Lo #2 manufacturing process primary secondary part 1

Manufacturing Technology 1
Manufacturing TechnologyManufacturing Technology
LO #2(Part-2) Manufacturing Processes
Reference pages in the e-text :
- 11 ~ 17 : Primary & Secondary Manufacturing Processes
- 230 ~ 247 & 316 ~ 326 : Casting & Molding
(See extended materials at LO 3 – Lecture Note)
- 709 ~ 720 : Conditioning / Heat Treatment
- 653 ~ 677 : Finishing Processes

Manufacturing CapabilitiesManufacturing Capabilities (See page 7 ~ 8)(See page 7 ~ 8)
2Manufacturing Technology
Manufacturing ProcessesManufacturing Processes

Manufacturing Processes –Manufacturing Processes – Processing OperationProcessing Operation
 Shaping operations alter the geometry of the starting work
material by various methods. Common shaping processes
include casting, forging, and machining.
Shaping Operation

 Most shape processing operations apply heat, mechanical force or a
combination of these to effect a change in geometry of the work
material.
 There are various ways to classify the shaping processes.
1. Solidification processes
2. Particulate processing
3. Deformation process
4. Material removal process
Shaping Operation

 In solidification processes the starting material is heated to liquid
or semifluid that cools and solidifies to form the part geometry.
 Nearly all materials can be processed this way if it has relatively low
melting point, such as polymers, metals, and glass ceramics.
 The molted material is forced or poured into a mold to form the
required shape.
 Casting is the name used for metals, and molding is the common
term used for plastic.
Shaping Operation – 1. Solidification

Plastic Molding processes
Shaping of plastic material is achieved by the
application of heat and pressure. There are many
ways in which this can be done, depending on the
nature of the polymer, the type and size of the
product and the quantity and dimensional accuracy
required.
The methods described here are
 Compression molding
 Transfer molding and
 Injection molding.
6

Plastic molding processes
Forms of supply :
Plastic materials used in molding are normally in the
form of powder or small chips known as granules or
as
Preforms.
Additives :
Before molding granules are mixed with other
ingredients –Known as additives in order to modify or
eliminate undesirable properties and to develop their
useful characteristics.
7

Additives
 Plasticizers- added particularly to PVC,to give greater flexibility and make it easy to
form.
 Stabilizers- added to avoid decomposition of PVC
 Lubricants- added to reduce the adhesion between polymer and hot metal surfaces used
for molding.
 Fillers- Used to improve physical properties (fillers could be wood flour, cork dust,
asbestos, carbon black, chalk and chopped fiber glass.
 Ultra-violet absorbers- added to reduce adverse effect of sunlight.
 Colorants- added to give the final product greater appeal, as a means of identifying (in
cable insulation) to simulate a natural or traditional product (like leather bags),
8

Molding process consideration
 Metals have definite melting point and in general tend to be free- flowing in a molten
state but plastic have no definite melting point, they are just soft by the application of
heat as thick viscous fluid hence, result high pressure is required for molding.
 The viscosity is reduced by the application of heat, but there is an upper temperature
limit at which the polymer begins to break down in some way. This is known as
degradation.( all polymers are bad conductor of heat and are susceptible to overheating)
 There is also lower limit of temperature below which the polymer will not be soft
enough to flow in to the mold. Therefore the temperature of the mold must be between
upper and lower limits and will directly affects the viscosity of the polymer.
 All the molding process require three stages:
1) Application of heat to soften the molding material;
2) Forming to the required shape in the mold
3) Removal of heat
9

Types of molding Processes
1.Compression Molding:
Used for thermosetting plastics
The process is carried out in a hydraulic press with
heated platens.
Compression molding is used to produce a wide
variety of products, including electrical and domestic
fittings, toilet seats and covers, bottle tops and various
closures and tableware.
10

2.Transfer molding
 Used for thermosetting plastics
 This process is similar to compression molding except that the plasticizing and molding
functions are carried out separately
 This process is suited to the production of parts incorporating small metal inserts, and
those products having variation of section thickness can be produced.
 Curing time is less and greater accuracy is achieved than with compression molding.
 The main limitation of this process is the loss of material in sprue, runners and gates-as
thermosetting material cure during molding, this cannot be reused.
 Molding tools are usually more complex and therefore more costly than compression
molding tools.
 Typical products produces by this process are motor- car distributors cap and domestic
electric plugs.
11

