Computer control in process planning Unit 4 (ME CAD/CAM) ANNA UNIVERSITY Syllabus 2013

1. COMPUTER CONTROL IN PROCESS PLANNING
UNIT – 4
COMPUTER AIDED PROCESS PLANNING
SYSTEMS

2. IMPLEMENTATION CONSIDERATIONS
 Process
planning
function
is
manufacturing
system
dependent.
 A one single process planning system cannot satisfy all of the
different manufacturing system’s needs.
 Same process planning system can be used for two different
manufacturing systems with little modification of process
database if these two manufacturing systems are similar.
 This is not true when manufacturing systems are
significantly different

3. Several factors that must be considered when
one attempts to implement a process planning
system. They are as follows,
 Manufacturing System Components
 Production families/batch size
 Number of different production families

4. MANUFACTURING SYSTEM COMPONENTS
 Planning function is affected
by capability of
manufacturing system available.
 Manufacturing system with precision machining
centers can produce products on a single machining
center.
 In other systems, several machines are required to
achieve same precision
 Process knowledge database depends on the
manufacturing system

5.  Variant process planning system contains no process
knowledge since process plans are retrieved from a
database.
 The capability of the manufacturing system was
embedded in process plans by the process planners.
 These standard plans must be changed when major
factory renovation takes place.
 Generative process planning system has its own
knowledge database in which the user can modify to
suit the particular system.

6. PRODUCTION VOLUME/BATCH SIZE
 Different process plans are used for same product when
production volume differs. For example, to turn a thread on
single screw, lathe can be used, but to turn a thread in 10000
screws, a threading die is required.
 In variant process planning system, changing process plans
based on production volume is not feasible so some
components may quit when production volume increases.
 In generative process planning system, processes, machine and
tool selection are based not only on shape, tolerance and
surface finish, but also on production volume

7. NUMBER OF PRODUCTION FAMILIES
 Certain manufacturing systems specialize in making
similar components for different assemblies, which are
designated by their features.
 Each feature can be machined by one or series of
processes. A model is developed for each family in
which the processes corresponding to each feature are
stored.
 A process plan can be generated by retrieving processes
that correspond to the features on a new component.

8.  For a moderate number of component families and many
similar components in each family, a variant process
planning system is the most economic automated planning
alternative.
 Although a long variant preparation stage is still necessary,
a variant process planning system
is much easier to
develop.
 Variant process planning systems can be used effectively
when there are many similar components, but significant
product variation usually generative process planning
system as economic alternative.

9. Average number of components per family
Economic regions for different planning
alternatives
Variant
Planning
Generative
Planning
Manual Process
Planning
Number of part families

10. CAM-I CAPP
 CAM-I CAPP is a variant system developed by McDonnell
Douglas Automation company (Mc Auto) under a contract
from CAM-I.
 It is the most widely used of all process planning system.
 It is a database management system written in ANSI
standard FORTRAN.
 It provides a structure for a database, retrieval logic and
interactive editing capability.
 Coding scheme for part classification and output format are
added by user. (36 digits alphanumeric code is allowed)

11. CAM-I CAPP
Standard
sequence
file
Part family
matrix file
Part family
Search
Header
data input
Operation
plan file
Application
programs
Standard
sequence
retrieval file
Operation
plan
retrieve/edit
Work
element
processor
Part classification
code
Process
plan
Process
plan
formatter
Process
plan
store

12.  The main menu for the CAPP system contains 11 entries as shown
below :
•
PART FAMILY SEARCH
FS
•
MATRIX SEARCH
MS/CLASSIFICATION CODE
•
SEARCH ATTRIBUTES
SA/CODE NO., VALUE (S)
•
FORMAT PLAN
FB/PART NO, PLAN TYPE, STATUS
•
DELETE PLAN
DB/PART NO, PLAN TYPE, STATUS
•
CREATE NEW PLAN
HD
•
RETRIEVE OPCODE SEQ
OS/PART NO, PLAN TYPE, STATUS
•
RETRIEVE OP PLAN
OP/PART NO, PLAN TYPE, STATUS
•
PROCESS PLAN REVIEW
PP/PART NO, PLAN TYPE, STATUS
•
GROPP TECHNOLOGY
GT
•
LOGOFF
LO

13.  Part family matrix file is represented below.
 The code used is a five digit code with five values for each digit.
Family 02
Family 01
0 1
1
2
1
1
0
1
1
1
1
1
1
1
1
1
2
1
1
1
3
3
4
0
1
1 1
1
2
1
4
1
1
1
1
4
Family 04
Family 03
3
1
1
1
1
1
1
1
1
2
1
0
1
1
3
4
1
1
1
1
1
1
1

14. MIPLAN
 MIPLAN was developed in conjunction with OIR
(Organization for Industrial Research, Inc.)
 It is variant system that uses MICLASS coding system for
part description
 It is data retrieval system which retrieve process plan
based on part code, part number, family matrix and
code range.
 By inputing a part code, parts with a similar code are
retrieved. Then the process plan for each part is
displayed and edited by the user

15. APPAS
 APPAS is an acronym for “Automated Process Planning
and Selection”.
 The major difference between APPAS and other
planning systems is in the surface description.
 APPAS describes the detailed technological information
of each machined surface by means of a special code.
 A single machined surface is typically described using a
data string of 30 to 40 code.

16.  The system is capable of selecting multiple passes and
processes for the designated machined surface such as
twist drill → rough bore → finish bore.
 Multiple diameter holes with special features such as
an oil groove , slot or thread can be planned as single
machined surfaces.
 The details of APPAS include the selection of feed rate,
cutting speed, diameter of the tool, number of milling
cutter teeth, length of the tool, depth of cut for each
tool pass.