Abstract: The in mold processing high-speed processing required for a number of key technologies, and high speed machining in plastic mold making significance, and the processing method with the conventional EDM contrast, describes the advantages and limitations of high-speed machining . Illustrated in both high-speed cutting process is the development direction of modern mold one.Recent, high-speed machining (High Speed Cuting) the rapid development of technology for improving the level of mold manufacturing and product quality to provide a new direction.
1 A high-speed machining parameters
In the use of high speed machining process, the typical high-speed cutting parameters cutting speed (referring to the cutting tool speed cutting place), feed rate, spindle speed, tool diameter, cutting depth, cutting volume, etc. (Figure 1).
In general, the cutting speed based mold material is processed and used cutting tool material varies, criteria can be identified by the experience of different materials, steel cutting tool when the cutting speed in the range. According to spindle speed and tool diameter and cutting speed relation N = V × 1000 / ( p× D) (r / min) required to calculate spindle speed: the tool feed rate and spindle speed related, their expression for the relationship between F (feed rate) = single-blade cutter blade feed rate × number × spindle speed (mm / min). Typically, a single blade feed rate is 0.1 ~ 0.25mm: cutting the amount per minute = F × A d × Rd (mm 3/ min).
2 high-speed machining compared to conventional processing
High-speed cutting CNC machining and conventional machining method main difference is the feed rate, processing speed and cutting depth value of the three different parameters. High-speed machining with high feed rate and small depth of cut (Figure 2),
while NC was a low feed rate and the large depth of cut (Figure 3).
In addition, high-speed machining of the spindle, cutting tools, computer numerical control system, servo system and CNC programming requirements and routine processing in different ways. The past is the spark die cavity machining (EDM) dominating the world. But in recent years, apart from narrow, deep grooves and a very fine texture, other than non-use of EDM, the general shape of the cavity and less complex three-dimensional profile has high stiffness in the milling and machining center, milling Coating Tool for high speed machining, EDM higher than its processing efficiency. In fact, more suitable for high speed milling process is not very complicated shape of a shallow cavity mold, and for deep pockets and a clear angle of the cavity within the mold, the surface of the mold pattern or patterns up there are some difficulties. In fact high-speed milling and EDM manufacturing in the cavity mold is complementary, in the cavity mold making process, what kind of processing method used depends on the geometry of the cavity, the hardness and the required parameters .
- High-speed cutting and precision manufacturing practice shows that, compared with the traditional cutting, machining with high-speed production and cut easily chip, when chip thickness is reduced, the chip temperature increases, the chip is more Suixiao. When the stress and the chip is reduced, the tool load becomes smaller, the same time, reduce the heat generated by friction, heat was a lot of cutting away the high-speed chip away, so mold and tool thermal deformation is small, the mold surface does not degenerate and micro-cracks, thus greatly improving the processing quality of the workpiece, and effectively improve the precision. Compared with conventional processing, high-speed machining with the machining cycle time is short, the required number of small tools, cutting stress is small, large chip production, processing and precision. Generally speaking, high-speed machining precision can reach 10? M below surface roughness Ra1? M the following. Can effectively reduce the workload of call processing and polishing.
- Tool life in high-performance computer numerical control systems, high-speed processing technology to ensure the tools work at different speeds, the load constant. Coupled with the cutting tool edge amount of each small, help to extend tool life.
- Processing high-speed machining of hardened die in high speed, large feed means to complete the finishing of hardened steel and can achieve high quality mold surface (Ra0.4? M), 4 higher efficiency than conventional methods ~ 6 times, the processing of the material hardness up to 62HRC. And because less high-speed machining to improve the processing and follow-up surface smoothness, so eliminating the need for machining and EDM in the past for grinding and polishing processes.
