Glossary of terms used in plastic injection molding

GLOSSARY OF TERMS – PLASTIC INJECTION MOLDING

Accumulator – A device that stores energy for quick injection of plastic.
Additive – A substance added to resin to improve or modify properties.
Annealing – A heat treatment process to relieve stress in molded parts.
Antioxidant – An additive that prevents degradation of plastic due to oxidation.
Back Pressure – Resistance applied to the screw during recovery to improve mixing.

B

Barrier Screw – A type of screw used in injection molding to enhance mixing and melting.
Blush – A surface defect that appears as a cloudy or dull spot on a molded part.
Boss – A raised feature on a molded part, typically used for fastening or alignment.
Brittleness – The tendency of a material to break or crack without significant deformation.
Burn Mark – A black or dark brown discoloration on a molded part caused by trapped air or excessive heat.

C

Clamp Force – The force applied by the machine to keep the mold closed during injection.
Cold Runner – A channel in the mold that guides molten plastic to the cavities without being heated.
Core – The part of the mold that creates internal features in a molded part.
Crazing – Fine cracks that appear on the surface of a molded part due to stress.
Cycle Time – The total time required to complete one injection molding process, from closing the mold to ejecting the part.

D

Degassing – The process of removing trapped air or gas from the mold or material.
Delamination – Separation of layers in a molded part, often caused by contamination or poor adhesion.
Draft Angle – The taper on a molded part’s surface to facilitate easy removal from the mold.
Drying Hopper – Equipment used to remove moisture from plastic pellets before molding.
Ductility – The ability of a material to deform without breaking under tensile stress.

E

Ejector Pins – Pins that push the molded part out of the mold during ejection.
Elastomer – A rubber-like material that can stretch and return to its original shape.
Embossing – Creating raised or recessed designs on a molded part’s surface.
End of Arm Tooling (EOAT) – Custom tools attached to a robot for handling parts during molding.
Entrapped Air – Air pockets that get trapped inside a molded part, causing defects.
Erosion – Wear on the mold surface due to continuous exposure to molten plastic.
EVA (Ethylene Vinyl Acetate) – A flexible, rubbery plastic often used in foam applications.
Exothermic Reaction – A chemical reaction that releases heat during curing or processing.
Extruder – A machine that melts and forms plastic by forcing it through a die.
Eye Bolt – A threaded fastener used for lifting and positioning molds.

F

Family Mold – A mold with multiple cavities producing different parts in one cycle.
Fan Gate – A wide, thin gate that helps reduce shear and improve part quality.
Fatigue – The weakening of material due to repeated stress over time.
Fill Time – The time it takes for the mold cavity to fill with molten plastic.
Flash – Excess plastic that flows outside the cavity, creating a thin ridge on the part.
Flow Lines – Visible streaks or patterns caused by improper flow of plastic in the mold.
Foaming Agent – A chemical used to create bubbles in plastic, reducing density and weight.
Friction Heat – Heat generated by the movement of the screw and molten plastic.
Full Shot – A shot size that completely fills the mold cavity without short shots or voids.
Funnel Gate – A gate shaped like a funnel to direct plastic into the cavity.

G

Gate – The opening through which molten plastic enters the mold cavity.
Glass-Filled Plastic – Plastic reinforced with glass fibers for added strength.
Gusset – A rib-like feature added to a molded part to increase strength and stability.
Guide Pin – A pin used to align the mold halves during closure.
Gating System – The network of channels that delivers plastic from the runner to the cavity.
Gelation – The point at which plastic starts to solidify during cooling.
Gloss Level – The shininess or dullness of a molded part’s surface.
Grain Texture – A surface finish applied to the mold to create texture on the part.
Gate Vestige – The small remnant of plastic left where the gate is trimmed.
Ground Plastic – Recycled plastic that has been ground into pellets for reuse.

H

Heat Sink – A component that absorbs and dissipates heat to prevent overheating.
Hopper – A container used to feed plastic pellets into the injection molding machine.
Hot Runner – A mold system that keeps the plastic molten, reducing waste and improving cycle time.
Hydraulic Press – A press powered by hydraulic fluid to apply clamping force on the mold.
Hygroscopic Material – Plastic that absorbs moisture from the air (e.g., nylon, PET).
Hot Tip – A heated gate design used in hot runner systems to maintain molten plastic flow.
Homopolymer – A polymer made from a single type of monomer, offering uniform properties.
Heat Deflection Temperature (HDT) – The temperature at which plastic deforms under stress.
Hardness – A measure of a material’s resistance to indentation or scratching.
Hot Melt Adhesive – A thermoplastic adhesive that melts when heated and solidifies upon cooling.

I

Injection Pressure – The pressure used to push molten plastic into the mold cavity.
Insert Molding – A process where pre-formed inserts (usually metal) are placed in the mold before injection.
Impact Strength – The ability of a material to resist impact without cracking or breaking.
In-Mold Labeling (IML) – A process where labels are placed in the mold and bonded to the part during injection.
Isotropic – Having the same properties in all directions.
Injection Unit – The part of the machine that melts and injects plastic into the mold.
Insulator Plate – A plate used to reduce heat transfer between the mold and platen.
Irradiation Cross-Linking – A process that improves material properties through radiation.
Isocyanate – A component used in the production of polyurethane plastics.
Insert – A pre-formed part (metal, ceramic, etc.) placed in the mold to be encapsulated by plastic.

J

Jetting – A defect caused by high-pressure plastic squirting into the cavity, resulting in a snake-like pattern.
Jig – A custom tool used to hold parts in place during machining or assembly.
Junction Line – The line where two flow fronts of plastic meet in the cavity.
Just-In-Time (JIT) – A production strategy to minimize inventory by receiving materials only as needed.
Jounce Bumper – A molded part used in automotive suspension systems for impact absorption.

K

Knit Line – A weak spot where two flow fronts meet and fail to fuse properly.
Kevlar-Filled Plastic – Plastic reinforced with Kevlar fibers for increased toughness.
Keyway – A slot or groove in a molded part for alignment or assembly purposes.
Kelvin – A temperature scale often used in material testing.
Knockout Pin – Another term for an ejector pin that removes the molded part from the cavity.

L

Lamination – Layers of plastic fused together to improve strength and reduce permeability.
Latch Lock – A mechanism used to keep the mold closed during injection.
Living Hinge – A thin, flexible hinge made of plastic, molded as part of the main body.
Lubricant – An additive used to reduce friction and improve flow during processing.
Luminous Plastic – Plastic that glows in the dark, often used for novelty items.
Linearity – The degree to which a material maintains consistent properties in one direction.
Low-Density Polyethylene (LDPE) – A soft, flexible plastic with good impact resistance.
Light Pipe – A clear molded part used to transmit light from an LED.
Lifter – A mold component that moves to release undercuts during part ejection.
Laminar Flow – A smooth, uniform flow of molten plastic into the cavity

M

Manifold – A component in a hot runner system that distributes molten plastic to multiple cavities.
Melt Flow Index (MFI) – A measure of the flow rate of melted plastic under specific conditions.
Masterbatch – A concentrated mixture of pigments or additives used to color plastic.
Multi-Cavity Mold – A mold that produces multiple identical parts in a single cycle.
Mold Base – The main structure of a mold that holds all the components together.
Mold Release Agent – A substance applied to the mold to prevent parts from sticking.
Molecular Weight – The average mass of molecules in a polymer, affecting its strength and flow.
Moiré Pattern – A visual defect that appears as a repetitive, wavy pattern on molded parts.
Modulus of Elasticity – A measure of a material’s stiffness or resistance to deformation.
Melt Temperature – The temperature at which plastic becomes molten and can flow.

N

Nozzle – The part of the injection molding machine that directs molten plastic into the mold.
Non-Return Valve – A valve in the injection unit that prevents backflow of molten plastic.
Nylon – A strong, durable engineering plastic often used for mechanical components.
Notch Sensitivity – The tendency of a material to crack at a notch or sharp corner.
Necking – A defect where a molded part becomes thinner in certain areas due to stress.
Nominal Wall Thickness – The intended thickness of the molded part’s walls.
Nitrogen Purging – A process to remove oxygen and moisture from the molding environment.
Negative Draft – A draft angle that prevents easy part ejection from the mold.
Non-Fill – A defect where the mold cavity is not fully filled with plastic.
Notched Izod Impact Test – A test that measures the impact resistance of notched plastic samples.

