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Glossary of Terms (3)

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SPRUE PULLER PIN Pin located directly under the opening of the sprue. Used to pull the molded sprue out of the bushing after a shot has been made.
SPRUE BUSHING RETAINER RING See LOCATING RING
STONING The process of refining all surfaces of the cavity or core with manufactured stones.
SUCKER PINS See SPRUE PULLER PIN
SUPPORT PLATE Mounted behind the core retainer plate to keep this plate from bending under the high pressure used in injection molding. (Also called BACK-UP PLATE)
SHOCK RESISTANCE The ability to resist the sudden application of an external force that results in the rapid build-up of stress.
SHORT SHOT Partial filling of a mold cavity or cavities.
SINK Small depressions on the molded surface caused by different cooling and shrinkage rates, typically between thick and thin sections.
SLIDE A portion of the mold that is designed to travel at an angle to the normal ejection movement of the mold base. Typically used to produce holes, recesses, or undercuts, by the use of a core attached to the slide mechanism. The slide pulls away before the molded part is ejected.
SPLAY Material flow marks, visible on the molded part. Caused by either contaminated or degraded material, or by material that is too cold and fills too slowly. 
SPRUE The round, tapered portion of the runner system that connects the machine injection nozzle with the runner system of the mold.
STOP PINS See SPACER BUTTONS
STRESS A force exerted upon a body that tends to put a strain on its shape. AII plastic parts have some degree of internal stress molded in. Too much internal stress is undesirable.
SUCKER PIN Typically a pin with a ball-shaped end. Plastic is molded around it, and it serves as an undercut and holds the plastic. The ejection system then forces the molded undercut off of the sucker pin.
TENSILE STRENGTH The resistance of a material to a force tending to stretch or extend the material.
THERMOPLASTIC RESIN A group of plastic materials that are capable of being molded when heated and hardened when cooled. A physical change takes place during the molding process, but a chemical change does not.
THERMOSETTING RESIN A group of plastic materials that are set by the application of heat and pressure. A chemical reaction takes place during molding, and the material cannot be restored to its original state after molding.
THREE PLATE MOLD A mold base with three separate parting lines, designed to automatically separate the runner system from the molded part.
TOOLS Special fixtures, molds, dies, or other devices that enable a manufacturer to produce parts.
TOOL STEELS Steels used to make cutting tools and dies. Many of these steels have considerable quantities of alloying elements such as chromium, carbon, tungsten, molybdenum, and other elements. They form hard carbides that provide good wearing qualities but at the same time decrease machinebility. Tool steels in the trade are classified for the most part by their applications, such as hot die, cold work die, high speed, shock resisting, mold, and special purpose steels. 

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TOP FRONT CLAMPING PLATE Holds the stationary part of the mold to the stationary platen of the injection machine.
TOUGHNESS The ability of a metal to absorb energy and deform plastically before fracturing.
TURBULENT An agitated flow of a liquid that is desired in a cooling circuit, because it removes more heat than one that is not agitated. The Reynolds Number is a measure of turbulent flow.
UNBALENCED RUNNER SYSTEM A runner system typically used for a family of parts. The Unbalanced Runner System has unequal diameters or length runners, and/or different size gates, and is used to achieve equal fill on molded cavities. This system is not a preferred method.
UNDERCUT A raised or recessed area of the mold cavity or core that impedes, or makes impossible, ejection of the molded part.
UNIT DIE SET A master mold base used in molds for injection moldings into which individual molds are inserted. These molds are filled by a centrally located sprue.
VENT A shallow groove or recess typically machined into the parting line of a mold. The vent allows trapped air or gases to escape the cavity as it is being filled with molding resin.
VISCOSITY The internal friction of a fluid to resist the tendency to flow.
WATERLINES See COOLING CHANNELS
WEAR RESISTANCE The capacity to withstand surface damage from contact with other metals, non-metallic particles or flowing liquids. Wear generally involves the progressive loss of surface material due to motion of that surface and a contacting surface or substance. 
WELD LINES A visible line appearing on a mold surface where two or more streams of material meet, then fuse together. 

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