3 high-speed machining tool
High-speed cutting tool materials, the mold must have less chemical affinity, has excellent mechanical properties and thermal stability, that is a good impact, wear and thermal fatigue properties. Currently, ceramics, cubic boron nitride (CBN), coated cemented carbide cutting tools, etc. can be used as high-speed cutting tool materials, tool steel parts. Obtained using methods such as polycrystalline Polycrystalline Cubic Boron Nitride (PCBN) blade hardness up to 3500 ~ 4500HV, has become the first choice for high-speed cutting of hardened steel tool materials. Tool coating technology is to improve the ability of high-speed cutting one of the key technologies.
4 high-speed demands on machine
- Spindle required balancing performance, rigidity, high precision turning, good thermal stability, can deliver enough torque and power, can withstand the high centrifugal force, with a temperature measurement devices and cooling devices. Such as Makino’s A55 high-speed milling spindle with spindle and through the realization of high-speed internal cooling of high power output, and to always maintain spindle temperature below the box.
- Machine tools machine tools must have a sufficiently high rigidity and optimum damping to prevent the cutting tool vibration on surface quality flutter adverse effects: exercise flexibility to adapt to the fast moving feed shaft: to have high dynamic performance, in addition to high spindle speed and feed rate, but also a high increase / decrease speed.
- Tool clamping technology should be used with the spindle nose cone has contacted the Department of dual positioning holder. Such as the German HSK hollow shank. Cutter knife handle and the clamping device to make a good connection with the spindle must ensure does not occur in high speed tool traverse.
5 high-speed machining CAM software on demand
Different from the traditional processing of high-speed machining with the special processing requirements, it is used in high speed machining CAM programming system must have a very high programming speed of calculation, with the full automatic processing and automatic cut-off knife handle interference checking function, with Jin to the Rate of processing, when processing path monitoring, optimization of tool path editing features, a strong interpolation functions, “processing residual analysis” function.
China mold company use high qulity CNC machine and state the art of equipment to make high precision injection molds
High-speed machining program should note that due to processing or clear the root residual processing is an important means to improve processing efficiency, the general process should be repeated or series of tools from big to small sub-sub-process, until it reaches the die size requirements, not use a knife finishing at one time. Knives cut into the workpiece should be slow, the transition between the lines under the knife or some of the best use of oblique arc under the knife or knife, not perpendicular to the knife directly to the mold material: the same time, slowly cutting into the layers from one layer to another cut than cut and then suddenly cut out another layer of better access to: Besides, as much as possible to maintain stable cutting parameters, including cutting to keep thickness, feed and cutting speed of consistency: In addition, when faced depth of cut may be increased somewhere should reduce the feed rate, because changes in the load will cause the tool deflection, which reduces machining accuracy, surface quality and shorten tool life. The success of high-speed machining is crucial.It is noteworthy that not all CAM software can be used for high speed machining CNC programming. Abroad have been some very mature for high-speed processing of programming packages, such as the UK’s PowerMill DelCAM software modules, and some machine tool manufacturers developed for high speed machining CAM software, such as Makino will it FFAUT software FF processing module integrated into the United States UGS CAM software company. Domestic-related software has Beihang Haier Co., Ltd. China is the software development CAXA-ME software.
6 Application of high-speed cutting
In the high-speed machining, different workpiece materials and tool diameter required spindle speed and feed rate are different. Table 1 lists out the different diameter ball end mill TiAlN coating hardness of different rough hard steel used in the spindle speed and feed rate.
Machine tool spindle speed N and the tool material and cutting speed and tool size. Table 2 lists the use of 20mm diameter end mills of different materials in different cutting speed used when the spindle speed.
To injection mold cavity mode handsets (Figure 4), for example, mold materials HI3, hardness is 50HRC, now with the Japanese Makino HYPER5 machine for processing, the maximum spindle speed 32000r/min, the maximum feed rate 60000mm/min . When roughing and semi-finishing with? 6mm ball end mill, finishing with a time? 4mm ball end mills, the total processing time 41min. Used in the processing stage of processing parameters and processing time used as shown in Table 3. This example shows the main high-speed processing can shorten processing time, improve precision and reduce the workload or eliminating the need for polishing polishing process.