Proposes a methodology and architecture suitable for generating the process plan of machining parts.
Rahimic, S. ; Visekruna, V.
Abstract: This paper proposes a methodology and architecture
suitable for generating the process plan of machining parts. It is a
proposal in which the peripheral processes needed for these parts are
taken into account and they also enable the development of alternative
process plans. The architecture supports the construction of CAPP
systems from prepackaged, plug-compatible software components. The
specifications of the architecture and its building blocks are defined.
A prototype system is under development to prove the concept. This paper
proposes a methodology and architecture suitable for generating the
process plan of machining parts. It is a proposal in which the
peripheral processes needed for these parts are taken into account and
they also enable the development of alternative process plans.
Key words: methodology, architecture, CAPP system
1. INTRODUCTION
The manufacturing industry has been pushed to adopt more effective
and efficient production strategies to meet the challenge of shorter
life cycle, higher quality, lower cost, wider variety of customer
demands. This increased emphasis on achieving highly adaptive
manufacturing to reduce manufacturing costs and to better utilize
manufacturing capacity has led to a critical focus on agile
manufacturing as a strategy to achieve these goals. In manufacturing,
process planning is the task that transforms the design information into
the manufacturing processes and determines the operation sequence. CAPP
is considered a crucial link between Computer -Aided Design (CAD) and
Computer -Aided Manufacturing (CAM). Research of over 30 years in CAPP
has resulted in a wealth of knowledge on CAPP and many experimental and
commercial CAF'P systems have been developed as a result. Most
researchers have focused on a particular aspect of process planning and
very few have addressed the issue of system architecture and integration
of sub-systems. The current CAPP systems are general and in a closed
form, i.e., it is very difficult to modify these systems to suit a
user's dynamic needs. This, along with other obstacles in CAPP
research, inevitably resulted in the unsuccessful practical
implementation of CAPP, particularly in manufacturing environments with
constantly changing products and manufacturing resources. In this study,
a novel architecture is proposed for rapid development of CAPP systems
for agile manufacturing.
2. PROPOSED METHODOLOGY FOR PROCESS PLANNING
As mentioned above, the methodology indicates the procedure adopted
for determining the process plan of a part. It therefore establishes the
steps to be resolved and the order they take. It also has a considerable
influence on the planning system's degree of generality and
flexibility (Van Houten and Van't Erve 1988). A suitable
methodology will establish the functions to be performed--they should be
straightforward--the degree of generality each of them must achieve, and
how the plan is built up. This is a very important aspect when not only
one plan is to be generated, but when there is a group of alternative
plans. The requirements demanded of a methodology for developing general
and flexible CAPP systems for machining parts are as follows. Take into
account not only the machining processes, but also other processes
closely linked to it in the final stages of part manufacture such as
heat treatment, coating, cleaning and debarring operations.
Assess process plans with regard to the quality obtained in the
product and the manufacturing costs, performing an in-depth study of the
resources used that play a part in these factors. . Enable the
generation of alternative process plans at all levels: processes,
machines, fixtures, etc., assessing the production cost in each case. A
process planning methodology is influenced by the input data or part
data, and the output data or process plan chart data. Before the
methodology proposed is discussed, we will take a look at the part and
process plan data.
3. METHODOLOGY
The proposed methodology is shown in figure 1. As mentioned above,
the methodology starts from part information using machining features
and its quality (Gonzalez F.; & Rosado, P.) specifications.
[FIGURE 1 OMITTED]
Its purpose is to establish all the viable alternative process
plans, organizing them as sequences of phases, set-ups and operations.
The different steps of this methodology are as follows raw material. The
first stage is to determine the raw material for machining the part. In
a part model based on machining features, this raw material may be
specified in the part model. Otherwise, this stage is responsible for
specifying raw material taking into account other forming processes to
obtain the pre form (molding, plastic deformation, cutting, welding,
etc.). Therefore, this is a function that includes process planning for
processes that are different to machining. As a result, it is placed in
the context of a generic planning or a macro-plan before machining.
