Topic 4-Process Planning Techniques

MECHANICAL ENGINEERING DEPARTMENT
KNUST, KUMASI
ME 477 PRODUCTION ENGINEERING I
PROCESS PLANNING
TECHNIQUES
Jan 2014
Process Planning Techniques
 Product design is a plan for the product and its
components and subassemblies.
 To convert the product design into a physical

entity, manufacturing plan is needed.
 The activity of developing such a plan is called

process planning.
It is the link between product design and manufacturing.
Definition of Process Planning
Development of the most appropriate manufacturing
and assembly processes and the sequence in which
they should be accomplished to produce a given part
or product according to specifications set forth in the
product design documentation.
Scope is limited by the available processing

equipment and technological capabilities of the
company or plant.
Tasks Involved In Process Planning
• Interpretation of Design Drawings - The part for product

design must be analysed (including materials,
dimensions, tolerances, surface finishes) at the start of
the process planning procedure.
• Processes and Sequence - Select which processes are
required and their sequence. A brief description of all
processing steps must be prepared.
• Equipment Selection - Develop plans that utilize existing
equipment in the factory. Otherwise, the component must
be purchased, or an investment must be made in new
equipment.
Tasks Involved In Process Planning Cont’d
• Tools, Dies, Moulds, Fixtures, and Gauges -

Decide what tooling is required for each processing
step. The actual design and fabrication of these
tools is usually delegated to a design department
and tool room, or an outside vendor specialized in
that type of tool is contracted.
• Cutting Tools and Cutting Conditions - These must
be specified for machining operations, often with
reference to standard handbook
recommendations.
Tasks Involved In Process Planning Cont’d
• Method Analysis - Workplace layout, Small tools,

Hoists for lifting heavy parts, even in some cases
hand and body motions must be specified for
manual operations. The industrial engineering
department is usually responsible for this area.
• Work Standards - Work measurement

techniques are used to set time standards for
each operation.
Process Planning for Parts
For individual parts, the processing sequence
is documented on a form called : Route Sheet,
sometimes known as an Operation Sheet.
Let’s discuss Information on Route or

Operation Sheet
A typical Route Sheet includes the following Information
1) All operations to be performed on the work part,

listed in the order in which they should be
performed.
2) A brief description of each operation indicating the
processing to be accomplished, with references to
dimensions and tolerances on the part drawing.
3) The specific machine, on which the work is to be
done
4) Any special tooling, such as dies, moulds, cutting
tools. Jigs or fixtures, and gauges. Some companies
also include setup times, cycle time standards, and
other data. It is called a route sheet because the
processing sequence defines the route that the part
must follow in the factory.
Guidelines in Preparing a Route Sheet
1) Operator numbers for consecutive processing steps should

be listed as say 20, 30, 40 etc. This allows new operations
to be inserted if necessary.
2) A new operation and number should be specified when a
work part leaves one workstation and is transferred to
another station
3) A new operation and number should be specified if a part
is transferred to another work holder (e.g., jig or fixture),
even if it is on the same machine tool
4) A new operation and number should be specified if the
work part is transferred from one worker to another, as on
a production line.
Process Planning for Parts Cont’d
1) Decisions on processes to be used to fabricate a given part
are based largely on the starting material for the part.
2) This starting material is selected by the product designer.

Once the material has been specified, the range of possible
processing operations is reduced considerably.
3) The product designer's decisions on starting material are

based primarily on functional requirements, although
economics and manufacturability also play a role in the
selection.
Process Planning for Parts Cont’d
Processing Sequence to fabricate an individual Part consists of:
– Basic/Primary Process – Starting Geometry
– Secondary Processes – Refining the Starting
Geometry
Example - Sand casting is the basic process, machining
operations are generally the secondary processes.
– Operations to enhance Physical Properties –
Heat Treatment
– Finishing Operations –
Coating
Process Planning for Assemblies
The type of assembly method used for a given product depends on
factors such as:
– The anticipated production quantities
– Complexity of the assembled product - number of distinct
components
– Assembly processes used - mechanical assembly versus
welding.
For a product that is to be made in relatively small quantities,

