# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


2-Component Molding A means of producing a part with two or more materials, 1st part is generally thermoplastic injection molded part or a plastic or metal part inserted into the mold. Liquid silicone rubber or plastic is then injected onto to the part, attaching by means of mechanical or chemical bond


Abrasion Surface wear caused by relative motion between two or more contacting objects

Abrasion Resistance The ability of a rubber compound to resist surface wearing by mechanical action

Absorption The physical mechanism by which one substance takes up another substance into its interior

ABS Acrylonitrile-butadiene-styrene

Accelerated Life Test Any set of test conditions designed to reproduce, in a short time, the deteriorating effect obtained under normal service conditions

Accelerator A substance that speeds up curing or vulcanization of natural/synthetic rubbers

Acid Resistance Withstands the action of acid

Acrylic A polymer for which resistance to air and hot oil at temperatures above 30 degrees Fahrenheit is required

Adhere To cling or stick together

Adhesion Tendency of rubber to bond or cling to a contact surface

After Cure Continuation of curing after heat source removed i.e. injection mold or compression mold

Aging The change in physical and chemical properties of an elastomer that has been exposed to a particular environment over time

Aging, Accelerated Tests run on destructive influence of light, oxygen, heat and ozone in as short a period as possible

Air Trap Surface markings or depressions due to air caught between the material being cured and the mold surface

Ambient Temperature The temperature of the environment surrounding a particular object

Aniline Point The lowest temperature at which equal volume of pure, fresh aniline and oil will completely dissolve in one another is the aniline point of the oil.

Annealing A process of holding a material at a temperature near, but below, its melting point, to permit stress relaxation without distortion of shape.

Antioxidant Any organic compound that slows the process of oxidation

Anti-ozonant Any substance that slows the severe oxidizing effect of ozone on elastomers. Exposure to ozone typically causes surface cracking in many rubbers

AQL Accepted quality level

ASA Acrylic-styrene-acrylonitrile

ASTM American Society for Testing and Materials, An organization for issuing standard specifications on materials

Axial Seal A face seal squeezed on both the top and bottom surfaces of the seal's cross section


Back Rind Distortion of the mold parting line, usually in the form of a ragged or torn indentation

Backup ring A washer-like device of a relatively hard, tough material installed in the gland on the downstream side of the seal to prevent seal extrusion into the diametrical gap while under pressure

Backup washer A washer made from certain material that will add strength or support when installed next to the seal. This prevents the seal from being pinched and evenly distributes the load

Bake Out A process whereby a vacuum system is heated for a given time at some predetermined temperature to de-gas all the components, such as gauges, fittings, valves, seals

Base Line The mark from which all features are dimensioned or measured from.

Batch The product of one mixing operation or shipment of Liquid Silicone Rubber

Batch Number The assigned number that identifies a batch of Silicone Rubber

Blemish A mark, deformity or injury which impairs appearance

Blisters A raised spot on the seal's surface created by an internal void, or air-filled pocket

Bloom A milky surface discoloration caused by the migration of certain compound components (i.e. antiozonants) to the rubber\'s surface after molding or storage. The milky film serves as a protective coating shielding the part from oxidation

Bond The term commonly used to denote the attachment of a given elastomer to some other member, classified as follows:

  1. Mechanical: purely physical attachment accomplished by through holes, interlocking fingers, envelope design in silicone rubber
  2. Cold: adhesion of previously vulcanized elastomer to another member through use of suitable bonding agent
  3. Chemical: adhesion of an elastomer to a previously primed or glass particle surface using heat and pressure, thus curing the silicone rubber

Bore A hole machined in a component which permits the passage of a shaft

Bore Seal A sealing system, usually in a radial orientation, in which the primary sealing surface is between the OD of a silicone rubber seal ring and the ID of a bore

Boss Protuberance on a plastic part designed to add strength, facilitate alignment, provide fastenings, etc

Brittleness Tendency to crack upon physical deformation


Carbon Black A black material used as a filler in rubber. It gives the rubber its black color and the hardness characteristics

Cavity The features of a mold which are directly responsible for forming the final shape of a molded part

Chemical bonding A method for bonding rubber to secondary parts by applying special adhesives or having a glass element on part prior to liquid silicone molding

Clamping Plate A plate fitted to a mold and used to fasten the mold to a plate

Clamping Pressure The pressure applied to the mold to keep it closed during a cycle of an silicone injection molding machine

Clearance The space between components in a mechanical system which is present to allow for manufacturing, thermal, and dynamic variations in the size and position of the components.

Coating A uniform layer of chemical primers or adhesives applied to a surface to produce a chemical bond between the liquid silicone rubber and substrate. May also refer to 2-component silicone molding or special surface treatments that can be applied to silicone rubber to achieve desired properties

Coefficient of Thermal Expansion Average expansion per degree over a stated temperature range, expressed as a fraction of initial dimension, linear or volumetric

Cold Flexibility Flexibility following silicone rubber exposure to a specified low temperature for a specified period of time

Cold Flow A term describing the tendency of certain materials to continue to deform or "creep" under constant sealing pressure

Cold Runner Runner less liquid silicone injection molding system of delivering liquid silicone to heated cavity

Cold Slug The first bit of material to enter a silicone injection mold; so called because in passing through a sprue orifice it is cured

Compound A mixture of a polymer and associated chemical ingredients necessary to produce a finished high consistency rubber material. The term is commonly used when referring to a specific rubber not liquid silicone rubber which is delivered in closed system

Compression Molding A traditional molding process in which the uncured high consistency rubber compound is placed directly into the mold cavity, and compressed to its final shape by the closure of the mold. Considered unacceptable for many applications because parts must be de-flash causing debris.

