34th INTERNATIONAL CONFERENCE ON
PRODUCTION ENGINEERING
29. - 30 September 2011, Niš, Serbia
University of Niš, Faculty of Mechanical Engineering
AN INTERACTIVE CAD/CAE SYSTEM FOR MOLD DESIGN
Ivan Matin, Miodrag Hadzistevic, Janko Hodolic, Djordje Vukelic
Department for Production Engineering, Faculty of Technical Sciences, Trg Dostiteja Obradovica 6, Novi Sad, Serbia
matini@uns.ac.rs, miodrags@uns.ac.rs, hodolic@uns.ac.rs, vukelic@uns.ac.rs
Abstract: In injection molding, the design of the molds is of critical importance for the product quality
and efficient processing. This paper describes a knowledge-based parametric design system for mold
design, which requires only a minimum set of injection molding parameters to be established before being
able to complete the design of the main components of a mold. This CAD/CAE system contains of Pro/E
and special developed modules for calculation, selection, modification and design. Developed CAD/CAE
system can greatly improve the design quality while reducing the development time and cost.
Key words: CAD/CAE system, injection molding, mold design
1. INTRODUCTION
The highly competitive environment makes it necessary
to reduce the time and money spent on mold design while
maintaining high standards for product quality. Therefore,
using computer-aided systems has become one of the
most important manners to increase productivity. Most
CAD software offers only simple geometrical modeling
function. However, they fail to provide users with the
sufficient design knowledge, which is of great help in
most design tasks. Therefore, the design of automatic,
knowledge-based, and intelligent systems has been an
active research topic for a long time. Regarding the
construction of a dedicated system, Deng et al. [1]
developed an expert mold design system based on the
configuration design method. This system allows users to
design a mold in the CAD/CAE environment. Kong et al.
[6] developed a Windows-native plastic injection mold
design system based on the Solid Works using Visual
C++. Lou et al. [7] utilized the set-based design approach
with the parametric modeling technique to handle the
uncertainties that are intrinsic at early stages of the mold
design. In the stamping tool design area, authors [8, 9]
developed a knowledge-based strip layout integrated
design system in Pro/E. An interactive mold design
systems were developed for dividing the mold design into
four major steps, as well as for parting surface design,
core and cavity design, runner system design, and mold
base design [2,7]. It also provided the ability to control
and manage projects, and assist designers in completing
projects correctly. Systems have been constructed using
the experience and knowledge of a product design and
mold manufacturers. The researchers first determine the
parting line for the plastic part, followed by the
calculation of the number of cavities required. The cavity
layout is created based on the input information of the
layout pattern and the orientation of each cavity. The
mold base is loaded automatically to accommodate the
layout. Alternatively, Low and Lee [8,9,10] proposed a
methodology of standardizing the cavity layout design
system for plastic injection mold such that only standard
cavity layouts are used. When only standard layouts are
used, their layout configurations can be easily stored in a
database for fast retrieval later in the mold design stage.
Other mold design system was developed by Ma [11],
offering collaborative design systems, a standard mold
base, and a decision-making system to improve the
concurrent mold design efficiency in CAD software.
Constructing standard components is an efficient manner
to shorten the mold design cycle in the mold
development. The advantages of using standard
components include the ability to ensure the consistency
of mold development and the reduction of manufacturing
costs and time. The most important purpose of an
interactive CAD/CAE environment’s standard mold base
is to assist designers in managing and using standard
components correctly and efficiently. A mold base
controls components via a three-level classification by
class, type, and order number. Using the standard
components library, designers browse for the components
they need and save valuable time lost in searches. The
standard components library includes three techniques for
constructing models: general type, program type, and
family table type [14]. General type components are
typically complicated and invariant. Users need only to
specify the component needed, and are not required to
specify any dimensions, such as slide groups. Program
type components have similar shapes but different
features, such as date-code inserts. Family table type
components, such as ejector pins, have variable
dimensions. There are two ways to find components in the
mold base by class and type, or by directly linking to the
window containing the desired components.
