ABS PP PC And ASA For Moulded Industrial Parts

The material choice reaches back into the steel

Material is usually decided by the product engineer and the mould is quoted afterwards, which hides how much the two interact. Shrinkage sets the cavity size. Melt temperature sets the cavity steel. Abrasiveness sets the gate wear. Change the material after the tool is cut and you are not changing a process setting, you are changing the size of the part.

ABS

The default for bathroom and consumer parts, and the most common material in this catalogue. It moulds easily, plates well and is forgiving at the press. Its one awkward habit is off-gassing in the tool, which corrodes plain cavity steel over time. That is why the ABS tools here so often run stainless grades such as S136.

An ABS tool in stainless steel

PP

Polypropylene is cheap, chemically resistant and shrinks considerably more than the styrenics. That shrinkage is the whole story for the mould maker: the cavity is cut oversize by a calculated amount, and if the allowance is wrong the parts come out the wrong size and no setting fixes it. It also needs cooling laid out for the part rather than carried over from an ABS tool.

A PP cover plate tool

PC and PC ABS

Polycarbonate is strong, clear and runs hot. It wants a hotter, more stable mould than ABS and will not hold cycle in a tool cooled for a styrenic. PC ABS sits between the two: easier to fill than straight PC, stiffer and hotter than ABS. Both push the cavity steel towards a hot work grade such as SKD61, especially in filled or flame retardant versions.

A PC appliance tool

ASA

ASA is chosen for one reason: it keeps its colour and surface outdoors where ABS chalks and fades within a season. It costs more per kilogram, and substituting ABS to save that cost is a decision that shows up as a warranty claim a year later rather than as a moulding problem.

An ASA family tool