Chapter 1 Introduction
Chapter 1 Introduction
1.1 Basis for topic selection
Molds occupy an important position in the product manufacturing process. The level of mold design largely determines the level of productivity. Effective mold design can reduce the number of resource adjustments and adjustment time, and provide greater optimization space for production planning and scheduling to achieve the purpose of improving production efficiency [1]. Mold design is an important part of the tooling system, which affects the efficiency and quality of product production. In-depth research on mold design is of great significance.
The mold industry is the basic industry of industry, and molds are widely used in various fields of industry [2l. In products such as electronics, automobiles, motors, electrical appliances, instruments, meters, home appliances and communications, 60% to 8% of parts are formed by molds. The high precision, high complexity, high consistency, high
productivity and low consumption demonstrated by using molds to produce parts are unmatched by other processing and manufacturing methods. Molds are also "efficiency amplifiers".
The value of the final product produced with the mold is often dozens or hundreds of times the value of the mold itself. The level of mold production technology
to a large extent determines the quality, efficiency and development capabilities of new products,
and has become a measure of a country’s product manufacturing level. An important sign of high and low[3]. As the basic process equipment for industrial production, molds occupy an important position in the national economy. In the past 10 years, mold CAD technology has developed rapidly, and its application scope has been expanding. Mold CAD technology provides an efficient, economical, and fast method for the design and manufacturing of molds, which greatly improves the quality of the mold, shortens the design and manufacturing cycle of the mold, and reduces the cost. >
Reduced mold cost['].
At present, there are many mold CAD systems at home and abroad. Although these systems have strong analytical computing capabilities
and graphics processing capabilities, they can provide interactive design 5]l. However, in these systems, the mold design process is mainly carried out through human-computer interaction. Most designs rely on the operator's design experience, and the computer only performs some rule matching. As well as calculation work, the molds successfully designed by predecessors cannot be effectively used, resulting in a long mold design cycle, high costs, and low development efficiency.
Mold design based on case-based reasoning technology (Case-based Reasoning, CBR) can enable designers to use
past design experience and construct new ones by combining and modifying past design plans. design plan; at the same time, in
actual production, many mold families with exactly the same types of mold parts and assembly relationships have been accumulated, which can
become the basis for new designs 6] I. cRB technology abandons the previous construction and calculation operations of abstract knowledge rules,
directly uses existing examples to solve problems, and achieves the design of new molds by confirming and revising old examples
Gauge[7]. In an instance-based reasoning system, previous experience is saved in the instance library in the form of instances according to a certain organizational structure. When a new problem is to be solved, appropriate methods are used through relevant attributes. The algorithm searches the instance library,
finds one or several instances that are most similar to the new problem, and then modifies the instances to solve the new problem [9l.
The CRB method is applied in mold design, and the thinking activities of the human brain in computer mold design are used to complete the tasks that were previously completed by designers. Not only does it make full use of the mold The design experience of experts is suitable for the actual situation in the project and is also in line with human thinking habits. At the same time, the mold obtained by this method is based on previously successfully designed examples, thus reducing the possibility that the new mold will not work properly and shortening the development cycle.
1.2 Mold CAD development status and trends
1.2.1 Mold CA.
Overview of system development at home and abroad
Mold CAD systems have continued to develop with the development of 3D technology and modern design theories and methods.
From the initial use of two-dimensional graphics technology The basic system has developed to the current stage 110, Sichuan, which is mainly characterized by three-dimensional graphics technology and feature configuration
.
Overseas, D mold research began in the late 1960s, and it was put into production in the early 1970s.
For example, the American Diecomp Company successfully developed the PDDc system for computer-aided design of progressive dies in 1973 [’21.
The system already includes the input of product graphics and material properties: based on the input, the mold structure type selection, concave mold layout, punch mold and other Insert design; final drawing of mold assembly drawings and parts drawings and NC programming.
