Fabricating: The manufacture of plastic products by appropriate operations. This includes plastics formed into molded parts, rods, tubes, sheeting, extrusion and other forms by methods including punching, cutting, drilling, tapping, fastening or by using other mechanical devices.

Family mold: A mold that produces non-identical parts simultaneously from multiple cavities.

Fan Gate: A gate used to help reduce stress concentrations in the gate area by spreading the opening over a wider area. Less warping of parts can usually be expected by the use of this type of gate.

Fatigue Strength: The maximum cyclic stress a material can withstand for a given number of cycles before failure occurs.

Fill pattern: the contours of the advance of the material as the cavity fills. (See flow pattern)

Fill pressure: the pressure required to fill the cavity.

Fill Time (also known as Injection): Time required to fill the cavity or mold.

Fill: The packing of the cavity or cavities of the mold as required to give a complete part or parts that are free of flash and porosity.

Filler: A relatively inert substance added to a plastic compound to reduce its cost and/or to improve physical properties, particularly hardness, stiffness and impact strength.

Fines: In the classification of powdered or granular materials such as molding compounds according to particle size, fines are the portion of the material composed of particles which are smaller than a specified size.

Finish: The surface texture and appearance of a finished article.

Finite element analysis: the solution of simultaneous equations for each element with resulting pressure, temperature and elapsed time at each node.

Flame Retardant: Having the ability to resist combustion (A flame retardant plastic is considered to be one that will not continue to burn or glow after the source of ignition has been removed.)

Flash Gate: Wide gate extending from a runner which runs parallel to an edge of a molded part along the parting line of a mold.

Flash: Any excess material that is formed with and attached to the component along a seam or mold parting line.

Flexural Strength: The maximum stress in the outer fiber at the moment of crack or break. In the case of plastics, this value is usually higher than the tensile strength.

Flow Balancing: modifying flow paths, particularly runner sections, so that all flow paths within a mold fill in equal time with equal pressure.

Flow Leader: local increase in thickness to encourage flow in a particular direction.
Flow Marks: Wavy surface appearances on a molded part caused by the improper flow of the melt into the mold.

Flow Pattern: The contour the melt takes sequentially as it fills the cavity.

Flow Rate: the volume of material passing a fixed point per unit time.

Foaming Agent: Any substance which alone or in combination with other substances is capable of producing a cellular structure in a plastic mass.

Fracture: The separation of a body, usually characterized as either brittle or ductile.

Freeze off: the temperature of the material is reduced to the point that it blocks an area it would fill if it were hotter.

Frictional heating: heat generated by the friction of the chains of molecules slipping past each other or over a surface.


Edge Gate: entrance to the part from the runner located on the parting line.

Ejection Pin Marks: A residual mark on the part caused by the profile of the ejection pin.

Ejection Pin: A rod, pin or sleeve that pushes a molded part off of a core or out of a cavity of a mold.

Ejector Return Pins: Projections that push the ejector assembly back as the mold closes. Also called surface pins or return pins.

Ejector Rod: A bar that actuates the ejector assembly when the mold opens.

Elastic Memory: A characteristic of certain plastics evidenced by their tendency to revert to a previously existing shape or dimension.

Elasticity: The ability of a material to quickly recover its original dimensions after removal of a load that has caused deformation.

Elastomer: A rubber-like material which at room temperature can be stretched repeatedly to at least twice its original length and, upon immediate release of the stress, will return with force to its approximate original length.

Element: a triangle defined by at least three nodes, creating the basis for the finite element analysis.

Elongation, Break: The increase in distance between two gauge marks at the breakpoint divided by the original distance between the marks. A zero value in the field indicates that it measured less than one.

Elongation, Yield: The increase in distance between two gauge marks at a yield point divided by the original distance between the marks. A zero value indicates that it measured less than one.

Engineering Plastics: A broad term covering plastics, with or without fillers or reinforcements, which have improved mechanical, chemical and thermal properties of commodity grades of resins.

Extender: A filler material added to a plastic compound used to reduce the amount of resin required per unit value.

Extrudate: The product or material delivered from an extruder, for example, film, pipe profiles.

Extrusion: The process of forming continuous shapes by forcing a molten plastic material through a die.


Damping: The effect on a mass that causes decreasing amplitude.

Deflection Temperature: The measurement of temperature at which a specimen deflects to a set point under a defined load.

Degassing: The momentary opening and closing of a mold during the early stages of the cycle to permit the escape of air or gas from the heated compound.

Degradation: A deleterious change in the chemical structure, physical properties or appearance of a plastic caused by exposure to heat, light, oxygen, weathering or other external influence.

Delamination: When the surface of a finished part separates. Strata or fish-scale-type appearance may be visible where the layers may be separated.

Density: Mass per unit volume of a substance.

Design Review: A review of a blueprint, of an application, to be molded in a plastic material, with recommendations given for design, material, processing, tooling.

Diaphragm Gate: Used in symmetrical cavity filling to reduce weld-line formations and improve fill rates.

