Sink mark

Where it comes up

• Plastic injection moldingMolten thermoplastic injected into a steel or aluminum mold. Lowest piece price for plastic parts at 5,000+ a year.

Related terms

Gate

A gate is the opening where molten plastic or metal enters the mold cavity from the runner. Gate type, size, and location affect fill, knit lines, sink, and the mark left on the part. Common types include edge, submarine, pin point, and valve gates.

DFM

DFM is design for manufacturability, the review of a part design against the limits of the process that will make it, before tooling is cut. It checks wall thickness, draft, radii, tolerances, and material choice. DFM changes are cheap before steel is cut and expensive after.

Draft angle

Draft angle is the taper applied to part walls parallel to the direction of mold opening so the part releases without dragging. Injection molded parts typically need 1–2° of draft, plus about 1–1.5° more per 0.001 in (0.025 mm) of texture depth. Die castings typically need 0.5–2°.