High-speed machining is the development trend of automotive mold manufacturing

High-speed machining technology is an advanced manufacturing technology in the 21st century, with strong vitality and broad application prospects. Through high-speed machining technology, it can solve a series of problems that are troubled in the conventional cutting of automobile molds. In recent years, high-speed machining technology in the industrialized countries of the United States, Germany, Japan, etc. has been widely used in most mold companies, and about 85% of the mold EDM process has been replaced by high-speed machining. High-speed machining technology combines high efficiency, high quality and low consumption, and has become the mainstream in the international mold manufacturing process.

Through the practical application of high-speed machining technology in the automotive mold manufacturing industry at home and abroad, high-speed machining technology has the following advantages:

First, high-speed cutting processing improves processing speed

High-speed machining performs high-speed machining of automotive molds at a cutting speed of about 10 times higher than conventional cutting. Since the excitation frequency of the high-speed machine tool spindle far exceeds the natural frequency range of the “machine tool-tool-workpiece” system, the automotive mold processing process is smooth and without impact.

Second, high-speed cutting processing production efficiency

Machining the mold with a high-speed machining center or a high-speed milling machine can complete the roughing and finishing of the profile and the machining of other parts of the automobile mold in one-time clamping of the workpiece, the so-called "One Pass Machining". The application of high-speed machining technology has greatly improved the development speed of automotive molds.

Third, high-speed machining can obtain high-quality processed surface

Thanks to the extremely small step and depth of cut, high-speed machining results in a high surface quality and even eliminates the need for a trimmer.

Fourth, simplify the processing

Conventional milling can only be carried out before quenching, and the deformation caused by quenching must be manually finished or electroformed to form. Now it can be done by high-speed machining without surface hardening caused by electrical machining. In addition, due to the reduced amount of cutting, high-speed machining can use smaller diameter tools to machine smaller fillet radii and mold details, saving some machining or manual finishing, thus shortening the production cycle.

Fifth, high-speed cutting processing makes the car mold repair process more convenient

In the process of using the automobile mold, it is often necessary to repair it several times to prolong the service life. If high-speed machining is used, the work can be completed faster, the machining effect of the milling machine can be obtained, and the original NC program can be used without reprogramming. And can be accurate.

Sixth, high-speed machining can process rigid automotive molds with complex shapes

According to the high-speed cutting mechanism, the cutting force is greatly reduced during high-speed cutting, and the cutting process becomes easier. The high-speed cutting process has great advantages in cutting high-strength and high-hardness materials, and can be processed with complex profiles and high hardness. Car molds.

The significance of research on high-speed cutting technology of automobile mold

High-speed machining technology has been widely used in the automotive mold manufacturing industry at home and abroad, and has achieved great benefits, but the mechanism and related theory of high-speed machining is still not perfect, and the high-speed cutting database for automotive molds has not yet been established. Domestic and foreign companies choose high-speed cutting tool parameters and high-speed machining parameters. The traditional "trial cutting" method and "experience" method are still used. When processing a new type of material, it is often necessary to use a variety of tools for repeated cutting tests. Research and analysis of tool wear, damage and its causes, to find a set of the best tool materials and processing parameters, so repeated many times, blindness, and a lot of manpower, financial resources and resources. For high-speed machining of special materials such as alloy cast iron, high-strength alloy steel, super alloy (such as titanium alloy), how to choose the right cutting tool according to material characteristics, how to design reasonable cutting parameters, is still researching and developing. in.

Regarding the establishment and use of high-speed cutting databases, there have been few relevant literature reports at home and abroad. This is mainly because the high-speed cutting technology started late, and the practical high-speed cutting data currently available for production is still very scarce.

China's research on high-speed cutting technology for automotive molds started late. In recent years, many mold companies have purchased a large number of high-speed processing equipment and cutting tools from the United States, Germany, France, Japan and other countries, and in the practice of exploring the process technology of automotive mold high-speed cutting, and achieved some successful experience. However, on the one hand, the introduction of equipment does not mean the introduction of technology. High-speed cutting, especially for high-speed cutting of large-scale automotive panel molds, has no successful experience for reference. How to make the imported equipment play its due role as soon as possible is a major issue facing enterprise managers and engineering technicians; On the other hand, technicians use and learn while working, explore and accumulate certain high-speed machining examples, process parameters and work experience. How to save these valuable experiences and lessons for other technical personnel to learn from, avoid more Detours are also a problem.

