When I went to a mobile phone stamping mold factory to learn about precision mold technology, the deepest impression I got was not the superior level of mold design and precise processing technology, but rather the development concept of precision molds.
On my second day there, the team leader told us he wanted to instill in us the concept of precision. What is the concept of precision mold? I was somewhat skeptical. The products here are made of fine materials and I have done some of these jobs before.
How could I lack the concept of precision?
However, as my study gradually deepened, I began to realize my superficial understanding!
The first stop on our learning journey was the assembly of the high-speed module. In terms of mold accuracy, high-speed terminal molds should be considered the most accurate here. Stamping materials are generally 0.08~0.2mm stainless steel and aluminum, with shear gaps as small as 0.008mm, the minimum width of small punched holes is 0.25mm, and the punch gives an impression fragile.
How are these small holes made? How can such a small shear gap ensure mold manufacturing accuracy? It's hard to imagine without seeing it with my own eyes.
By studying the drawings, understanding the mold structure, the design's manufacturing tolerances, and its special manufacturing process, we were able to understand the pulse of this mold set.
All punch parts from top to bottom are blocks and punches, the blade is made of tungsten steel. The block holes, JG fixed holes ground on the upper mold plate, ejection plate and lower mold plate, sliding adjustment clearance c + 0.005 ~ 0.010mm, anti-slip adjustment c + 0.003mm, machining accuracy +/- 0.002mm .
The main frame guide parts are spherical bushings with precision guide pillars, the small hole drilling frame adopts a local structure separated from the upper mold, locked into the lower mold plate with equal height sleeves, compensating for equipment accuracy errors of stamping.
The guide parts of the local structure are precision graphite self-lubricating internal guide pillars, the internal guide bushing of the ejection plate and the bottom plate of the mold are filled with glue, compensating for the machining errors of the guide parts, improving the guide accuracy, ensuring the accuracy of the mold plate position during the stamping process and the shortest possible stamping stroke can make the punch length as short as possible.
Appropriate punch reinforcement can improve punch strength. This completely reflects the mold designer's tendency towards high-precision design, maximally ensuring the high quality and high requirements of the mold.
Modern processing equipment and high-precision processing technology further enable these design concepts to be fully utilized.
After heat treatment, the mold plate undergoes deep cryogenic aging treatment to eliminate internal stress, prevent deformation of the mold plate, ensure the processing stability of the mold plate, flat grinding ensures the flatness of the mold plate mold, 0.005mm parallelism, electrical discharge machining (EDM) accuracy is controlled within ±0.002mm, wire slow cutting accuracy is controlled within ±0.0015mm.
For high-precision machining, the temperature issue must not be ignored, because temperature differences are the enemy of precision. Due to the thermal expansion and contraction of materials, the linear expansion of steel will produce a change of 12μm per meter when the temperature changes by 1°C.
This is an immutable fact in all corners of the world, on all types of machines. If we don't care about this important issue of temperature, how can we discuss accuracy?
Controlling the temperature in the workshop is very important because the precision of the part to be machined is highly related to it. The temperature for precision machining is generally kept constant at 20°C, requiring temperature fluctuations of less than 0.5°C per hour, and the air conditioning system maintains a constant temperature difference of ±1°C throughout the day .
The meticulousness of the mold assembly engineer also impressed me. They first carefully understand the mold drawings, familiarize themselves with the product information, analyze the mold structure, and understand the design intention.
They meticulously check the parts, chamfer, polish and mark; the mold plates are deburred, lubricated to prevent rust, and assembled in an orderly manner; external guide columns and guide bushings are installed using special positioning tools to ensure their verticality; the actual thickness of the mold plate is measured at four points, with a difference of 0.005 mm being considered acceptable; the punch and block are paired, the pairing must be smooth, the grinding has a pattern, the judgment pattern is clear; During mold testing and adjustment, self-inspection of the product must be carried out with a projector, and when repairing the mold block, it must be accurate to 0.003mm.
Without the concept of precision it is impossible to develop high-quality molds or assemble high-precision molds.
Mold development is mainly divided into three stages: mold design; mold processing; and mold assembly, testing and refinement. Each one is indispensable. A high-precision mold requires precise design, precise machining and precise assembly.
Designers give the mold a soul, processors shape the mold body and assemblers give life to the mold. The precision mold concept runs through the entire mold manufacturing process.
The inheritance of the concept goes from top to bottom, and from master to apprentice, good habits become natural, and the birth process of each mold masterpiece is not difficult to imagine.
Cultivating the concept of precision molding should be the key content of my learning this time, learning good habits from others, developing my own good habits, establishing concepts and integrating them into work.