O

Overmolding – The process of molding a second layer of plastic over an existing part.
Optical Clarity – The transparency of a molded part, often important for lenses and covers.
Orifice Gate – A small, circular gate used to control plastic flow into the cavity.
Orange Peel – A surface defect that resembles the texture of an orange peel.
Offset Core – A mold core positioned off-center to create a specific feature in the part.
Outgassing – The release of gases from the plastic during molding, which can cause defects.
Overflow Groove – A channel in the mold to capture excess plastic and prevent flash.
Oxygen Barrier – A material property that prevents oxygen from passing through the plastic.
Overpacking – Injecting too much plastic, leading to stress and deformation in the part.
Open Nozzle – A nozzle without a valve, allowing plastic to flow freely when pressure is applied.

P

Parting Line – The line where two mold halves meet, often visible on the molded part.
Polycarbonate (PC) – A tough, transparent plastic with high impact resistance.
Pressure Profile – The sequence of pressure changes during the injection process.
Pack and Hold – A stage in the molding process where pressure is maintained to reduce shrinkage.
Polypropylene (PP) – A lightweight, flexible plastic used in packaging and consumer goods.
Pin Gate – A small gate that leaves minimal vestige on the part after trimming.
Preform – A partially molded part, typically used in blow molding.
Purging Compound – A cleaning material used to remove residual plastic from the machine.
Projection – A raised feature on a molded part for alignment or attachment.
Polyethylene (PE) – A common plastic known for its flexibility and moisture resistance.

Q

Quality Assurance (QA) – A process to ensure molded parts meet specified quality standards.
Quenching – Rapid cooling of a molded part to set its shape and improve properties.
Quick Mold Change (QMC) – A system to reduce downtime by enabling faster mold changes.
Quarter-Degree Draft – A small draft angle used for parts with minimal taper requirements.
Quench Line – A visible line on a molded part caused by sudden cooling.

R

Runner – A channel in the mold that directs molten plastic from the sprue to the cavities.
Regrind – Recycled plastic from rejected parts or excess material, ground into pellets for reuse.
Rib – A thin wall feature added to improve strength and stiffness of a molded part.
Radial Gate – A gate designed in a circular pattern for uniform flow into the cavity.
Reinforced Plastic – Plastic combined with fibers or fillers to improve strength and performance.
Rapid Prototyping – Fast fabrication of prototype parts using 3D printing or other technologies.
Residence Time – The duration molten plastic remains in the injection unit before injection.
Rockwell Hardness – A scale used to measure the hardness of plastic materials.
Rotary Mold – A mold with rotating cavities for multi-shot or multi-color molding.
Runner Balancing – Designing runners to ensure even plastic flow to all cavities.

S

Short Shot – A defect where the mold cavity is not fully filled with plastic.
Shear Rate – The rate at which plastic layers move relative to each other during flow.
Shrinkage – The reduction in part size as the plastic cools and solidifies.
Side Action – A mold feature that moves sideways to create undercuts or side holes.
Snap-Fit – A joint that allows parts to be assembled without fasteners.
Sprue – The main channel through which molten plastic enters the runner system.
Submarine Gate – A gate located below the parting line, leaving no visible mark.
Splay – A cosmetic defect caused by moisture or trapped air, resulting in streaks on the part.
Screw L/D Ratio – The ratio of screw length to its diameter, affecting plasticizing performance.
Stack Mold – A multi-level mold that increases production capacity without enlarging the machine.

T

Tensile Strength – The maximum stress a plastic can withstand while being stretched.
Tooling – The design and fabrication of molds and other tools for injection molding.
Thermoplastic – A type of plastic that becomes soft when heated and hardens upon cooling.
Texture Finish – A patterned surface applied to molds for aesthetic or functional purposes.
Tie Bars – Steel rods in the molding machine that maintain clamping force.
Transfer Molding – A process similar to injection molding, often used for thermoset materials.
Two-Shot Molding – A process that combines two different materials in a single part.
Toggle Clamp – A clamping mechanism using a toggle linkage for applying force to the mold.
Thermal Degradation – The breakdown of plastic due to excessive heat.
Threaded Insert – A metal insert with internal threads for attaching fasteners to a molded part.

U

Undercut – A feature that prevents the molded part from being ejected straight from the mold.
Ultrasonic Welding – A process to join plastic parts using high-frequency vibrations.
Uniform Wall Thickness – Consistent wall thickness to reduce warping and improve strength.
UV Stabilizer – An additive that protects plastic from ultraviolet light degradation.
Utility Mold – A basic mold design used for prototype or low-volume production.

V

Vent – A small channel in the mold to allow trapped air to escape.
Vacuum Forming – A process where plastic is heated and formed over a mold by applying a vacuum.
Viscosity – A measure of how easily molten plastic flows.
Vacuum Loading – Using a vacuum to transfer plastic pellets to the hopper.
Valve Gate – A gate system with a valve to control plastic flow, reducing gate vestige.

W

Warping – A defect where the molded part distorts due to uneven cooling or internal stresses.
Water Cooling – A method of cooling the mold using water channels for temperature control.
Weld Line – A visible line on the molded part where two plastic flow fronts meet.
Wall Thickness – The thickness of the walls in a molded part, affecting strength and cooling time.
Wear Plate – A replaceable plate in the mold to protect it from wear and tear.
Whitish Mark – A cosmetic defect caused by moisture or excessive pressure during molding.
Witness Mark – A visible mark left on the part from the molding process, such as from a gate or ejector pin.
Wireframe Model – A 3D model showing the shape of a part using lines and curves without solid surfaces.
Workpiece – The part or material being processed during injection molding.
Wraparound Insert – An insert that encircles the part for added strength or functionality.

X

Xylene Test – A test to determine the resistance of plastic to certain solvents like xylene.
X-Axis Movement – Horizontal movement in the mold or injection machine for positioning.
Xenon Arc Test – A test to simulate long-term exposure to sunlight for UV resistance evaluation.
X-Ray Inspection – A non-destructive test method to detect internal defects in molded parts.
Xenoy® – A blend of polycarbonate and polyester with high impact resistance and chemical stability.

Y

Yield Point – The stress level at which plastic deforms permanently.
Yellowing – Discoloration of plastic due to UV exposure, oxidation, or thermal degradation.
Y-Tube Runner – A runner design shaped like a Y for balanced flow distribution.
Yarn Reinforcement – Fibers woven into a matrix to reinforce the plastic material.
Young’s Modulus – A measure of the elasticity of a material, indicating its stiffness.

Z

Zebra Stripe Defect – A visual defect where alternating light and dark bands appear on the surface.
Z-Movement – Vertical movement in the injection molding process, such as mold opening and closing.
Zero Draft – A straight-walled mold design with no taper, making part ejection more difficult.
Zone Heating – Dividing the mold into multiple heating zones for precise temperature control.
Zytel® – A brand of nylon resin known for toughness, chemical resistance, and durability.

A (continued)

Annealing – A heat treatment process to reduce internal stresses in molded parts.
Anti-Static Agent – An additive used to reduce static electricity buildup on plastic surfaces.
Abrasion Resistance – The ability of plastic to withstand surface wear and friction.
Accumulator – A device in the injection unit that stores and releases high-pressure plastic.
Actuator – A mechanical device that moves or controls mold components like slides or ejectors.
Additive Masterbatch – A concentrated mixture of additives to modify plastic properties.
Air Trap – Pockets of air trapped inside the mold, causing defects like voids or burns.
Alignment Pin – A pin that ensures proper alignment of mold halves during closing.
Amorphous Polymer – A polymer with a random molecular structure, typically transparent (e.g., ABS, PC).
Automatic Shutoff Nozzle – A nozzle with a valve to prevent plastic drooling when not injecting.

B (continued)

Back Pressure – The resistance applied to the screw during plasticizing to improve mixing.
Brittleness – The tendency of a plastic to crack or break under stress without significant deformation.
Blow Molding – A process for making hollow plastic parts by inflating a heated preform in a mold.
Breakaway Force – The force required to eject a part from the mold.
Bead Blast Finish – A textured mold surface created by blasting it with fine beads for a matte appearance.
Barrel – The cylindrical component of the injection unit that houses the screw and melts plastic.
Bridge Gate – A gate design that allows plastic to flow around an insert or obstacle.
Boss – A raised cylindrical feature used for fastening or alignment on a molded part.
Blush – A cosmetic defect appearing as a dull, whitish mark near the gate.
Bi-Injection Molding – A process where two different plastics are injected into the same mold sequentially.

