Custom Compounders Since 1973

TPGOA Technical Insights

Overcoming Injection Mold Design Issues

During any injection mold design, the layout and sizing of primary runners, secondary runners, lands, and gates, are of the utmost importance.

I see many instances where poor design of these components, results in unbalanced mold filling and packing of the molded part.

A customer had a 2-cavity mold made in China that was a typical example. One part was almost completely filled and showed signs of over-packing while the other part was about 50% filled. There was evidence of flashing the primary and secondary runners as well. Clearly, these components were undersized and not positioned correctly.

The Customer believed using a higher MFI PP resin would solve the problem.

My suggestion was to use a mold-filling program to balance the filling of both cavities, by adjusting the dimensions and layout of the runners and gates.

Keep in mind that these programs will get you close, but they are not absolute. Even after modeling, it is suggested to cut these details steel safe. Additional steel can removed incrementally if required. Milling steel is preferred over welding and machining.

Of course, you do not want these dimensions to be larger than required, otherwise, cycle time will increase to set these components.

TPG makes every effort to insure that the information contained herein is accurate - however, we accept no liability for the content of this piece, or for the consequences of any actions taken on the basis of the information provided.
 Download PDF Version