of the casting produced by this method is limited.
● Special skill is required for maintenance and supervision of die.
● Die casting usually contains some porosity due to entrapping of air.

DIE CASTING DIES
● In die casting, the die consists of two halves. One is called stationary die
which is fixed to die casting machine. The second part is ejector or movable
die which is moved out for the extraction of the casting.
● The casting is machined into the both halves of the inserts that are installed
in the die block.
● The die is designed so that castings remains in the ejector half when
separates.
● The casting is ejected with ejector pin which is ejected by ejector plate.

DIE CASTING DIE MATERIAL
CHARACTERISTICS
1. It should have high resistance to heat.
2. It should resistant corrosion
3. It should be dimensionally stable
4. It should have high wear resistance and toughness.
5. It should not get solder to the cast alloy.
● Hot working tool steel are generally used for preparation of dies, die inserts and cores.
● The die material for various casting alloys are
1. Tin and lead: carbon steel without heat treatment
2. Zinc and aluminium: heat treated low alloy steel
3. Copper: heat treated special alloy steel

DIE CASTING MATERIAL SELECTION CRITERIA
● This should be based on research and not a trial and error or unapproved
theories. It is through a proper understanding of each metal or metal alloy that
one will be able to choose the right material and die casting technique.
● As matter of fact, these alloys and metals have different mechanical and physical
properties. This explains the reason why they react differently when subjected to
certain manufacturing processes.
● It is advisable to work closely with experts to establish the right material for any
given application. This may involve a simple comparison process that may be
simplified as:

DIE CASTING MATERIAL SELECTION CRITERIA
1. It is vital to consider all the vital mechanical properties of those materials. This
is what we shall also expound on every material. The mechanical properties
include elongation, tensile strength, hardness, impact strength and yield
strength. These will be based on actual tests.
2. The physical properties of the metal alloy; it is important to understand the
behavior of the metal when subjected to extreme environmental conditions.
These may include high temperature or extreme stress and heat.
3. It is vital to examine and understand the composition of the alloys. This should
be based on the basic composition of individual element and their uses.

DIE CASTING ALLOYS
● Not all metals or alloys can be die cast. This is due to the varying chemical and
physical properties.
● The Die Casting Material Selection Criteria should be based on research and not
a trial and error or unapproved theories.
● It is through a proper understanding of each metal or metal alloy that one will be
able to choose the right material and die casting technique.
● Below are the most common materials that can die cast

ZINC DIE CASTING
CHARACTERISTICS
● Ideally, these are the basic facts that make zinc the best choice for a number of
manufacturing processes. Opting for zinc alloys should be designed for
individuals who wish to achieve the following key aspects
● Process flexibility : This is a critical aspect in the metal alloy processing industry.
The zinc alloys can be die cast to any shape of choice.
● Precisions and tolerance: This eliminates any additional machining operations
that would otherwise increase the production costs. This is due to the fact that
zinc alloys can be die cast to closer tolerances that other metal alloys

ZINC DIE CASTING
CHARACTERISTICS
● Strength and ductility: A number of plumbing or machinery component are die
cast. Zinc alloys can withstand very extreme pressure – as high as 60,000 psi.
Due to its ductility, the end products are suitable for riveting, bending and
crimping operations. Again, it is also worth noting that the zinc alloy is tougher
than most metal alloys.
● Excellent thermal properties
● excellent rigidity
● anti-sparking
● good bearing properties
● easy finishing, thin wall cast ability, long tool life, recyclable and machinability

ZINC DIE CASTING
ZINC ALLOYS
● casting zinc requires that one understands its basic alloys. The available zinc
alloys can be categorized as:
● ZA alloys: these alloys are mainly used to cast components that require superior
strength. This strength is due to the fact that they contain higher amount of
aluminum.
● Zamak alloys: these alloys contain about 4% aluminum. Like the ZA alloys, they
are known to have provide good cast ability and strength.

