Since the reform and opening up, with the rapid development of the national economy, the market demand for molds has been increasing. The mold industry has been developing rapidly with the growth rate of about 15%, and the equity structure of enterprises in the mold industry has also undergone tremendous changes. In addition to state-owned professional mold factories, collective, joint venture, sole proprietorship and private enterprises have also developed rapidly. Ningbo and Huangyan, Zhejiang's "Hometown of Moulds"; Some large group companies and rapidly rising township enterprises in Guangdong, Kelon, Midea, Konka and other groups have established their own mold manufacturing centers; There are thousands of Sino-foreign joint ventures and wholly foreign-owned mold enterprises. With the acceleration of the pace of international integration and the intensification of market competition, people are increasingly aware of the importance of product quality, cost and new product development ability. Mold manufacturing is one of the most basic elements in the whole chain. Many mold enterprises have increased their investment in technological progress, which is regarded as an important driving force for their development. Some domestic mold enterprises popularized 2D CAD and began to use international general-purpose software such as Pro/E, PDX, UG NX, NX progressive mold design, I-DEAS, Euclid-IS, Logopress3, 3DQuickPress, MoldWorks and Topsolid Progress. Some manufacturers also introduced CAE software such as Moldflow, C-Flow, DYNAFORM, Optris, MAGMASOFT, etc., and successfully applied them to the design of stamping dies.
The manufacturing technology of large stamping dies such as automobile panel dies has made great progress. The mold factories of Dongfeng Motor Corporation and FAW Mold Center have been able to produce some auto panel molds. In addition, many research institutions and universities carry out research and development of mold technology. After years of efforts, the technology of mold CAD/CAE/CAM has made remarkable progress. It has made contributions to improving the quality of molds and shortening the design and manufacturing cycle of molds.
For example, KMAS auto panel stamping analysis software independently developed by auto panel forming technology of Jilin University, injection mold, auto panel mold, progressive die CAD/CAE/CAM software developed by State Key Laboratory of Mold Technology of Huazhong University of Science and Technology, cold die and precision die CAD software developed by National Engineering Research Center of Mold CAD of Shanghai Jiaotong University, etc., have many users in the domestic mold industry.
Although China's mold industry has made remarkable progress in the past ten years, there is still a big gap compared with developed countries in many aspects. For example, the proportion of precision machining equipment in mold machining equipment is relatively low; The popularization of CAD/CAE/CAM technology is not high; Many advanced mold technologies have not been widely used, and so on, resulting in a considerable number of large, precise, complex and long-life molds relying on imports. The development of mold technology should serve to meet the requirements of short delivery time, high precision, good quality and low price of mold products.
(1) Fully popularize CAD/CAM/CAE technology.
Mold CAD/CAM/CAE technology is the development direction of mold design and manufacturing. With the development and progress of microcomputer software, the conditions for popularizing CAD/CAM/CAE technology are basically mature, and enterprises will increase the intensity of CAD/CAM technical training and technical services; Further expand the application scope of CAE technology. The development of computer and network makes it possible for CAD/CAM/CAE technology to be popularized across regions, enterprises and research institutes in the whole industry, realizes the re-integration of technical resources and makes virtual manufacturing possible.
(2) high-speed milling
The high-speed milling developed abroad greatly improves the machining efficiency and obtains a high surface finish. In addition, it can also process modules with high hardness, which has the advantages of low temperature rise and small thermal deformation. The development of high-speed milling technology has injected new vitality into the manufacture of large cavity molds in automobile and household appliances industries. It has developed towards higher agility, intelligence and integration.
(3) Mold scanning and digitization system
High-speed scanner and mold scanning system provide many functions needed from model or object scanning to machining expected model, which greatly shortens the mold development and manufacturing cycle. Some fast scanning systems can be quickly installed on existing CNC milling machines and machining centers to realize fast data acquisition, automatically generate machining programs of different CNC systems and CAD data of different formats, and use them in "reverse engineering" of mold manufacturing industry. Mould scanning system has been successfully applied in automobile, motorcycle, household appliances and other industries, and it is believed that it will play a greater role during the Tenth Five-Year Plan period.
(4) EDM milling.
