The technological development of high-speed machining centers has laid the foundation for improving the milling efficiency and production quality of graphite electrodes, especially for the milling of small electrodes with complex shapes and thin-walled properties.
The graphite electrodes used in EDM mold processing require a high-speed machining center (HSM) to mill them, so the demand for HSM machines is also growing. However, for some time due to technological developments in hard steel processing, it seems likely that graphite electrodes will become an outdated technology. However, there are many factors that determine the need to continue to produce graphite electrodes, so high-speed machining has become a key manufacturing process in the mold manufacturing industry.
The processing of high-rigidity hard steel still takes longer than the time required for graphite electrode milling. When milling pockets, cavities and complex 3D profiles on hard steel, radial runout errors and tool deviations tend to cause tool breakage. When the tool breaks, it will not only stop the continuous processing of the steel, but also affect the quality of the product, resulting in scrapping of parts and waste of materials.
From the foreseeable future, graphite electrodes will occupy a very high position. Any mold manufacturer that uses the most efficient equipment to process graphite electrodes will continue to expand and expand with those manufacturers who are determined to use hard steel processing. The competitive gap.
The basis of micro tools
As far as graphite electrodes are concerned, one of the most magical words is "high speed." The spindle speed of the high-speed machining center can reach 30,000 to 60000r/min, and the feed rate can be increased to shorten the machining cycle and improve the quality of the surface and the edge. The motors required to drive such spindles are smaller and lighter, which helps to reduce cutting forces and reduce tool breakage. This is critical because many of the electrodes are complex and their production involves small, easily broken microtools.
(1) Spindle
The smaller the tool, the higher the spindle speed required. This is the only way to improve the machining quality of the part and avoid tool breakage. For high-frequency spindles with speeds up to 60,000 r/min, it is ideal to use micro-tools for milling, drilling and engraving graphite electrodes. High-speed machining technology uses extremely high speeds, small spans, and a greatly increased feed rate.
When you brush your hand from the burning candle flame, if you move slowly, the flame will have enough time to burn your hand. But if the hand quickly passes the flame, then the flame does not have enough time to burn the skin. The principle of high speed machining using micro tools is the same. Moving too fast, the heat does not have enough time to conduct into the part, causing some problems.
Machining graphite or other materials with very small micro tools is not an easy task, especially on a 40-taper spindle of a conventional CNC machine. It is difficult to find a chuck that can hold such a small tool. Because this spindle is specifically designed for clamping 3 inch (1 inch = 25.4 mm) flying knives for deep cutting of high density matrix materials. Therefore, the torque is large, and it is easy to break the small tool, and the efficiency is not high and the cost is large.
In this case, the only way the operator can choose is to reduce the speed and feed rate, so that the machine is in a slow working state, which is inevitable and the processing cycle is unacceptable. If you compare it in a more visual way, this is like the relationship between a semi-powered truck and a racing car. In reality, the two are incomparable. Because trucks are designed to require power and power to haul transport large quantities of cargo, the design of the car requires speed and maneuverability. In essence, a machine tool manufacturer who says that its ordinary CNC machine tools can use micro-tools, like the car manufacturer, installs the spoiler on the SUV and sprays the racing stripes, and then claims that it also has the same quality as the Porsche. . In fact, after installing the spoiler on the SUV and spraying the racing stripe, you can't use it as a racing car. You can't install a refurbished high-speed spindle on a normal machine. I hope it can be used. High-speed machining machine for micro tools.
(2) Geometric shape
Like ordinary CNC machines, it is impossible to rebuild a machine that can effectively use micro tools. The geometry of ordinary tools (large tools) cannot be scaled down to micro tools. The geometry of the tool used to mill the electrode plays a key role in the quality and efficiency of the machined electrode. Small format tools made by scaling down the geometry of large tools are unsatisfactory in feed speed and surface quality.
As the diameter of the tool shrinks and the speed of the spindle decreases, the tool requirements also change. Ordinary tools that use inserts are not suitable as micro tools. This is mainly due to its high speed, not the diameter of the tool.
(3) Tool wear
Increasing the speed requires proper balancing of the tool to greatly increase the cutting space and ensure that the chips are well removed. When milling graphite, the geometry of the tool helps to increase production efficiency and product quality. However, due to the inherent abrasive nature of this material, tool wear is still a concern. Special coatings are a powerful weapon to protect the tool from excessive wear. Coatings that can be considered are diamond coatings, titanium nitride coatings (TiAlN) used in steel processing, and aluminum chrome alloy coatings (AlCrN). It is generally used for the processing of high-hardness aluminum (such as cast aluminum or sand cast aluminum). In short, this coating shows a good advantage for processing other abrasive matrix materials such as fiberglass.
　　
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