Dielectric Strength: The voltage that an insulating material can withstand before dielectric breakdown occurs.

Differential Cooling: occurs when one area of the part cools at a different rate or when the mold surfaces are at different temperatures. Warping can result from differential cooling.

Dimensional Stability: Retention of the precise shape of the part.

Direct Gate: A sprue that feeds directly into the mold cavity.

Discoloration: Any change from the designated color of the material or component.

Dispersion Aids: Flow alteration components placed at the entry point of an additive to aid in mixing or dispersing actions of a compounding process.

Dominant Flow Path: At the juncture of two confronting flows the dominant flow will reverse the direction of the other.

Draft: A Slight taper in a mold wall designed to facilitate removal of the molded object from the mold.

Drag Marks: A form of deep scratch or scratches on the surface of the component usually caused by the ejection of the part.

Drooling: The extrudate or leakage of molten resin from nozzle or nozzle sprue bushing area while filling or shooting the mold.

Drying: The removal of moisture from the resin pellets by exposure to certain time and temperature. All Hydroscopic Material must be dried prior to molding.

Durometer: An instrument used for measuring the hardness of a material.

Dwell :  A pause in the applied pressure to a mold during the injection cycle just before the mold is completely closed. This dwell allows any gases formed or present to escape from the molding material.


Casting: The process of forming solid or hollow articles from fluid plastic mixtures or resins by pouring or injecting the fluid into a mold or against a substrate with little or no pressure, followed by solidification and removal of the formed object.

Cavity: A depression, or a set of matching depressions, in a plastics-forming mold which forms the outer surfaces of the molded articles.

Charge: The amount of material used to load a mold at one time or during one cycle.

Charge: The measurement or weight of material necessary to fill a mold during one cycle.

Charpy Impact Test: A destructive test of impact resistance, consisting of placing a test coupon in a horizontal position between two supports, then applying a blow of known magnitude. If the specimen does not break, a new specimen is put in position and the magnitude is increased until the specimen breaks.

Chopped Strand: A type of fiber reinforcement consisting of strands of individual glass fibers which have been chopped into short pieces.

Clamp: The part of an injection molding machine incorporating the platens that provides the force necessary to hold the mold closed during injection of the molten resin and open the mold to eject the molded part.

Clamping Area: The largest rated molding area an injection press can hold closed under full molding pressure.

Clamping Force: The force applied to the mold to keep it closed, in opposition to the fluid pressure of the compressed molding material within the mold cavity and the runner system.

Clamping Plate: A plate fitted to a mold and used to fasten the mold to a platen.

Clamping Pressure: The pressure applied to the mold to keep it closed during the molding cycle.

Clarifiers: Additive used in resins to improve transparency or translucency.

Closed-loop Control: System for monitoring and automatically adjusting injection molding process conditions such as temperature, pressure and time. The automatic changes keep part production within preset tolerances.

Coefficient of Thermal Expansion (CTE): The change in length of a material for a unit change in temperature, per unit of length.

Co-Injection: Simultaneous or near simultaneous injection of multiple materials. Cold Flow Lines: Imperfections within the part wall due to thickening or solidification of resin prior to full cavity fill.

Cold Molding: The process of compression molding involving shaping an unheated compound in a mold under pressure then heating the article to cure it.

Color Concentrate (also know as Colorant, Pigment): A plastic compound which contains a high percentage of pigment, to be blended in appropriate amounts with the base resin so that the correct final color is achieved.

Composite: A structural non-homogenous material consisting of a combination of materials. Typically, one of the materials is a strengthening agent, the other being a thermoset or thermoplastic resin.

Compound: A mixture of resin(s) and additives usually formed in a separate machine downstream for the primary reactor.

Compounding: The process required to mix polymer(s) with all of the additives that are necessary to provide the end user with a finished grade with suitable properties.

Compression Molding: A method of molding in which the molding material, generally
horizontal position between two supports, then applying a blow of known magnitude. If the specimen does not break, a new specimen is put in position and the magnitude is increased until the specimen breaks.

Compression Molding: A method of molding in which the molding material, generally preheated, is placed in an open heated mold cavity, the mold is closed with a top force, the pressure is applied to force the material into contact with all mold areas.
Compressive Strength: The ability of a material to sustain a force in a direction opposite of tension.

Conditioning: Subjecting a material to standard environmental and/or a non-standard stress state prior to testing or use.

Constant pressure gradient: pressure drop per unit length. The constant pressure gradient principle says that the most efficient filling pattern is when the pressure gradient is constant along the flow path.

Cooling Channels: Channels located within the body of a mold through which a cooling medium is circulated to control the mold surface temperature.

Cooling time: the elapsed time required for the melt to reach it’s Vicat softening temperature.

Copolymer: The chemical reaction of two different monomers with each other, resulting in a unique new polymer.

Core: A protrusion, or set of matching protrusions, in a plastics forming mold which forms the inner surfaces of the molded articles.

Corona Treatment: Impingement of AC power on a component to bombard with free radicals thus improving the ability to bond to a surface.