EDM milling technology, also known as EDM generating processing technology, is a new technology that replaces traditional cavity processing with special-shaped electrodes. It is a simple high-speed rotating tubular electrode, which is used for three-dimensional or two-dimensional contour machining (like CNC milling), so it is no longer necessary to manufacture electrodes with complex shapes, which is obviously a major development in the field of EDM. Machine tools using this technology have been applied to mold processing abroad. It is expected that this technology will be developed.
(5) Improve the standardization of molds.
The standardization of molds in China is constantly improving, and it is estimated that the coverage rate of mold standard parts in China has reached about 30%. Generally, it is about 80% in developed countries.
(6) High-quality materials and advanced surface treatment technology
It is very necessary to select high-quality steel and apply corresponding surface treatment technology to improve the service life of dies. Die heat treatment and surface treatment are the key links to give full play to the properties of die steel materials. The development direction of mold heat treatment is vacuum heat treatment. In addition to improving mold surface treatment, advanced technologies such as vapor deposition (TiN, TiC, etc. ) and plasma spraying technology.
(7) Mold grinding and polishing will realize automation and intelligence.
The surface quality of die has a great influence on the service life of die and the appearance quality of parts. It is an important development trend to study automatic and intelligent grinding and polishing methods instead of existing manual operations to improve the surface quality of molds.
(8) Development of automatic mold processing system.
This is the long-term development goal of our country. Automatic mold processing system should have a reasonable combination of multiple machine tools; Equipped with a matching positioning fixture or positioning disk; Have a complete CNC machine tool library; Have a complete CNC flexible synchronization system; There are quality monitoring and control systems. A large number of leading enterprises in the mold industry have emerged in China. For example, there are "Big Four" automobile panel molds, large-scale plastic molds are Haier, Huawei and Qundaxing, precision stamping molds are Guo Sheng and Huafu, automobile tire molds are Haomai and Hulun, casting molds are FAW Casting, Ningbo Heli, Guangzhou Automobile Cavity and Beilun Wang Hui, and precision plastic molds are Waco and Ningbo Yokogawa. According to Wu Bingshu, 95 enterprises in the mould industry have been awarded the title of "Key Key Mould Enterprises in China". During the Shanghai International Mould Exhibition, China Mould Association will award the fourth batch of 10 enterprises. By then, there will be about 1 10 "key mold enterprises in China".
For a long time, the development of China's mold industry has been unbalanced in geographical distribution. The southeast coastal areas develop faster than the central and western regions, and the south develops faster than the north. Mold production is most concentrated in the Pearl River Delta and Yangtze River Delta, and its mold output value accounts for about two-thirds of the national output value. Bright Lo, CEO of Mould Network and Deputy Secretary-General of Shenzhen Mould Technology Society, said that this model is undergoing profound changes. China's mold industry is expanding from the developed Pearl River Delta and Yangtze River Delta to the north, and some new mold production areas such as Beijing-Tianjin-Hebei, Changsha, Chengdu-Chongqing, Wuhan and Anhui have appeared in the industrial layout. Mold agglomeration has become a new feature, mold park (city, gathering place, etc. ) is constantly emerging. In the eastern region, Kunshan and Wuxi precision mould industrial cluster production bases have been formed. Botou and Wuhu automobile mold industry cluster production bases; Ningbo, Huangyan, Shenzhen and Dongguan large-scale precision mould industry cluster production bases. Bright Lo said that the mold industry is widely valued in China. China's mold industry has accelerated the pace of system reform and mechanism transformation, and the industrial structure has become increasingly reasonable, mainly because the development speed of large-scale, precise, complex and long-life mold standard parts is higher than the overall development speed of the industry; The ratio of plastic mold to die-casting mold increases; The number and production capacity of professional mold manufacturers facing the market have increased rapidly; With the deepening of economic system reform, foreign-funded enterprises and private enterprises have developed rapidly. Stamping die is the main process equipment for stamping, and stamping parts are completed by the relative movement of upper and lower dies. Due to the continuous separation and combination of the upper and lower molds in the processing process, if the operator's fingers always enter or stay in the closed area of the mold, it will pose a serious threat to his personal safety.