C (continued)

Core Pull – A mechanism that moves mold cores to form undercuts or side features.
Cooling Channel – A network of channels in the mold for water flow to cool the plastic.
Creep – The gradual deformation of plastic under continuous stress.
Chemical Foaming Agent – An additive used to reduce part weight and create a cellular structure.
Cavity Insert – A removable insert in the mold cavity for easier maintenance or customization.
Cycle Time – The total time required to produce one molded part, including injection, cooling, and ejection.
Charge Time – The time taken for the screw to retract and plasticize material for the next shot.
Compression Molding – A molding process where plastic is compressed into shape using heat and pressure.
Cold Slug – A portion of cooled plastic that can block the gate or cause defects in the part.
Conformal Cooling – Cooling channels designed to follow the mold contour for more uniform cooling.

D

Dampening Time – The time required to slow down the movement of mold components to avoid impact.
Debossing – A process to create recessed features or text on the surface of molded parts.
Degassing – The removal of trapped gases from molten plastic before injection.
Delamination – A defect where thin layers of plastic peel or separate from the part’s surface.
Density – The mass per unit volume of a material, affecting part weight and strength.
Dielectric Strength – The maximum electric field a plastic can withstand without breaking down.
Dimensional Stability – The ability of plastic to retain its dimensions under varying conditions.
Draft Angle – An angled feature on mold walls to ease part ejection.
Deflashing – The process of removing excess material (flash) from molded parts.
Desiccant Dryer – A machine that removes moisture from hygroscopic plastics using desiccant beads.

E

Ejector Pin – A pin that pushes the molded part out of the mold cavity during ejection.
Edge Gate – A gate located at the part’s edge for easy removal and minimal cosmetic impact.
Elongation at Break – The amount a plastic stretches before breaking, expressed as a percentage.
Engraving – Adding raised or recessed designs on a mold surface for branding or text.
Endothermic Reaction – A chemical reaction that absorbs heat, often used in foaming agents.
Elastic Modulus – A measure of a material’s stiffness, indicating how much it resists deformation.
Encapsulation – Completely surrounding an insert or component with plastic during molding.
Energy Chain – A flexible chain that protects and guides machine cables and hoses.
Ejector Plate – A plate that holds multiple ejector pins and moves them simultaneously.
Exothermic Reaction – A chemical reaction that releases heat, commonly found in thermoset curing.

F

Family Mold – A mold with multiple cavities for different parts made in a single cycle.
Fill Time – The time taken to fill the mold cavity with molten plastic.
Fan Gate – A wide gate used to reduce stress and improve flow in large parts.
Flash – Excess plastic that escapes the mold cavity at the parting line, requiring removal.
Fiber Reinforcement – Adding glass, carbon, or other fibers to enhance the mechanical properties of plastic.
Flow Lines – Visible marks on the part surface caused by variations in plastic flow.
Fillet Radius – A rounded transition between surfaces to reduce stress concentration.
Flow Rate – The volume of plastic passing through a given point per unit of time.
Fixture – A tool or device that holds a part in place during secondary operations.
Foam Molding – A process to create lightweight parts with a foamed core and solid outer layer.

G

Gate – The entry point where molten plastic flows into the mold cavity.
Gas Assist Molding – A process that uses pressurized gas to hollow out thick sections, reducing weight.
Glass Transition Temperature (Tg) – The temperature where plastic changes from rigid to rubbery.
Glow-Wire Test – A test to determine the flame resistance of plastic materials.
Gusset – A rib-like structure used to reinforce corners and improve strength.
Graining – A texture applied to the mold surface for a specific appearance or grip.
Gate Vestige – A small mark left on the part where the gate was removed.
Guide Pin – A pin that ensures alignment of mold halves during closing.
Gating System – The network of sprues, runners, and gates directing plastic flow.
Grounding Insert – A metal insert used to create an electrical ground in molded parts.

H

Hot Runner System – A system that keeps plastic molten in runners, reducing waste and cycle time.
Hygroscopic – Describes plastics that absorb moisture from the air (e.g., nylon).
Hopper Dryer – A drying unit that removes moisture from plastic pellets before molding.
Heat Deflection Temperature (HDT) – The temperature at which plastic deforms under a specific load.
Hinge Gate – A gate used for parts with integrated hinges, ensuring flexibility.
Hot Tip – The heated end of a hot runner nozzle, ensuring consistent plastic flow.
Hydraulic Press – A machine that uses hydraulic pressure to close and clamp the mold.
Hardness – A measure of a material’s resistance to surface deformation.
Homopolymer – A polymer made from a single type of monomer, offering consistent properties.
Heat Sink – A component that absorbs and dissipates heat from a part or mold.

I

Impact Modifier – An additive that improves the impact resistance of plastic.
Injection Pressure – The force used to push molten plastic into the mold cavity.
Injection Speed – The rate at which molten plastic is injected into the mold.
Insert Molding – A process that molds plastic around a pre-placed insert (usually metal) for added strength or functionality.
Injection Unit – The part of the injection molding machine responsible for melting and injecting plastic.
Inspection Fixture – A tool used to check the dimensional accuracy of molded parts.
Interlock – A device that ensures mold halves align correctly during closure.
ISO Certification – International standards for quality and safety in manufacturing processes.
In-Mold Decoration (IMD) – A process where decorative films are applied inside the mold for high-quality finishes.
Ionomer – A copolymer known for high impact strength and clarity.

J

Jetting – A defect caused by high-speed plastic flow, leaving snake-like marks on the part surface.
Junction Line – Another term for weld line, where two flow fronts meet.
Jig – A custom tool used to hold or guide parts during assembly or secondary operations.
Joint Strength – The strength at the point where different materials or sections meet in the part.
Jaw Inserts – Replaceable components in clamps used for gripping and handling parts.
Just-In-Time (JIT) – A manufacturing strategy to produce parts only as needed, reducing inventory costs.
Jounce Bumper – A molded part used in automotive suspension systems for impact absorption.
Joule Heat – Heat generated by electrical resistance in conductive materials.
J-Slot Gate – A gate design shaped like a “J” for controlled plastic flow.
Junction Box – An enclosure for protecting electrical connections, often made using injection molding.

K

Knockout Pin – Another term for ejector pin, used to push parts out of the mold.
Knit Line – A type of weld line that occurs when plastic flows around an obstacle and rejoins.
Kevlar® Reinforcement – Adding Kevlar fibers to plastic for improved tensile strength and abrasion resistance.
K-Factor – A coefficient used to describe shrinkage behavior in plastic.
Keep Plate – A mold plate that holds cavity and core inserts in position.
Keyway – A slot or groove in a mold used for precise alignment of components.
Knurling – A surface finish with ridged patterns for grip or decorative purposes.
Kelvin Scale – A temperature scale used in scientific measurements, including mold temperature settings.
Knockout Plate – A plate that moves ejector pins during part ejection.
K-Resin – A styrene-butadiene copolymer known for transparency and toughness.

L

Laminating – The process of bonding layers of plastic together for enhanced properties.
Land Area – The flat area around a gate that controls plastic flow into the mold cavity.
Living Hinge – A thin, flexible section of plastic that allows a part to bend repeatedly without breaking.
Lubricant Additive – A compound added to plastic to reduce friction during molding or operation.
Loading Arm – A device used to place inserts into the mold during automated processes.
Latent Heat – Heat energy required for phase changes in plastic without changing its temperature.
Light Pipe – A molded component that guides light from a source to another location, often used in electronics.
Locking Plate – A mold plate that locks core and cavity components in position.
LCP (Liquid Crystal Polymer) – A high-performance plastic with excellent chemical resistance and thermal stability.
Lubricity – The measure of a material’s smoothness and ability to reduce friction.

M

Melt Flow Index (MFI) – A measure of the flow rate of molten plastic, indicating its viscosity.
Multi-Cavity Mold – A mold with multiple cavities for producing multiple parts simultaneously.
Masterbatch – A concentrated mixture of pigments or additives for coloring or modifying plastic properties.
Mold Base – The main structure of the mold, holding cavity and core inserts.
Mold Flash – Excess plastic that leaks out of the mold cavity along the parting line.
Mold Flow Analysis – A simulation used to predict plastic flow behavior and optimize mold design.
Mechanical Properties – Physical properties of plastic like strength, flexibility, and toughness.
Mold Lifters – Mold components that lift undercut features for easy ejection.
Mold Temperature Controller (MTC) – A device that regulates mold temperature for consistent part quality.
Molded-In Stress – Internal stresses in a part caused by uneven cooling or molding conditions.

