/Precautions for mold test before injection

Precautions for mold test before injection

In our plastic molding company, after a new set of plastic injection molds is completed, mold test is an indispensable part before injection. Quality of mold test results will directly affect whether subsequent production of factory is smooth. Therefore, in the trial process, reasonable operation steps must be followed and useful technical parameters in the test process should be recorded to facilitate mass production of plastic molded products.

Pay more attention to mold test: whether opening and closing mold is smooth and whether ejection is smooth. Secondly, pay attention to gate position and feeding method of mold, as well as size of gate and size of cavity, in order to select appropriate pressure, speed and material amount for injection molding. After mold is warmed up, carefully check all the joints of mold for excessive hardness, and then confirm bonding line and exhaust. After product is full, please arrange quality personnel to confirm size and appearance of plastic molded products.

Main steps of mold test:

  • Check whether plastic in the barrel is correct and whether it is baked according to regulations (if different materials are used for test and production, it is likely to have different results);
  • Clean up material pipe, in order to prevent inferior compound or miscellaneous materials from being injected into mold, because inferior compound and miscellaneous materials may cause mold to be stuck. Check whether temperature of tube and mold are suitable for processing raw materials;
  • Adjust pressure and amount of injection to produce a finished plastic injection molded parts with satisfactory appearance. However, it cannot have burrs, especially when some cavity products are not completely solidified. Before adjusting various control conditions, you should think more about it, because filling rate is slightly changed, which may cause a large filling change;
  • Be patient and wait until conditions of machine and mold are stable. Medium-sized machine may have to wait for more than 30 minutes. You can use this time to check possible problems that may occur in the finished product.
  • Advancement time of screw should not be shorter than solidification time of gate plastic. Otherwise, weight of plastic injection molded parts will be reduced, which will impair performance of finished plastic molded products. And when mold is heated, screw advance time also needs to be lengthened to compact finished plastic molded products;
  • Reasonable adjustment to reduce total processing cycle;
  • Run newly transferred conditions for at least 30 minutes to stabilize, and then at least continuously produce a dozen full-mode samples, mark date and quantity on a holder, and place them separately according to cavity to test stability of operation, export reasonable control tolerances (especially valuable for multi-cavity molds);
  • Measure continuous sample and record its important size (should be re-sampled when sample is cooled to room temperature);
  • Compare dimensions of each mold sample;
  • If finished plastic molded products size does not change and processing conditions are normal, it is necessary to observe whether quality of each finished product of cavity is acceptable, and size can be within tolerance. Write down number of cavity that is continuous or large or less than average value to check whether size of mold is correct;
  • Make processing run time longer to stabilize melt temperature and hydraulic oil temperature;
  • According to size of all finished plastic injection molded parts is too large or too small to adjust machine conditions, if shrinkage rate is too large and finished product appears to be insufficient, it can also be used to increase gate size;
  • If size of each cavity is too large or too small, if cavity and gate size are correct, then machine conditions should be changed, such as filling rate, mold temperature and pressure of each part, and whether hole is filled slowly;
  • According to matching situation of finished cavity products or displacement of core, it may be individually modified. It may be possible to test filling rate and mold temperature again in order to improve uniformity;
  • Inspect and modify failure of injection machine. All future data that will help to successfully establish same processing conditions should be saved in order to obtain a product that meets quality standards.

At present, when plastic molding company test mold, mold temperature is often neglected, and in the short-term mold test and future mass production, mold temperature is the most difficult item to grasp, and incorrect mold temperature is enough to affect sample size, luminosity, shrinkage, flow pattern and if you do not use mold temperature controller to master phenomenon, you may have difficulty in mass production in the future.

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