In 1978, the Japanese Mechanical Engineering Laboratory developed a CAD system for punching progressive dies. The system consists of product drawing
input, mold type selection, blank layout, and strip layout. It consists of 10 modules such as sample, die layout, process calculation, and drawing.
In the 1980s, with the development of computer technology, the number of manufacturers using mold CAD technology increased greatly
. In the bending forming progressive die and automobile panel mold CAD system, plastic forming simulation technology is applied. The representative one is the D/M system for bending progressive dies developed by Hitachi Corporation of Japan in 1982, using a batch processing method that combines manual and
computer design.
In the 1990s, many commercial CAD/CAM systems appeared, such as Pro/E, SolidWorks, etc.
Due to the late development of computer technology in my country, mold CAD research began in the 1980s. Huazhong University of Science and Technology, Institute of Mechanical and Electrical Engineering, Shanghai Jiao Tong University and other units have successively launched research on blanking die systems. In the mid-1990s, the feature-based design progressive die CAD system of Huazhong University of Science and Technology was a representative product of this period.
口
口 mouth.
1.2.2 Development Trend of Mold CAO
In recent years, global manufacturing is shifting to the Asia-Pacific region, and my country is becoming an important base for the world's manufacturing industry
[3]l. Changes in the manufacturing model will inevitably create demand for new technologies and will also promote the development of CAD technology;
The popularization of network technology applications will change our lives and the manufacturing industry to a greater extent. mode. With
my country's accession to the WTO, our products are required to be innovative, with higher quality, lower cost,
and provided to consumers in a faster time User[4l1. As an important process equipment for product manufacturing, the mold industry, one of the basic industries of the national economy, will face the front line of competition. In addition to requiring "high-skilled" practitioners, the mold industry also needs more "high-tech" guarantees.
(1) Collaborative innovation design will become the main direction of mold design
The vertical integration model of the manufacturing industry has enabled product sales, product design, product production and molding worldwide
The division of labor in tool manufacturing is clearer. In order to shorten the product launch cycle and enable mold designers to fully understand the intent of product design, during the product design stage, mold design also begins at the same time, product design engineers and mold design engineering
Engineers need to enter the collaborative design state as early as possible. In addition, the mold standard parts required by mold manufacturers are generally provided by the mold
standard parts factory. It is best to refer to various standards during the mold design stage and make full use of the mold standard parts provided by the mold standard parts
< p>Provide data for design. Since the CAD systems used in each link in the manufacturing process are not necessarily the same,This requires the CAD system to have the ability to collaborate, be able to exchange upstream and downstream data at any time, and be able to process each other
This data, data generation and processing are standardized.
Currently, mold manufacturers have widely adopted CNC machining technology.
In order to ensure processing quality, improve processing efficiency and improve manufacturing processes, a considerable number of mold manufacturers have begun to use multi-coordinate CNC processing, high-speed milling processing and molds based on rapid prototypes Manufacturing and other methods. Due to the abundance of manufacturing equipment and the increase in manufacturing information, manufacturing information in the future will not only be codes for CNC programming processing, but more importantly, manufacturing will be considered from the beginning of design. The process is to provide the process flow of mold manufacturing, which not only includes process tables and processing parameters, but also includes the fixture design of mold processing, the processing clamping process and the codes of each process. Each process is simulated and shared using the network.
(2) The ASP model of mold CAD technology will become the development direction
Today's mold industry has become a high-tech intensive industry. For any enterprise to master all advanced technologies, the cost will be very high, and it will also be very difficult to train and retain talents who master these technologies. As a result, the APS model of mold CAD came into being, that is, application service units with various specialized technologies provide technical services to mold companies. In this way, the entire society has formed a large mold manufacturing enterprise, which divides labor according to the value chain and manufacturing process to optimize manufacturing resources. Application services include, for example, rapid prototyping
manufacturing, CNC machining outsourcing, mold design, mold forming process analysis, etc.
