Precision manufacturing of molds

As far as the precision of the mold is concerned, the high-speed terminal mold should be regarded as the most precise here. The stamping materials are generally 0.08~0.2 mm stainless steel and aluminum. The blanking gap is as small as 0.008 mm. The minimum width of the punching hole is 0.25 mm. The punch looks like a weak wind. How to punch such a small hole? How can such a small blanking gap ensure the precision of mold manufacturing?

Turning over the picture, understanding the mold structure, design and manufacturing tolerances and its special manufacturing process, we can easily feel the pulse of this set of molds.

All punching parts are made of block and punch from top to bottom, and the knife edge is made of tungsten steel. The block-in holes and fixed pin holes of the upper template, stripper plate and lower template are ground by JG, sliding fit clearance c+0.005~0.010 mm, non-slip fit c+0.003 mm, machining accuracy +/-0.002 mm; main structure guide In order to match the ball sleeve with the precision guide post, the small hole punching structure adopts a local structure separated from the upper mold, and is locked on the lower template with a contour sleeve to compensate for the accuracy error of the stamping equipment; the guide part of the local structure is a precision graphite self-lubricating inner guide The inner guide bushing of the column, stripper plate and lower template is filled with glue to compensate for the processing errors of the guide components and improve the guiding accuracy to ensure the position accuracy of the template during the stamping process; the smallest possible stamping stroke can make the punching The length should be as short as possible, and proper punch reinforcement can improve the strength of the punch. This can fully reflect the design concept of mold designers tending to high precision, and ensure the high quality and high requirements of molds as much as possible.

Modern processing equipment and high-precision processing technology make these design concepts more effective. After the heat treatment of the template, it undergoes cryogenic aging treatment to eliminate internal stress, prevent template deformation, and ensure the processing stability of the template. Plane grinding ensures the flatness of the template, the parallelism is 0.005 mm, the precision of EDM is controlled within ± 0.002 mm, and the wire is processed slowly. The accuracy is controlled within ± 0.0015mm.

For high-precision machining, the temperature problem must not be ignored, because temperature difference is the enemy of accuracy. Because of the thermal expansion and contraction of the material, the linear expansion of steel is 12 μm per meter of length when the temperature changes by 1°C. This is the fact that every machine in every corner of the world is unchanged. If we don't care about the important issue of temperature, how do we discuss accuracy? The control of workshop temperature is very important because the accuracy of the processed workpiece has a lot to do with it. The temperature of precision machining is generally controlled at a constant 20°C, and the temperature fluctuation is required to be less than 0.5°C/hour, and the air conditioning system maintains a constant temperature difference of ± 1°C throughout the day. I admire the precision of the mold assembly engineers. First understand the mold drawing carefully, be familiar with the product information, analyze the mold structure, understand the design intent; check the parts, chamfering, polishing, and engraving to make the mark meticulously; the template deburring, oiling and rust prevention are step by step, and the outer guide pillar and guide bushing Use a special positioning tool to ensure its verticality; the actual thickness of the template is measured, and the four-point measurement difference is within 0.005 mm as qualified; the punch and the block should be matched with each other, and the matching should be smooth, the grinding degree should be smooth, and the judgment standard should be clear; The self-inspection of the product during mold adjustment should use a projector, and the accuracy is 0.003mm when the mold is inserted into the block; without the concept of precision, it is impossible to develop high-quality, and it is impossible to install high-precision molds.

Mold development is mainly divided into three stages: mold design; mold processing; mold assembly, mold trial and repair. The three are indispensable. A set of high-precision molds must have precise design, precise processing, and precise assembly.

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