Using the part's input model, this step consists of determining the
model that the system will use to work with. This model will be based on
the definition of the part with certain machining features, complying
with two conditions that distinguish it from the input format. The
volume of data is growing at an unprecedented rate, both in the number
of features (attributes) and object (instance). For example, many data
base with genetic information may contain thousands of features for
large number of patients. (Ben-Arieh, D.; Gutin, G. ; Penn, M.; &
Zverovitch, Y.)
The first condition is that all the machining features will be
simple. For this purpose, compound features will be broken down into
simple features. The second condition is that the properties for each of
these simple machining features include both their shape and quality
specifications for manufacturing of features. It also considers the part
as a whole, taking into account factors such as, for example, and its
accessibility. This means moving on to a model of machining features
where the definition of each feature contains individual information as
well as information about the rest of the part, assignment of processes
and operations.(Kusiak, A.) Using the part model obtained in the
previous stage and based on simple machining features, it is possible to
determine the processes that are technologically able to achieve them
and the operations necessary for these processes. The strategy proposed
is to assign to each feature all the processes and operations that may
be applicable to the usually, an automatic process planner should be
able to reason about manufacturing features that may be machined in a
single opration and/or with s single tool and/or on a single machine.
The set of frames is usually obtained through the interface between
process planning and design, show on figure 3. (Visekruna, V.; Petkovic,
D.; & Rahimic, S.)
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
4. AN OBJECT-ORIENTED KNOWLEDGE REPRESENTATION SCHEME
We propose an appropriate knowledge representation scheme which
attems to address various facets of the process planning task. We
recommendanobject-oriented approach for describing process planning
related entities and the relations among them, and for development of
automated process planning systems. The object-oriented approach object
which during process planning exchange messages (Figure 2). Each object
carries data that identify it through a set of attributes, functions
that define its behaviour thriugh appropriate methods, and links to
other object through associations with other objects. Each kind of
object is represented as a hierarchy with realationship is-a between
them and instance at the bottom level. Lower objects in the hierarchy
inherit common attributes and/or their values from higher level objects.
Taxonomies of features, processes, machines and tools exist in the
sematic network. Inheritance is used to infer attributes and behaviour
of more specific object. (Hang-Wai, L.; & Hon-Yuen, T.) a number of
represent manufacturing capabilities and reasoning in process planning.
Now we will explain some of these taxonomies and relations in more
detail.
5. CONCLUSION
In this paper proposed a methodology and architecture suitable for
generating the process plan of machining parts. It is a proposal in
which the peripheral processes needed for these parts are taken into
account and they also enable the development of alternative process
plans. These characteristics enable standardized CAPP systems for
general application in industry. These characteristics are largely based
on the methodology proposed, the functional structure, the use of
general information models and the general functional procedures. All
these factors working together give the system its qualities. The
development of the CAPP system based on this proposal has demonstrated
the system's feasibility and its optimal qualities. The process
plans offered by the system constitute all of the alternatives for the
sequence of phases, guaranteed by a high degree of optimization with
regard to cost and number of phases. These alternatives explicitly
include feasible alternatives for machines and, as a consequence,
alternative processes for operations (depending on the type of machine
for each phase). Using different alternatives at phase level leaves the
solution open in a passive way at lower resource levels (fixtures and
tools), yet also, in an active way, since the extreme capacities of
fixtures and tool resources have been taken into account in the machine
capacities.
6. REFERENCES
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Gonzalez, F.; & Rosado, P.; General and flexible methodology
and architecture for CAPP: GF-CAPP system, int. j. prod. res., 2003,
vol. 41, no. 12, 2643-2662
Hang-Wai, L.; & Hon-Yuen, T.; Object-oriented analysis and
design of computer aided process planning system, Int. Journal CIM--vol.
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