The machine tool has high precision and good stability, and special attention should be paid to greatly reducing the comprehensive errors of the spindle, fixture, and tool. The horizontal micro drilling machine developed by Louis Levin&Son is a machine tool suitable for machining small diameter holes. This is a small lathe with a base, equipped with special drilling accessories, capable of high-precision machining of small diameter holes. The device has horizontally and vertically adjustable guide rails, which facilitate coaxial connection with the host. The straightening of the main shaft and drill shaft uses a special instrument that can adjust both shafts at low speeds. Compared with the general machining method that relies solely on the rotation of the drill bit, the method of simultaneously rotating the spindle and drill shaft can achieve higher synchronization. Axial degree.
There are roughly two types of handle shapes for micro drills, one is a small straight handle and the other is a thick straight handle. The tool material is still mainly cobalt high-speed steel. In recent years, coated drill bits and hard alloy drill bits have emerged in large numbers, especially fine-grained hard alloys, whose wear resistance and toughness have been greatly improved. Ultra fine WC with a particle size of less than or equal to 5 μ m has been formed. Grain hard alloys, such as AFI fine-grained hard alloy developed by Jiayou Electric Co., Ltd., have a bending strength of 500kg/mm2 and a hardness of 92.5HRA. Used for manufacturing micro drills with ideal cutting performance.
Before drilling, the spare drill bit should be carefully inspected using a microscope. If a drill bit with low grinding accuracy is used, it will not only reduce the accuracy of drilling, but also cause the drill bit to break. Regarding the dimensional accuracy of drill bits, when processing materials such as stainless steel or iron nickel cobalt alloys, it is required that the height error of the cutting edge be around 0.001-0.02mm to prevent cutting edge wear and extend tool life.
Artificial objects - The processed parts should have high coaxiality, perpendicularity, and good surface roughness, especially at the entrance and exit of the drill bit. If the accuracy is poor, the cutting edge will increase wear and even cause the drill bit to break; After grinding or polishing, the accuracy of hole processing can be improved. In addition, the point angle of the center drill must be consistent with the point angle of the drill bit used.
Processing conditions - The core thickness of the micro drill bit is relatively large, and the cutting edge is small. If machining is carried out according to the general circumferential speed calculation, not only will the dynamic balance of the drill bit be lost, reducing the accuracy of the machining hole, but the drill bit is also prone to breakage. Therefore, when processing small holes, factors such as hole diameter and depth must be considered, and appropriate processing conditions must be determined for different workpiece materials. If the tool used is a cobalt high-speed steel drill bit, the speed should be 1000-1500m/min; For hard alloy drill bits, due to their high longitudinal elastic modulus, the centrifugal force during high-speed rotation has less impact on the vibration of the blade tip, so high-speed cutting can be used. The smaller the cross-sectional area and diameter of a micro drill, the lower the stiffness of the drill bit. Therefore, the selected clamping system should maintain high clamping stiffness and vibration accuracy during high-speed rotation, and the selected machining center must also have high-precision positioning characteristics. In general, when the aspect ratio of a small diameter hole is greater than 3 times, the cutting depth should be determined to be 20% to 30% of the drilling diameter.
Special attention should be paid to the lubrication performance of cutting oil when machining small diameter holes. Cutting fluid with good lubricity is prone to adhere to the drilling groove and is more likely to reach the machining site through the drilling groove. This can reduce friction and minimize tool wear. Chip removal. If the spray device can be used, it will be more conducive to chip removal and improve processing efficiency.