Auto mold companies must not only establish a high-speed machining and cutting database, but also a "characteristic" cutting database for the processing characteristics of automotive panel molds. The established cutting database can not only store high-speed cutting parameters, but also store excellent high-speed cutting. Processing examples and decision-making knowledge, so this is a database that can “automatically grow knowledge”; on the basis of data and experience, it is also necessary to effectively manage high-speed machining CNC programming tasks. Establishing such a database for the unique situation of the mold company has gone far beyond the scope of general cutting database, but the establishment and application of this "characteristic" database will certainly improve the quality and efficiency of high-speed processing of automotive molds, and bring considerable benefits to enterprises. Economic benefits.

The research content of high speed cutting technology of automobile mold

I. Research on the mechanism of high speed machining

The development of high-speed machining technology at home and abroad is short, and there is still much room for further research and improvement in the cutting mechanism. It is mainly due to the significant increase in speed, cutting force, cutting heat, tool wear and machining during machining. The surface conditions will be significantly different from the phenomena produced by the traditional processing factors and the results. The lack of high-speed cutting mechanism will hinder the deep application of high-speed machining technology. Therefore, we must first study the mechanism of high-speed machining to deepen the understanding of high-speed machining technology by technicians and operators, and make full use of high-speed machining technology to cover automobiles. The molds are processed with high efficiency and high quality.

Second, the optimization of high-speed machining parameters

Practice has proved that the use of reasonable processing parameters in the case of equipment, materials and processing strategies will greatly improve work efficiency and achieve the best combination of processing efficiency, tool wear and processing quality. Therefore, the optimization of machining parameters in the high-speed machining of automobile panel molds is an important technical link to improve work efficiency and mold processing quality of automobile panel parts.

Research on high-speed machining strategy of complex mold surface

An important prerequisite for successful high-speed machining is to withstand nearly constant cutting loads, which guarantees good high-speed machining results under these conditions. For complex mold surfaces, it is necessary to study the machining strategy of removing material volume change and constant cutting load during machining to avoid faster tool wear and reduce tooling error.

Fourth, the establishment of high-speed machining and cutting database for automobile molds

High-speed machining and cutting database stores data such as high-speed cutting parameters for technicians and operators to query and use, and plays an important role in managing process data and assisting technicians in process planning. In order to improve the efficiency of technicians and operators, and to promote the stable and sustainable development of enterprises, it is imperative to establish a cutting database for high-speed machining of automotive panel molds.

Technical means for research on high-speed cutting technology of automobile mold

First, cutting processing finite element simulation technology

The rapid development of computer technology makes it possible to use numerical simulation methods to study the relationship between cutting process and various parameters. The finite element simulation technology of metal cutting machining started in the 1970s has also been developed in the development of computer technology. Great progress. The finite element simulation of metal cutting considers material properties, tool geometry, cutting parameters (cutting speed, feed rate, depth of cut) as well as cutting force loads, thermal loads and residual stresses caused by machining. Based on the test aid and verification, the relative movement of the tool and the part during the virtual cutting process, the dynamic physical simulation of the chip forming process, can show the machining behavior and the internal stress, strain, strain rate and temperature of the machined part. The distribution of physical quantities, such as the processing quality of the parts and the wear and tear of the tools. Furthermore, by optimizing the process parameters, the processing quality of the parts can be improved, the degree of wear of the tools can be effectively reduced, and the expensive cost and time required to determine the new process by the traditional trial and error method can be reduced. In addition, the metal cutting process simulation can define the relationship between the relevant factors (processing parameters, tool geometry and the upper limit of heat and force) and material removal rate. Under the premise of ensuring the quality of the parts, the material removal rate is improved by changing the cutting parameters, thereby achieving the purpose of improving productivity.

The high-speed machining mechanism and processing parameter optimization technology of automobile panel molds involve many disciplines such as materials science, mechanics, metal physics, machinery manufacturing, etc., and it has been difficult to solve in the field of CNC machining. The existing CAM software can only perform NC programming according to the surface features of the parts, ensuring that the tool path does not collide or interfere, but it is difficult to ensure that the processed parts are also optimal in physical targets such as surface quality and tool life, often resulting in products. The accuracy is low and the tool wear is severe, so optimizing the high-speed machining process is a difficult but important issue. From the above overview of the cutting processing finite element simulation technology, the combination of digital simulation and experimental research is an effective measure to solve the practical problem. The finite element simulation of the cutting process and the chip forming process provides a new and more effective analysis method for in-depth study of cutting mechanism and improvement of cutting quality.

