Part Details Review
| Mold Finish |
Mold finish plays an important role in the part ejection process. Pay special attention to the surface finish. In general, highly polished surfaces cause less friction and drag on the part during ejection. Some elastomeric or ductile polymers, however, have difficulty breaking the vacuum created by the highly polished surfaces. A lightly bead-blasted surface sometimes improves release in such situations.
Specify polishing the mold surfaces in the direction of mold opening or part ejection (also known as draw polish), which reduces the drag caused by fine scratches introduced on the mold surfaces during polishing. The fine scratches act as undercuts, causing drag marks on the part during ejection and increasing the force required for part ejection. Draw polishing keeps any polishing related scratches or undercuts in the line of draw (see figure)
With the increase in surface roughness, as in frosted sidewalls, increase the draft angles accordingly. As a general rule, for textured sidewalls, use the standard 1° draft plus an additional 1° draft for every 0.001" texture depth.
