When we manufacture the mold core and cavity inserts during the mold manufacturing, there are some dimensions that we need to manufacture with some tolerances so that it fits well in the pocket of the insert plate or mold cavity/core.
And this will save some work when we will fit the mould cavity & core, high tolerance, and good manufacturing technology will save lots of time for the mold-master, below are some manufacturing mold core /cavity insert Guideline that we need to pay attention to make high quality plastic mold.
When we make the corner radius In the manual milling machine, make a 0.2mm big step there, after hardening, we don’t have to grind on the corner when we fit the insert.
For the outside dimension of the mold cavity/core Inserts, the tolerance should be +0/-0.015mm, this will be easy fit into the pocket, smooth and good quality.
The tolerance for the hole to the sprue bushing should be H7 (0/+0.015mm).
The depth of the treading should be 1.5-2 multiply by the diameter of the tread. In this case for M8 screw, the depth of the treading should be 1.5 to 2 multiply by 8, equal to 12-16mm.
The guidance of the ejector pin should be about 15-20mm long, this will make sure that the ejector pins ejecting smoothly with long lifetime.
The clearance area for the ejector pins should be 1mm bigger than the diameter of the ejector pins., please see below illustration with explaining.