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Raised Ejector Site: Where the ejector site is either heightened or raised above the surface of the component.

Ram: The forward motion of the screw in the plasticator barrel that forces the melt into the mold cavity.

Reaction Injection Molding (RIM): A process that involves the high-pressure impingement mixing of two or more reactive liquid components and injecting into a closed mold at low pressure.

Reagent Resistance: The ability of a plastic to withstand exposure to chemicals.

Recovery Time: The length of time for the screw to rotate, create a shot, and return to original position.

Regrind: Waste material such as sprues, runners, excess parison material and reject parts from injection molding, blow molding and extrusion, which has been reclaimed by shredding or granulating. Regrind is usually mixed with virgin compound at a predetermined percentage for remolding.

Reinforced Plastic: A plastic composition in which fibrous reinforcements are embedded, with strength properties greatly superior to those of the base resin.

Release agent: a material sprayed on the mold which facilitates removing the part.

Resin (Synthetic): The term is used to designate any polymer that is a basic material for plastics.

Restricted Gate: A very small orifice between runner and cavity in an injection mold. When the part is ejected, this gate readily breaks free of the runner system. Generally, the part drops through one chute and the runner system through another leading to a granulator and scrap reclaim system.

Retainer Plate: The plate on which demountable pieces, such as mold cavities, ejector pins, guide pins, and bushings are mounted during molding.

Retractable Cores: Used when molding parts in cavities not perpendicular to the direction in which the part is ejected from the mold. The cores are automatically pulled from the mold prior to the mold opening and reinserted when the mold closes again and prior to injection.

Rib: A reinforcing member of a molded part.

Ring Gate: Used on some cylindrical shapes. This gate encircles the core to permit the melt to the first move around the core before filling the cavity.

Robot: Automated devices for removing parts upon ejection from an open mold rather than letting the parts drop. Also, see parts picker. Robots also can perform secondary functions, such as inspection, degating, precise placement of parts on a conveyor, etc.

Rockwell Hardness: A measure of the surface hardness of a material. A value derived from the increase in depth of an impression as a load of a steel indenter is increased from a fixed minimum value to a higher value and then returned to the minimum value. The values are quoted with a letter prefix corresponding to a scale relating to a given combination of load and indenter.

Runner Balancing: developing a runner system which delivers the required amount of melt to each cavity with the correct pressure to finish filling all the cavities simultaneously at the correct temperature for the part.

Runner Design: using the runner as a flow control device (positioning the gate and using the size of the runner to control the filling pattern within the cavity) in addition to getting the melt into the cavity.

Runner System: This term is sometimes used for the entire resin feeding system, including sprues, runners and gates, in injection molding.

Runner: In an injection mold, the feed channel, usually of the circular cross-section, which connects the sprue with the cavity gate. The term is also used for the plastic piece formed in this channel.

Runnerless molding (also known as Hot-Runner Mold or Insulated Runner): A mold in which the runners are insulated from the chilled cavities and are kept hot. Hot-runner molds make parts that have no scrap.

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