ZINC DIE CASTING
APPLICATION
● To manufacture complex metal parts; this is due to the fact that it is easier to
manufacturer items that are accurate with very tight tolerances. Moreover, this
is also attributed to the fact that the zinc can be manipulated to a wide range of
shapes.
● These alloys are also used to manufacture parts that should be wear resistance
with the ability to maintain high structural integrity. This is essential in the
electrical and automotive industry.
● The fact that zinc alloys can be used to manufacture very thin parts makes it a
perfect choice for a number of consumer products, especially the consumer
electronics

ALUMINUM DIE CASTING
● This is a versatile metal with a wide range of desirable physical and chemical
properties. This is actually the reason why the aluminum die cast parts are used
in a number of domestic and industrial applications
CHARACTERISTICS
● Superior corrosion resistance; this explains the reason why these die cast parts
are used in chemical and petroleum industries. This metal cannot be attacked by
most organic and inorganic compounds.
● Lightweight; it has an average density of 2.70 g/cm3. The aluminum alloys are
some of the lightest alloys available. This implies that the die cast components
can be used in applications where the overall weight of the product should be
reduced as much as possible. They are commonly used in the aerospace industry

CHARACTERISTICS
● Superior thermal and electrical properties; this is due to its position in the
periodic table. Aluminum has an oxidation no. +3. It as free electrons that can
conduct electricity and thermal energy
● High operating temperature; this is the main reason why the die cast aluminum
parts can be used in a number of electrical applications. These include heat sinks,
electrical connectors, thermometer covers, etc. This is also the main reason why
the die cast parts are used as utensils. On average, the aluminum alloys have a
melting point of about 660 °C

CHARACTERISTICS
● Strength and hardness; generally, the aluminum alloys are stiff with superior
strength to weight ratio. This explains the reason why they can be used as rails
● Environmentally friendly; these metals are fully recyclable thus, reducing the
scrap metal in the environment
● RFI and EMI shielding properties; this is the main reason why they are used in
electrical components where these radiations may reduce or interfere with the
systems performance
● superior surface finish

ALUMINIUM ALLOYS
● The K-alloy; this aluminum allow is known to possess the following key
properties: resistance to corrosion, improved cooling and zero post die casting
operations.
● Alloy 413; superior die casting properties and it possess good fluidity and
guarantee better pressure tightness.
● Alloy 383; it possesses the following key properties: dimension stability, ease of
casting and good mechanical properties. It has superior corrosion resistance too.
● Alloy B390; it is known for its superior wear resistance and high hardness. They
are mainly used to die cast the internal combustion engine pistons.

ALUMINIUM ALLOYS
● The A360; it is mainly used to cast aluminum parts where pressure tightness and
fluidity is a priority. It maintains corrosion resistance and strength even at
elevated temperature.
● Alloy A413; its properties are similar to that of the alloy A360. This alloy is mainly
used to die cast hydraulic cylinder components.
● Alloy A380; it has good thermal and mechanical properties. Its performance
properties is similar to most alloys listed above

APPLICATION
● They are used in the automotive and aerospace industry. This is because their
lightweight contribute significantly in fuel efficiency.
● They are used in electrical, thermal and electronics industries. This is due to
superior electrical and thermal properties and good shielding properties. The die
cast aluminum can be used as electrical connectors in the high temperature
applications.
● The die cast parts are used in networking in both computers and communication
industries. This is because they can dissipate heat and act as the radio frequency
filter. Again, they provide a good RFI/EMI shielding making a perfect choice for a
number of handheld devices.

APPLICATION

BRASS DIE CASTING
● Brass, is an alloy of mainly copper and zinc. By varying the amount of copper and
zinc in the final product (brass), we are able to obtain different types of brass
alloys.
● In most cases, the standard brass may have about 67% of copper and 33% of
zinc.
● lead can be added to the alloy (about 2%) to improve the machinability property
of brass. This implies that, without lead, then it will be difficult to die cast brass.

BRASS DIE CASTING
CHARACTERISTICS
● Easy to machine/die cast; It is important to note that brass is not inherently easy
to machine. Adding about 2% of lead enhances the machinability properties. In
some instances, silicon can be used instead of lead. However, brass alloys with
silicon must not be mixed with the ones having lead.
● Corrosion resistance; brass alloys can be modified to offer high level of corrosion
resistance. This is the main reason why the die cast brass parts are used in
plumbing systems with high temperature or high concentration of chloride

BRASS DIE CASTING
CHARACTERISTICS
● Low melting temperature; this makes die casting brass a cost effective process.
The melting point of brass is about 900 °C. This implies that less energy will be
required to melt and subsequently process it to obtain the desired shapes.
● Bright or gold like appearance; this makes it a perfect choice for most decorative
applications. The brass parts that have been die cast are used to make door
knobs, window locks, flowers vases, bearings, etc.
● Low co-efficient of friction; brass is generally soft thus, it can be used to make
die cast parts that do not require friction. These include bearings and fittings.

