The method of selecting the drill bit of the CNC drilling machine:
1. Understand the types and characteristics of drill bits
The drill bit for printed board has a straight shank twist drill, a fixed shank twist drill and an undercut drill. Straight shank twist drills are mostly used in single-head drilling machines, and simpler printed boards or single-panels are now rarely seen in large circuit board manufacturers, with drilling depths up to 10 times the diameter of the drill. In the case where the substrate stack is not high, the drill sleeve can be used to avoid the drill deviation. At present, most of the manufacturers use CNC drilling machines, and the CNC drilling machine uses a hard alloy fixed-handle drill bit, which is characterized by automatic replacement of the drill bit. High positioning accuracy, no need to use a drill sleeve. Large helix angle, fast chip removal, suitable for high speed cutting. In the entire length of the chip flute, the diameter of the drill bit is an inverted cone, and the friction with the wall of the hole during drilling is small, and the quality of the drill hole is high. Common shank diameters are 3.00mm and 3.175mm.
2, pay attention to the material of the drill
Dieboard drill bits are generally made of cemented carbide because the epoxy glass cloth has a particularly fast wear on the tool. The cemented carbide is formed by using tungsten carbide powder as a matrix and cobalt powder as a binder by pressurization and sintering. It usually contains 94% tungsten carbide and 6% cobalt. Due to its high hardness, it is very wear-resistant and has a certain strength, suitable for high-speed cutting. However, the toughness is poor and very brittle. In order to improve the performance of the cemented carbide, some chemically vapor deposited a 5-7 micron hard titanium carbide (TIC) or titanium nitride (TIN) on the carbonized substrate to make it Has a higher hardness. Some use ion implantation technology to inject titanium, nitrogen, and carbon into a certain depth of the substrate, which not only improves the hardness and strength, but also injects the components during regrind. There is also a physical method to form a diamond film on the top of the drill bit, which greatly improves the hardness and wear resistance of the drill bit. The hardness and strength of cemented carbides are not only related to the ratio of tungsten carbide to cobalt, but also to the particles of the powder. The ultrafine particle cemented carbide drill has an average grain size of tungsten carbide phase of 1 micron or less. This drill bit is not only high in hardness but also has improved compression resistance and bending strength. In order to save costs, many drills now use a welded shank structure. The original drill bit is made of cemented carbide. The rear shank is made of stainless steel. The cost is greatly reduced. However, due to the different materials, the dynamic concentricity is not as good as the overall hardness. Alloy drill bits, especially in small diameters.
3, choose a good brand to ensure product quality
At present, there are many manufacturers of drill bits, which are divided into domestic and imported. The domestic products are slightly different from the foreign products. The price is of course slightly more expensive. The market also has Taiwan and Hong Kong, and some Taiwanese production of American and European brands of drill bits, compared to Europe and the United States. The quality of the drill bit imported from Japan is stable. Although the price is slightly expensive, it is worthwhile for the craftsman. In actual use, the probability of the problem due to the quality of the drill bit is very small. If the demand for the product is higher, it is recommended to use the imported drill bit. In Europe and the United States, the bit hardness is higher and Japan is softer. The taps in Europe and the United States are not easy to be used in the bending process, but the probability of breaking is higher. The flexibility of the drill bit in Japan is not easy to break, but the hole is prone to partial hole deviation, especially small. drill. In the process of actual use, it can be selected according to requirements.
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