This manufacturing tip is for plastic injection molds that have round inserts with o-rings and cooling channel on the outside.

When we put the insert with the o-ring into the hole in the insert sometimes we damages the o-ring, because the edge in the cooling hole is too sharp and the edge cuts away a part of the o-ring and damaged the o-ring, to avoid this issue we need to add small chamfer to the edge of the cooling hole in the insert plate, when the o-ring comes to the cooling hole the o-ring will not be damaged since the edge area is smoothly.

Below red cycle area, the edge is too sharp, it will damage the O-ring, if we add some chamfer at the pocket of O-ring, this issue could be solved.

cooling sharp area

Below areas are another type of case, at the open area of the cooling hole has a very sharp edge, this may cut the toolmaker’s hands if touch that area, to avoid this issue we need to add some radius and make this area roundness.

Cooling Chamfer

 

Step to make radius for this issue,

  1. Find a hand grinder machine and choose a grinding pin that is round not a sharp one.
hand grinding machine

hand grinding machine

2. Checking on the drawing how big fillet you can make, if the fillet is too big maybe the water will go out under the o-ring, in this case, there is 1.5mm from the o-ring to the cooling hole so we can make a radius 1mm fillet all around the cooling hole.

3. Grind the fillet around the cooling hole by hand, be careful so that you don’t damage the surface around the cooling hole, below picture is good cooling chamfer should be.

good cooling channel

good cooling channel