N

Nest – The cavity in a mold that forms the external shape of the molded part.
Non-Fill – A defect where the mold cavity is not completely filled with plastic.
Nozzle – The tip of the injection molding machine that directs molten plastic into the mold.
Nylon (PA) – A versatile, strong, and abrasion-resistant thermoplastic commonly used in injection molding.
Notch Sensitivity – A material’s tendency to fracture at a notch or sharp corner.
Nominal Wall Thickness – The target thickness of a part’s walls for optimal strength and performance.
Nozzle Heater Band – A heating element wrapped around the nozzle to maintain plastic temperature.
Nitrogen Gas Assist – A process that injects nitrogen to create hollow sections in thick-walled parts.
Non-Return Valve – A valve in the injection molding screw that prevents backflow of molten plastic.
Nitriding – A surface hardening process for mold components to improve wear resistance.

O

Offset Gate – A gate positioned away from the center of a part to improve flow distribution.
Overmolding – The process of molding one material over another to create multi-material parts.
Open Loop Control – A control system without feedback, relying on preset parameters.
Orientation – The alignment of plastic molecules during molding, affecting part strength and shrinkage.
O-Ring Groove – A feature molded into parts to hold O-rings for sealing applications.
Oxidation Resistance – The ability of a plastic to withstand exposure to oxygen without degradation.
Operator Station – The area where the machine operator controls the injection molding process.
Outgassing – The release of gases from plastic during molding, which can cause surface defects.
Optical Clarity – A measure of how transparent a plastic material is.
Overspray – Excess coating material that extends beyond the intended area in secondary processes.

P

Parting Line – The line on a molded part where the two halves of the mold meet.
Packing Pressure – The pressure applied after filling to compact the plastic and reduce shrinkage.
Polycarbonate (PC) – A strong, impact-resistant plastic with excellent optical properties.
Pinch-Off – The area of the mold that seals and cuts off the flow of plastic in certain molding processes.
Post-Mold Shrinkage – The additional shrinkage that occurs after the part is removed from the mold.
Purging Compound – A cleaning material used to remove residues from the molding machine.
Preform – A partially molded component that is later reshaped or overmolded.
Prototype Mold – A temporary mold used for testing and development before creating a production mold.
Polymer Chain – The repeating molecular structure of plastics that determines their properties.
Pad Printing – A process for applying images or text to molded parts using silicone pads.

Q

Quick Mold Change (QMC) – A system that speeds up mold changeover time.
Quenching – Rapid cooling of parts to improve their properties or prevent warping.
Quality Assurance (QA) – Procedures to ensure molded parts meet specified standards.
Quantitative Analysis – A data-driven approach to measure and evaluate process performance.
Quarter Mold – A mold that produces a quarter of a complete part, later assembled.
Quick Ejector System – A mechanism for fast and reliable part ejection.
Quality Control (QC) – The monitoring of production to detect defects in real time.
Quartz Heater – An infrared heater used to preheat molds or plastic materials.
Quench Tank – A tank used for cooling and solidifying extruded parts.
Quick Connect Coupling – A fitting for fast connection of cooling lines or air supply.

R

Runner – The channel that directs molten plastic from the sprue to the mold cavity.
Regrind – Recycled plastic from rejected parts or runners, often mixed with virgin material.
Resin – The raw plastic material used in injection molding.
Rib – A thin support feature in molded parts for added strength and rigidity.
Rotational Molding – A process for creating hollow plastic parts by rotating molds in multiple axes.
Rockwell Hardness – A measure of a material’s hardness using a Rockwell scale.
Radiused Edge – A rounded edge on a mold or part to reduce stress concentration.
Rotating Core – A mold component that rotates to create threads or undercuts.
Reverse Engineering – The process of analyzing a molded part to recreate its design.
Release Agent – A chemical applied to the mold surface to prevent sticking and improve part release.

S

Screw Barrel – The heated chamber in an injection molding machine where plastic is melted and conveyed.
Shear Rate – The rate at which plastic layers slide over one another during injection, affecting viscosity.
Shrinkage – The reduction in size of a molded part as it cools and solidifies.
Sprue – The main channel that carries molten plastic from the injection nozzle to the runner system.
Submarine Gate – A gate located beneath the part surface for automatic separation during ejection.
Semi-Crystalline Polymer – A plastic with both amorphous and crystalline regions, offering high strength and chemical resistance.
Stress Cracking – Cracks caused by internal or external stresses on molded parts.
Shot Size – The volume of molten plastic injected into the mold for each cycle.
Silicone Mold – A flexible mold used for rapid prototyping and low-volume production.
Surface Finish – The texture or smoothness of a molded part’s surface.
Stack Mold – A multi-level mold that increases production capacity without needing a larger machine.
Static Mixer – A device used to mix plastic uniformly inside the injection barrel.
Sprue Bushing – A component that aligns the sprue with the machine nozzle and mold.
Snap Fit – A molded feature that allows parts to be assembled without fasteners.
Stiffness – The ability of a molded part to resist deformation under load.
Sprue Puller – A feature that ensures the sprue is removed along with the molded part during ejection.
Shut-Off Valve – A valve that controls plastic flow into the mold.
Sliders – Mold components that move laterally to form undercuts or complex shapes.
Spray Coating – A secondary process for adding protective or decorative finishes to molded parts.
Short Shot – A defect caused by insufficient plastic filling the mold cavity.

T

Thermoplastic – A plastic that can be melted and reformed multiple times.
Tie Bars – Steel rods that hold the mold platens together under clamping force.
Tooling – The mold and related equipment used to produce injection-molded parts.
Transfer Mold – A mold that moves inserts or components during the molding process.
Tensile Strength – The maximum stress a plastic can withstand when stretched.
Thermal Conductivity – The ability of a material to conduct heat, affecting cooling rates.
Tapered Pin – A pin with a slight taper for precise alignment in molds.
Two-Shot Molding – A process that injects two different plastics in a single mold for multi-material parts.
Tumbling – A finishing process where parts are placed in a rotating drum with abrasive media for smoothing.
Threaded Insert – A metal insert molded into plastic for securing screws or bolts.
Thermocouple – A device for measuring mold temperature.
Toughness – The ability of a plastic to absorb energy without breaking.
Tool Life – The expected lifespan of a mold before it requires replacement or major repair.
Texturing – The process of adding patterns or roughness to a mold surface for improved aesthetics or grip.
Trim Line – The line where excess plastic is removed from a molded part.
Toggle Clamp – A clamping mechanism used in injection molding machines to apply clamping force.
Tab Gate – A type of gate that leaves a tab on the molded part, later trimmed off.
Thermoforming – A process for shaping plastic sheets using heat and pressure.
Thin-Wall Molding – The process of molding parts with extremely thin walls for lightweight applications.
TPE (Thermoplastic Elastomer) – A rubber-like plastic that can be processed using injection molding.

U

Undercut – A feature that prevents the part from being ejected straight out of the mold.
Ultrasonic Welding – A process that joins plastic parts using high-frequency vibrations.
Uniform Wall Thickness – Ensuring consistent wall thickness for strength and dimensional stability.
UV Stabilizer – An additive that protects plastic from degradation caused by UV light.
Utility Core – A core used for molding internal features such as holes or recesses.
Unfilled Resin – A plastic material without added fillers or reinforcements.
Unscrewing Mold – A mold with rotating cores for creating threaded parts.
Underfill – An incomplete filling of the mold cavity, resulting in missing material.
Urethane – A plastic known for its flexibility and toughness.
Upstream Process – The initial steps in injection molding, including material preparation and mold setup.

V

Vent – A small opening in the mold to allow air to escape during injection.
Viscosity – A measure of how easily plastic flows when melted.
Volatile Organic Compounds (VOCs) – Emissions from plastic that can affect air quality.
Vacuum Forming – A process where plastic sheets are shaped using a vacuum.
Valve Gate – A gate that opens and closes using a valve mechanism for precise control.
Vertical Press – An injection molding machine with a vertical clamping orientation.
Vent Depth – The depth of the mold vent, crucial for air release without plastic escape.
Vibration Welding – Joining plastic parts using high-frequency vibrations.
Vinyl (PVC) – A durable plastic used in a wide range of applications.
Void – An air pocket or empty space inside a molded part.

W

Warping – A distortion in the molded part caused by uneven cooling or residual stresses.
Water-Cooled Mold – A mold with internal water channels to speed up cooling.
Weld Line – A visible line on the molded part where two flow fronts meet and fuse.
Weight Tolerance – The acceptable variation in part weight due to process fluctuations.
Wear Resistance – The ability of a material or mold component to resist abrasion or surface damage.
Witness Mark – A slight indentation or mark left on the part from a mold feature.
Wide-Spec Resin – A less expensive resin with wider property tolerances, often used for non-critical parts.
Window Defect – A transparent or cloudy area on a molded part caused by inconsistent material flow.
Wiper Seal – A seal used to prevent plastic leakage in moving mold components.
Wireframe Model – A 3D model consisting only of lines and vertices, used for mold design and simulation.