In the past 20 years, due to the continuous adoption of new technologies, mold manufacturing is far from the "handmade workshop" in people's impression.
2.3 Characteristics and advantages of the mold CAO system
(1) Characteristics of mold design
Different from the traditional design of a single part, the mold is made of multiple Assemblies of parts, mold design is an extremely complex process, including product modeling, process analysis, formulating mold plans, selecting mold bases, molds
General assembly drawing design, The design of working parts, the design of auxiliary devices and the detailed design of parts are required to be able to generate final assembly drawings, partial assembly drawings and mold parts drawings. The particularities of mold modeling are as follows:
>a. Most molds are used to process complex parts, and the mold shapes are complex.
b. Generally, there are relatively few processes for processing mold parts, and most of them are formed at one time, so the shape of the mold must
have all the details of the processed parts.
C. The mold design has a high probability of iteration, so the mold CAD geometric model should be updated repeatedly and repaired in a timely manner
(2) Mold CAD modeling characteristics [4]
Mold CAD modeling technology is a precise modeling technology, which can be divided into solid modeling and surface modeling:
a. Solid modeling technology can meet the design requirements for molds with simple structures, but it is not enough for parts with complex structures and high requirements for detailed description accuracy, such as on the draft surface, Face fillet transition and cavity design are subject to certain restrictions.
b. Surface modeling technology uses different surface construction characteristics to produce smooth surface models. It mainly includes core technologies such as multi-surface equivariant fillet transition processing technology, automatic surface trimming technology, surface editing, surface analysis technology and
smoothing processing, which can assist entities. Molding technology completes the design of all details described in the mold design
. Surface modeling technology is suitable for mold design of products with complex shapes and high precision in detail description.
(3) The superiority of mold CAD['"}
The superiority of mold CAD gives it unlimited vitality, allowing it to develop rapidly and be widely used.
Whether it is in terms of increasing productivity, improving quality, or reducing costs and reducing labor intensity, the advantages of D
technology are incomparable to traditional mold design methods.
p>a.ACD can improve the quality of mold design. Comprehensive technical knowledge of various relevant majors is stored in the computer system, providing a scientific basis for mold design and process formulation. .
The interaction between computers and designers can help bring into play the respective strengths of people and machines, making the mold design and manufacturing process more rational.
b.CAD can save time and increase productivity. The automation of design calculations and drawings greatly shortens design time
. The quality is improved, the reliability is enhanced, the decoration time is significantly reduced, and the delivery time of the mold is greatly shortened.
c.CAD can significantly reduce costs. The high-speed operation and automatic drawing of computers greatly save labor
. Optimized design brings savings in raw materials.
d.CAD technology frees technicians from tedious calculations and drawings to engage in other creative labor
.
1.3 Research content of the paper
Systematically proposes the theory and method of mold design based on case reasoning, and conducts research on the application of CRB technology in mold design
conducted in-depth research. On the basis of theoretical research, a mold design system based on case reasoning was developed, which strongly confirmed that the application of CRB technology can improve the efficiency of mold design. The main research content of this article
includes:
Chapter 1 Introduction: Outlines the research significance of the paper, introduces the source of the topic and the background of the topic selection, briefly
Describes the application of CRB technology in mold design, and studies the domestic and foreign overview and development trends of mold CAD
.
Chapter 2 Overall Design of Mold CAD System: Mainly includes process analysis of mold CAD, system requirements
analysis, as well as system structure customization and functional module division.
Chapter 3 Key Technologies of Case-Based Reasoning: Describes the case-based reasoning technology and introduces in detail the representation of instances, the retrieval strategy of instances, and the storage of instances. technology.
Chapter 4: Instance-based mold design: introduces the representation content and methods of mold instances, and proposes a solution for the storage and retrieval of mold instances.
Chapter 5 Prototype System Development: Introduces the UG development platform and development tools, and describes the system business process
.
Chapter 6 Conclusion and Outlook. Summary and outlook of the research content of this article