BRASS DIE CASTING
CHARACTERISTICS
● Relatively strong; a given quantity of aluminum can be added to improve its
strength. Tin also serves the same purpose.
● Environmentally friendly; nearly 90% of brass cast parts can be recycled. This
makes it a sustainable metal as it reduces the amount of scrap metal. This is due
to the fact that brass is a non-ferromagnetic metal

BRASS DIE CASTING
BRASS TYPES
● Admiralty brass; it is mainly used in applications where dezincification is a
problem. It is made of zinc, copper and tin.
● Aich's alloy; it is mainly used in marine applications. This is due to its high
corrosion resistance. The main constituents include copper, zinc, tin and iron
● Alpha brass; they are mainly used in pressing applications. They have less than
35% zinc.
● Duplex brass; it has α and β' phase and it contains between 35 to 45% of zinc.
● Aluminium brass; they’re mainly used to cast brass parts that should be resistant
to corrosion. They contain aluminum.

BRASS DIE CASTING
BRASS TYPES
● Arsenical brass; the die cast parts from this brass alloy are mainly used in boiler
fireboxes
● Beta brass; they can be die cast easily. They contain between 45 and 50% zinc.
● Cartridge brass; they are mainly used to make ammunition cases and the have
30% zinc.
● Rivet brass; it contains 37% zinc.
● DZR brass; contain arsenic and very resistant to most weather conditions
● Red brass; it contains 85% copper with the other three elements (tin, zinc and
lead) available in same proportion (5% each).

BRASS DIE CASTING
BRASS TYPES
● Rich low brass; it is mainly used to cast jewelry. It contains 15% zinc.
● White brass; contains more 50% zinc and it’s also brittle.
● Yellow brass; contains 33% zinc

BRASS DIE CASTING
APPLICATION
● The brass electrical components such as the socket termination parts and coaxial
cables.
● Mechanical parts such as those that are used in the plumbing industry. These
may include pipe joints, washers, nuts, flanges and T-joints just to mention a
few.
● The house accents such as brass candle holders, vases, canisters, decorative
pillows, etc.
● The furniture hardware such as door knobs, locks and handles.
● The brass precision components such as clips, connectors and taps among other
sections.

STEEL DIE CASTING
● Like other metals, steel is also a common metal that can be die cast. This is due
to its versatility and functionality
● Steel itself is an alloy of carbon and iron. This implies that, the steel die cast parts
have both properties of iron and carbon. Again, it is also worth noting that this
alloy may contain other elements that enhance its performance
● Steel may also contain other elements such as vanadium, chromium, tungsten
and chromium, just to mention a few. All these alloying elements are mainly
used to alter the mechanical properties of steel.

STEEL DIE CASTING
CHARACTERISTICS
● High strength; steel is stronger than most metals that are used in engineering
applications. This strength is determined by the carbon content in the alloy. A
die cast steel part with higher carbon content will be both harder and stronger.
● Resistance to corrosion; the stainless steel is corrosion resistant. It doesn’t
corrode easily when it is subjected to any adverse environmental conditions.
● Lightweight; it has a relatively lightweight than a number of building materials.
However, the die cast aluminum parts are lighter than die cast steel parts.
● Dimensional stability; the steel cast parts do not change with time even when
subjected to extreme environmental conditions

STEEL DIE CASTING
CHARACTERISTICS
● Thermal and electrical conductivity; steel has free electrons thus, it conducts
both heat and electricity. This is the main reason why steel parts can be used in
boilers and other electrical components/sections.
● Recyclability; steel can be recycled effectively. This reduces the amount of scrap
metal in the environment. Again, it cuts the production costs making the die cast
parts cheaper.

STEEL DIE CASTING
TYPES OF STEEL
● There are very many types of steel that can be die cast. The American Iron &
Steel Institute has classified all the available steel based on their chemical
composition as:
● The alloy steels; these steels contain the alloying elements in varying
proportions. These alloying elements include: nickel, copper, aluminum,
chromium, copper and titanium. These elements impart different properties on
the alloy such as strength, corrosion resistance, strength and ability to be die
cast.
● The tool steels; they are mainly known for their high strength. They contain
vanadium, cobalt, tungsten and molybdenum in different quantities.