X

X-Axis Movement – The horizontal movement of the mold or machine components.
Xylene – A solvent occasionally used for cleaning or processing plastics.
X-Ray Inspection – A non-destructive testing method to check internal features or defects in parts.
Xenon Test – A test for UV resistance using simulated sunlight.
X-Linking (Cross-Linking) – A process that connects polymer chains to improve mechanical properties.
X-Section – A cross-sectional view of a part or mold to analyze internal features.
Extrusion Crosshead – A device for distributing plastic in cross-sectional shapes during extrusion.

Y

Yield Strength – The stress level at which a plastic permanently deforms.
Yellowing – Discoloration caused by heat, light, or chemical exposure.
Y-Split Runner – A runner system branching into two paths to balance flow.
Yoke Clamp – A clamp system that holds the mold shut during injection.
Young’s Modulus – A measure of a material’s stiffness or elasticity.
Y-Injection – A multi-directional injection technique used for complex molds.
Yarn Reinforcement – Fibers added to plastic for increased strength and durability.

Z

Zero Draft – A mold design without taper, used for straight vertical walls on parts.
Z-Axis Movement – Vertical movement in mold components or machines.
Zinc Alloy Insert – A metal insert made of zinc for added strength and corrosion resistance.
Zytel – A DuPont brand of nylon resins commonly used in injection molding.
Zone Heating – A heating system that divides the mold into zones for precise temperature control.
Zebra Striping – A defect in molded parts with alternating light and dark bands due to uneven flow.
Z-Level Milling – A machining process used to create complex mold surfaces.
Zero Shrinkage Material – Special plastics designed to minimize dimensional changes during cooling.
Zinc Stearate – A mold release agent and lubricant used in plastic processing.
Zipper Effect – A sudden crack propagation in molded parts caused by high stress concentrations.

A

ABS (Acrylonitrile Butadiene Styrene) – A durable, impact-resistant thermoplastic often used in automotive components, consumer electronics (e.g., phone cases), and toys like LEGO bricks.
Additives – Substances mixed into plastics to enhance properties like UV resistance, flame retardancy, or color. For example, UV stabilizers are critical in outdoor furniture to prevent sun damage.
Amorphous Polymer – A type of plastic with no organized crystalline structure, making it transparent and easy to thermoform (e.g., acrylic and polycarbonate).
Annealing – A heat treatment process that reduces residual stresses in molded parts, improving dimensional stability and reducing the chance of cracking.
Anisotropy – When a material exhibits different properties (like strength or shrinkage) in different directions due to fiber orientation or flow patterns. This is common in reinforced plastics.
As-Molded Condition – The state of a plastic part immediately after ejection, before any secondary processes like trimming or painting.
Automatic Degating – A feature in molds where gates are trimmed automatically during ejection, reducing the need for manual labor.
Auxiliary Equipment – Machines supporting the molding process, such as dryers for removing moisture from resins, chillers for cooling water, and granulators for regrinding scrap plastic.

B

Back Pressure – Resistance applied to the screw during plasticizing, ensuring the melt is homogeneous and air bubbles are eliminated. Excessive back pressure can degrade the material.
Bimetallic Barrel – A barrel with a wear-resistant inner lining to handle abrasive or corrosive materials like glass-filled resins or PVC.
Blistering – A surface defect caused by trapped gas or improper cooling, resulting in bubbles or raised areas on the molded part.
Brittleness – The tendency of a material to break or shatter under stress rather than deform. Polystyrene, for instance, is brittle compared to polypropylene.
Burn Mark – A dark spot or discoloration caused by trapped air heating up during injection. This is often resolved by improving mold venting.
Barrier Screw – A screw design that separates molten and unmelted resin to ensure uniform melting in the barrel.
Boss – A cylindrical protrusion on a molded part used for assembly, often reinforced for strength when screws or fasteners are applied.

A

Abrasion Resistance – The ability of a plastic to resist wear caused by friction or mechanical action.
Acetal (POM) – A strong, low-friction thermoplastic commonly used in automotive, consumer goods, and industrial applications.
Aging – The change in a material’s properties over time due to environmental exposure, such as UV light, oxygen, and heat.
Air Trap – A defect where air is trapped in the mold cavity, causing voids or surface blemishes. Proper venting prevents this.
Alignment Pin – A pin that ensures the mold halves align accurately during clamping.

B

Backflow – The unwanted flow of molten plastic back into the screw during injection.
Balanced Runner – A runner system designed to ensure equal flow to all cavities, improving part consistency.
Barrel Temperature – The temperature setting of the injection molding machine’s barrel, crucial for melting and processing plastic.
Batch Processing – Molding parts in discrete production runs rather than continuous operations.
Blending – The process of mixing two or more materials to achieve desired properties.
Bridge Gate – A gate that directs plastic around a core before entering the cavity.
Buffer Zone – A section in the mold where material flow is controlled to reduce stress or defects.
Burst Pressure – The maximum pressure a molded part can withstand before failure.

C

Calibration – The process of adjusting equipment to maintain accuracy and consistency.
Cavity Pressure – The pressure within the mold cavity during injection, critical for part quality.
Chemical Resistance – The ability of a plastic to withstand exposure to chemicals without degrading.
Clamping Force – The force used to keep the mold closed during injection. Measured in tons.
Co-injection Molding – A process that injects two different materials into the same mold for multi-material parts.
Cold Slug – A piece of solidified plastic that enters the mold, often causing defects.
Core Shift – Misalignment of the core due to high pressure, leading to uneven wall thickness.
Creep – The gradual deformation of a plastic under long-term load.
Cycle Time – The total time to complete one molding cycle, from clamping to ejection.

D

Deflashing – Removing excess material or flash from a molded part.
Delamination – A defect where thin layers of plastic peel away, often due to contamination.
Dielectric Strength – The ability of a material to resist electrical breakdown.
Draft Angle – The slight taper applied to part surfaces for easy ejection.
Dry Cycle – Running the machine without plastic to test its functions.
Degassing – The removal of trapped gas from plastic material before molding.

E

Edge Gate – A gate positioned on the edge of the part, commonly used for simple designs.
Ejector Pin – A pin that pushes the part out of the mold after cooling.
Elastomer – A rubber-like material that can stretch and return to its original shape.
Embossing – Adding raised patterns or textures to a part surface.
Energy Chain – A protective guide for cables and hoses in moving mold parts.

F

Family Mold – A mold that produces multiple different parts in a single cycle.
Fiber Reinforcement – The addition of glass, carbon, or other fibers to improve strength.
Fill Time – The time taken to fill the mold cavity with molten plastic.
Flash – Excess plastic that forms at the parting line, requiring trimming.
Flow Marks – Visible lines or streaks on a part due to inconsistent material flow.
Flow Rate – The speed at which molten plastic fills the mold.
Flow Simulation – A software tool for analyzing how plastic flows in a mold.

G

Gate Blush – A surface blemish caused by improper gate design or high injection speed.
Gate Location – The point where plastic enters the mold cavity.
Glass Transition Temperature (Tg) – The temperature at which a plastic changes from a hard, glassy state to a rubbery state.
Gloss Level – The shininess or matte appearance of a molded part.
Gusset – A triangular support feature that adds strength to a molded part.

H

Hardened Steel Mold – A mold made from hardened steel for long production runs.
Heat Deflection Temperature (HDT) – The temperature at which a plastic deforms under load.
Hopper Dryer – A device that removes moisture from plastic pellets before processing.
Hot Runner – A runner system that keeps plastic molten, reducing waste.

I

Impact Modifier – An additive that improves a plastic’s toughness and resistance to impact.
Injection Pressure – The pressure used to inject molten plastic into the mold cavity.
Insert Molding – A process where metal or other materials are placed into the mold and encapsulated by plastic.
Interlock – A mechanism that aligns and secures mold halves together for precision.
Isotropic Material – A material with uniform properties in all directions, unlike fiber-reinforced plastics.
In-Mold Labeling (IML) – A process where labels are placed inside the mold and become part of the finished part.

J

Jetting – A defect where plastic shoots into the mold in a narrow stream, causing irregular patterns.
Jig – A tool used to hold parts during secondary operations like drilling or assembly.
Joint Line – Another term for weld line, where two plastic flow fronts meet.
Junction Gate – A type of gate used at the intersection of two runners.

