TERMS AND DEFINITIONS

Injection molding has hundreds of special terms used related to the machines, tools, parts, plastics, etc.  Below we have highlighted the nomenclature that is applicable to MicroMolder and MicroMolder+ to help you.

Annealing - Annealing is the heating and slow cooling of a plastic part which allows the polymer chains to recoil and relieve internal stresses.

Blister – As the name says, this is a part defect which appears as a small bubble or blister on the surface of a part and it generally created by gas or air bubbles.

Bubbles – Similar to blisters, gas pockets, or voids that have formed inside the plastic.

Cavity - The machined shape within a mold which created the form of the plastic part.

Clamp – The mechanism that holds the mold in location during the molding process.

Cold slug – A defect characterized by a small non-uniform area on the part caused by an improperly heated piece of plastic becoming attached to the part.

Colorant – A pigment system, usually in pelletized form, powder or liquid, which is mixed with resin to produce the desired color.

Core - A protrusion or set of matching protrusions, which form the inner surface of a plastic part. They are often considered they “male” side of the part.

Crazing – A defect that causes small cracks often caused by over-stressing the plastic material.

Creep – The “set” that a molded part takes under stress and does not return to its original shape. Also known as “memory”.

Cure – The process of allowing a plastic to harden or stabilize.

Cycle – The overall time it takes for the plastic injection process to complete a finished part.

Density – Mass per unit volume of a substance.

Draft – The angle or degree of taper in a side wall to help facilitate removal of the parts from the mold.

Ejection pin – Metal rods in the mold which push the parts from the mold.

Ejector return pins – Pins that push the ejectors back into position once the parts have been released.

Ejector rod – A bar that engages the ejector assembly and pins when the mold opens.

Fan gate – A gate with a wider width that helps reduce warping through stress.

Fill – The packing of material into the mold.

Flash gate – An alternative to a fan gate, which conveys the melted resins into a thinner gate section creating a linear melt flow into the cavity.

Flash or burrs – A thin lip or protrusion beyond the body of the part that is generally caused by poor clamping force, improper mold design and/or mold damage.

Flow marks - A wavy pattern or discoloration caused by a slow injection speed which allows the material to cool too quickly.

Flow rate – The volume of material passing a fixed point per unit time.

 

Gate – The channel into which melted plastic flows into a mold.

 

Hot-runner mold – Hot runner molds consist of 2 plates that are heated with a manifold system.   The manifold sends the melted plastic to nozzles which fill the part cavities.

 

Insert – An object, such as a magnet or screw, which is inserted into the molded part.

 

Machine shot capacity – The maximum volume of resin which can be injected in a single stroke.

 

Mold – A hollow form that plastic is injected or inserted into to manufacture a plastic part.

 

Mold release – A surface preparation used to aid in the ejection of the part from the mold.

 

Multi-shot molding – A process where two or more plastic substances are injected into the mold to form a part. 

Toothbrushes are often manufactured using this technique.

 

Nozzle - The hollow-cored metal nose screwed into the injection end of the barrel which forms a seal under pressure.

 

Orange peel – A patchy rough surface defect caused by moisture in the mold cavity, or by incomplete pack-out.

 

Over molding – A two-shot process, in which two plastic substances, are injected into a mold sequentially, usually a harder base material with a coating of softer material.

 

Parting line – A line on a part formed when the two sides of the mold come together.

 

Pinpoint gate – A very small gate, used in hot runner molds, to control the flow of material.

 

Platens – Steel plates in the molding machine onto which the mold is fastened.

 

Prototype tool – Also called a soft tool, a preliminary mold built to produce prototype parts and used to make adjustments to the final production tool.

 

Purging – The process of cleaning the injection machine of remnant color or materials prior to running a new part.

 

Release agent – A compound, which is sprayed on the mold, or as an additive, molded into the part to help facilitate the release of the part.

 

Runner – The channel system that allows the flow of the melted material to fill the part cavities.

 

Short shot – A defect where the material does not fully fill the part cavity.

 

Shot – A complete cycle of the injection machine.

 

Shrinkage – The amount of volume reduction that takes place when a plastic material cools.

 

Sprue – The opening feed that conveys material from the nozzle to runner system in the mold.

 

Tool – The mold used to form plastic parts in an injection machine.

 

Undercut – Can be a design flaw that results in an indentation or protrusion that inhibits the ejection of the part from the mold.  Other times undercuts are designed into a mold to ensure a part holds onto the correct side of the mold.

 

Vent – A channel from the mold cavity that allows gas and air to escape as resin is being injected into the cavity to prevent many types of defects from occurring.

 

Weld line - Also called a knit line, the juncture where two flow fronts meet and are unable to join-together during the molding process. These lines usually occur around holes or obstructions and cause localized weak areas in the molded part.