I. Overview
1. Current development status and trends of mold manufacturing
As an important process equipment, molds play an important role in the industrial sectors such as consumer goods, electrical appliances, automobiles, and aircraft manufacturing. As an important process equipment, molds play an important role in the industrial sectors such as consumer goods, electrical appliances, automobiles, and aircraft manufacturing. 75% of roughing of industrial product parts, 50% of finishing and 90% of plastic parts will be completed by mold.
At present, the demand for mold market in China has reached 50 billion yuan. The annual growth rate of automobile molds, especially the cover molds, will exceed 20%; the building materials molds will also develop rapidly, and various profile molds, wall and floor molds will become new growth points for molds, and plastic doors and windows and plastic drain pipes will grow in the next few years. It will exceed 30%; the annual growth rate of home appliance molds will exceed 10%; the IT industry will grow at an average annual rate of more than 20%, and the demand for molds will account for 20% of the mold market.
In 2004, the output value of China's machine tool industry will continue to grow. China's mold manufacturing market has great potential. According to statistics, in recent years, the annual output value of China's molds reached 3 billion US dollars, imports exceeded 1 billion US dollars, and exports exceeded 100 million US dollars. Growth increased from 25% in 1995 to 50% in 2005. Foreign experts predict that Asia's share of global mold manufacturing will increase from 25% in 1995 to 50% in 2005.
China's mold industry has developed rapidly, forming two bases in East China and South China, and has gradually expanded to other provinces. (Shandong, Anhui, Sichuan) From 1996 to 2002, the output value of the mold manufacturing industry increased by an average of 14% annually, and in 2003 it increased by 25%. In 2003, China's mold production value was 45 billion yuan. The total output ranked third in the world, and the export mold was 336.8 million US dollars, an increase of 33.5% over the previous year. However, China's low-tech molds have been oversupplied, and sophisticated and complex high-end molds rely heavily on imports. Imported molds exceed $1 billion annually. Exports exceed $100 million.
Precision mold precision requirements are 2μm ~ 3μm, large molds need to meet the requirements of 8000kN clamping force injection molding machine; small molds need to meet the requirements of 1mm diameter plastic pipe. At present, the use of high-speed cutting production molds has become a major trend in mold manufacturing. In some foreign mold manufacturers, high-speed machine tools have replaced EDM machines in large areas, and high-speed cutting has greatly improved mold production efficiency.
2. Application of high speed machining in mold manufacturing
Advantages of high speed cutting:
1) The high speed of the tool and the high feed rate and high acceleration of the machine tool greatly improve the metal removal rate;
2) High speed cutting reduces cutting force;
3) The high-speed cutting heat is mostly carried away by the chips, and the workpiece generates less heat;
4) High-speed cutting reduces vibration and improves processing quality;
5) Benefits of high speed machining applied to mold processing
Fast roughing and semi-finishing to improve machining efficiency; high-speed and high-precision finishing hard cutting instead of finishing, indicating high quality, improved shape accuracy, 50% higher efficiency than EDM processing, reducing manual grinding; hard cutting final forming Surface, improve surface quality, shape accuracy, (not only low surface roughness, and high surface brightness), it is more advantageous for processing complex surfaces; avoid surface damage caused by EDM processing, improve mold life by 20%; combined with CAD/ CAM technology quickly processes electrodes, especially those with complex shapes and thin-walled electrodes.
3. Problems to be solved by high-speed machining of molds
In China, due to capital, technology and other reasons, the application of high-speed cutting production molds is still in its infancy. There are also problems with machine tools, tools, processes, and other issues that need to be solved step by step.
The disadvantage is that the processing cost is high, the use of the tool has high requirements, the tool cannot be used too much, and the complicated computer programming technology is required to support, and the operation cost of the device is high.
1) Machine tools for high speed machining of molds
2) Select cutting tool
3) Reasonable processing technology
4) Programming and tool path
5) A large number of process experiments according to production conditions
Second, the high-speed processing machine tool for processing molds
Mold finishing and hard cutting require CNC high-speed machine tools. Templates and formwork machining require precision and high-efficiency CNC machine tools. Many machine tool companies aim at mold production, and more than 60% of the machine tools in the processing center are sold to mold companies. In the next few years, the mold industry will invest 5 billion yuan in fixed assets, 80% of which will be purchased from mold processing equipment, which means that 4 billion yuan will be purchased every year.
At present, the average utilization rate of CNC machine tools in China is about 20%, and the utilization rate of high-speed machine tools is 3% to 5%. Mold companies also have considerable units to buy high-speed machine tools, from 6000r/min to 40,000r/min.
