Your Resource Guide To Plastic Injection Molding Terminology

Resource Guide To Plastic Injection Molding Terminology


The GreenLeaf Industries team is passionate about integrating Engineered Quality, Reliable Delivery and Cost Containment into every design and project. We are a family owned, made in America manufacturer that is committed to supporting our clients and the Plastic Injection Molding Industry.

It is our pleasure to introduce some helpful terminology that is covered in our latest resource guide to help designers, engineers and purchasing professionals navigate the world of plastic injection molding. You will soon be able to receive The full, “Ultimate Resource Guide”, with over 200 terms for free… by requesting an immediate download from this site.

ADDITIVE MANUFACTURING – This is actually the technical term for 3-D printing. It is the process of manufacturing a three-dimensional object by placing layer on top of layer based on a specific CAD model.

AGING – Refers to the change of a material with time under defined environmental conditions, leading to either improvement, or the deterioration of certain properties.

ANTISTATIC AGENT – An agent added to the molding material (or applied on the surface of the molded object) to make it less conducive, whereby hindering the fixation of dust.

BACKING PLATE – A plate used in mold construction, as a support for the cavity blocks, guide pins, bushings etc.

BLISTER – A raised area on the surface of a molding that is caused by the pressure of gases inside it on it’s incompletely hardened surface.

BOSS – Not what you might think ;-)… In molding terms, it is a projection on a plastic part designed to add strength and facilitate alignment during assembly. It is also used to provide for fastenings.

CAST – To form a “plastic” object by pouring a fluid monomer-polymer solution into an open mold where it finishes polymerizing.

CAVITY – A depression in mold, which usually forms the outer surface of the molded part. Depending on the number of such depressions, molds can be designated as single cavity or multi-cavity.

DEFLASHING – Covers the range of finishing techniques used to remove the flash (excess, unwanted material) that occurs on plastic molding such as filing, sanding, milling or tumbling.

DEGRADATION – A change in plastic physical properties resulting from heat, light exposure, exposure to oxygen, and/or general weathering.

DESSICANT – A substance that can be used for drying purposes because of its affinity for water.

DISCOLORATION – Any change that occurs from the original color that likely has resulted from overheating, light exposure or chemical exposure.

ELASTICITY – The property of a material by virtue of which tends to “recover” to its original size and shape… after deformation.

FILLER – An additive to resins for the purpose of improving physical properties (for example: impact resistance, hardness or dimensional stability). It can also be used to reduce the expense of resin.

FLASH GATE – Usually a long gate extending from a runner, which runs parallel to an edge of a molded part… along the flash or parting line of the mold.

GATE – In injection molding, the orifice through which the melt enters the cavity, is called the gate.

INJECTION MOLDING – The process of creating plastic parts and components by way of heating granular or powdered plastics and then forcing the liquid into a mold.

INSERT – An integral part of a plastic molding consisting of metal, or other material, which may be molded into position or may be pressed into the molding after the molding is completed.

JETTING – A turbulent flow of resin from an undersized gate, or thin section, into a thicker mold section. This is opposed to a laminar flow of material progressing radially from a gate to the extremities of the cavity.

LIGHT-RESISTANCE – The ability of a plastic material to resist fading after exposure to sunlight or ultraviolet light is it’s resistance.

MASTERBATCH – The concentration of pigments, fillers, additives and other substances within a polymer base.

MICA – Any of the group of mineral silicates, crystallizing in monoclinic forms that readily separate into very thin leaves. It is used as filler for plastic molding materials.

MELT FLOW – The viscosity of a polymer based on the polymer’s weight when extruded under certain pressure and temperature.

MOLDING SHRINKAGE – The difference in dimensions between a molding and the mold cavity in which it was molded.

NOZZLE – The hollow cored metal nose screwed into the extrusion end of the heating cylinder of an injection machine.

OUT-OF-ROUND – When an item has a non-uniform radius or diameter.

PLASTIC DEFORMATION – A change in dimensions of an object under load that is not recovered when the load is removed. If it is recovered, you have elastic deformation.

PREMIX – A molding compound prepared, prior to and apart from the molding operations, and containing all components required for molding (resin, fillers, catalysts, release agents, and other compounds).

REINFORCED MOLDING COMPOUND – A material reinforced with special fillers to meet specific requirements (carbon, glass, etc.)

RUNNER – In an injection mold, the channel that connects the sprue with the gate to the cavity is the runner.

SHORT SHOT – A molded part produced when the mold has not been filled completely.

SILK SCREEN PRINTING –The laying of a pattern of insoluble material on a finely woven fabric, so that when ink is drawn across it… it is able to pass through the screen only in the desired areas.

SPRUE – A feed opening provided in the injection mold.

SPRUE GATE – A passageway through which molten resin flows from the nozzle to the mold cavity.

SINK – Imperfections such as dimples that occur as plastic cools at different rates along the surface.

TOGGLE ACTION – Pressure exerted by the application of force on a knee joint. It is often used as a method of closing presses.

ULTRASONIC INSERTION – The inserting of a metal insert into a thermoplastic part by the application of vibratory mechanical pressure at ultrasonic frequencies.

UV STABALIZER – Any chemical compound which, when admixed with a thermoplastic resin, selectively absorbs UV or ultra violet rays.

VISCOSITY – The measure of a material’s ability to resist flow. In fluids, viscosity can known as “thickness.”

WARP (WARPAGE) – A curving or bending that results as a part cools, and shrinks, at varying rates along a surface.

YIELD VALUE –The lowest stress at which a material undergoes plastic deformation. Below this stress, the material is elastic… above it… viscous.

About GreenLeaf: GreenLeaf Industries is an ISO 9001 registered manufacturer that consistently adheres to all its standards to provide our clients with consistent, reliable, quality automotive and industrial plastic parts. We are an American injection molding company, unafraid to compete in the world market and determined to succeed. Established in 1999, we take pride in our high-quality craftsmanship and superior customer service. Visit us:

GreenLeaf Industries
310 Bussell Ferry Road
Lenoir City, TN 37771
(865) 988-5661