assembly is generally accomplished at individual workstations
where one worker or a team of workers perform all of the assembly
tasks. For complex products made in medium and high quantities
assembly is usually performed on manual assembly lines.
 Process planning for assembly involves development of assembly
instructions.
 For low production quantities, the entire assembly is completed at a

single station.
 For high production on an assembly line, process planning consists of

allocating work elements to the individual stations of the line, a
procedure called line balancing.
 The assembly line routes the work units to individual stations in the
proper order as determined by the line balancing solution.
 Process planning for individual components, any tools and fixtures

required to accomplish an assembly task must be determined,
designed, and built; and the workstation arrangement must be laid out.
Computer Aided Process Planning (CAPP)
CAPP is considered to be part of computer-aided

manufacturing (CAM). However, this tends to imply
that CAM is a stand-alone system.
In fact, a synergy (combined effect) results when CAM

is combined with computer-aided design to create a
CAD/CAM system.
In such a system, CAPP becomes the direct connection

between design and manufacturing.
Types of CAPP
Computer-aided process planning systems are

designed around two approaches. These
approaches are called:
- Retrieval CAPP systems
- Generative CAPP systems.
Some CAPP systems combine the two
approaches in what is known as
- Semi-Generative or Hybrid CAPP System.
Retrieval CAPP Systems
 In this type of CAPP, a standard process plan (route/operation

sheet) is stored in computer files for each part code number.
 The standard route sheets are based on current part routings in use
in the factory or on an ideal process plan that has been prepared
for each family.
 It should be noted that the development of the data base of these

process plans requires substantial effort. One of the commercially
available retrieval CAPP systems is Multi Capp, from the
Organization for Industrial Research.
 It is an on-line computer system that permits the user to create

new plans or retrieve and edit existing process plans.
Generative CAPP Systems
• Instead of retrieving and editing an existing plan

contained in a computer data base, a generative system
creates the process plan based on logical procedures
similar to the procedures a human planner would use.
• The problem of designing a generative CAPP system is

usually considered part of the field of expert systems -
branch of artificial intelligence.
• An expert system is a computer program that is capable

of solving complex problems that normally require a
human with years of education and experience.
Advantages of CAPP Systems
1) Process Rationalization and Standardization - Automated process planning leads to
more logical and consistent process plans than when process planning is done
completely manually. Standard plans tend to result in lower manufacturing costs and
higher product quality.
2) Increased Productivity of Process Planners - The systematic approach and the

availability of standard process plans in the data files permit more work to be
accomplished by the process planners.
3) Reduced lead Time for Process Planning - Process planners working with a CAPP
system can provide route sheets in a shorter lead time compared to manual
preparation.
4) Improved legibility - Computer-prepared route sheets are neater and easier to read
than manually prepared route sheets
5) Incorporation of other Application Programs - The CAPP program can be interfaced

with other application programs, such as cost estimation and work standards.

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MECHANICAL ENGINEERING DEPARTMENT

ME 477 PRODUCTION ENGINEERING I

 To convert the product design into a physical

 The activity of developing such a plan is called

Scope is limited by the available processing

• Interpretation of Design Drawings - The part for product

• Tools, Dies, Moulds, Fixtures, and Gauges -

• Method Analysis - Workplace layout, Small tools,

• Work Standards - Work measurement

Let’s discuss Information on Route or

1) All operations to be performed on the work part,

1) Operator numbers for consecutive processing steps should

2) This starting material is selected by the product designer.

3) The product designer's decisions on starting material are

For a product that is to be made in relatively small quantities,

 For low production quantities, the entire assembly is completed at a

 For high production on an assembly line, process planning consists of

 Process planning for individual components, any tools and fixtures

CAPP is considered to be part of computer-aided

In fact, a synergy (combined effect) results when CAM

In such a system, CAPP becomes the direct connection

Computer-aided process planning systems are

 In this type of CAPP, a standard process plan (route/operation

 It should be noted that the development of the data base of these

 It is an on-line computer system that permits the user to create

• Instead of retrieving and editing an existing plan

• The problem of designing a generative CAPP system is

• An expert system is a computer program that is capable

2) Increased Productivity of Process Planners - The systematic approach and the

5) Incorporation of other Application Programs - The CAPP program can be interfaced

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