1. Technical parameters of high speed machine tools
The machining center spindle has high power and high speed to meet the rough finishing; the precision machining mold requires small diameter tools, and the machine tool generally needs to reach 15000r/min~20000r/min. Generally, a machine with a spindle speed of 10,000 rpm or less can perform roughing and semi-finishing, and the precision of finishing can not be achieved; the cutting speed of 400 m/min or more cannot be achieved. The general requirements for rapid feed are different from those of automobiles and aircraft companies; rapid feed is 30m/min to 60m/min. Choose vertical and horizontal machining centers or gantry machining centers according to the type of mold production. Has a high-speed control system: high-precision interpolation, contour look-ahead control, high acceleration, high-precision position control. Therefore, machine tools that choose high-speed machining molds must consider specific production conditions.
2. Increased application of five-axis machine tools
1) Flexible processing route and complex surface shape;
2) Large processing range, suitable for processing of various types of molds;
3) Good cutting conditions, reduce tool wear and improve tool life;
4) For the mold type, choose a bench-top or milling-head five-axis machine.
5) Multi-head machine tools and multi-electric spindle heads can better expand the processing range.
3. Purchase CAD/CAM software and high-speed machine tools
According to statistics, billions of dollars are used each year for imported machine tools, and most of the electric machine tools and high-speed machine tools need to be imported.
Third, the cutting technology of high-speed cutting mold
High-speed cutting tools need to solve the problem:
1) Tool cost
2) Tool durability
3) Cutting process parameters suitable for the tool
Solution:
Develop high-speed cutting domestically produced coated tools and tool holders. According to the difference in the performance of the tool itself, the difference in the mold material, the difference in the machine tool, etc., the actual process test is used to obtain the data, and the parameters of the tool manufacturer are referred to. Use all aspects of strength to carry out research and application, such as the combination of production, study and research, and national fund support.
Carbide-coated tools and polycrystalline reinforced ceramic tools make it possible to combine high-hardness blades and high-toughness substrates. Polycrystalline cubic boron nitride (PCBN) inserts with hardnesses ranging from 3500 HV to 4500 HV. Polycrystalline diamond (PCD) has a hardness of 6000 HV to 10000 HV. In recent years, Germany's SCS, Japan's Mitsubishi (Kobelco) and Sumitomo, Switzerland's Sandvik, the United States Kenner Feishuo and other foreign famous tool companies have successively launched their own high-speed cutting tools, not only high-speed cutting of ordinary structural steel tools, but also Superhard tools such as ceramic tools capable of directly cutting hardened steel at high speed, especially the coating tools, have played a huge role in the semi-finishing and finishing of hardened steel. The emergence of new tool materials and tooling techniques has made bottlenecks in high-speed machining no longer appear on tools.
However, the expensive price of imported tools also hinders important factors in high-speed cutting dies.
In general, the acceleration of the tool and the tool holder is more than 3g, the radial runout of the tool is less than 0.015mm, and the length of the tool cannot be greater than 4 times the tool diameter. According to SANDVIK's actual statistics, when using a titanium carbide titanium nitride (TiCN) coated solid carbide end mill (58HRC) for high-speed milling, the roughing tool line speed is about 100m / min, while finishing and super At the time of finishing, the linear velocity exceeded 280 m/min. This places high demands on the tool material (including hardness, toughness, red hardness), tool shape (including chip removal performance, surface accuracy, dynamic balance, etc.) and tool life.
According to the experience of high-speed precision machining of domestic molds, when the small-diameter ball-end milling cutter is used for mold finishing, the linear speed exceeds 400m/min to 800m/min. Choose a high-speed machine tool for hard-cutting mold finishing.
Delcam uses a 0.8 mm diameter tool to machine a narrow groove with a speed of 40,000 r/min, a depth of 0.1 mm and a feed rate of 30 m/min.
The tools are chosen according to different machining objects: carbide coated tools, CBN and diamond sintered layers. Small-diameter ball-end milling cutter for surface finishing of the mold; according to Millstar's introduction, TiAlN (aluminum titanium nitride) ultra-fine grain carbide coated tool is better than the (TiCN) carbide coated tool due to good lubrication conditions. Better wear resistance. Cutting die steel.
Select tool parameters such as negative rake angle tools. The tool requirements are higher than the normal machining requirements, and the thermal shock resistance is required. Various methods are used to increase tool life and reduce tool costs. With high-speed tool holders, the most widely used tools are HSK tool holders and hot-press clamping tools. Pay attention to the overall dynamic balance after the tool is clamped.
The current tool companies have done a lot of work in solving high-speed cutting tool technology. The tool-oriented machining service will help solve many problems. The tool manufacturer becomes the main body and refers to the technical parameters provided by the tool manufacturer.
