The document discusses Computer Aided Process Planning (CAPP), which automates the generation of machining operation sequences to reduce reliance on individual planners' judgments. It outlines two approaches: variant systems and generative process planning (GPP), with GPP creating plans from scratch utilizing algorithms based on detailed geometric and process knowledge. The advantages of generative CAPP include process rationalization, increased productivity, faster planning, improved document clarity, and software integration, while its drawbacks are complexity and high development costs.

1. GENERATIVE APPROACH
UNDER COMPUTER
AIDED PROCESS
PLANNING (CAPP)

2. PROCESS PLANNING
 Is concerned with determining the sequence of individual
machining operations needed to produce a given part or
product.
 The resulting operation sequence is documented on a
form typically referred to as a route sheet.
 This is a manual process, mainly dependent on experience
and judgement of the planer.
 Here, there are differences among operation sequences
developed by various planners, thus often leads to
disputes

3. Cont..
 There are various other difficulties in traditional process
planning procedure, for example:
• New machine tools in the factory make the old routings
less optimal
 Hence the need for a program which automatically
generates the manufacturing operation sequence in order
to eliminate these difficulties (CAPP)
 CAPP incorporates logic, experience and judgement into a
computer system

4. Introduction to: COMPUTER AIDED
PROCESS PLANNING (CAPP)
 The use of computer technology to aid in the process
planning of a part or product in manufacturing.
 CAPP works as the interface between CAD and CAM.
 It takes CAD data, converts it to production data.
 The production data is then fed to a production system.
 CAPP has 2 alternative approaches:
 Variant Systems and Generative Process Planning systems

5. GENERATIVE PROCESS PLANNING
 It generates process plans utilizing decision logic,
formulas, manufacturing rules, geometry based data to
determine the processes required to convert the raw
materials into finished parts.
 GPP involves the use of the computer to create an
individual process plan from scratch, automatically and
without human assistance.
 The computer would employ a set of algorithms through
the various technical and logical decisions to determine
the final plan for manufacturing

6. Generative CAPP cont..
 Inputs to the system would include a comprehensive
description of the workpart, such as:
• part code number to summarize the workpart data.
 Generative process plan mainly consists of two major
components :
 (i) Geometry based coding scheme.
 (ii) Knowledge Based

7. Generative CAPP cont..
 Geometry-based Coding Scheme:
 All the geometric features for all process such as related
surfaces, feature dimension, locations, on the features are
defined by geometry based coding scheme.
 The level of detail is much greater in generative system
than a variant system
 Knowledge Based:
 Process knowledge in the form of decision logic and data
are used for matching of part geometry requirement with
the manufacturing capabilities.

8. Generative CAPP:
Ingredients required in fully generative
process planning system
 1.The first ingredient is the technical knowledge of
manufacturing and the logic that is used by successful
process planners must be captured and coded into a
computer program. In an expert system as it would be
applied to process planning, the knowledge and logic
of the human process planners is incorporated into a
"knowledge base".
 The generative CAPP system would then use that
knowledge base to solve process planning problems
(i.e., create route sheet).

9. Generative CAPP cont..
 2.The second ingredient in generative process planning is
a computer-compatible description of the part to be
produced.
 This description contains all of the pertinent data and
information needed to plan the process sequence.
 Two possible ways of providing this description are:
 The geometric model of the part that is developed on a
CAD system during product design.
 A GT code number of the part that defines the part
features in significant detail.

10. Generative CAPP cont..
 3.The third ingredient in a generative CAPP system is the
capability to apply the process knowledge and planning
logic contained in the knowledge base to a given part
description.
 The problem-solving procedure is referred to as the
"inference engine" in the terminology of expert system. By
using its knowledge base and inference engine, the CAPP
system synthesizes a new process plan from scratch for
each new part it is presented.
 -Other planning functions, such as machine selection, tool
selection, and process optimization, can also be
automated using generative planning techniques.

11. Block Diagram for Generative CAPP

12. Examples of the Generative CAPP
Systems

13. Advantages of Generative CAPP
 1) Process rationalization: In CAPP the same software carries out the process
planning and its procedure remains the same whoever uses it. Thus the process
planning becomes logical, consistent and rationalized as it does not depends on
the individualistic experience or judgment.
 2) Higher productivity of the process planners: With CAPP the amount of the
clerical work is greatly reduced for the process engineers and there are fewer
chances of errors. The planners can invest their time on more skilled jobs and also
attain the better process plan that is eventually translated into their higher
productivity.
 3) Faster planning: With CAPP system the engineers can make the routing sheets
for the jobs faster resulting in lesser lead times for the manufacturing process.
 4) Good visibility: The documents made from the computer are neat, clean and
clear, which makes reading the routing sheets easier.
 5) Operate with other software: The CAPP software can be easily integrated with
the other software like designing and manufacturing software. This makes the
whole process of designing, planning and manufacturing an integrated process.

14. Disadvantages
 Drawbacks is complex and very difficult to develop
 Generative process plan design requires long term
investments of people, machinery, and time.