K

Knit Line – A weakness or visible line on a part caused by converging plastic flows.
Keyway – A slot or groove used for aligning or securing components in a mold.
Knock-Out Pin – Another term for an ejector pin, used to remove parts from the mold.
K-Factor – A correction factor for predicting shrinkage in plastic molding.

L

Lamp Test – A quality test for translucent parts to detect cracks or inclusions.
Lattice Structure – A lightweight structure with a repeating pattern, often used in 3D-printed molds.
Living Hinge – A thin section of plastic that acts like a hinge, typically used in caps and containers.
Lubricated Resin – A plastic with built-in lubricants to reduce friction in moving parts.

M

Melt Flow Index (MFI) – A measure of how easily a plastic flows when melted.
Melt Temperature – The temperature at which plastic melts and becomes injectable.
Micro Injection Molding – The molding of tiny, high-precision parts.
Multi-Cavity Mold – A mold that produces multiple identical parts in one cycle.

N

Nozzle Tip – The end of the injection unit that connects to the mold sprue.
Nucleating Agent – An additive that promotes faster crystallization in semi-crystalline plastics.
Non-Fill – A defect where the mold cavity is not completely filled with plastic.
Notched Impact Strength – A measure of how much impact force a material can withstand with a pre-cut notch.

O

Offset Pin – A pin used to correct misalignment in molds.
Over-Molding – Molding plastic over an existing part to create multi-material components.
Open Mold – A mold with a cavity that isn’t fully enclosed, typically used for compression molding.
Outgassing – The release of trapped gases from plastic during molding.

P

Parting Line – The line where the two mold halves meet, often leaving a slight seam.
Packing Pressure – Additional pressure applied after injection to compensate for shrinkage.
Pelletizing – The process of forming plastic into small, uniform pellets for easier handling.
Pinch-Off – A feature in blow molding molds that seals and trims excess plastic.
Post-Mold Shrinkage – Dimensional changes in the part after it has cooled.

Q

Quality Assurance (QA) – Procedures to ensure parts meet specified standards.
Quenching – Rapid cooling of plastic parts to lock in properties.
Quick Mold Change – A system for reducing mold changeover time in production.

R

Radiused Corner – A rounded edge in part design to reduce stress concentration.
Regrind – Recycled plastic ground into small pieces for reuse.
Runner Balancing – Adjusting runner design to ensure even filling of all cavities.
Rheology – The study of how plastic flows, critical for mold design and process optimization.

S

Shear Rate – The rate at which plastic deforms while flowing through the mold.
Short Shot – A defect where the cavity isn’t fully filled with plastic, leaving incomplete parts.
Side Action – Movable components in a mold used to create complex features like undercuts.
Sink Mark – A surface depression caused by uneven cooling or material shrinkage.
Sprue Bushing – A removable insert in the mold for connecting the nozzle to the sprue.

T

Thermal Expansion – The tendency of a plastic to expand when heated.
Tie Bar – A structural component of the injection molding machine that supports the clamping unit.
Toggle Clamp – A type of clamping system using a mechanical linkage for high clamping force.
Tool Steel – A type of steel used for making molds due to its durability and hardness.

U

Undercut – A feature in a part that prevents it from being ejected without additional mold components.
Ultrasonic Welding – A process that joins plastic parts using high-frequency vibrations.
UV Stabilizer – An additive that protects plastic from degradation due to UV exposure.

V

Vent Depth – The size of mold vents that allow trapped air to escape during injection.
Viscosity – A measure of how easily plastic flows when molten.
Vacuum Forming – A process where heated plastic sheets are drawn over a mold using vacuum pressure.

W

Warping – Distortion caused by uneven cooling or internal stresses.
Water Injection Molding – A technique that injects water into the mold to create hollow sections.
Wear Plate – A replaceable part of the mold to reduce wear on moving components.

X, Y, Z

X-Ray Inspection – A non-destructive test for checking internal features or defects.
Yield Point – The stress level at which plastic begins to deform permanently.
Zero Draft – A part design without any taper, often challenging for mold ejection.
Zinc Alloy Mold Insert – A metal insert used for added strength and durability.

A

Acrylic (PMMA) – A transparent thermoplastic known for its clarity and weather resistance.
Annealing – A heat treatment process to relieve internal stresses in molded parts.
Anti-Static Agent – An additive that reduces static electricity buildup on plastic surfaces.
Aramid Fiber – A high-strength, heat-resistant fiber used for reinforcement in plastics.
Auto Degating – Automatic removal of gates from parts after molding.
Auxiliary Equipment – Additional machinery such as dryers, chillers, and robots used in molding processes.
Axis Control – The control of multiple axes for robotic or automated systems in molding operations.

B

Barrel Insulation – Material wrapped around the barrel to conserve heat and improve efficiency.
Batch Number – A unique identifier for tracking specific production batches.
Bead Blasting – A surface finishing process that imparts a textured finish using blasting media.
Bimetallic Barrel – A barrel with a special lining to resist wear and corrosion.
Blow Molding – A process for making hollow plastic parts like bottles.
Bonding Strength – The adhesion strength between plastic and an insert or another material.
Breakaway Force – The force required to separate a molded part from the mold surface.

C

Charge Time – The time required for the screw to retract and prepare the next shot.
Clamp Stroke – The distance the clamping unit travels to close and lock the mold.
Coefficient of Thermal Expansion (CTE) – A measure of how much a material expands with temperature changes.
Compression Molding – A process that compresses material in a heated mold to form a part.
Cooling Circuit – The network of channels in a mold used for circulating coolant to remove heat.
Core Lifters – Mold components that lift and support complex cores during ejection.
Crystalline Polymer – A polymer with an ordered molecular structure, providing high strength and heat resistance.

D

Degating Fixture – A tool for removing gates from molded parts.
Density – The mass per unit volume of a plastic material.
Desiccant Dryer – A dryer that uses desiccants to remove moisture from hygroscopic materials.
Die Lock – A condition where the part cannot be ejected due to undercuts or interference.
Draft Analysis – A CAD tool for checking if a part has adequate draft angles for easy ejection.

E

Edge Crush Test (ECT) – A test to determine the compression strength of a material’s edge.
Electrical Discharge Machining (EDM) – A precision tool-making process for creating intricate mold features.
Elongation at Break – The amount a material stretches before breaking.
Encapsulation – Fully covering an insert or component with plastic.
Erosion – Damage to mold surfaces caused by abrasive flow of plastic.

F

Family Tooling – A tool that molds different part designs in a single shot.
Fan Gate – A wide, shallow gate used for even plastic flow and reduced shear.
Fill Balance – The balance of material flow into multiple cavities.
Flame Retardant – An additive that makes plastic resistant to ignition.
Flow Front – The leading edge of molten plastic as it fills the mold cavity.

G

Gate Freeze – The point at which plastic in the gate solidifies, stopping material flow.
Glass-Filled Nylon – Nylon reinforced with glass fibers for increased strength.
Gloss Meter – An instrument for measuring the surface gloss of a part.
Grain Texture – The textured finish applied to mold surfaces for aesthetic or functional purposes.

H

Heat Sink – A feature or material used to dissipate heat in electronics or molded parts.
Helical Gear Mold – A mold for producing helical gears with precise geometry.
High-Pressure Injection – Injection at elevated pressures for thin-wall or high-strength parts.
Hygroscopic Material – A material that absorbs moisture from the air, like nylon or polycarbonate.

I

Impact Resistance – The ability of a material to withstand sudden force without cracking.
Inductive Heating – A heating method using electromagnetic fields for rapid mold heating.
In-Mold Decoration (IMD) – Applying decorative layers directly inside the mold.

J

Junction Box Mold – A mold for electrical enclosures with multiple cable entry points.
Joule Heating – Heating caused by electrical resistance, used in certain hot runner systems.

K

Kinematic Fit – A precise fit that ensures correct part alignment.
Keyed Core – A core with a locking feature to prevent rotation during molding.

L

Lamination Layer – A defect caused by improper bonding between plastic layers.
Laser Engraving – A process for marking or texturing parts with lasers.

M

Melt Fracture – A defect where the plastic surface appears rough due to excessive shear stress.
Metal Insert Overmolding – Molding plastic around metal components for added strength.
Microcracking – Tiny cracks in the part surface due to stress or environmental exposure.

N

Nanocomposite – A composite material with nanoscale fillers for enhanced properties.
Non-Return Valve – A valve on the screw tip that prevents backflow of molten plastic.

