Process parameters calculation for various production processes-Selection jigs and fixtures election of quality assurance methods - Set of documents for process planning-Economics of process planning.

1. ME8793
PROCESS PLANNING AND COST ESTIMATION
UNIT II
PROCESS PLANNING
ACTIVITIES
PREPARED BY
KARPAKARAJ M
ASSISSTANT PROFESSOR/MECH
THAMIRABHARANI ENGINEERING COLLEGE
TIRUNELVELI.

2.  The process planning involves the various
activities such as drawing interpretation,
material evaluation and process selection,
selection of machines and tooling, setting
process parameters, selection of work
holding devices, selection of quality
assurance and inspection methods, cost
estimating and documenting the details using
route sheets.

3.  Cutting speed
 Feed rate and
 Depth of cut.

4.  The cutting speed also known as surface cutting
speed or surface speed, can be defined as the
relative speed between the tool and the work
piece.
 It is the speed at which the metal is removed by
the cutting tool from the work piece. In case of
lathe machine cutting speed is the peripheral
speed of the work past the cutting tool. It is
expressed in meter/min. or mm/min.
 Cutting speed (V) = π DN/60 × 1000 mm/min

5.  Nature of the Cut
 Work Material
 Cutting Tool Material
 Cutting Fluid Application
 Purpose of Machining
 Kind of Machining Operation
 Capacity of the Machine Tool
 Condition of the Machine Tool

6. Cutting Speeds for different
combinations of operation and
material

11.  Feed is the distance through which the
advances into the work piece during one
revolution of the work piece of the cutter.
 It is the relative motion of tool in one
revolution of work piece. It is expressed in
mm/rev.

12.  Work material (type, strength, hardness etc.)
 Capacity of the machine tool (power, rigidity
etc.)
 Cutting tool (material, geometry and
configuration)
 Cutting fluid application
 Surface finish desired
 Type of operation
 Nature of cut

14.  Depth of cut is the thickness of the layer of
metal removed in one cut or pass, measured
in a direction perpendicular to the machined
surface.
 It is the total amount of metal removed per
pass of the cutting tool. It is expressed in
mm. It can vary and depending upon the type
of tool and work material. Mathematically, it
is half of difference of diameters.
 Depth of cut (t) = D-d/2 mm
D- Outer diameter, d- Inner diameter.

16.  Depth of cut for Turning and Boring
6 mm for roughing and 0.4 mm for finishing.
 Depth of cut for Milling
Half of the cutter diameter.
 Depth of cut for Drilling
Half the feed rate of the tool and minimum
considered to be 0.3mm.
 Depth of cut for Shaping and Planing
The range of 1-4 mm.
 Depth of cut for Grinding
The values for feeds selected in mm/pass.

17.  The process planner has to identify the need
for a work holding device or a jig or a fixture
for the selected operation.
 The process planner will communicate the
identified requirements of the work holding
device to a specialised tool engineer for the
detailed design and drawings that are needed
for manufacturing it.

18. • The main purpose of any work holding device
is to position and hold a work piece in a
precise location while the manufacturing
operation is being performed.
• Types of work holding devices are:

19.  A jig may be defined as a work holding device
which locates and holds the work piece for a
specific operation. It is also provided with
tool guiding elements.
 Jigs are usually lighter in construction and
direct the tool to the correct position on the
work piece.
 Jigs are usually fitted with hardened steel
bushings for guiding or other cutting tools. a
jig is a type of tool used to control the
location and/or motion of another tool.

20.  A jig's primary purpose is to provide
repeatability, accuracy, and interchangeability
in the manufacturing of products.
 A device that does both functions (holding
the work and guiding a tool) is called a jig.
 An example of a jig is when a key is
duplicated, the original is used as a jig so the
new key can have the same path as the old
one.

21.  It is a work holding device that holds,
supports and locates the work piece for a
specific operation but does not guide the
cutting tool. It provides only a reference
surface or a device.
 What makes a fixture unique is that each one
is built to fit a particular part or shape. The
main purpose of a fixture is to locate and in
some cases hold a work piece during either a
machining operation or some other industrial
process.

22. Jigs Fixtures
It is a work holding device that
holds, supports and locates the
work piece and guides the cutting
tool for a specific operation.
It is a work holding device that
holds, supports and locates the
work piece for a specific operation
but does not guide the cutting tool.
Jigs are not clamped to the drill
press table unless large diameters
to be drilled and there is a necessity
to move the jig to bring one each
bush directly under the drill.
Fixtures should be securely
clamped to the table of the machine
upon which the work is done.
The jigs are special tools
particularly in drilling, reaming,
tapping and boring operation.
Fixtures are specific tools used
particularly in milling machine,
shapers and slotting machine.
Gauge blocks are not necessary. Gauge blocks may be provided for
effective handling.
Lighter in construction. Heavier in construction.

