Precautions for drilling and machining of the hott

2022-10-21
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Precautions for small diameter drilling processing

machine tool

in order to ensure that micro hole processing has good dimensional accuracy, roundness and flatness, an important prerequisite is to use machine tools with high feed accuracy and good stability; In particular, it should be noted that the comprehensive errors of spindle, fixture and tool should be vigorously suppressed

one of the machine tools suitable for processing small diameter holes is the horizontal micro drilling machine developed by Louis Levin & son company. This is a small lathe with a base, equipped with special drilling accessories, which can process high-precision small diameter holes. The device is equipped with a guide rail that can adjust the data display in horizontal and vertical directions, which is convenient to realize coaxial with the main. The alignment of the main shaft and the drill shaft uses a special instrument, which allows the two shafts to be adjusted during low-speed rotation. Compared with the general processing method of rotating only by the drill, using the method of rotating the main shaft and the drill shaft at the same time can obtain higher coaxiality

there are roughly two kinds of handle shapes of micro drill, one is a small straight handle, and the other is a thick straight handle. The cutting tool material is still cobalt high speed steel. In recent years, coated bits and cemented carbide bits have appeared in large numbers, especially fine-grained cemented carbide, whose wear resistance and toughness have been greatly improved. At present, a particle size of 0.5 has been developed μ WC ultra-fine Grain Cemented Carbide below m, such as AFI Fine Grain Cemented Carbide developed by Jiayou electric company, has a bending strength of 500kg/mm2 and a hardness of 92.5hra. Its cutting performance is very ideal for making micro drill bits

before drilling, the standby drill bit should be carefully checked with a microscope. If a drill bit with low grinding accuracy is used, it will not only reduce the accuracy of the processing hole, but also cause the drill bit to break in serious cases

in terms of the dimensional accuracy of the drill bit, if it is processing stainless steel or iron nickel cobalt alloy and other materials, the height error of the cutting edge is required to be about 0.001 ~ 0.02mm, which can prevent the wear of the edge band and prolong the service life of the tool

workpiece

the parts to be machined are required to have high coaxiality, verticality and good surface roughness, especially at the cut in and exit of the drill bit. If the precision electronic universal testing machine mainly adopts servo electromechanical as the power source, the poor degree will increase the wear of the cutting edge and even cause the drill bit to break; The cut in surface should preferably pass through the soft artificial eye, which is suitable for grinding or polishing patients implanted with various artificial eye platforms and hydroxyapatite artificial eye platforms, so as to improve the machining accuracy of the hole. In addition, the drill point angle of the center drill must be consistent with that of the drill bit used

processing conditions

the micro drill has a large core thickness and a relatively small cutting edge. If it is processed according to the general circumferential speed, it will not only lose the dynamic balance of the drill, reduce the accuracy of the hole, but also easily cause the drill to break. Therefore, when machining micro holes, we must consider the factors such as aperture and hole depth, and determine the appropriate processing conditions for different workpiece materials. For example, the tool used is a cobalt high-speed steel drill, and its rotation speed is appropriate to be 1000 ~ 1500m/min. For example, a cemented carbide drill, due to its high longitudinal elastic modulus, the centrifugal force during high-speed rotation has less vibration on the tip, so it can be processed by high-speed cutting

the smaller the cross-sectional area of the micro drill is, the smaller the diameter is, the lower the rigidity of the drill is. Therefore, it is required that the selected clamping system should maintain high clamping rigidity and swing accuracy when rotating at high speed. 7. Select the functional accessories of the experimental instruments and the experimental instruments related to the experimental instruments; The machining center must also have high-precision positioning characteristics. In general, when the l/d ratio of small diameter hole processing is more than 3 times, the cutting depth should be determined as 20% - 30% of the drill diameter

cutting fluid

for the cutting fluid used for machining small diameter holes, special attention should be paid to its lubrication performance. The cutting fluid with good lubrication is easy to adhere to the drilling groove, and it is easier to reach the machining part through the drilling groove, which can reduce friction, reduce tool wear, and facilitate chip removal. If the spray device can be used, it will be more beneficial to chip removal and improve processing efficiency. (end)

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