Main components and safety requirements
1. Working parts
The die is a working part that directly shapes the blank, so it is the key part of the die. The stamping die is not only precise, but also complicated, and should meet the following requirements:
(1) shall have sufficient strength and shall not be broken or destroyed during stamping;
(2) There should be appropriate requirements for its materials and heat treatment to prevent brittle fracture due to too high hardness.
2. Positioning parts
Locating parts are parts that determine the installation position of the blank, including locating pins (plates), retaining pins (plates), guide pins, guide plates, side cutters with fixed distance, side presses, etc. When designing positioning parts, it should be considered that the operation is convenient, there should be no over-positioning, and the position should be easy to observe. It is best to adopt forward positioning, profiling positioning and guide pin positioning.
3. Pressing, discharging and discharging parts
Blanking parts include blank holder ring and blank holder plate. The blank holder ring can suppress the blank holder force and prevent the blank from arching under tangential pressure to form wrinkles. The function of blanking plate is to prevent the blank from moving and jumping. The function of ejector and discharge plate is to facilitate the discharge and cleaning of waste. They are supported by springs, rubber and air cushion push rods on the equipment and can move up and down. Ejection parts should be designed with sufficient ejection force and limited movement. The unloading plate should be as small as possible in the closed area, or an empty slot should be milled in the operating position. Protective plates should be set around the exposed discharge plate to prevent fingers from entering or foreign objects from entering, and the edges and corners of the exposed surface should be blunt.
4. Guide parts
Guide post and guide sleeve are the most widely used guide parts. Its function is to ensure that there is an accurate fit gap between the punch and the die during stamping. Therefore, the gap between the guide post and the guide sleeve should be smaller than the blanking gap. The guide pillar is arranged on the lower die base, and the upper end surface of the guide pillar should be at least 5 to 10 mm higher than the top surface of the upper die plate at the lower dead center of the stroke. The guide post should be far away from the module and the blind plate, so that the operator's arm does not have to go through the guide post to get the material.
5. Supporting and clamping parts
It includes upper and lower templates, a die handle, a convex-concave die fixing plate, a backing plate, a stopper and the like. Upper and lower templates are the basic parts of stamping die; All other components are respectively installed and fixed on it. The plane size of the template, especially the front-back direction, should be suitable for the parts, and too large or too small is not conducive to operation.
Some dies (blanking and punching dies) need a backing plate under the die frame in order to make the parts convenient. At this time, it is best to connect the shim and the template with screws, and the thickness of the two shims should be absolutely equal. The spacing between pads shall be subject to the transportation of parts, and shall not be too large to avoid the template from breaking.
Fastening parts
It includes screws, nuts, springs, pins, washers, etc. Standard parts are generally used. There are many standard parts used in stamping die. When designing and selecting, it is necessary to ensure the need of fastening and elastic ejection, and the fasteners should not be exposed in the surface operation position, so as not to hurt hands and hinder operation.
Safety points of mold design
Try to ensure the convenience of feeding, ordering, discharging and cleaning up the garbage in the structure. For the processing of small parts, it is forbidden for the operator's fingers, wrists or other parts of the body to extend into the mold area for operation; For the processing of large parts, if the operator must work in the mold by hand, the scope of entering the mold should be reduced as much as possible, and the time for a certain part of the body to stay in the mold should be shortened as much as possible. The scope of dangerous areas of molds should be clearly defined and equipped with necessary protective measures and devices.
Various parts on the mold should have sufficient strength and rigidity to prevent damage and deformation during use, and the fastening parts should have anti-loosening measures to avoid accidental injury to the operator.
Waste materials or workpiece projectiles are not allowed during machining, which will affect the operator's attention and even hurt the operator. In addition, it is also necessary to avoid cutting people's hands by the burr of blanking parts. Operators are not allowed to have too large a range of activities during stamping operation to avoid losing their stable posture; Too many actions are not allowed in the operation. Strong noise and vibration should be avoided when stamping. Mold design should indicate the weight of the mold on the general drawing, which is convenient for installation and ensures safety. Lifting and handling measures should be taken for parts exceeding 20kg to reduce labor intensity. When assembling and disassembling die parts, it should be convenient and safe to avoid the possibility of pinching and cutting hands; The mold should be easy to disassemble and store. In short, even if there is a small problem in the mold, it will affect the safety. Only by analyzing the specific problems in each operation can we put forward the safety precautions in the mold.