Injection molding terms

Injection molding has hundreds of terms. This glossary highlights the most common ones generally used when discussing injection mould parts, materials, and problems.

Additives – These substances are incorporated into resins in order to improve their performance and appearance.The key factor of the present plastics industry is the use of organic additives, such as eggshells, wood pulp, rice hulls, or synthetic materials made from biodegradable materials.

Alloys – Plastic alloys are manufactured by physically modifying a plastic in order to make it more functional and/or perform better. These alloys are often utilized to substitute metal parts in the automobile industry.

Annealing – Annealing is the process of heating a plastic part into a solid state and allowing the chain of the plastic material to recoil. This will relieve internal stresses as well as the effect of expanding the material.

Assembly -is the process of putting parts together after they have been completed.

Backplate – An integral component of an injection mold that supports the mold, pins, and bushings.

Blister – This type of defect is characterized by the appearance of a small bubble or blister on the surface of a part, most often caused by gas or air bubbles.

Blow molding – A basic step of the procedure is to inflate the plastic mass with air. Once it is cooled, the plastic will squeeze against the shape of the mold cavity. It is often used to make plastic bottles.

Bridge tool– An injection tool used while a final tool is being produced. These tools are not intended to be used for mass production.

Bubbles – Often referred to as blisters, blisters, gas pockets, or holes in the plastic.

Cavity – The machined space found in a mold that is shaped to create the form of a plastic part.

Clamp – A device that allows the mold to be held in place during the injection molding process.

Colorant – A synthetic pigment usually available as a powder or liquid, which is mixed with resin and used to produce specific colors.

Compression molding – The technique is named soly, it involves placing heated plastic material in a heated mold and then compressing it. The plastic can be in bulk but most commonly in sheet form.This process, referred to as curing, ensures the final part will maintain its structural integrity. This method of manufacturing is regularly used to create large objects such as automobile components.

Copolymer – A polymer made of multiple monomers.

Core – A series of protrusions made of steel, usually make the inside surface of a plastic part. They are often referred to as the “male” side of the injection mold.

Crazing – A defect or flaw that results in small cracks that are commonly caused by over-stretching the plastic materials.

Creep – When a molded part loses its original shape after being subjected to stress it is said to have creep.

Cooling – The process by which a plastic hardens or stabilizes.

Cycle – The total number of steps required to complete an injection moulded plastic part.

Degassing – The removal of gases and air from a mold by opening and closing the mold. Trapped gases and/or air can lead to parts that can tear, bubble, or blister.

Delamination – like this normally appear as flaky areas on the surface of the part, and are often the result of contamination or moisture within the resin pellets.

Density – the mass of an object in relation to its volume.

Dimensional stability – An article’s ability to retain its original form after it was molded.

Draft – The angle of taper a sidewall has to enable the parts to be removed from a mold.

EDM – Is a process for constructing molds that remove metal material using an electrical discharge.or electric discharge machining

Ejection pin – Parts that are expelled from the mold by using metal rods.

Ejector return pins – In order to return the ejectors to an appropriate position, the pins need to push back the ejector contain plates.

Ejector rod – When the mold opens, the ejector assembly and pins engage the bar.

Elasticity – The ability of a material to recover its shape after being stretched or slacked.

Elastomer – A material similar to rubber that is highly elastic.

Extrusion – The process of forcing melted materials through a die to form tubes or continuous shapes.

Fabrication – The process of producing plastic goods by using various forming and molding processes.

Family mold – A mold consisting of various cavities for varying parts.

Fan gate – A gate with a wider width that helps decrease warping caused by friction.

Filling – packing a mold with material.

Filler – An inert additive that strengthens or hardens a component.

Finish – The quality of the part’s surface.

Flash gate – An alternate to fan gates, the melt is conveyed into a thinner gate to create a linear flow of resin into the cavity.

Flash or burrs – Protruding lips or sharp edges caused by inadequate clamping force, poor mold design, or mold damage.