STEEL DIE CASTING
TYPES OF STEEL
● The carbon steel; the die casting companies can choose from the low carbon (less than 0.3%
carbon), medium (0.3 to 0.6% carbon) and high carbon steel (more than 0.6% carbon).
Basically, this classification is based on the carbon content in the alloy.
● The stainless steel; they contain between 10% and 20%. This makes it corrosion resistant.
There are 3 types of stainless steel:
1. Austenitic stainless steel; contain about 18% chromium, 0.8% carbon and 8% nickel. It is
one of the most common and it is mainly used to die cast plumbing systems, kitchen
equipment, etc.
2. Ferritic stainless steel; contain between 12 and 17% chromium and less than 0.1% carbon.
The die cast stainless steel can be strengthened by cold working.
3. Martensitic stainless steel; it contains about 1.2% carbon and between 11 and 17%
carbon. The die cast parts can be treated by heat and are magnetic. Good examples are
surgical and dental equipment.

STEEL DIE CASTING
APPLICATION
● Some of the most common components that are manufactured via this
technique include valves, hydroelectric turbine wheels, tooling equipment and
pumps among other parts in food, electrical and power industries. All these parts
must be manufactured as per the international standards and regulations.

TYPES OF DIE CASTING
● Pressure die casting
1. Hot chamber pressure die casting
2. Cold chamber pressure die casting
● Gravity die casting (permeant moulding)
● Vacuum die casting

PRESSURE DIE CASTING
● The pressure die casting is suitable for high volume run parts. This manufacturing
technique can produce parts with thinner wall thickness without compromising
their quality.
● This process does not depend on the force of gravity to distribute the molten
metal within the mold. Instead, an external pressure must be exerted (air
pressure). This force distributes the molten metal within the mold.
● It is classified as
1. Cold chamber pressure die casting
2. Hot chamber pressure die casting

● Now, pressure die casting again is sub classified into two types one is the cold
chamber pressure die casting and the second one is the hot chamber pressure
die casting
● In the case of the cold chamber pressure die casting, the furnace which is
meant for melting metal is away from the this machine, it is not an integral part
of the machine.
● Whereas, in the case of the hot chamber pressure die casting machine the
furnace which is meant for melting the metal is an integral part of the machine.

1. COLD CHAMBER PRESSURE DIE CASTING
● In the case of the cold chamber pressure die casting, the furnace which is meant
for melting metal is away from the this machine, it is not an integral part of the
machine. Hence the name cold chamber die casting.
● Diagram consists of the schematic representation of cold chamber pressure die
casting.
● Which has movable die half and fixed die half. Also have Ejector pin and plunger
ram system.

● In the cold chamber process molten metal is loaded into the injection cylinder
.(shot chamber).
● The molten metal is forced into the die cavity. At pressure ranges from 20 to
70Mpa. There it solidifies and ejected with the help of ejector pin.

● VIDEO

ADVANTAGES
● Simple construction
● Low cost
● Low floor space
LIMITATIONS
● Slower cycle time to due to the need to transfer the molten metal from the
furnace to the cold chamber machine. Hence rate of production will be less

APPLICATION

2. HOT CHAMBER PRESSURE DIE CASTING
● This process is used for die casting metals that melts at lower temperature such
as zinc, tin ,lead and magnesium alloys.
● Types of hot chamber pressure die casting
a) GOOSENECK AIR INJECTION TYPE
b) SUBMERGED PLUNGER TYPE

● In the case of the hot chamber pressure die casting machine the furnace which is
meant for melting the metal is an integral part of the machine. Hence the name
hot chamber die casting.
● It consists of metal pot, fire box, gooseneck injector and die.
● Initially metal block is placed in the meal pot and heated through fire box using
coke or oil.
● The metal blocks will be melted and molten metal will be there. Here, furnace is
an integral part of the machine.

