Cracking or Crazing This fault occurs only when there is residual stress in a moulding which may be affected by an aggressive environment. The term ‘aggressive，may be considered a misnomer for such environments as a low concentration of ozone in…
Burn marks What is Burn Marks If an area of a moulding becomes the oxidized, discolored, or blackened, the first thing to do is to examine the venting of the mould. Air trapped in the mould is heated to a…
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 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 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…
Effects and Influence of Mould Design upon Maintenance It is an unquestioned truism that mould maintenance, in reality, originates in the design department when the core features of the mould mechanism are worked out.Moreover, they, in turn, are reflected in the manner…
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…
Where some secondary operations have to be performed on the mouldings, such as drilling，tapping, dressing-off, flash-removal, polishing, etc., these may be very adversely affected, increased in duration and complexity, or even rendered impracticable, as a result of failures to maintain…
Every mould user has to undertake some kind of maintenance activity.Since faults and damage to the complex mechanism of these tools inevitably occurs even when the greatest care is taken. However, as already hinted, experience reveals such activities to consist…
it is far from being sufficiently appreciated amongst injection mold users that the continued successful operation of plastic injection molds, which in reality are precision tools of a high order of mechanical accuracy and costliness,entails a well-thought-out scheme of maintenance…
