Development of Design Customization Systems for
MC Products
Dennis Janitza
Author Contact:
Dipl.-Ing. Dennis Janitza
Lehrstuhl für Feingerätebau und Mikrotechnik
Technische Universitaet Muenchen
Boltzmannstraße 15
85747 Garching, Germany
+49 89 289 15179
janitza@fgb.mw.tum.de
Acknowledgements:
We thank the Deutsche Forschungsgemeinschaft (DFG) for funding this project as part of the collaborative
research center “Production of Individualized Products Close to the Market”. DFG (Deutsche
Forschungsgemeinschaft) is the central public funding organization for academic research in Germany.
Abstract: The subproject “Modeling- and Analyzing Concepts for individual Products”,
part of the “Sonderforschungsbereich 582”, funded by the DFG, tries to integrate the
customer in the product developing process in order to develop individual products.
One major task is to retrieve a CAD model of the personalized product for further
analyses, process planning respectively. Therefore a software tool has to be
developed, that allows an unskilled customer to interact with the CAD Software.
Furthermore all changes have to be supervised to guarantee a functional and
producible product at any time. This paper describes derived requirements and
presents a first prototype of such a system.
1.
Introduction
Mass Customization presents a possible strategy for satisfying new customer demands
for more individual and adaptive products (Pine, 1993), that means to configure and
produce individual products for each customer with an acceptable increase of costs
(Piller, 1998). In order to develop new methods and models in this field the
Collaborative Research Center SFB 582 “Mass Customization” was founded at the
Technische Unviversität München. This project consists of several sub projects dealing
with business administration, product development and production.
Research on the sub project “Modeling and Analyzing Concepts for Individualized
Products” is carried out at the institute “Lehrstuhl für Feingerätebau und
Mikromechanik”. The project focuses on developing the active participation of the
customer in designing a personal product. In addition to material, geometry and
coloring of the product, physical properties (e.g. activity force) may be modified. Given
that the predefined product is supposed to be produced subsequently in a "mini-plant",
various analyses (e.g. producibility) have to be carried out. For this purpose methods,
procedures and tools for the interactive product definitions are being developed.
Research is targeting on developing a software tool, we call Design Customization
System (DC System), that allows a technically unskilled customer to modify or define
an individual product. After this process the derived data is forwarded to one of the
“miniature plants”. In order to achieve a primarily automated production in the “mini
plants”, it must be possible to use the obtained geometrical data in Computer Aided
Manufacturing (CAM) applications.
2.
Background
Multiple methodologies have been developed and presented on this topic. Platform and
module techniques are used in the approach to manage the divergent objectives
between production efficiency and product individuality. While Siddique/Rosen, (2001)
trie to identify common platforms with the use of mathematical tools. A concept called
“Target engineering” is developed to create variable products while harmonizing
potential target conflicts (Burkert/Kontny, 2001). Maupin/Stauffer, (1999) present a way
to combine Mass Customization with Product Family concepts. All these approaches
focus mainly on the conceptual phase of product development.
Other approaches deal with parametrization in product modeling (Anderl, 1994;
Vajna/Schabacker/Schmidt/Freisleben, 1999). These papers give an general overview
about the possibilities in using parametrization properly during the product developing
process. Gero (2001) describes a strategy to develop mass customization products
using design spaces and measures of complexity. Describing the functionalities of
modern Computer Aided Design (CAD) Systems Mendgen, (1999) and Shah/Mäntyla,
(1995) offer general methods to design parametrical products. More specified papers
(Cox/Roach, 2001; Hochgeladen, 2001) present examples for parametrical models. All
these approaches deal with the parametrization within to product development process.
Their aim is, to allow fast changes within the product structure. In all cases there is no
description of any user interfaces to deal with the flexible product, nor are any
configuration possibilities for potential customers offered.
In this paper a concept for an interactive product definition process through common
customers is presented. This is accomplished in appliance of flexible product models.
3.
Requirements for a DCS
Four groups of requirements concerning the DC System are differentiated.
•
Requirements concerning the variation of geometry: The customer has to be
allowed the choice out of a set of given geometries (e.g. accessories).
Furthermore the user should be free in the placement of his chosen objects and
be enabled to modify single attributes. These modifications are part of the
second approach. This allows the customer to make changes on the highest
level of detail, offering a highly flexible product definition.
•
Requirements concerning variation of functionality: Functional definitions
have no direct influence on the physical attributes but are only linked to the
product structure. There are different kinds of functionalities, for example the
power output of a product, advises based on personal desires or information
about costs or weight.
•
Software requirements: There are three different steps to gain an individual
product (see figure 1). First of all a configurator has to be derived of an existing
CAD model. Ideally this process is fully automated. In a second step the
customer defines his product using the configurators. The last process analyses
the gained data and forwards it to a production facility.
