（19） Dimensional differences of injection molded parts Injection Molding Process Defect Handling Manual (65 types)
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Characteristics of defects in injection molded parts
Changes in weight and size during injection molding exceed the production capacity of molds, injection molding machines, and plastic combinations.
2. Possible causes of problems
(1) . Input uneven plastic in the injection cylinder.
(2) The temperature or fluctuation range of the injection cylinder is too large.
(3) The capacity of the injection molding machine is too small.
(4) The injection pressure is unstable.
(5) The screw resetting is unstable.
(6) Changes in operating time and inconsistent solution viscosity.
(7) The injection speed (flow control) is unstable.
(8) A plastic variety that is not suitable for the mold was used.
(9) Consider mold temperature, injection pressure, speed, time, and pressure holding
The impact on the product.
3. Remedies
(1) Check whether there is sufficient cooling water flowing through the hopper throat to maintain the correct temperature.
(2) Check for poor quality or loose thermocouples.
(3) Check that the thermocouples used with the temperature controller are of the correct type.
(4) Check the injection quantity and plasticizing capacity of the injection molding machine, and then compare them with the actual injection quantity and hourly injection
Compare the amount of plastic used.
(5) Check whether there is stable molten hot material during each operation.
(6) Check the backflow prevention valve for leaks and replace it if necessary.
(7) Check for incorrect feed settings.
(8) Ensure that the screw is stable at the return position during each operation, i.e. no more than 0.4 mm change.
(9) Check for inconsistencies in operating time.
(10) Use back pressure.
(11) Check whether the hydraulic system operates normally and whether the oil temperature is too high or too low (25-60oC).
(12) Select the plastic variety suitable for the mold (mainly considering shrinkage and mechanical strength). (13) Readjust the entire production process.
