18 Knowledge Points About The Injection Molding Industry (Part 2)
- Aug 16, 2018 -

18 Knowledge Points About The Injection Molding Industry (Part 1)


10. Plasticizing ability

The evaluation of the injection molding machine is usually based on the amount of PS (in pounds and kilograms) that can uniformly melt the amount of PS in one hour or the temperature of the uniform melt, which is called plasticizing ability.

11. Plasticization capacity estimation

To determine whether the production of lysin can be maintained throughout the production process, a simple formula for yield and plasticizing capacity can be used, as follows: t = (total injection shot gX3600) ÷ (plastic injection molding machine kg/hX1000) t is the lowest cycle time. If the cycle time of the mold is lower than the t value, the injection molding machine cannot fully plasticize the plastic to achieve a uniform melt viscosity, so the injection molded parts often have deviations. In particular, when paying attention to the quality of injection molded thin walls or precision tolerances, the amount of shot and the amount of plasticization must match each other.

12. Shooting tank retention time

The decomposition of plastic is based on temperature and time. For example, a plastic will decompose after being exposed to high temperatures for a period of time; however, in a lower temperature environment, it will take longer to decompose. Therefore, the residence time of plastic in the shooting tank is very important.

The actual residence time can be determined experimentally. The method is to measure the time required for the colored plastic to pass through the shooting tank. The following formula can be roughly calculated: t=(the nominal volume of the shooting tank gX cycle time S)÷ (shot material) Amount gX300) Please note that some plastics have a longer residence time in the shooting tank than is required for calculation because they can accumulate in the shooting tank.

13. Calculate residence time and importance

As a general rule, the residence time of a plastic on a particular injection molding machine should be calculated. Especially when a large injection molding machine uses a small amount of shot material, the plastic is easily decomposed, which is not detectable from observation. If the residence time is short, the plastic will not be plasticized evenly; the retention time will be attenuated by the plastic properties.

Therefore, it is necessary to maintain the same residence time. Method: Ensure that the plastic input into the injection molding machine has a stable composition, consistent size and shape. If there is any abnormality or loss of the parts of the injection molding machine, it must be reported to the maintenance department.

14. Shooting cylinder temperature environment

It should be noted that the melt temperature is important and any shot cylinder temperature used is only indicative. If you have no experience in working on a particular plastic, start with the lowest setting. Usually the temperature in the first zone is set to the lowest value to prevent premature melting and blocking of the plastic in the feed port.

The temperature in the other zones then gradually increases until the nozzle is reached, and the temperature at the tip of the nozzle tends to be slightly lower to prevent dripping. The mold is also heated and cooled. Due to the size relationship of many molds, the mold is also distinguished, but unless otherwise stated, the zones should be set to the same size.

15. Melt temperature

The nozzle can be measured or measured by air jet. When using the latter for measurements, care must be taken to ensure that hot melt plastics are cleaned without accidents, as hot melt plastics can burn the skin and even corrode the skin. In the injection molding workshop, burns are accidental.

Therefore, gloves and masks should be worn when handling hot plastic or in case of hot melt plastic splashing. To ensure safety, the tip of the heat control needle should be preheated to the temperature to be measured. Each plastic has a specific melt temperature. To achieve this temperature, the actual injection cylinder adjustment value depends on the rotation speed, back pressure, shot volume and injection cycle of the screw village.

16. Mold temperature

Always check that the injection molding machine is set up and running at the temperature specified on the record sheet. this is very important. Because temperature affects the surface finish and yield of the molded part. All measured values must be recorded and the injection molding machine checked at the specified time.

17. Uniform cooling

Injection molded parts must be uniformly cooled, that is, different parts of the mold must be cooled at different rates so that the entire product is uniformly cooled. Injection molded parts must be cooled at the fastest speed while ensuring that defects do not occur, such as uneven surfaces and changes in physical properties. The cooling rate of each part of the injection molded part must be equal, but it means that the mold is cooled by a non-uniform method, for example, cold water is input into the inner core portion of the mold, and warm water is used to cool the outside of the mold. This technique should be used when the syringe is molded to a precision straight product or a large product with a long melt flow.

18. Temperature and cooling check

Always check that the injection molding machine is set up and running at the temperature specified on the record sheet. this is very important. Because temperature affects the surface finish and yield of the molded part. All measured values must be recorded and the injection molding machine checked at the specified time.

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