23.  Clamping Elements
 Locating Elements
 Tool guiding and Setting Elements
 Tool setting Elements.

24. 1. Location
2. Clamping
3. Loading
4. Stability and Rigidity
5. Clearance for Chips
6. Foot Proof Design
7. Provision for Tool Guides
8. Provision for Indexing
9. Weight
10. Safety
11. Coolant Supply
12. Economy

25.  Component
 Capacity of the machine
 Production requirements
 Location
 Loading and Unloading arrangements
 Clamping arrangements
 Clearance between Jig and Component
 Ejectors
 Base and Body construction
 Tool guiding and cutter setting
 Rigidity and vibration
 Safety
 Cost and Materials

26.  Types of Jigs:
Here are some simple drill jigs:
a) Template jig
b) Plate jig
c) Diameter jig
d) Channel jig
e) Ring jig
f) Box jig
g) Leaf jig
h) Angle plate jig
i) Indexing jig
j) Trunion jig

27.  Types of Fixtures:
These are some Fixtures available:
a) Plate fixture
b) Angle plate fixture
c) Vise-jaw fixture
d) Indexing fixture
e) Multistation fixture
f) Profile fixture

29.  The next activity of process planner is to
specify the quality assurance
methods/inspection criteria for all the critical
processing factors such as dimensional and
geometric tolerances and surface finish
specifications that are identified during the
drawing interpretation.
 Quality assurance (QA) is a way of preventing
mistakes and defects in manufactured
products and avoiding problems when
delivering products or services to customers.

30.  Identification of inspection locations
 Identification of the most appropriate
inspection and testing methods
 Determination of the frequency of inspection
and testing
 Evaluation of inspection and test data.
 Identification of corrective action.

31. Quality Defined:
1. Quality is fitness for use.
2. Quality is conformance to requirements.
Definition of TQM:
Total Quality Management (TQM) is the
management approach of an organisation,
centered on quality based on the
participation of all its members and aiming at
long-term success through customer
satisfaction, and benefits to all members of
the organisation and to society.

32.  Detection strategy and
 Prevention strategy.

36.  Statistical Quality Control (SQC) is
about employing inspection
methodologies derived from statistical
sampling theory to ensure
conformance to requirements.

37.  A control chart is a graph that displays data
taken over time and the variations of this
data.

38.  Process capability compares the output of an
in-control process to the specification limits
by using capability indices.
 Process capability may be defined as the
“minimum spread of a specific measurement
variation which will include 99.7% of the
measurements from given process.”
 In other words, Process Capability = 6σ

39. Objectives of Inspection
 To sort out the conforming and non-
conforming product.
 To initiate means to determine variations
during manufacture.
 To provide means to discover inefficiency
during manufacture.

40. 100% Inspection:
100% or cent percent inspection is quite
common when the number of parts to be
inspected is relatively small.
Sampling Inspection:
The use of sampling inspection is made when
it is not practical or too costly to inspect each
piece.

41.  Measurement: The different types of quality
characteristics that are to be measured are:
1. Dimensions/Size,
2. Physical properties,
3. Functionality, and
4. Appearance.

42.  Accuracy
 Linearity
 Magnification
 Repeatability
 Resolution
 Sensitivity
 Stability (or drift)

45.  The process planner should have the fundamental
knowledge on cost estimating, cost accounting,
various types of costs, components of costs and
calculation of manufacturing of a product.
 The knowledge of costing will help the process
planner and the management to take the following
decisions:
•Type of material to be used for a product.
•Volume of product to be manufactured.
•Make or Buy decisions.
•Design of a product.

46.  Definition:
Break-even analysis, also known as cost-
volume-profit analysis, is the study of inter-
relationships among a firm’s sales, costs and
operating profit at various levels of output.
It is a simple method of presenting to
management the effect of changes in volume
on profit.
It is concerned with finding the point at which
revenues and costs are exactly equal. This
point is known as break-even point.

47. I. To help in deciding profitable level of output,
below which losses will occur..
II. To compute costs and revenues for all possible
volumes of output to fix budgeted sales.
III. To take decision regarding make or buy.
IV. To take plant expansion decisions.
V. To take equipment requirement decisions.
VI. To indicate margin of safety.
VII. To fix the price of an article to give the desired
property.
VIII. To compare a number of facility locations.

48.  The break-even point may be defined as the level
of sales at which total revenues and total costs
are equal. It is a point at which the profit is zero.
 The break-even point (BEP) in economics,
business—and specifically cost accounting—is
the point at which total cost and total revenue
are equal, i.e. "even". There is no net loss or gain,
and one has "broken even", though opportunity
costs have been paid and capital has received the
risk-adjusted, expected return.

49. I. Break-even point in terms of physical units:
Let, FC = Fixed cost,
VC = Variable cost per unit,
TVC = Total variable cost,
TC = Total cost
TR = Total revenue i.e. total income,
Q = Sales volume and
SP = Selling price per unit.
TC = FC + (VC X Q)

50. TR = SP X Q
At Break-Even Point(BEP),
Total Cost= Total revenue
TC = TR
FC + (VC X Q) = SP X Q
Or QBEP = FC/(SP-VC)

51. II. Break-even point in terms of Sales Value:
This method is suitable for a multi-product
firm.
Break-even sales
(BEP in rupees) FC / 1 – (VC/SP)

52.  The difference between selling price and
variable cost per unit is known as
Contribution or contribution margin.
C = SP – VC
Contribution margin divided by selling price is
known as contribution ratio.
Contribution ratio = (Selling price-Variable cost)/ Selling price.

53.  Margin of safety represents the strength of
the business. It enables a business to know
what is the exact amount it has gained or lost
and whether they are over or below the
break-even point.
Margin of safety = (current output - breakeven output)
Margin of safety% = (current output - breakeven output)/current output × 100