2. KNOWLEDGE-BASED APPROACH
A knowledge-based approach broadly means to build up a
system, usually called a knowledge-based system (KBS),
for solving complex decision problems in a specific
domain. A KBS, normally in the form of an intelligent
computer program, uses knowledge and inference
procedures to solve problems that are difficult enough to
require significant human expertise for their solution. The
typical structure of a knowledge-based system is shown in
Fig. 1. [11, 14]
CAE/I
CAD/I
START
3. GENERAL STRUCTURE OF AN
INTERACTIVE CAD/CAE SYSTEM FOR A
MOLD DESIGN
Generally, plastic injection molding design includes a
plastic part design, a mold design, and an injection
molding process design, all of which contribute to the
quality of the molded product as well as the production
efficiency. The developed program system makes
possible to perform: 3D modeling of the parts, analysis of
part designs, numerical simulation of injection molding,
and mold design with calculation [3,4]. By the realization
of the proposed integrated system, this problem could be
solved. The main part of the system consists of a
knowledge base. The knowledge base is organized by
knowledge objects, and practically managed by a
commercial database system. A knowledge engine
accesses to the knowledge base, and invokes appropriate
applications. General structure of a developed interactive
CAD/CAE system for a mold design is presented in Fig.
2. [4,13]
Plastic
material
database
Numerical simulation
of injection molding
Acceptable model geometry and
injection molding parameters?
no
Calculation of injection
molding parameters
Fig. 1. The typical structure of a knowledge-based system
CAE/II
Thermal mold calculation
Rheology mold calculation
Mechanical mold calculation
WEB mold
database
- assembly
- component
- cooling medium
Final dimension mold calculation
Selection of type standard mold
assemblies and components
CAD/II
The developed interactive CAD/CAE system is based on
a typical structure of a knowledge-based system. It
comprises of the knowledge base, containing encoded
expertise from the expert. The inference engine on the
other hand provides strategies for processing the encoded
knowledge in order to reach KB solutions. The KB
system also provides a user interface for the KB
system/user interaction. Links to a traditional database
provide the KB system with the opportunity to import and
use data in the inference or reasoning process. Knowledge
is represented by a set of primitive components. Such
primitive component is called a knowledge object, and it
consists of a functional features and associated data. Mold
design represents a generic sequence of activities, and
each activity is represented by a mold function. A
function defines effects on associated data, and it is
represented by various forms, such as mathematical
formula, decision tables, constraints and logical formula.
Data types include simple data types, such as numerals
and their aggregation, and also complicated data types,
such as geometry and other objects.
CAD modeling of part
Mold design (Core /Cavity)
Design for assembly of the mold
END
Fig.2. General structure of an interactive CAD/CAE
system for a mold design
System consists of four foundation modules. These are:
 CAD/I module for the solid modeling of the part,
 CAE/I module for the numerical simulation of the
injection molding process,
 CAE/II module for the calculation of parameters of
the injection molding and mold design,
 CAD/II module for the final mold modeling (Core
and Cavity design and the design of all residual
mold components).
CAD/I module is the first module in an interactive
CAD/CAE system for a mold design. This module is used
for generating the CAD model of the plastic products. The
result of this module is a solid model of a plastic part with
all necessary geometrical specifications. CAE/I module is
utilized for the numerical simulation of the plastic
injection molding. Using Pro/Plastic Advisor, a user can
optimize the injection molding parameters and optimize
the part geometry and a plastic material. CAE/II module
has been developed to solve the problem of a mold
thermal, rheological and mechanical calculations and the
mold selection. The next section shows the details of the
general structure of the CAD/II module.
