When I went to a mobile phone stamping mold factory to learn precision mold technology, what impressed me most was not its superb mold design level and precise processing technology, but its precise mold development concept.
On the second day after we arrived, the team leader told us that he would instill precise mold concepts into us. What is the precision mold concept? I'm a little dissatisfied. What we make here are all thin-material products. I've made some before. How come I don't have the concept of precision?
As my studies gradually deepened, I began to realize my superficiality!
The first stop of our study trip was high-speed module assembly. In terms of mold precision, high-speed terminal molds should be considered the most precise here. Stamping materials are generally 0.08~0.2 mm stainless steel and aluminum. The punching gap is as small as only 0.008 mm. The minimum width of the punched hole is 0.25 mm. The punch looks weak. How to punch such a small hole? How to ensure the manufacturing accuracy of the mold with such a small blanking gap? It's hard to imagine if you haven't seen it with your own eyes.
Turning over the drawings to understand the mold structure, design and manufacturing tolerances and its special manufacturing process, it is not difficult for us to feel the pulse of this set of molds.
All punching parts are filled with blocks and punches from top to bottom, and the cutting edge is made of tungsten steel. The block entry holes and fixed pin holes of the upper template, stripper plate, and lower template are JG ground. The sliding fit clearance is c+0.005~0.010 mm, the non-sliding fit is c+0.003 mm, and the processing accuracy is +/-0.002 mm; the main structure guide parts The ball sleeve is matched with a precision guide post, and the punching hole structure adopts a local structure separated from the upper mold, and is locked on the lower mold plate with a contour sleeve to compensate for the accuracy error of the stamping equipment; the guide part of the partial structure is a precision graphite self-lubricating inner guide The inner guide sleeves of the column, stripper plate and lower template are filled with glue to compensate for the processing error of the guide components and improve the guide accuracy to ensure the position accuracy of the template during the stamping process; the smallest possible stamping stroke can make the punching head The length should be kept as short as possible. Appropriate punch reinforcement can improve the strength of the punch. This can fully reflect the high-precision design concept of mold designers and ensure the high quality and high requirements of the mold as much as possible.
Modern processing equipment and high-precision processing technology allow these design concepts to be fully utilized. After heat treatment, the template is subjected to cryogenic aging treatment to eliminate internal stress, prevent template deformation, and ensure the processing stability of the template. Surface grinding ensures template flatness, parallelism 0.005 mm, EDM processing accuracy is controlled at ±0.002mm, and slow wire processing The accuracy is controlled at ±0.0015mm.
When performing high-precision machining, temperature issues must not be ignored, because temperature differences are the enemy of precision. Because of the thermal expansion and contraction of the material, the linear expansion of steel will change by 12 μm per meter of length when the temperature changes by 1°C. This is true for every machine in every corner of the world. If we don't care about the important issue of temperature, how can 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. The air conditioning system maintains a constant temperature difference of ±1°C throughout the day.
I am even more impressed by the precision of the mold assembly engineers. First, carefully understand the mold drawings, familiarize yourself with the product information, analyze the mold structure, and understand the design intent; check the parts, chamfer, polish, and engrave the marks meticulously; deburr the template, apply oil and rust step by step, and install the outer guide posts and guide bushes. Use special positioning tools to ensure its verticality; the measured thickness of the template is qualified if the difference between the four-point measurements is within 0.005 mm; the punch and block must be matched separately, the fit must be smooth, the grinding must be accurate, and the judgment standards must be clear; test mold, When adjusting the mold, a projector is required for self-inspection of the product, and when the mold is repaired and inserted into the block, it is accurate to 0.003mm. 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. All three are indispensable. A set of high-precision molds requires precise design, precision processing, and precision assembly.
The designer gives the mold the soul, the processor creates the mold body, and the assembler makes the mold come alive. The precision mold concept runs through the entire process of mold manufacturing. Concepts are passed down from top to bottom, from master to apprentice, and good habits become natural. It is not difficult to imagine the birth process of each high-quality mold. Cultivating the concept of precision molds should be the focus of my study this time, learning other people's good habits, developing my own good habits, establishing concepts, and integrating them into work.
