Plastic Injection Molding Interview Questions and Answers

The minimum draft required for a plastic part depends on the material, geometry, and surface finish.

• Draft is the angle or taper added to the vertical walls of a plastic part to facilitate its ejection from the mold.

• The minimum draft angle is typically 1-2 degrees for thermoplastics and 2-5 degrees for thermosets.

• The draft angle should be increased for larger parts, deeper cavities, and higher surface finishes.

• The draft angle may also vary depending on the location of the part...read more

Common problems during plastic injection molding process

• Incomplete filling of the mold

• Warping or distortion of the molded part

• Flash or excess material around the parting line

• Sink marks or depressions on the surface

• Short shots or incomplete parts

• Bubbles or voids in the molded part

Problems during plastic injection molding trials

• Material flow issues

• Warpage or shrinkage

• Surface defects

• Injection pressure or temperature problems

• Mold design or tooling issues

• Machine malfunction or operator error

There are various types of plastic materials used in injection molding, including thermoplastics, thermosets, and elastomers.

• Thermoplastics can be melted and re-melted, making them easy to mold and recycle. Examples include polyethylene, polypropylene, and polystyrene.

• Thermosets cannot be melted and re-molded, making them more durable and heat-resistant. Examples include epoxy and phenolic resins.

• Elastomers are rubber-like materials that can stretch and return to their origin...read more