How to prevent sink marks during injection molding?

author: Universe plastic

2023-12-22

Sink marks are a common problem during the injection molding process, primarily caused by abnormal shrinkage of molten plastic resin during cooling and solidification. How to prevent sink marks during the injection molding process can be dealt with from the following aspects:

Prevent injection molding shrinkage—optimize mold structure design

Slightly lower the cavity surface temperature

Expanded injection gate

Expand runner size

Thick sprue

Recheck the cooling circuit of the mold to improve cooling efficiency

Change the cooling structure of difficult-to-cool parts to a structure that is easy to cool

Increase the number of gates

Change the gate setting position to the thick-walled part

Prevent injection shrink marks—Adjust injection molding condition parameters

Extend holding time

Increase holding pressure

Speed up injection molding speed setting

Reduce nozzle temperature

Try increasing the meter value

Try increasing buffer size

Try replacing the injection molding machine

Replacing the anti-backflow ring of the injection molding unit

Prevent injection molding sink marks—optimize injection molding product design

Remove thick-walled parts of molded products

Using amorphous resin

Additionally, there are other methods that can help prevent sink marks from occurring, such as:

1. The exhaust of the mold is smooth, higher pressure and speed can be used during injection molding, the effect of pressure maintaining and shrinkage is better, and the possibility of shrinkage marks or shrinkage holes is reduced.

2. If it cannot be eliminated by moderate cooling, it is necessary to adopt the method of freezing water to quickly harden the surface of the injection molded parts to prevent shrinkage, but internal shrinkage holes may still exist.

In general, the key to preventing sink marks is to reasonably control all aspects of the injection molding process, including mold design, injection molding condition selection, and product design. At the same time, attention should also be paid to the maintenance and upkeep of the mold to ensure its normal operation.

Two plate injection mold

Nearby Injection Molding Company: Universe Plastic