Plastic injection mold parting line

Plastic injection mold parting line

What is plastic injection molding parting line ?

The plastic injection mold cavity is composed of two half moulds synthesis, also the plastic injection molding products have to be taken out from mold, it much be two half of mold.

With this separated line and separated place, there is a line in plastic injection products, then we called this parting line.

Mold used for plastic injection filling using most of a few parts are spliced, and the joint location may not be absolutely smooth, there will be small gap. In the plastic injection filling production, the position will be small edge protuberance, this called parting line.

There is a simple way to understand.

Plastic parts need to be divided into several parts to be mold, there parts together to form a closed space, so between the various there parts of the line is the parting line.

There will be a few several possible that the plastic parts have the parting line

• The plastic parts make injection molds can not be manufactured.  There should be made inserts.


• Plastic product can not be demoulded(released) on the demoulding direction.


• Plastic injection mold parts strength shortage

Choose the right plastic injection mold parting line

Ensure the plastic products can be released

This is a first principles as this is the purpose that we have the parting line and ensure the plastic product can be released from mold. The parting surface should be preferred in the largest plastic products of contour line,the best in the a plane. And this plane is perpendicular to the direction of mold.

Ensure shallow depth of plastic mold cavity

This will be benifit on the plastic mold manufacturing, injection mold cost, plastic injection molding process and tolerance control etc.

Look after plastic product appreance and easy to clean the plastic injection mold parting line

Although the plastic mould fitting is very precise, but still will leave traces in the plastic parts plastic parts appearance effect, so the parting surface should be avoided in the plastic parts on smooth surface and exterior surface.

Prevent to use the slider or lifter etc.

On the plastic injection mold design, we prevent to use the slider and lifter etc. side core pulling system as possible as it will increase the plastic injection mold cost and injection molding cycle, it will also loose the tolerance.  But if your plastic products need the side pulling core, you should also consider.

Consider plastic injection mold parting line manufacture easier

If you can use the flat parting line, then you do not need to consider to use the curved surface and angular surface due to the curved surface and anglular surface increase the difficulty of injection mold manufacturing processing.

 Make the slider core shorter as possible

The shorter sider pulling core, the less moving distance of the slider or lifter. On the one hand it can reduce the thickness of the core and cavity and the plastic parts dimension deviation; On the other hand it will be propitious to demoulding.

Seasky Tooling offer the plastic mold parting line analysis and optimization on our design for manufacture process, also we will present the parting line on our DFM report to have your easier to understand. Also most of engineers have more than ten years experience for mold design and mold manufacturing.

Contact us now for plastic injection mold and plastic injection molding inquiry.

Plastic injection mold parting line