Category plastic mold

Sink marks and voids

Sink marks and voids Sink marks and voids are two manifestations of the same fault, and their complete eradication is extremely difficult. Diagnosis is easy. All plastics take up more volume when molten than when solid,and where there is more…

Undercuts and Surface finish

Undercuts An undercut is a part of the mould where the molten plastic flows behind a retaining section thereby preventing the hardened plastic moulding from being easily ejected. Undercuts, in general, require moulds with moving parts to allow the product…

Internal stress and warping

Internal stress and warping When thick sections are moulded,rapid changes in temperature can cause thermally induced stresses due to differential expansion. If surface layers cool faster than the interior through poor conduction, the contraction of the surface will be greater…

Sinking

Sinking The moulding of thermoplastics in thick sections presents other shrinkage problems, especially where mould shrinkage is high (e.g. highly crystalline materials). In a thick section of an injection moulded product,for example, the outside layers in contact with the cold…

Objectives of Planned Maintenance

The correct kind of maintenance for plastic moulds is one which certainly involves much more than is embraced in the all-too-customary practice of a merely perfunctory examination of the tool upon its removal from the production stage, with the almost…