Corrosion Resistance: A broad term applying to the ability of plastics to resist degradation in many environments, usually due to oxidation.

Crack/Splits/Chips: A physical separation or tearing of the part.

Crazing: Defect in plastics articles characterized by distinct surface cracks or minute frost-like internal cracks, resulting from stresses within the article which exceed the tensile strength of the plastic.

Creep: Due to its viscoelastic nature, a plastic subjected to a load for a period of time tends to deform more than it would from the same load released immediately after application, and the degree of this deformation is dependent of the load duration.

Cross-linking: The formation of chemical links between the molecular chains in polymers. This process can be achieved by chemical reaction, vulcanization, and electron bombardment.

Cryogenic Processes: Reduction of parts to very low temperatures usually associated with liquid nitrogen. Commonly used to create assemblies or to deflash or degate a part.

Crystal: A homogeneous solid having an orderly and repetitive three-dimensional arrangement of its atoms.

Crystallinity: A state of molecular structure in some resins attributed to the existence of solid crystals with a definite geometric form, Such structures are characterized by uniformity and compactness.

CSA: Abbreviation for the Canadian Standards Association.

C-stage: This term describes the final stage of the reaction where a thermoset material is relatively insoluble and infusible.

Cure Cycle: The time periods at defined conditions to which a reacting thermosetting material is processed to reach the desired property level.

Cure: The process of changing the properties of a polymer into a more stable and usable condition. This is accomplished by the use of heat, radiation, or reaction with chemical additives.


Back Pressure: The resistance of the molten plastic material to forward flow. In molding, back pressure increases the temperature of the melt, and contributes to better mixing of colors and homogeneity of the material. However, as back pressure increases, so does cycle time.
Backflow: molten resin flows back out of the mold, returning to the runners.
Backing Plate: A plate used as a support for the mold cavity block, guide pins, bushings, etc.
Balanced Runner: A runner system designed to place all cavities at the same distance from the sprue.
Barrel: The section of a molding machine that contains the feed screw, also the section where resin heating and mixing occurs.
Binder: A resin or other material used to hold particles together. The binder is the continuous phase in a reinforced plastic, which provides mechanical strength or ensures uniform consistency, solidification, or adhesion to a surface coating. Typical binder materials include resin, glue, gum and asein.
Biocides & Fungicides: Additives that are used to inhibit the growth and colonization of fungus, bacteria, and other pests.
Black Specks: A specific kind of inclusion/contamination often associated with heat-degraded materials.
Blast Finishing: The process of removing flash from molded objects and/or dulling their surfaces, by impinging upon them with sufficient force to remove the flash.
Blister: An imperfection on the surface of a plastic article caused by a pocket of air or gas beneath the surface.
Blocking & Anticaking Agents: These additives are used to prevent the adhesion and agglomeration of ingredients within a resin compound.
Bloom (also know as Migration): An undesirable cloudy effect or whitish powdery deposit on the surface of a plastic article or to the surrounding environment caused by the exudation of an ingredient such as a lubricant, stabilizer pigment, plasticizer, or other non-bonded component.
Blow Molding: Method of fabrication in which a warm plastic hollow tube is placed between the two halves of a mold cavity and forced to assume the shape of that mold cavity by use of internal pressure. This process forms hollow articles such as bottles, tanks, etc.
Blowing & Foaming Agents: Additives for plastics or rubbers that generate inert gases within the resin matrix when heated. The resulting part construction will contain a cellular structure.

Blushing: The tendency of a plastic article to turn white or chalky in areas that are highly stressed.
Boss: A raised feature of a molded part designed to add strength, facilitate alignment during assembly or for attachment to another part.
Branching: The modification of the molecular structure of a polymer derived from the growth of a new polymer chain from an active site on an established chain, in a direction different from that of the original chain.
Breakdown Voltage: The voltage required, under specific conditions, to cause failure of an insulation material.
Brighteners: Are used to add smoother or brighter coatings or finishes.
Brittle Temperature: A measure for judging the relative merits of materials for low-temperature flexing or impact – i.e., the temperature at which materials rupture by impact under specified conditions.
Broken Mold Marks: Part surface defects caused by mold damage.
B-stage: This describes an intermediate stage of a thermoset resin reaction where the material will soften when heated and swells in the presence of certain liquids, but may not completely fuse or dissolve. The resin is usually supplied in this uncured state.
Bubbles: Air or gas pockets that have formed in the material of the component. Bubbles may vary in size.
Bulk Density: A measurement of mass per unit volume of materials (such as powders) that describes the effects of the particle packing density.
Bulk Factor: The ratio of the volume of any given mass of loose plastic material to the volume of the same mass of the material after molding.
Bulk-molding compounds (BMC): Bulk-molding compounds are used as a premix in composite manufacturing. A BMC consists of a mixture of resin, reinforcements, inert fillers, and other additives which form a puttylike preformed shape, rope or sheet.
Burned: Showing evidence of excessive heating during processing or use of a plastic, as evidenced by blistering, discoloration, distortion or destruction of the surface.