 Injection molding is a process in which a
polymer is heated to a highly plastic state and
forced to flow under high pressure into a
mold cavity, where it solidifies.
 The molded part, called a molding, is then
removed from the cavity. The production cycle
time is typically in the range of 10 to 30 sec,
although cycles of 1 min or longer are not
uncommon for large parts.
 For small parts, the mold can be built to
contain multiple cavities, also making the mold
expensive. Thus, injection molding is
economical only for large production
quantities.
Shaping Operation – 1. Solidification – Injection MoldingInjection Molding

14
Process & EquipmentProcess & Equipment
Equipment for injection molding evolved from metal die casting. A large
injection molding machine is shown in Figure below. As illustrated in the
schematic in Figure below, an injection molding machine consists of two
principal components: (1) the plastic injection unit and (2) the mold
clamping unit.
Shaping Operation – 1. Solidification – Ex) Injection MoldingInjection Molding

 The injection unit is much like an extruder. It consists of a barrel
that is fed from one end by a hopper containing a supply of plastic
pellets.
 Inside the barrel is a screw whose operation surpasses that of an
extruder screw in the following respect: in addition to turning for mixing
and heating the polymer, it also acts as a ram that rapidly moves
forward to inject molten plastic into the mold.
 A non-return valve mounted near the tip of the screw prevents the
melt from flowing backward along the screw threads.
Injection Unit

 The clamping unit is concerned with the operation of the mold.
 Its functions are to (1) hold the two halves of the mold in proper
alignment with each other; (2) keep the mold closed during
injection by applying a clamping force sufficient to resist the
injection force; and (3) open and close the mold at the
appropriate times in the molding cycle.
 The clamping unit consists of two platens, a fixed platen and a
movable platen, and a mechanism for translating the latter.
Clamping Unit

ProcessProcess & EquipmentProcess & Equipment

Factors affecting selection of molding
method;
Type of material to be molded
The dimensional accuracy
The required output
Example:
small quantity, thermosetting plastic material and not
high degree of accuracy would favor –compression
molding
Larger quantities of higher accuracy from thermosetting
plastic would favor Transfer molding; while high volume
production from thermo plastic material would be carried
out using the injection molding process.
19

 In Particulate processing, the starting material are powders of metals or
ceramics.
 The process includes pressing of the powder into designed die, and
then sintering.
 Sintering is heating the material powder below its melting point make
the particles adhere to each other to form one piece.
 So the powder is first squeezed into a die cavity under high pressure
and then heated to bond the individual particles together.
Shaping Operation – 2. Particulate Processing

Shaping Operation – 2. Particulate Processing (Ex. Sintering)

 Deformation processes, in which the starting material is a ductile
solid (commonly metal) that is deformed to shape the part.
 In the deformation processes, the starting work part is shaped by
the application of forces that exceed the yield strength of the
material. For the material to be formed in this way, it must be
sufﬁciently ductile to avoid fracture during deformation. To
increase ductility (and for other reasons), the work material is
often heated before forming to a temperature below the melting
point. Deformation processes are associated most closely with
metalworking and include operations such as forging and
extrusion, shown in Figure 1.8. Figure 15.19 shows a forging
operation performed by a drop hammer.
Shaping Operation – 3. Deformation Process

Forging
Extrusion

 Also included within the deformation processes category is sheet
metalworking, which involves bending, forming, and shearing
operations performed on starting blanks and strips of sheet metal.
Several sheet metal parts, called stampings because they are
made on a stamping press, are illustrated in Figure 16.35.

 Material removal processes are operations that remove excess
material from the starting workpiece so that the resulting shape is
the desired geometry. The most important processes in this
category are machining operations such as turning, drilling, and
milling, shown in Figure 1.9. These cutting operations are most
commonly applied to solid metals, performed using cutting tools
that are harder and stronger than the work metal.
 Grinding is another common material removal process.
Shaping Operation – 4. Material Removal Process

Shaping Operation – 4. Material Removal Process : Finishing Processes
Grinding is a material removal process accomplished by abrasive particles
that are contained in a bonded grinding wheel rotating at very high surface
speeds. The grinding wheel is usually disk shaped, and is precisely balanced
for high rotational speeds.

