In the industrialized countries such as the United States, Germany and Japan, the mold industry is undergoing a large-scale technological revolution in recent years. This is to gradually replace electrical processing equipment with high-speed cutting machine tools to perform efficient and precise processing of mold cavities. These machine tools mainly include various high-speed CNC milling machines, machining centers, etc.
High-speed machining features
1. Large load-bearing and high rigidity
This is due to the fact that the mold is developing in the direction of large-scale, the processing equipment must have a large enough table size and working stroke to adapt to it. Nowadays, molds of several tons to dozens of tons are very common, and the work surface of the machine tool is required to bear heavy weight. The strength and hardness of the mold material are very high, and the mold cavity is often processed with a small-diameter end mill with a large elongation, so chattering is prone to occur during the processing process. In order to ensure the machining accuracy and surface quality of parts, high-speed machine tools used for mold manufacturing must have high dynamic and static stiffness to improve the positioning accuracy, tracking accuracy and vibration resistance of the machine tool.
2. High speed and high power
High-speed machining is the development direction, and high-speed milling has shown great advantages in mold processing. In order to adapt to the processing of the mold cavity surface, the radius of the tool should be smaller than the minimum circumferential radius of the cavity surface to avoid “interference” between the tool and the workpiece during the processing. Due to the small diameter of the tool, the spindle speed is required to be very high. The spindle speed of foreign high-speed machining machine tools has reached 40,000 to 100,000 r/min, and the rapid feed rate can reach 30,000 to 60,000 min. The roughing and finishing of cavity and other parts of mold parts are often completed in one clamping of the workpiece, so the spindle power must be large. The spindle power of medium-sized mold milling machines and machining centers is often 10-40kW, and some are even higher.
3. Multi-axis linkage and good deep cavity comprehensive cutting ability
Mold cavities are mostly composed of complicated space 6 curved surfaces and grooves, and many molds have deep cavities. In order to achieve high-precision, high-speed and high-stability machining of 3D surfaces, the machine tool needs multi-axis linkage and has a good comprehensive cutting ability for deep holes. A five-axis linkage machining center can be used. In addition to the linear motion of the three coordinates, there are also two feed motions of the rotating coordinates. The milling head or worktable can continuously rotate and feed in multi-axis linkage, which is suitable for processing mold parts with complex cavity surfaces.
The advantages of high-speed cutting technology in mold manufacturing
1. High processing efficiency
Using high-speed cutting, not only the machine speed is high, the feed is fast, but the rough and finishing machining can be completed at one time, which greatly improves the production efficiency. Combined with the numerical control technology, the mold manufacturing cycle can be shortened by about 40%.
2. High degree of automation
High-speed cutting molds do not require electrodes, nor subsequent grinding and polishing. It is also easy to automate the processing process, which improves the development speed of molds.
3. High surface quality
Hardened steel can be processed by high-speed cutting technology, and high surface quality can be obtained. The surface roughness is lower than Ra0.6μm, and the processing effect of milling instead of grinding is obtained. It not only saves a lot of time, but also improves the surface quality of the processing. .
4. Broad prospects for compound processing
Although the machining center has been able to combine many machining processes on one machine tool, it still cannot fully adapt to mold processing. It combines machining with electrical, chemical, ultrasonic and other different principles of processing methods, and has more than two process characteristics. The composite processing will have broad prospects in the future mold manufacturing.
At present, the mold processing and manufacturing process mainly focuses on ordinary machining and EDM. Ordinary machine tool processing mold cavity is generally rough machining, semi-finishing and finishing before heat treatment, and then grinding, polishing and polishing, which is time-consuming and laborious. EDM is cutting after annealing, then heat treatment, EDM, and finally grinding and polishing. With the acceleration of the upgrading of consumer products, higher and higher requirements are put forward for the production efficiency and manufacturing quality of molds, and the shortcomings of low production efficiency and unstable quality of EDM molds are gradually exposed. To shorten the manufacturing cycle and reduce costs, advanced cutting technology must be widely adopted. The emergence of high-speed cutting technology, which represents advanced manufacturing technology, has met the requirements and characteristics of modern mold processing.