Generally, drills with a diameter of more than 1 mm are called small hole drills, and drills with a diameter of less than 1 mm are called micro-hole drills. The processing of micro-holes is very difficult, which is a recognized processing problem at home and abroad. According to the processing principle, the processing methods of micro-hole drilling can be divided into two categories: mechanical processing and special processing. According to statistics, according to the basic conditions such as different micro-holes to be processed, precision, surface roughness, size and shape, there are about 50 types. A method of machining microholes, such as chemical, laser, twist drill, plasma beam and abrasive.
1. Tool selection skills
(1) The geometric shape of the micro drill is mostly a stepped drill, which can effectively increase the rigidity of the tool, prevent the cutting part from swinging, and facilitate manufacturing and clamping.
(2) The precision requirements of the tool holder and chuck are high, because any radial runout error will have a great impact on the micro drill.
(3) The matrix material of the micro-drill is mostly cobalt-containing powder high-speed steel and cemented carbide, and some have a composite structure, such as adding diamond and cubic boron oxide to the front of the drill, and coating the outside of the tool with TiC and PCD coatings.
(4) The general drilling depth of micro-drills is 10 to 15 times the diameter, and the roundness error of the aperture can be controlled within 0.0025mm.
2. How to use the tool
(1) During micro-hole drilling, since the chips formed are small or even powdery, the cutting heat introduced into the chips is not much, and oil mist and compressed air can be used to assist in chip removal and cooling of the drill bit.
(2) When the micro-hole drill is drilling the workpiece, the feed rate at the beginning of the cut is far lower than the normal feed rate of the subsequent cut into the workpiece. For example, when processing titanium alloys and high-temperature alloys, the initial feed rate is 0.002mm. The normal feed rate is 0.005mm.
(3) When micro-drilling parts, it is best to cut into the workpiece at a vertical angle.
(4) The feed axis of the machine tool must have sufficient sensitivity and small enough resolution. The spindle has high precision, good rigidity, good stability, and low vibration. Dynamic balance testing must be done before processing.
5) When drilling with micro-drills, the "pecking" drilling method is generally used.
6) The micro-drill must be selected to match the material to be processed, the geometry of the drill tip should be selected according to the material to be processed, and reasonable cutting parameters should be formulated in order to give full play to the maximum processing efficiency of the micro-drill.