● Now, the molten metal will be entering into the cylindrical gooseneck chamber.
Air will be coming and air exerts pressure on the molten metal, the molten metal
will be slowly transferred to the die. There it fills and solidifies. Finally ejected
the product with the help of ejector pin

● In this process the plunger and cylinder are submerged in the molten metal bath
in the holding furnace.
● The furnace is attached to the machine by a metal feed system called goose
neck.
● As the injection plunger rises, a part in the injection cylinder opens, allowing
molten metal to fill the cylinder.

● When the plunger forced down and it forces the molten metal through the
nozzle, past the sprue, through runners and gates into the cavity.
● After cavity is filled the metal is allowed to solidify. The casting is ejected and the
cycle is repeated

VIDEO

ADVANTAGES

LIMITATIONS

APPLICATION

GRAVITY DIE CASTING
● This metal die casting technique depends on the force of gravity. That is, the
molten metal is allowed to flow without an external force or pressure. The
nature of the final product will depend on the design of the gravity die casting
machine
● Before the process begins, the mold must be heated and sprayed with a
lubricant. The molten metal is poured in the die and allowed to flow with the
help of gravitational force. The metal alloy then cool and the die cast part
removed.
● The gravity die casting technique is mainly used to cast light alloys

GRAVITY DIE CASTING

VACUUM DIE CASTING
● The vacuum die casting technology has been adopted by companies that
manufacture large parts.
● The vacuum die casting has to be the best way to eliminate the porosity
problem.
● It has two receivers – outlet top and sprue through which the molten metal
enters the die and the vacuum.
● The molten metal flows into the die due to pressure difference. The molten
metal flows up the sprue to the die where the metal solidifies. This cycle keeps
on repeating itself.

VACUUM DIE CASTING
● In the vacuum die casting, the desired pressure differential is controlled by
varying the vacuum. This is between the molten metal and cavity.

VACUUM DIE CASTING
ADVANTAGES
● The die cast parts have good welding properties.
● The parts possess high mechanical strength.
● They are associated with low production scatter.
● It is superior when it comes to reducing gas porosity.
● The die produces accurate parts that may not require secondary operations

VACUUM DIE CASTING
LIMITATIONS
● The initial setup cost is relatively high.
● It is cumbersome to setup a vacuum die casting process.
● Some parts may requires secondary operations. They may not be as precise as
those produced by pressure die casting.

DIE CASTING DIES
TERMINOLOGY
● EJECTOR DIE HALF

DIE CASTING DIES
TERMINOLOGY
● COVER DIE HALF

DIE CASTING DIES
TERMINOLOGY
● Two dies halves are used in die casting; one is called the "cover die half" and the
other the "ejector die half".
● Parting line: The line where two die halves are meet
● Sprue( hot chamber) or shot hole (cold chamber): which allows the molten
metal to flow into the dies; this feature matches up with the injector nozzle on
the hot-chamber machines or the shot chamber in the cold-chamber machines
● Sprue pin: located in the ejector half, makes the sprue hollow and deflects metal
entering the die into the runner system

DIE CASTING DIES
TERMINOLOGY
● Runner: These are channels located at the parting line to route liquid metal from
the sprue hole to the gate
● Gate: These are passages through which metal enters the die cavity. They have
an important function in directing metal flow so that the cavity is correctly filled.
Air is expelled through vents as molten metal enters the die cavity
● Guide pin: It assure proper alignment of die halves and correct register of
cavities

DIE CASTING DIES
TERMINOLOGY
● Draft: It is the amount of slope or taper given to cores or other parts of the die cavity to allow
for easy ejection of the casting from the die. All die cast surfaces that are parallel to the
opening direction of the die require draft for the proper ejection of the casting from the
die. Die castings that feature proper draft are easier to remove from the die and result in high-
quality surfaces and more precise finished product.
● Fillet: It is the curved juncture of two surfaces that would have otherwise met at a sharp
corner or edge. Simply, fillets can be added to a die casting to remove undesirable edges and
corners.
● Bosses: These are added to die castings to serve as stand-offs and mounting points for parts
that will need to be mounted. For maximum integrity and strength of the die casting, bosses
must have universal wall thickness.

