Simple Straight Pull Moulded Parts
Protomold can make many complex features, however, a mould costs less if it is a straight pull, i.e. it doesn’t have undercuts.
What is a straight pull mould?
A part that can be made with a straight pull mould has all its features designed so that when the two halves of the mould pull straight away from each other, there is no mould metal that wants to pass through part plastic. Undercuts on the part require mould pieces to pull out sideways, perpendicular to the direction of pull.
Consider using telescoping shutoffs to create through-holes
As noted earlier, telescoping shutoffs benefit from drafted sliding surfaces whenever possible.
But they are also useful in the implementation of part features that might otherwise not be possible with straight-pull moulds.
This example shows how the redesign of a part with an undercut (e.g. the through-hole) can be changed into a part with no undercuts through the use of a telescoping shutoff approach, without losing its functionality.
Note: we require at least 3 degrees draft on shutoffs.
Through-hole in part cannot be moulded with straight-pull mould
An equally functional redesigned part without undercuts can be moulded using telescoping shutoffs