O

Optical Clarity – The transparency of a plastic material.
Overpack – Excessive material injected into the mold, causing stress and warping.

P

Part Weight – The weight of a single molded part, important for cost and quality control.
Preform Mold – A mold used for making preforms for blow molding.

Q

Quality Control Plan (QCP) – A document outlining inspection criteria and procedures.

R

Radial Flow – Material flow that spreads out from a central gate.
Reinforced Thermoplastic – Plastic reinforced with fibers or fillers for improved strength.

S

Shot Capacity – The maximum volume of plastic the machine can inject in one cycle.
Structural Foam Molding – A process that creates lightweight, rigid parts using a foaming agent.

T

Tab Gate – A small rectangular gate used for thick-walled parts.
Tensile Strength – The maximum stress a material can withstand before breaking.

U

Ultraviolet (UV) Resistance – The ability of a plastic to resist degradation from sunlight.

V

Vent Blockage – A defect caused by clogged mold vents.

W

Weld Line Strength – The strength at the joint where two flow fronts meet.

X, Y, Z

XPS (Expanded Polystyrene) – A rigid foam plastic with high thermal insulation properties.
Yield Stress – The stress at which a material begins to deform permanently.
Zero Compression Mold – A mold designed for minimal part compression during ejection.

A

Abrasion Resistance – The ability of a plastic material to withstand wear and friction.
Accelerated Aging – A test to simulate long-term environmental effects on plastics in a short time.
Additive Masterbatch – A concentrated mixture of additives blended with base resin for improved properties.
Adiabatic Heating – Temperature rise due to high-speed deformation without heat dissipation.
Air Shot – An injection of molten plastic into the air to check melt quality.
Alloy Polymer – A blend of two or more polymers to achieve specific performance characteristics.
Anti-Oxidant – An additive that prevents degradation of plastic due to oxidation.

B

Back Pressure – Resistance applied to the screw during recovery to improve melt uniformity.
Balanced Runner System – A runner system designed for equal material flow to all cavities.
Batch Processing – A manufacturing method where parts are produced in specific quantities.
Biodegradable Plastic – A plastic that breaks down in the environment over time.
Blooming – The migration of additives to the surface of a molded part.
Blush Mark – A surface defect often caused by improper gate design.
Brittleness – The tendency of a material to break without significant deformation.

C

Casting Resin – A resin used for making molded parts without pressure, typically in open molds.
Charge Density – The amount of material accumulated in front of the screw during injection.
Chemical Resistance – The ability of a plastic to resist attack from chemicals.
Clamp Force – The force applied by the clamping unit to keep the mold closed during injection.
Cold Runner – A runner system that remains unheated and solidifies with the part.

D

Deflashing – The process of removing excess material (flash) from molded parts.
Delamination – Separation of layers in a molded part, causing weak areas.
Density Gradient – Variation in material density within a molded part.
Direct Gate – A gate that feeds plastic directly into the cavity without runners.
Draft Angle – The taper on molded surfaces to aid ejection.

E

Ejection Pin Marks – Visible marks left on parts by ejection pins.
Elastic Modulus – A measure of a material’s stiffness.
Embossing – Creating raised patterns on a molded part’s surface.
Energy Chain – A cable management system used in robotic and automated machines.

F

Fiber-Reinforced Plastic – A plastic reinforced with fibers for enhanced strength and stiffness.
Fill Pattern – The way molten plastic flows into the cavity.
Fish Eye – A surface defect caused by improper mixing or contamination.
Flash Gate – A wide gate that leaves flash on parts, often trimmed later.

G

Gate Blush – A blemish around the gate area due to improper pressure or temperature.
Gate Shear – Shear stress occurring at the gate during injection.
Glass Transition Temperature (Tg) – The temperature where a material changes from a rigid to a rubbery state.

H

Heat Deflection Temperature (HDT) – The temperature at which a plastic deforms under load.
High-Flow Resin – A resin designed for easy flow into complex molds.
Hot Half – The heated portion of a hot runner mold system.

I

Impact Modifier – An additive that improves a plastic’s impact resistance.
Injection Pressure – The pressure applied to push molten plastic into the mold.
Insert Core – A core placed into a mold cavity to form internal features in a part.

J

Jetting – A flow defect where molten plastic enters the cavity in a thin stream, causing surface marks.
Jig Fixture – A tool for holding parts during secondary operations like machining.

K

Knockout Bar – A rod that pushes ejection pins during part ejection.
Knit Line – A weak line where two flow fronts meet.

L

Light Pipe – A molded part used to direct light from one point to another.
Liquid Silicone Rubber (LSR) – A highly flexible thermosetting elastomer used for medical and automotive parts.

M

Melt Flow Index (MFI) – A measure of how easily a plastic flows when melted.
Microcellular Foam Molding – A process that creates lightweight parts with a cellular structure.
Molded-in Stress – Stress trapped in a part due to uneven cooling.

N

Notched Impact Strength – Impact strength measured on a sample with a pre-cut notch.
Nylon (PA) – A strong, abrasion-resistant thermoplastic used in various applications.

O

Overmolding – Molding a second material over an existing part for additional functionality.
Oxidative Degradation – Deterioration caused by exposure to oxygen and heat.

P

Pack Pressure – Pressure applied after filling to pack more material into the mold.
Photopolymer – A light-sensitive resin used in 3D printing.

Q

Quick Change Mold – A mold designed for fast swapping in and out of a machine.

R

Rheology – The study of material flow behavior.
Runner Balancing – Adjusting runner sizes to ensure equal filling of cavities.

S

Shrinkage – The reduction in size of a part as it cools and solidifies.
Sink Marks – Surface depressions caused by internal shrinkage.

T

Tab Gate – A flat, rectangular gate that feeds plastic into the part.
Tear Strength – The resistance of a material to tearing forces.

U

Underfill – Incomplete filling of the mold cavity.
UV Stabilizer – An additive that protects plastic from UV degradation.

V

Vent Depth – The depth of a vent channel in the mold.
Viscosity – A measure of a fluid’s resistance to flow.

W

Warping – Distortion caused by uneven cooling or internal stresses.
Water-Assisted Injection Molding (WAIM) – A process where water is injected into the mold to form hollow parts.

X, Y, Z

Xylene – A solvent used in polymer processing.
Yield Point – The point at which a material begins to deform permanently.
Zinc Alloy Insert – A metal insert made from zinc alloy for enhanced strength.

A

Acetaldehyde Content – The residual acetaldehyde level in molded PET products, critical for food packaging.
Aging Resistance – The ability of plastic to resist degradation over time.
Annealing – A heat treatment process to reduce internal stress and improve material properties.
Anti-Static Agent – An additive that reduces static electricity on plastic surfaces.
Aramid Fiber – A strong, heat-resistant synthetic fiber used to reinforce plastics.

B

Balanced Cavity Filling – Ensures equal flow of material into multiple cavities for consistent part quality.
Birefringence – Optical distortion caused by internal stress in transparent plastics.
Boss – A raised feature on a molded part used for fasteners or alignment.
Buttress Thread – A type of screw thread with high shear strength, often molded into plastic parts.
Bypass Valve – A valve in the injection unit that controls melt flow.

C

Cavity Insert – A removable insert in the mold cavity for forming specific features.
Chemical Coupling Agent – An additive that enhances the bond between fillers and the resin matrix.
Clamp Stroke – The distance the mold opens during the ejection cycle.
Compression Zone – The section of the screw where melt compression occurs for proper plasticization.
Cooling Time – The duration the molded part spends cooling in the mold.

D

Dampening Plate – A plate that reduces vibration in the injection molding machine.
Dehumidifying Dryer – A device that removes moisture from hygroscopic resins.
Differential Shrinkage – Uneven shrinkage that causes warping or distortion.
Discoloration – An undesired change in part color due to overheating or contamination.
Double-Shot Molding – A process that molds two materials in a single cycle for multi-material parts.

E

Edge Gate – A gate located at the edge of a molded part for easy removal.
Elastomer – A flexible, rubber-like material with high elasticity.
Exothermic Reaction – A chemical reaction that releases heat, common in thermosetting resins.
Extruder Barrel – The heated cylinder in which the plastic is melted and mixed.
Extended Nozzle – A longer nozzle for better access to deep molds.

F

Fan Gate – A gate that spreads the flow of plastic over a wider area to reduce stress.
Fill Time – The time it takes to fill the mold cavity with plastic.
Flame Retardant – An additive that reduces the flammability of plastic materials.
Flash Trap – A groove in the mold that traps excess material (flash) during molding.
Flow Front – The leading edge of molten plastic as it fills the cavity.

