At present, CNC high-gloss machining processes (milling, turning) are not well known to technicians in most industrial industries. Practical work shows that they are only truly mastered by a few producers. The main reason is that the demand in the past is not very strong, of course, this is also closely related to cognition. Today we were fortunate enough to find out. Let’s take a look at the shell diagram of CNC milling high-gloss processing.
In recent years, with the development of high-performance, high-precision CNC machine tools and the emergence of metal cutting tools with excellent performance, CNC high-gloss machining has made great breakthroughs, and it has become possible to replace grinding with milling (turning), which has become a machining industry. successive goals. The principle of CNC high-gloss machining is to use special special tools on precision CNC machining equipment, and cooperate with scientific and reasonable cutting parameters and processes to achieve sparkling surface effects.
machine tool
The use of precision CNC machine tools is a prerequisite for high-gloss machining. Machine tools must have good rigidity and precision, such as precision CNC engraving machines (general speed: 20,000 rpm).
cutter
The high-gloss effect is achieved thanks to the use of diamond tools. Diamond tools are standard in the CNC high-gloss machining industry.
The cutting edge of a good diamond tool cannot see any notch burrs under a high-power microscope. The cutting edge can withstand long-term cutting without change. The friction coefficient between diamond and non-ferrous metal is very small, the chips are not easy to stick to the cutting edge, and no built-up edge occurs. Therefore, the cutting edge is always kept directly cutting the workpiece during the processing, and the brightness can be guaranteed.
The high-gloss milling tool has a wider cutting edge, and adopts a small rake angle or a negative rake angle and a near-zero edge inclination angle. When the high-gloss milling is performed, the tool performs high-speed cutting on the one hand, and on the other hand, due to the small rake angle of the tool, Therefore, the cutting edge of the tool forms a scraping and squeezing effect on the machined surface, so that the workpiece surface obtains a high smoothness and produces a hardened layer, which improves the surface hardness and wear resistance of the workpiece.
In addition to the geometry of the workpiece, the geometry of the tool mainly depends on the physical properties of the workpiece material. When machining plastic materials such as copper, aluminum and nickel, the rake angle of the tool is 0º, and the relief angle is generally between 5º and 10º. The radius of the tool nose arc is usually 0.5 to 5 mm. If the rigidity of the machine tool is high, a larger radius can be used to reduce the surface roughness of the workpiece. If a smaller tool nose radius is used, the feed rate must be reduced accordingly in order not to deteriorate the surface roughness. . When processing sparse materials such as silicon, germanium, CaF2 and ZnS, the rake angle of the tool is generally selected between -15º and -45º. The optimum rake angle depends not only on the material itself, but also on the stiffness of the machine tool and the clamping system, which is best determined by production trials.
Disc milling cutters are used for high-gloss milling. The diameter of the cutter head should be as large as possible according to the size of the plane to be milled, with better rigidity and good insert positioning accuracy. The size of the cutter head will change the texture and effect of the plane to be milled. The number of blades can be single or multiple. However, it is difficult and time-consuming to adjust the consistency of each blade with multiple blades. Using a single blade milling effect is better.
Diamond tools look expensive and require a large investment, but natural diamonds are extremely hard and wear-resistant. According to statistics, the life of diamond turning tools is 25 times that of high-speed steel turning tools, and each diamond tool can be reground 6 to 15 times. Therefore, the tool consumption per part is very small, and stable size and high brightness can be obtained.
workpiece
Materials suitable for high-gloss processing include aluminum, copper, and stainless steel. When processing aluminum, its brightness is the brightest, and the wear on the tool is the least; when processing copper, its brightness is relatively bright, and the wear on the tool is second. When machining stainless steel, its brightness is gray and matte, and the wear of the tool is also large.
craft
The cutting speed of mirror milling is usually around 30m/s. In order to process a perfect workpiece, the spindle must be dynamically balanced after tool change to minimize the ripples on the surface of the workpiece caused by the dynamic imbalance.
The thermal conductivity of diamond tools is good, and the cutting amount is not large, so there is no need to add coolant. On the contrary, adding coolant not only increases the trouble of cleaning after machining, but also the coolant mixed with iron filings often becomes the bane of blade chipping.
The defect of the highlight is that the outline of the product is required to be high and stable, otherwise the highlight will be uneven (large and small edges, etc.).
To obtain safety technical data including all relevant information (such as tools, materials and processing technology, etc.) and make it an optimal combination, it often requires an experience and a running-in process.
application
In Guangdong, the trend of high-gloss processing of hardware is obvious. Aluminum high-gloss is the most widely used in digital product casings, and it can be oxidized a second time after high-gloss to enhance the wear resistance of the high-gloss area. Stainless steel high-gloss is used in some high-end digital cameras. and mobile phones have also begun to use.
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