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ข้อผิดพลาดของ การฉีดพลาสติก Plastic Molding

How to reduce Short Shot and Flash

Common problems in injection molding

Injection molding, as we know it, is the process of molding the plastic resin into a shape according to the design.

Defects or NG, that happen during the operation of Injection molding come in many different kinds and different types. Each type of defect may occur from many causes, and Raw material (Plastic resin or Plastic Pellet) is one of the main reasons for Defect NG outcomes. We may need to ensure that the properties of plastic resin are right and can be used together with the parameters of injection molding.

The top priority properties that need to be considered in injection molding for increasing the efficiency of operation and quality of the finished product are…. MFR (Melt Flow Rate) is how to measure the flow rate of thermoplastic material. The MFR test will show the result of flow rate at a controlled temperature and controlled pressure. The MFR test is an important process before starting an injection molding operation.

Short shot and Flash (burr): Common problem from not testing MFR before operation

Short shot cause is from plastic that flow too slow (low plastic fluidity)

Short shots may happen due to many causes, but from all the causes, they lead to low plastic fluidity. The causes of low fluidity (Short shot) may be found on low pressure, speed of injection, not enough melting temperature, or wrong material information of Viscosity, Positioning of Runner or gate are not accurately set or aligned, lack of air ventilation, or a problem with Mold directly.

From all the causes, it is the result of plastic hardening before completely filling up Cavity

Short shot ปัญหาพลาสติกไหลช้า

Flash or Burr cause is from plastic that flow too fast and exceed over the mold

When the operator increases the controlled temperature for reducing viscosity, increases the pressure, or increases the speed of injecting more than the clamping pressure of mold, it causes the problem of Flash or Burr. The operator may need to check the MFR of the material before starting the injection process.

Too much high pressure will result in plastic flowing out of the splice seal of the mold as well. It is also called Flash

Flash burr การฉีดพลาสติกเร็วเกินไป

For every purchase of Raw material (Plastic resin) or recycled plastic, we would recommend doing the testing MFR operation before every injection molding operation. As a result of the MFR Test, the user is able to set the proper melting temperature, injecting pressure, or proper speed of injection adjustment for each of the materials.  After all of the parameter adjustments for each material, it would surely reduce the problem that may happen with a finished product defect or NG.

The quality checking of plastic resin and properties checking of plastic resin are the main important processes that must be done before the injection molding process. 

MFR testing – Preventing and reducing all the problems from happening and to ensure the quality of Raw Material (Plastic resin) 

L260 – Melt Indexer or Plastometer for testing melt flow rate and inspecting Mold quality is important too

Quality Insert Mold is one of the ways to be concerned.