Shaping Operation – 4. Material Removal Process

Lapping is an abrasive process used to produce surface finishes of extreme
accuracy and smoothness. It is used in the production of optical lenses,
metallic bearing surfaces, gages, and other parts requiring very good finishes.

Honing is an abrasive process performed by a set of bonded abrasive sticks.
A common application is to finish the bores of internal combustion engines.
Other applications include bearings, hydraulic cylinders, and gun barrels.

Superfinishing is an abrasive process similar to honing. Both processes use a
bonded abrasive stick moved with a reciprocating motion and pressed against the
surface to be finished. Superfinishing differs from honing in the following
respects [4]: (1) the strokes are shorter, 5 mm (3/16 in); (2) higher frequencies are
used, up to 1500 strokes per minute; (3) lower pressures are applied between the
tool and the surface, below 0.28 MPa (40 lb/in2); (4) workpiece speeds are lower,
15 m/min (50 ft/min) or less; and (5) grit sizes are generally smaller.

Polishing is used to remove scratches and burrs and to smooth rough
surfaces by means of abrasive grains attached to a polishing wheel rotating
at high speed— around 2300 m/min (7500 ft/min). Buffing is similar to
polishing in appearance, but its function is different. Buffing is used to
provide attractive surfaces with high luster.
Polishing
Buffing

 The second major type of part processing is performed to
improve mechanical or physical properties of the work material.
 These processes do not alter the shape of the part, except
unintentionally in some cases.
 The most important property-enhancing processes involve heat
treatments, which include various annealing and strengthening
processes for metals and glasses.
 Sintering of powdered metals is also a heat treatment that
strengthens a pressed powder metal work part. Its counterpart in
ceramics is called ﬁring.
Property-enhancing Operation

 Surface Processing Surface processing operations include (1)
cleaning, (2) surface treatments, and (3) coating and thin film
deposition processes.
 Cleaning includes both chemical and mechanical processes to remove
dirt, oil, and other contaminants from the surface.
 Surface treatments include mechanical working such as shot peening
and sand blasting, and physical processes such as diffusion and ion
implantation.
 Coating and thin film deposition processes apply a coating of material
to the exterior surface of the work part. Common coating processes
include electroplating, anodizing of aluminum, organic coating (call it
painting), and porcelain enameling. Thin film deposition processes
include physical vapor deposition and chemical vapor deposition to
form extremely thin coatings of various substances.
Surface Processing

Surface Processing
Sandblasting
Shot Peening

Surface Processing
Electroplating is a process that uses electric
current to reduce dissolved metal cations so that
they form a coherent metal coating on an electrode.
The term is also used for electrical oxidation of
anions onto a solid substrate, as in the formation
silver chloride on silver wire to make silver/silver-
chloride electrodes
Anodized Aluminum
Anodizing is an electrolytic passivation process used to
increase the thickness of the natural oxide layer on the
surface of metal parts.
The process is called anodizing because the part to be
treated forms the anode electrode of an electrical circuit.
Anodizing increases resistance to corrosion and wear,
and provides better adhesion for paint primers and glues
when compared to anodizing done on bare metal.
Electroplating

Manufacturing Processes –Manufacturing Processes – Assembly OperationsAssembly Operations
 Permanent joining processes ; include welding, brazing, soldering, and
adhesive bonding. They form a joint between components that cannot be
easily disconnected.
 Mechanical fastening ; Certain mechanical assembly methods are available
to fasten two (or more) parts together in a joint that can be conveniently
disassembled. The use of screws, bolts, and other threaded fasteners are
important traditional methods in this category. Other mechanical assembly
techniques form a more permanent connection; these include rivets, press
ﬁtting, and expansion ﬁts.
Permanent Joining Processes & Mechanical Fastening
 (Note : Details of welding shall be studied at Fabrication and Welding course later.

Lo #2 manufacturing process primary secondary part 1

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