At present, the definition of micro-holes at home and abroad is as follows: holes with diameter of 0.1-1.0ram are called small holes, and holes with diameter of less than 01.mm are called micropores. With the rapid development of emerging microelectronics industry, micro-mechanics and micro-electro-mechanical system industry, more and more components with micro-holes as key structures are used, the size of the hole is becoming smaller and smaller, and the accuracy requirements are becoming higher and higher. For example, the cooling holes of aero-engine turbine blades, and the gem bearing holes, Electron microscope grating, PCB microporous plate, polymer composite material hole, diamond wire drawing die, precision chemical fiber spinneret, RP technology rapid prototyping equipment nozzle hole, optical fiber connector, fuel nozzle, printer inkjet hole, red blood cell filter, microjet, micropump and other high-end products’ micro-structure, etc. The workpiece materials of these products are mostly metal alloy materials, and the depth to width ratio of micro-hole is large, The feature size is between 50 and 100 pm.
For the processing of micro-holes, due to the development of workpiece materials in the direction of high strength and high hardness, many parts need to use refractory materials such as heat-resistant steel, stainless steel, mold steel, hard alloy, ceramics, diamond and other polymer composite materials. In addition, the shape of micro-holes is no longer a single circle, but tends to various complex shapes that can achieve specific functions, such as the trilobal arc shape in the spinneret, The trilobal, v-shaped, hexagonal and other special-shaped holes put forward higher and newer requirements for the processing technology of micro-holes. Specifically, the miniaturization industry requires that the processing technology should meet the characteristics of mass production, high efficiency, high precision, high density, short cycle, low cost, pollution-free, and net forming. In the traditional macro-manufacturing field, the plastic forming process (blanking, bending, drawing, deep drawing, superplastic extrusion, undulation, embossing, etc.) exactly has these industrial advantages. Micro-punching is the key technology in the micro-plastic forming technology. This paper studies the micro-punching technology from the aspect of the development of processing equipment for the processing of micro-holes.
The diameter of micro-hole drilling bit in manufacturing industry is generally φ= Above 0.27, the tool material is tungsten steel or white steel imported from Japan. In the past, due to the high cost of etching processing and poor laser precision, it has been basically eliminated with the improvement of the metal hole punching process. Stable realization of batch production. With the increase of mobile phone functions, the distribution of printed circuit board lines is becoming increasingly dense, and the micropore diameter of the copper foil on the circuit board is also smaller, and the processing difficulty is further increased. The development trend of the application of the filter screen used for the fuel nozzle of the internal combustion engine is also roughly the same, so the requirements for the small hole punching process are becoming higher and higher.
There are many reasons why the punching needle is easy to break, which may be the reason of the punching needle itself or the design defect of the mold. It is also possible that there are a series of problems such as blanking materials. In fact, no matter what the problem is, we should find a solution to the problem. The specific methods are different from each factory. The foreign precision mold is generally loose, and the stripper plate is tight. The stripper plate and the female mold must be inserted with guide post guide sleeve. The wire cutting uses slow wire or oil cutting. The male plywood is 0.02-0.06mm on both sides, and the stripper plate is 0.01mm or even tight. There are some differences in domestic practices, and the unilateral tolerance of common plywood is ± 5 μ， 0.01mm on one side of the stripper plate,; When using slow walking wire, you can consider to increase it appropriately. The punching needle is offset. The punching needle should be made as short as possible, and the gap should be properly placed. The guide pillar should be larger, and the gap with the guide sleeve of the female die should not exceed 0.005mm on one side. The gap of the stripper plate is smaller than the lower formwork, generally 0.005mm on both sides, 0.02mm on both sides of the male splint. It doesn’t matter if the loose point, the punch should not be knocked in by force, but should be pushed in by hand.