Flow marks – A wave-like structure or color change caused by an injection speed that is too slow and allows the material to cool too rapidly.

Flow rate – defined as the volume of material that passes through a fixed point in a particular amount of time.

Gate – The channel that allows plastic to flow into a mold when it is melted.

Hardness -A measure of how hard a substance is to compression, indentation and scratching.

Hot-runner mold – This type of mold consists of runners,gates heated by a manifold. Melt plastic is squirted into hollow cavities through the manifold.

Injection blow molding – A type of blow molding in which the parts are injected into the mold and blown out of the mold.

Injection molding: This manufacturing process involves injecting melting plastic into a mold to create a product.

Insert: An item that is inserted into a molded part, for example, a magnet or screw.

Jig – A machine tool used for holding and guiding the tool during manufacture.

Machine shot capacity – The amount of resin that can be injected into one piece of material at a time.

Masterbatch – An additive for plastics that can be used as a coloring agent or impart other properties to plastics.

Mold – A hollow tool that is used to produce a plastic component by injecting or inserting plastic into it.

Mold release – A surface treatment that facilitates ejection of molded parts from the mold.

Multi-shot molding – The process in which two or more plastic materials are simultaneously injected into a mold to form a part. Dental tools are often manufactured in this manner.

Nozzle-The injection end of the barrel is fitted with a hollow-core metal nose that forms a seal under pressure.

Orange peel – a roughened, patchy surface defect that is caused by water vapor in the mold cavity, or because there was an incomplete packing-out process.

Overmolding-Two plastic substances, usually a hard base material and a coat of softer material is successively injected into the mold.

Parting line – A line that is left on a part after the two halves of the mold are joined together.

Pinpoint gate-To control the flow of material, a pinpoint gate, used in 3 plates molds, is a very small gate.

Plastic – A polymer with a large molecular weight.

Plasticity – describes a material’s ability to be easily shaped or molded.

Platens – Steel plates that hold the mould together.

Polymer – A substance that consists of molecular units bonded together mainly, or completely, in order to form a molecular structure, for example many synthetic organic materials used as plastics and resins.

Prototype tool – A tool built to produce prototypes, also known as a soft tool – which can be used to achieve design adjustments prior to the final production tool.

Purging – The process of removing remnant colors or materials from an injection machine prior to running a new part.

Ram – The melting material is forced into the mold using the plunger-like part.

Release agent – An additive placed in the mold to help facilitate its release. A compound sprayed on the mold, or an additive included in the part, to facilitate its release.

Retainer plate – A plate upon which a mold is mounted with its removable parts.

Runner system – Channels that allow melted plastics to flow into cavities in parts.

Short shot – An error which occurs when the material does not completely fill the part’s interior cavity.

Shot – An injection molded part complete cycle.

Shrinkage – The degree to which the volume of plastic material is reduced during cooling.

Sprue – The opening feed is a tube through which the material is conveyed from the nozzle to the runner system.

Thermoplastic – A substance is through a heating and cooling process that does not destroy the crystalline structure of a material. It is thus highly recyclable.

Thermoset – A material heated to a certain temperature that is then forced into a mold. The heating process changes the structure of the material, and as a result the material can not be heated again.

Tie bars – The tie bars are supportive bars that help the mold to open and close. Their spacing determines the size of the mold that can be inserted into the press.

Toggle – An alternative to hydraulic clamping in which the mold is mechanically closed.

Tool – A mold requiring an injection machine in order to form plastic parts.

Undercut – Can be caused by a design defect resulting in an indentation in the part or a protrusion that prevents the part from ejecting from the mold. Other times molds are designed with undercuts to ensure the part is held onto the correct side of the mold.

Vent – An air or gas release channel in the mold cavity that prevents the formation of many different kinds of defects while the resin is injected into the cavity.

Weld line – Also called a knit line, this is the spot on a molded part where flow fronts that do not unite during the molding process meet. They usually cause localized weak spots at the edges of holes or obstructions, and cause them to look rough or rougher around the edges.