DIE CASTING DIES
TERMINOLOGY
● Ribs: These are added to a die casting to provide added support for designs that
require maximum strength without increased wall thickness.
● Holes and windows: It require special consideration when die casting because
the perimeters of these features will grip to the die steel during solidification. To
counteract this effect, generous draft should be added to hole and window
features

DIE CASTING DIES
TERMINOLOGY
● Ejector pin: These helps to push the casting out of that die half
● Ejector pin plate: The ejector pins are driven by an ejector pin plate, which
accurately drives all of the pins at the same time and with the same force, so
that the casting is not damaged
● Cores and slides: Cores are components that usually produce holes or opening
● Other features in the dies include water-cooling passages and vents along
the parting lines These vents are usually wide and thin , so that when the molten
metal starts filling them the metal quickly solidifies and minimizes scrap.
● No risers are used because the high pressure ensures a continuous feed of metal
from the gate

TYPES OF DIE CASTING DIES
● There are various types of die casting dies and each serves a critical need for the
customer.
● The choice of which type of die casting die the customer requires is usually
determined by the following:
○ Size of the part to be cast
○ Volume of parts required either annually or over the life of the project
○ Requirements for “family” sets of parts
○ Desirability of core slides to replace a machine operation
○ Requirements for cast-in inserts to avoid assembly operations

● The different types of dies are
1. Production die
2. Unit die
3. Trim die

1. PRODUCTION DIE
● These are the most common types of tools produced. They range from a single-
cavity die with no slides, to a multiple-cavity die with any number of slides. The
cavities are made from high-quality tool steel, retained in a quality holder block.
The tool steel is heat treated to exacting standards that increase the life of the
die cavities. Slides are components in the die that allow the casting to be formed
with undercuts thus eliminating secondary machine operations and reducing
part cost for higher quantity parts.
● Production dies are built to critical dimensions, coring the maximum amount of
stock from the casting, and allowing the agreed-upon amount of machining.

1. PRODUCTION DIE
● These are mainly classified in to following types.
● Single cavity dies: only one cavity
● Multi cavity dies: dies have several cavities which are all identical
● Combination or Family dies: die has cavities of different shapes

1. PRODUCTION DIE
● Left: single cavity die
● Right: multi cavity die

1. PRODUCTION DIE
● Family die

2. UNIT DIE
● A unit die is a special type of production die that is used for lower volume and
smaller sized parts. It is a lower cost production tool that has a standardized
main die frame and replaceable cavity units. These replaceable units are
designed to be removed from the main die frame without removing the standard
frame from the die casting machine. This feature allows for quicker die set up
time and becomes more effective for lower volume production runs.
● The most common commercial types of unit dies are single and double unit
holders. These types of dies are generally used for smaller parts, or a family of
parts, with no slides or a minimum number of slides. Unit dies limit the use of
core slides because of the configuration needed for interchangeable unit inserts
and the limited space available

2. UNIT DIE
● Unit frame with Die A & Die B. Die A is a unit mould with 1 cavity; Die B is a unit
mould with 3 cavities. The centre is part of the unit frame.

3. TRIM DIE
● The trim die is a tool that trims the runner, overflows, and flash from the casting.
The trim dies are single or multiple cavity tools, made in the same configuration
as the die casting die.
● Depending on the shape of the casting, the trim die may be a simple open-and-
close trim die or it may include as many slides as the die casting tool. In some
cases multiple station trim dies will be used for successive trimming operations.
● Trim dies require as much attention to detail in design as the die casting tools,
and the use of quality materials should be specified to extend their productive
life. They also reduce the labour cost in the de-flashing of the die casting

PART A
1. Choose the merits of aluminium metal over zinc in casting
2. Breakdown the methods of pressure application in die casting process
3. Identify the ingredients of die steel used for making die casting dies
4. State the basic difference between casting and moulding techniques
PART B & C
1. Identify the factors which govern the selection of a die casting alloy for a component
2. Explain cold chamber die casting with sketch
3. Explain the advantages and disadvantages of die casting process

PART B & C
4. Illustrate the hot chamber die casting process with direct air pressure type casting machine
5. Explain characteristics of die steel material
6. Compare hot chamber and cold chamber die casting machines
7. Illustrate the hot chamber die casting process with submerged plunger type casting machine
8. Discuss about the zinc base and aluminium base die casting alloy
9. Classify different types of die casting die
10. Discuss the advantages of die casting
11. Indicate the chemical composition of copper base die casting alloy
12. Discuss the characteristics of steel used in die casting die
13. Discuss the advantages of die casting over sand casting

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