Second, based on case-based reasoning high-speed machining database construction technology

CBR (Case-Based Reasoning) originated in the 1970s and is a kind of reasoning model that emerged during the development of artificial intelligence technology. To put it simply, it is to solve the new problem by using solutions and knowledge of similar problems in the past. Case-based reasoning is a kind of reasoning method widely used in various problem solving fields. Applying this reasoning method to solve problems does not depend on the rules of the problem domain, but relies on previous accumulated experience and similar examples of successful solutions. . This is very close to the ideas and methods of human experts to solve problems.

In fact, the case-based reasoning technique is a problem solving method that can be applied to many fields. In the field of high-speed machining of automotive molds, there are many factors to consider in solving problems. Some parts of the solution can be determined by simple rules, but in most cases, the actual situation should be noted. If a cutting tool is selected, the tool type can be easily determined using rules, but the determination of data such as tool size, geometry, blade type, size, angle, machining parameters, etc., is difficult to determine with simple and effective rules. Sometimes, using certain rules that already exist may even lead to erroneous conclusions. In this case, the application of rule-based reasoning is greatly limited. It is difficult to deal with non-numeric data in the problem domain by using artificial neural network algorithm, and applying case-based reasoning technology to solve such problems It is easy to overcome the above difficulties.

In addition, due to the lack of accumulated experience, the optimal matching of parts and tool materials, the selection of cutting amount, the selection of cutting fluid, the rigidity of the machine tool and the rigidity of the workpiece on the machining accuracy and surface quality, and the cutting method are The choice of machine tool, the reasonable matching between tool life and cutting amount and processing cost, and the influence of parts and machining surface types on the process plan cannot be expressed by simple formulas or rules. And this information and experience is significant for the promotion of high-speed cutting technology, so how to collect and process is very important. The method of solving problems based on case-based reasoning can just use the above experience and processing examples to solve various problems in the high-speed machining process. In the current high-speed machining field lacking a large number of systematic applicable cutting data, experience and rules, the application of case-based reasoning technology to solve problems can provide a practical and feasible way to establish a high-speed cutting database and promote high-speed cutting technology. way.

Figure 1 Technical route of high-speed cutting technology for automotive molds

Figure 2 High-speed milling of automotive cover moulds on high-speed machining centers

Technical route of automotive mold high speed cutting technology

The high-speed cutting database construction technology based on finite element simulation technology and case-based reasoning is used to study the supporting technology, and theoretical analysis and experimental research are used as auxiliary technologies to carry out in-depth research on the high-speed cutting process of automobile molds, especially the cover parts. The research process is as follows: firstly, the mechanical properties test of materials is carried out, and the finite element model is constructed by using experimental data. The mechanism of high-speed machining is discussed, the parameters of high-speed machining are optimized and the laws of high-speed machining are revealed. The source data of machining parameters and the law of high-speed machining are optimized. The high-speed cutting database was established by using case-based reasoning method. The high-speed cutting strategy of automobile cover mould with complex surface features to maintain approximate constant cutting load was studied. The key application technology of 3+2 axis CNC machining method was broken, and the car cover mould 3+2 axis CNC was developed. Auxiliary programming tools are used to finally apply these results to actual high-speed machining. Figure 1 is a schematic diagram of the research route.

Application examples of high speed cutting technology for automotive molds

Dongfeng Auto Mould Co., Ltd. is one of the largest and most technologically advanced companies in the domestic automotive mold industry. Since 2000, the company has organized technicians to carry out research on high-speed machining technology, closely combined with the actuality of automobile molds, especially the manufacture of cover molds, to solve a series of key technologies, and summarized a set of high-speed machining for automobile cover parts. Technical solutions and methods, including: the basic concept of high-speed machining of automotive panel molds; the selection of high-speed machining equipment; the installation and commissioning of high-speed machining tools; the use of high-speed cutting tools; CAM software suitable for high-speed machining; 3+2" axis high-speed machining technology; high-speed machining technology and measurement technology. In the past two years, it has jointly carried out the optimization of process parameters and database system development and application projects for automobile molds with Zhejiang University and Hubei Automotive Industry Institute. This project takes the high-speed finishing of the complex profile of large automobile cover parts as the main research object. Based on the introduction of foreign large-scale high-speed CNC machining center equipment, the combination of metal cutting finite element simulation and experimental technology is used to study the common molds. The high-speed machining mechanism of materials; the high-speed cutting database of automobile molds with self-learning function was established based on the case-based reasoning method; the tool axis inclination optimization tool was developed in close cooperation with the UG CAM software function, so the complex profile of the automobile cover mould was “ When the 3+2 axis is machined, it meets the processing requirements of high speed, high quality and high reliability of automotive molds. After practical application, good application results have been achieved.

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