Fourth, the process technology to improve the efficiency of high-speed cutting mold
Basic requirements for high speed cutting tools:
1) High cutting speed > 400m/min. Small diameter tool, high speed.
2) Small feed rate, small knife pattern. 0.01mm to 0.1mm per tooth.
3) The cutting load is continuously stable, reducing the mutation and slowing down.
4) Maintain single-edged cutting.
5) Maintain a uniform finishing allowance.
Purpose: Reduce tool wear and improve surface quality.
Foreign high-speed milling parts have good material quality, the same material quality standards, and stable processing performance; while the tools produced by foreign companies are also tested according to their material standards; the recommended processing parameters are generally suitable for their standards, if they are used The tool has a certain difference from the domestic material. In high-speed milling, this difference is more obvious. Some parameters can be applied directly, but some effects are worse.
Domestic enterprises generally use certain materials for parts. The materials used, especially those that can be processed at high speed, are generally limited to certain parts and materials, which also provides favorable benefits for our application of high-speed machining technology. Conditions will be applied within a small range of processed materials. It should be emphasized here that it is necessary to select and optimize a set of processing parameters suitable for the enterprise on these materials and incorporate them into the enterprise standard.
When using domestically produced tools, there are few technical parameters that recommend high-speed milling. It is necessary to test and obtain satisfactory parameters. It is best to use fixed tool manufacturers to reduce the number of tests and form processing technology standards. The utilization rate and the reduction of production costs can achieve better economic benefits.
Five, high-speed cutting machining tool path and programming
1) Plane feed path selection
2) Contour processing path selection
3) Keep the cutting load stable
4) Maintain a relatively smooth feed and feed rate
5) Keep the corner in the plane cutting
6) Reasonable selection of finishing allowance
HSC finishing requires programming of CAM:
Try to avoid the milling movement of the corner; try to avoid the infeed and retraction movement outside the workpiece, and directly enter the next depth from the contour. Or use a spiral or oblique feed cut; constant feed per blade, improve quality, extend tool life; contour processing is maintained on a horizontal surface.
High-speed cutting CAM software: Delcam started research on high-speed cutting programming technology several years ago and developed high-speed cutting automatic programming software module. Recently, MasterCAM has also developed high-speed cutting automatic programming software module; domestic North Nauer is also developing High-speed cutting automatic programming software module.
High-speed cutting die programming software features:
1) Determine cutting parameters according to high-speed cutting characteristics
2) Special tool feed motion trajectory is required
3) Protect the tool and reduce wear.
Six, the characteristics of high-speed machine tool CNC system
1) High-speed data processing
2) Corner prediction processing
3) NURBS non-rational spline interpolation curve processing
Seven, the safety of high-speed cutting mold
Tool wear and damage monitoring; the strength of the blade connection; unlike ordinary machine tool processing, safety protection and strict inspection of the machine and tool before starting is very important.
8. At present, China has problems in adopting high-speed machining mold technology.
1. machine tool
1) There is still a gap in the overall performance of domestic high-speed machine tools, and the performance of functional components cannot meet the requirements. Including the power and speed of the electric spindle, the price of imported machine tools is high;
2) The research on the dynamic characteristics of the machine tool at high speed is not enough, thus affecting the performance of the whole machine;
3) Five-axis machine tools are not mature enough, and the price of imported machine tools is too high;
4) The supporting technologies and equipment are not yet complete.
2. Tool
Domestically produced tools are not yet able to adapt to high-speed cutting applications, especially high-speed hard-cutting finishing. The price of imported tools is high. Tool technology is an important factor affecting high-speed machining molds. The supporting technology is not enough, including the tool holder and the set of online dynamic balance.
3. High-speed mold processing technology and experiment
1) Due to the short history of high-speed machining molds, lack of application experience accumulation;
2) There are few researches on high-speed cutting technology, and the investment is not enough, and it is difficult to establish the project;
3) The lack of high-speed cutting database or manual is still blank;
4) Mold manufacturers have insufficient understanding of high-speed cutting and lack analysis and comparison of long-term benefits;
5) Lack of high-speed cutting automatic programming software;
6) Lack of five-axis linkage high-speed cutting automatic programming CAM software.
IX. Conclusion
The mold market has a strong demand for high-speed machining, but the technology can't keep up. Late start, the foundation is poor, the overall technical level is not high, and the development is slow. It is necessary to coordinate development in all aspects, combine production, study and research, increase investment, and comprehensively utilize various forces to promote the application of high-speed cutting in mold manufacturing. We hope that through all efforts, driven by market demand, through technological advancement, like automobiles, machine tools, and home appliances, in the near future, China will not only become a big mold producing country, but also become a mold producing country.
Ningbo Wason Lighting Technology Co.,Ltd , https://www.nbwasonled.com