The runner pin failures took a little bit more effort to figure out, but the root cause is the same-pin deflection. More relief and less bearing surface allowed the components to function freely. I never questioned this when I was working in the tool-shop environment, It made sense based on technology in use when I started in the trade. In smaller molds, I have seen as little as 0.5 to 0.75 in. I was trained myself to accept that you need only 1 to 1.5 in. Too many people have been programmed with moldmaking standards that have not evolved with the technology. Please keep an open mind in this discussion. The only area of support that resists deflection is where there is bearing surface (Fig. I refer to the portion of the component that has no support. Let me briefly explain “unsupported length,” since many of you readers probably have not heard this term in relation to mold design. But this standard for ejector-pin bearing surface is a contributor to tool failures by increasing the unsupported length of the component. I never questioned this standard use of minimal bearing surface back then because it was needed to get the components to function. in diameter) to where there was only 1 to 1.5 in. At times the ejector-pin holes were gun drilled, but in either case we drilled relief (opened up the holes approximately 1/32-in. When drilling and reaming ejector-pin holes on the radial drill press, the holes would wander slightly, which required adding relief (increasing the diameter for clearance) so the ejector pins would fit smoothly. A good part of the buildup work was completed on this piece of equipment. This piece of equipment is not very popular nowadays, but back in the 1980s you couldn’t build a large tool without one. When I was an apprentice, I spent a good part of my life on the radial drill press. The hands-on man-hours were a big part of the process back then, with the buildup work, manually made electrodes, spotting, and polishing. Pre-CAD/CAM, tools were cut from cast models on duplicating machines (aka tracers). But I consider myself fortunate to have been involved with the pre-CAD/CAM process, as I can see now that some tooling standards carried on when they should have been updated along with technology. When I entered the moldmaking trade in 1988, it was starting to move into the CAD/CAM era.
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