Pre Processing:
Product Structure,
Relations, Parameters,
etc. are retrieved from the
CAD model to build a
DC System
Parametrical
CAD Model
DC System
(Configurator)
Configuration:
Product Structure,
Geometry, Functionality,
etc. is modified by the
customer
Post Processing:
The individualised
product is analysed for
durability, producibility,
etc.
Modified,
Individualised
Product
Validated
Product
Figure 1. Three steps to an individual Product
•
4.
User interface requirements: In order to derive a software tool, that users with
a minimal amount of computer experience are able to use, five basic parameters
for designing a user interface are considered (DIN, 1995). These are adequacy
of tasks, capability of self description, controllability, conformity of expectations
and error robustness.
Knowledge Bases for DC Systems
Knowledge Based Systems(KBS) emerged from artificial intelligence research around
1970. They were developed from the idea to create a computer program that performs
tasks usually done by a human expert using heuristic knowledge (Swift, 1990).
For the DC System, knowledge bases are necessary to validate and restrict input data.
For example indispensable attributes, can not be set to zero by the customer. Or a
relations between two attributes could restrict the possible input. During the
development of the software tool different models of KBS’s have been examined.
The first approach was to implement all needed knowledge in the source code of the
configurator (see section 4). On the one hand that is probably the easiest way to
ensure the necessary functionality. But on the other hands it means that there has to
be a new source code for every new product.
Therefore a new way to define a knowledge base was examined. CATIA V5 offers the
possibility to save a significant number of parameters, attributes, rules and relations
within the CAD model (Braß, 2002). This information can be retrieved and stored in the
source code by using self implemented pre processing tools (see figure 1). Thus it is
not necessary to develop a new configurator for every new product. Another approach
is a heuristic knowledge base.
Within this database common facts, beliefs and heuristic knowledge is stored. The
base can be loosely connected to the DC System for analyzing common sense
questions. This specific approach is highly complex and has not been realized yet.
USER
CATIA
Product
Database
DCS
Inference
Engine
User Data
Base
Heuristic
Knowledge Base
Figure 2: Databases within the DC System
Figure 2 shows the different databases within the DC System. Additionally a user
information database and an inference engine can be found. The inference engine is
the interface between the DC System and the databases (Dym/Levitt, 1991).
5.
DC System
So far two prototypes of DC Systems have been realized. Both prototypes were
implemented using Visual Basic. The first prototype concentrates on the interaction
process with the customer. The user interface consists of four different tabs for a
product definition. On the first tab the user is asked to enter personal data. Using this
data the system derives an advise for a possible configuration. On other tabs the user
can chose between different colors or accessories. One tab offers the possibility to
modify two geometrical attributes (diameter, length). By using a simple graphic these
modifications are continuously visualized. The gained data is stored as string or integer
variables in a MS Access database. Using this version of the DC System no CAD data
was created. Therefore a second prototype was developed in order to retrieve this
geometrical data.
The second prototype uses a parametrical CAD model as a basis. For basic
applications of different methods and functionalities the CAD model is kept simple. As
shown in figure 3 it consist of several cylinders on a square pad. This version of the DC
System is used to test the software interface between CATIA V5 and Visual Basic 6.0.
Several functionalities have been applied.
Figure 3: Screenshot DC System
On the first tab the customer is enabled to modify the geometrical parameters (length,
height, radius) of the cube. The second tabs allows the user to create new geometries
(cylinders) and place them all over the surface of the cube. On the third tab the user is
enabled to add predefined geometries on a cylinder of his choice and the last tab offers
the possibility of coloring single parts of the whole product. Thereby most of the basic
geometrical requirements are covered. All modifications are stored within the CAD
model and can be forwarded to a software tool for production planning.
Several routines to avoid mismatches and input errors have been implemented. For
example the user is only allowed to place a cylinder on the surface of the cube but not
next to it. Furthermore cylinders can not be placed on the same position and it is only
possible to place one extra object on one cylinder. These rules, knowledge respectively
are implemented in the source code of Visual Basic. Later on it should be possible to
model such knowledge within the CAD model to avoid the necessity of a new source
code for every new product.
6.
Conclusion and Future Work
Methods for the development of DC Systems have been presented in this paper. After
the implementation of the second prototype new tasks have been derived. Therefore a
brief introduction in Knowledge Based Systems and their use for this project was given.
A new concept for the structure of a DC System was developed. The work has shown
that the CATIA V5 software interface is powerful enough to build such a configuration
tool.
In the near future, methods for designing parametrical products as a basis for the DC
System will be developed. Furthermore concepts and approaches for analyzing
modified product structures will be acquired.
References
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