Glossary

Plastic Injection Moulding – Glossary of Terms

 

Abrasion Resistance The ability of a material to withstand mechanical actions such as rubbing, scraping or erosion that tend progressively to remove material from its surface.
Acceptable runner/cavity ratio Runner systems designed for high pressure drops to minimise material usage and increase frictional heating in the runner.
Additive A substance compounded into a resin to enhance or improve certain characteristics.
Adhesive Assembly The process of joining two or more plastic parts by means of an adhesive
Aging The process of, or the results of, exposure of plastics to natural or artificial environmental conditions for a prolonged period of time.
Air Burn A patch or streak of brown or black material on the component caused by air or gases that have not been properly vented from the mould and have caused the material to overheat and burn.
Ambient Temperature The temperature of a medium surrounding an object.  The term is often used to denote prevailing room temperature.
Amorphous Devoid of crystallinity or stratification.  Most plastics are amorphous at processing temperatures.  Material assumes more random molecular structure when cooling.
Anisotropy The tendency of a material to react differently to stresses applied in different directions.
Annealing The process of relieving internal stresses of moulded plastic articles by heating to a predetermined temperature, maintaining this temperature for a predetermined length of time and slowly cooling the articles.
ANSI Abbreviation for American National Standards Institute.
Antiozonants These additives are used to prevent the negative effects of ozone on the resin materials.
Antistatic Agent Additive used to improve the electrical conductivity of the plastic part so that any charge can readily go to ground and not remain in the part.  Artificially balanced runner system balancing a runner system by adjusting the pressure drop of a long large diameter runner against a short small diameter runner.  Since pressure drop over the small diameter runner will be much more affected by heat loss than the large diameter runner, an artificially balanced runner system will work with a set range of moulding conditions.  The width of this range of moulding conditions determines the stability of the moulding
Ash Content The solid residue remaining after a substance has been incinerated or heated to a temperature sufficient to drive off all combustible or volatile substances.
Aspect Ratio Ratio of total flow length to average wall thickness.
A-stage This is a early stage in the reaction of certain thermosetting resins where the molecular weight is low and the resin is still soluble in some liquids and still fusible.
ASTM Abbreviation for American Society for Testing and Materials.
Back Pressure The resistance of the molten plastic material to forward flow.  In moulding, back pressure increases the temperature of the melt and contributes to better mixing of colours and homogeneity of the material.  However, as back pressure increases, so does cycle time.
Backflow Molten resin flows back out of the mould returning to the runners.
Backing Plate A plate used as a support for the mould cavity block, guide pins, bushings etc.
Balanced Runner A runner system designed to place all cavities at the same distance from the sprue.

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