Two Plate Mould Design

by Satyajit
(bbsr, Orissa, India)

Question by Satyajit: How to design a two plate injection mould?

My answer:

The 2 plate plate mould has one parting line opening as opposed to a 3 plate mold which has 2 openings.

A 2 plate mold is very simple to design because the cold runner and mould cavities are on the same part line surface which means they are machined into the same plate (see photos above).

The 2 plate mold is good for shallow parts and it is a very easy mold to manufacture. A 2 plate mold can also be used for taller parts.

The best runner shape is a full round runner for easiest processing and for optimum part quality . This means 2 semi circular shapes must be machined into both the fixed and moving side plates(see photos above). However, with some materials such as PP (polypropylene) a trapezoidal shape (which is a U shape with draft) is sufficient and only needs to be machined into one plate.

Whats more, as with all mold designs, the mold must be rigid enough to withstand clamp tonnage and the cavity pressure created inside the mould during the filling and holding time or part quality will suffer (such as flash). This means reasonably thick back plates especially on the fixed side and sufficient pillar support where ejector plates are part of the design so that mold deflection is kept to a minimum.

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