Ocaps Polymer Processing Terms

Front 1

Boss

Back 1

Portuberance on a plastic part designed to add strength, facillitate alignment, provide fastenings

Front 2

Clamping plate

Back 2

plate fitted to a mold and used to fasten the mold to a plate

Front 3

Daylight opening

Back 3

clearance between 2 platens of a clamping press in the open position

Front 4

delamination

Back 4

surface of the finished part separates or apperas to be composed of layers-- fish scale appearance

Front 5

diaphragm gate

Back 5

used in symmetrical cavity filling to reduce wel-line formation and improve filling rates

Front 6

drooling

Back 6

extrusion or leakage of molten resin from a nozzle

Front 7

dwell

Back 7

pause in application of pressure to a mold -- made just beore the mold is completely closed allowing gas to escape

Front 8

fan gate

Back 8

used to help reduce stress concentrations in the gate area by spreading the opening over a wider area

Front 9

fin

Back 9

web of material reminging in holes or openings in a molded part which must be remove for final assembly

Front 10

flash

Back 10

extra plastic attatched to along parting sides

Front 11

hob

Back 11

master model of hardened steel--sink the shape of a mold into soft metal block

Front 12

jetting

Back 12

turbulent flow in the resin melt caused by an undersized gate or where a thin section becomes thicker

Front 13

jig

Back 13

tool for holding parts of an assambly

Front 14

knit lines

Back 14

marks visible on a finished part made by the meeting of 2 flow fronts during molding

Front 15

laminar flow

Back 15

flow of a resin in a mold is accompanied by solidification of the layer in contact with the mold surface that acts as an insulator through which material flows to fill the remainder of the cavity

Front 16

machine shot capacity

Back 16

(polystyrene--determines) max weight of plastic which can be displaced or injected by single stroke

Front 17

pinch-off

Back 17

raised edge around mold cavity that seals off the part and separates excess material as the mold closes around the parison in the flow-molding operation

Front 18

ram

Back 18

delivers a shot of resin to the nozzle and mold

Front 19

restricted gate

Back 19

very small orifice between runner and cavity in an injection mold--when part is ejected, this gate breaks free of the runner system

Front 20

runner

Back 20

channel that connects the sprue w/ the gate for transferring the molten plastic into cavities

Front 21

side bars

Back 21

loose pieces used to carry one or more molding pins and operated outside the mold

Front 22

side draw pins

Back 22

projection used to core a hole in a direction other than the line of closing of a mold and which must be withdrawn before the part is ejected from the mold

Front 23

split-ring mold

Back 23

mold in which a split cavity block is assembled in a chase to permit the forming of undercuts in a molded piece

Front 24

spreader

Back 24

streamlined metal block placed in the flow of molten resin in the heating cylinder or extruder systems to spread the flow into thin layers for better heat trans.

Front 25

sprue brushing

Back 25

hardened steel insert in mold that accepts extrusion nozzle and provides opening for transferring molten plastic

Front 26

striations

Back 26

marks on the molded par surfaces that indicated resin flow directions or impingement

Front 27

stringing

Back 27

occurs between the finished part and the sprue--when mold opens, resin in this area has not cooled enough

Front 28

stripper plate

Back 28

plate that strips a molded piece from core pins or force plugs--set into operation by opening the mold

Front 29

submarine gate (tunnel gate)

Back 29

type of edge gate where the opening from runner into mold is located below the mold parting line

Front 30

tab gate

Back 30

small removable tab -- same thickness as molded item but perpendicular to it for easy removal

Front 31

undercut

Back 31

having a protuberance or indentation that impedes withdrawal from a two-piece rigid mold

Front 32

valve gating

Back 32

gate--pin held in gate/channel by sprin tension & as spring comes forward, compresses plastic into runner. when pressure overcomes tension of spring, pin is pushed back & fast decompression of plastic fills cavit @ high speeds

Front 33

vertical flash rin

Back 33

clearance between force plug & vertical wall of cavity in a pos. or semi-pos. mold; the ring of excess material which escapes from cavity into clearance space

Front 34

warpage

Back 34

dimensional distortion in molded object

Front 35

wisps

Back 35

(smaller than stringing) flashing when mold overpacked, forced open or due to mold parting line wear