3.1. Structure of the CAD/II module
CAD/II module is used for the final CAD modeling of the
mold (core and cavity design). This module uses
additional software tools for the automation, creating a
core and a cavity from the CAD model, including the
shrinkage factor of plastic materials and the automation
splitting mold volumes of the stationary and movable
plates. The product information standard in a CAD/CAE
system has different types which deal with the geometry
representation, the feature representation and the
integrated representation. The integrated representation
can incorporate some kinds of non-geometry information,
such as expert experience and knowledge, into product
modeling, resulting in an efficient manner to realize the
intelligence and the automation of a product design and a
mold design.
Additional capability of the CAD/II module are software
tools that:
 Apply a shrinkage that corresponds to the designed
plastic part, geometry, and molding conditions,
which have been computed in the CAE/I and CAE/II
module for the automation of core and cavity design;
 Make a conceptual CAD model for non-standard
plates and mold components;
 Design core and cavity inserts, sand cores, sliders,
lifters, and other components that define a shape of a
molded part;
 Populate a mold assembly with standard components
such as standard D-M-E mold base, and CAD
modeling ejector pins, screws, and other components
creating the corresponding clearance holes;
 Create runners and waterlines, whose dimensions
have been calculated in the CAE/II module;
 Check the interference of components during the
mold opening, and check the draft surfaces.
After applying the dimensions and selecting the mold
components, the CAD/II module generates a 3D model of
the fixed and movable plates. Geometry mold
specifications, which are calculated in the CAE/II
module, are automatically integrated into the CAD/II
module; as a result, the CAD/II outcomes are an assembly
of mold plates. Features and specifications of the CAD/II
module are as follows: specialized 2D GUI enables the
instant customization of a mold base and components;
automatic assembly of components – ‘pick and place’;
necessary clearance holes, threads, counter bores, etc. are
automatically added to plates; part-level features are
already fully dimensioned; custom components can be
created, saved and reused; mold base consists of „D-ME“ mold components. The structure of the CAD/II module
is presented in the Fig.3.
Fig.3. Structure of the CAD/II module
Mold base assemblies and components with automatic
functions, such as the on-the-fly customization
component, sizing, placement, trimming, and clearance
cut and thread creation, are provided for the following:
Complete Mold Base Assemblies, Plates, Leader and
Return Pin Assemblies, Locating Rings and Sprue
Bushing, Screws and Washers, Automatic Drawing, and
BOM Creation. The drawings of the mold assembly and
plates, completed with hole charts, are created
automatically. Mold opening simulation, completed with
the slider and ejector simulation is created automatically.
4. CONCLUSION
Completing the mold design stage in the shortest possible
time is the goal of every mold designer. Design
automation substantially increases the overall efficiency
of the design process, reducing the occurrence of the
design flaws as well as the time-to-market reduction. An
interactive CAD/CAE system proves to be a confident
software tool for the plastic industry for the injection
molding dental parts whose material is an integral part of
the plastic material database. All modules of the
CAD/CAE system are 3D solid-based, feature oriented,
and parametric. Plastic flow simulation product is in the
CAE/I and allows engineers to determine the injection
molding parameters. CAD/II module also enables
engineers to capture their own unique design and best
practices directly within the database components. The
module for the calculation of the mold specification and
the parameters of injection molding (CAE/II) improves
the design efficiency, reduces the mold design errors, and
provides the full information needed for the mold
selection. The future work of this research can focus on
two issues. The first one is to analyze the market to define
which plastic parts used in dental laboratories are in
deficit and to determine the commercial for the injection
molding in the Serbian industry. The second one are
research possibilities for the full application of an
interactive CAD/CAE system for the mold design for
plastic parts, which is used in the dentistry.
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ACKNOWLEDGMENTS
Results of the investigation presented in this paper are a
part of the research realized in the framework of the
project “Research and Development of Modeling
Methods and Approaches in the Manufacturing of Dental
Recoveries with the Application of Modern Technologies
and Computer Aided Systems“– TR-035020, financed
by the Ministry of Education and Science of the Republic
of Serbia.