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Computer-Aided Process Planning

IP.com Disclosure Number: IPCOM000112308D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 94K

Publishing Venue

IBM

Related People

Okano, A: AUTHOR

Abstract

Disclosed is a method of computer-aided process planning for assembly.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Computer-Aided Process Planning

      Disclosed is a method of computer-aided process planning for
assembly.

      In process planning, a planner decides on an assembly operation
sequence and assigns resources to assembly operations, taking account
of the cost and cycle time.  After the sequence of assembly
operations has been determined, some consecutive operations are
collected into groups for resources that execute assembly operations.
The number of resources is limited, so each resource executes one or
more assembly operations.  When a production volume is given, an
operation time for resources can be calculated.  No resource can
execute operations that take longer than this time, which is called a
cycle time.  A planner makes a process in which the operation time of
each group of operations is less than the cycle time, and resources
are selected for maximum economy by effective utilization of a
plant's existing resources.  After obtaining valid combinations of
resources, the planner evaluates the processes in which the resource
is used by means of a production line simulator and selects a process
according to the result of the simulation.

In this method,

1.  All possible combinations of operations that satisfy conditions
    for the grouping of assembly operations are generated.

2.  Propositional logic expressions are generated that can manage the
    order of precedence of operations, the correspondence between
    operations and resources, and resources themselves.  Combinations
    of operation groups and resources are generated from the
    expressions by using an ATMS (Assumption-based Truth Maintenance
    System).

3.  A user selects a combination of operations and resources, taking
    account of cost, work-in-process, and so on.  The selected
    combination is a good assembly process.

A relational model of a process for process planning can be described
as follows:

(N, O, R, res(o), assembly (o), parts(o), time(o,r)).

      N, O, and R are sets of symbols and n, o, and r are members of
the sets, respectively.  res(o), assembly(o), and parts(o) are
functions for mapping between N, O, and R, and time(o,r) is a
function for process planning.  N is a set of assembly parts and
subassemblies.  O is a set of assembly operations and R is a set of
resources.  res(o) returns a list of resources that can execute an
operation o. assembly(o) returns a subassembly that is assembled by
an operation o and parts(o) returns a list of assembly parts and
subassemblies that are used by an operation o. time(o,r) returns the
time taken by a resource r to perform an operation o. If r cannot
perform the operation o, an infinite value is returned.

The algorithm for grouping assembly operations is as follows:

For all o sub i memberof O, o sub j memberof O, r sub k memberof R,
where i ne j,
 if o sub i, o sub j, r sub k satisfies

  <assembly(o sub i) memberof parts(o sub j)>
 ...