G

Gas Counter Pressure (GCP) – A technique to improve surface quality in gas-assisted injection molding.
Gate Seal – The point where molten plastic solidifies in the gate, stopping flow.
Glass-Filled Plastic – Plastic reinforced with glass fibers for added strength and stiffness.

H

Heat Sink – A feature or material that dissipates heat from a molded part.
Hinge Line – A thin, flexible section in molded parts to create a living hinge.
Hot Sprue – A heated sprue that maintains molten plastic for continuous flow.

I

Injection Cushion – The amount of molten plastic left in front of the screw after injection.
Impact Resistance – The ability of a molded part to absorb energy without breaking.
In-Mold Labeling (IML) – Embedding a label within a part during the molding process.

J

Junction Line – A visible seam where two flow fronts meet.

K

K-Factor – A coefficient used in shrinkage calculation for molded parts.

L

Latch Lock – A mechanism that ensures mold halves stay aligned during operation.
Linearity – The consistency of a material’s properties in different directions.

M

Melt Fracture – A defect caused by turbulent flow in the nozzle or runner.
Melt Pool – The reservoir of molten plastic in the barrel.
Micromolding – Injection molding of very small parts with high precision.

N

Nozzle Tip – The end of the nozzle that contacts the sprue bushing.
Notch Sensitivity – A material’s tendency to fail at sharp corners or notches.

O

Overpack – Excessive material packing that leads to flash or part damage.
Oxidation Stability – The ability of a plastic to resist degradation when exposed to oxygen.

P

Packing Time – The time during which packing pressure is applied to the mold.
Parting Line – The line where the two halves of the mold meet.
Plasticizer – An additive that increases a plastic’s flexibility.

Q

Quick-Disconnect Nozzle – A nozzle that can be quickly removed for maintenance or material changes.

R

Radial Flow – Plastic flow that radiates outward from a central point.
Reinforced Resin – Resin blended with fibers or other materials to improve properties.

S

Screw Recovery Time – The time the screw takes to rotate back and prepare for the next shot.
Shot Weight – The total weight of plastic injected in a single shot.

T

Toggle Clamp – A clamping mechanism that uses levers and pivots for high force.
Torque Rheometer – An instrument that measures the viscosity of molten plastic.

U

Undercut – A feature in a part that makes ejection difficult without special mold designs.
Ultrasonic Welding – A process that joins plastic parts using high-frequency vibrations.

V

Vent Plug – A removable venting element in the mold cavity.
Viscoelasticity – The combination of elastic and viscous behavior in plastic materials.

W

Water-Cooled Mold – A mold that uses water to cool parts more efficiently.
Weld Line – A weak line where two flow fronts meet and fail to fuse properly.

X, Y, Z

Xenon Test – A test to evaluate UV resistance using a xenon light source.
Yield Strength – The stress at which a material begins to deform plastically.
Z-Molding – A specialized molding technique for complex geometries.

Additive Loading – The concentration of additives in a plastic compound.
Air Entrapment – Trapped air bubbles inside the molded part, causing defects.
Alignment Pins – Pins that ensure proper alignment of mold halves.
Annealing Temperature – The specific temperature range for relieving internal stress in molded parts.
Anti-Wear Agent – An additive to reduce friction and wear on plastic surfaces.

B

Backflow – Melt flow that reverses direction during injection.
Barrel Liner – The wear-resistant lining inside the extruder barrel.
Blowback – Unintended backward flow of molten plastic in the barrel.
Bridging – When material sticks together and blocks flow in the feed throat.
Bulk Density – The mass per unit volume of granulated or powdered material.

C

Co-Polymer – A polymer made from two or more different monomers.
Co-Injection Molding – Simultaneously injecting two different materials into the same mold.
Cold Runner – A runner system that allows material to solidify between cycles.
Color Concentrate – A highly pigmented masterbatch used for coloring plastics.
Creep Resistance – The ability of a material to resist deformation under constant stress.

D

Decoupled Molding – A process control technique that separates filling, packing, and holding phases.
Degassing – Removing gases from plastic melts to prevent defects.
Density Compensation – Adjusting process parameters to account for material density changes.
Dielectric Strength – The maximum electrical voltage a plastic can withstand before breaking down.
Ductility – The extent to which a material can stretch without breaking.

E

Elastic Modulus – A measure of a material’s stiffness.
Electroplating – Applying a metal coating on molded plastic parts for enhanced appearance and conductivity.
Ejector Pin Mark – A visible mark on the part where the ejector pin pushes it out of the mold.
Elongation at Break – The percentage a material stretches before it breaks.
Epoxy Resin – A thermosetting resin known for its strong adhesion and chemical resistance.

F

Fan Gate – A wide gate that reduces stress and flow lines.
Fiber Orientation – The alignment of reinforcing fibers within a molded part.
Fill Pressure – The pressure required to fill the mold cavity.
Flame Treatment – Surface treatment that improves adhesion for printing or painting.
Flow Channel – A path for plastic melt in the mold.

G

Gate Blush – A surface defect near the gate caused by premature solidification.
Gate Vestige – The small remaining piece of material after gate trimming.
Glass Transition Temperature (Tg) – The temperature at which plastic changes from rigid to rubbery.
Grain Finish – A textured mold surface for aesthetic or functional purposes.

H

Hardness Shore D – A measure of the hardness of rigid plastics.
Heat Deflection Temperature (HDT) – The temperature at which a plastic deforms under load.
High-Gloss Finish – A polished mold surface for shiny, smooth parts.
Hygroscopic Resin – A resin that absorbs moisture from the air, requiring drying before molding.
Hydraulic Clamp – A clamping system that uses hydraulic pressure for high clamping force.

I

Impact Modifier – An additive that improves impact strength.
In-Line Screw – A screw with a constant diameter for uniform plasticizing.
Insulation Plate – A plate that prevents heat transfer between the mold and machine.

J

Jetting – A defect caused by high-velocity melt flow, resulting in wavy patterns on the surface.
Junction Temperature – The temperature at the point where two mold surfaces meet.

K

Kevlar Reinforcement – Use of Kevlar fibers for added strength and impact resistance.
Knockout Pin – Another term for an ejector pin.

L

Laminar Flow – Smooth, uniform melt flow during injection.
Lightweighting – Reducing the weight of molded parts without compromising strength.
Living Hinge – A thin, flexible section in molded parts that acts as a hinge.

M

Melt Flow Index (MFI) – A measure of the flowability of molten plastic.
Microvoids – Tiny air pockets inside the molded part that reduce strength.
Mold Base – The main structure that holds the mold components.

N

Non-Return Valve – A valve on the screw tip that prevents backflow.
Notch Radius – The radius of a notch, affecting stress concentration.

O

Overmolding – A process that molds one material over another for multi-material parts.
Oxidative Degradation – Plastic breakdown due to prolonged exposure to oxygen.

P

Pack Pressure – The pressure applied during the packing phase to ensure the part is fully filled.
Polymer Blend – A mixture of two or more polymers to enhance properties.
Post-Mold Shrinkage – Shrinkage that occurs after the part is ejected.

Q

Quality Audit – Inspection process to ensure parts meet specifications.
Quick Mold Change – A system for fast mold swaps to reduce downtime.

R

Radiused Edge – A rounded edge in a molded part for improved aesthetics and reduced stress.
Regrind – Recycled plastic used in molding.

S

Shear Rate – The rate at which plastic deforms during flow.
Sink Mark – A surface defect caused by uneven cooling or insufficient packing.

T

Thermal Conductivity – The ability of a material to conduct heat.
Tie Bar – A structural component of the injection molding machine frame.

U

Ultrasonic Insert – An insert placed using ultrasonic vibration for precise positioning.
UV Stabilizer – An additive that protects plastic from ultraviolet light degradation.

V

Vacuum Venting – Using vacuum pressure to remove trapped air from the mold cavity.
Viscosity Index – A measure of how fluid a plastic melt is under different temperatures.

W

Warpage – A distortion defect caused by uneven cooling.
Weld Line Strength – The strength of the joint where two flow fronts meet.

X, Y, Z

Xylene Solubility – A test to measure solubility in xylene for specific plastics.
Yield Point – The stress at which a material begins to deform plastically.
Zero Clamp Force – Condition when no clamping force is applied, used for maintenance.
Zipper Effect – A defect where a crack propagates rapidly along a part.

Zoned Heating – Heating system with multiple zones for precise temperature control.

Glossary of 400+ terms used in plastic injection molding

GLOSSARY OF TERMS – PLASTIC INJECTION MOLDING

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A