Compression Set Permanent deformation experienced by a rubber material when compressed for a period of time. The term is commonly used in reference to a test conducted under specific conditions wherein the permanent deformation is expressed as a percentage and measured after a prescribed period of time. Low compression set is desirable in molded rubber parts such as seals and gaskets, which must retain their dimensions to maintain an effective seal

Compressive Strength The maximum compressive stress carried by a test specimen during a compression test

Concentricity A condition in which two or more features (cylinder, cones, spheres, hexagons, etc..) in any combination, have a common axis

Conductive Silicone Rubber A silicone rubber capable of conducting electricity. Most generally applied to silicone rubber products used to conduct static electricity or as an RF shield

Conversion Fahrenheit to Celsius F = (° C x 9/5) +32 or C = (° F - 32) x 5/9

Cooling Channels Channels located within the body of a plastic injection mold through which a cooling fluid is circulated to control the mold surface temperature

Core The male portion of a liquid silicone rubber injection or plastic mold.

Core Bar A steel bar used to hold machined core in place in the liquid silicone injection mold

Core & Cavity Set A sub set of a liquid silicone rubber injection or plastic mold that fits within a mold base. This technique generally lowers silicone or plastic tooling investment

CPE Chlorinated Polyethylene

CPVC Chlorinated Polyvinyl Chloride

Cracking Sharp breaks or fissures in silicone rubber surfaces resulting from excessive strain or exposure to adverse environmental factors

Creep The progressive relaxation of an elastomeric material under constant sealing pressure (compressive load)

Cross-linking Agents A chemical or chemicals that bond the silicone rubber polymer chains of a silicone rubber together during the liquid silicone molding process

Cross Section-Axial When the part is flat (relative), the cross section that is at 90 to the linear plane

Cross Section-Radial When the part is flat (relative), the cross section in the linear plane

Cure The heat induced process that causes a chemical change in the liquid silicone rubber material, turning it into the finished silicone rubber part

Cure Time The preset time needed to complete the liquid silicone rubber curing process

Curing temperature The temperature of liquid silicone rubber thermoset vulcanization

Cross-Sectional Compression The deformation placed on a silicone rubber part to affect a seal. It is expressed as a percentage of the seal\'s original cross-section


Damping The ability of a silicone elastomer to absorb forced vibrational energy

Daylight Opening The clearance between two platens of a silicone injection molding machine in the open position

Deburr Removal of material from a drilled or punched hole, waste from saw cuts of material or sharp or rough edges

Deep Injection A common molding defect identified by the deep depression in the rubber part at the point of injection

DeflashingAny of various processes used to remove extraneous silicone rubber from a silicone injection molded rubber part. Generally the sign of poor mold design or maintenance.

Density Weight per unit volume of a substance expressed in grams per cubic centimeter

Diametrical Clearance The gap between the two mating metal surfaces forming a gland\'s internal cavity. Through slight oversizing and accompanying compression of the O-Ring seals this gap to prevent system leakage

Diaphragm Gate Used in symmetrical cavity filling to reduce weld-line formation and improve filling rates

Die Cut The process of stamping out the ID or OD by placing the part on a mechanical fixture to perform this function

Direct Gate The sprue feeds directly into the mold cavity

Dispersion Finely divided particles of a material in suspension in another substance

Draft The degree of taper of a side wall or the angle of clearance designed to facilitate removal of parts from a mold

Drooling The extrusion or leakage of molten liquid silicone rubber from a nozzle or nozzle sprue bushing area while or prior to shooting

Durometer Standard rubber industry hardness test for liquid silicone rubber molded or extruded parts. The hardness scale most commonly used for silicone rubber durometer is the Shore A scale

Dwell A pause in the application of pressure to a mold, made just before the mold is completely closed, allowing any gases formed or present to escape from the molding material

Dynamic Seal A seal used in an environment that subjects it or a mating surface to movement


EC Ethyl cellulose

Edge Gate A method of injecting liquid silicone rubber into the mold cavity

Ejector Housing "U" shaped frame which is an integral part of the tool containing the ejector retainer plate and ejector plate

Ejector Pin (knockout "KO" Pin) A pin or plate that is driven into a mold cavity from the rear as the mold opens to force out the finished part

Ejector Plate A bar that actuates the ejector assembly when the mold opens

Elastic Limit Maximum stress that a material will stand before permanent deformation occurs

Elasticity The property of an article, generally liquid silicone rubber, which tends to return to its original shape after deformation

Elastomer Any natural or synthetic material with resilience or memory sufficient to return to its original shape after major or minor distortion, i.e. liquid silicone rubber

EMI Electromagnetic interference

Encapsulating Enclosing an article in a closed envelope of liquid silicone rubber or plastic, by immersing or over molding the object in a silicone rubber or plastic

EP Ethylene propylene

EPDM Ethylene propylene diene monomer rubber

ESCR Environmental stress crack resistance

ETFE Ethylene-tetrafluoroethylene

EVA Ethylene-vinyl acetate

Extending Flash Flash that is formed at the parting line of a liquid silicone mold, can be minimized by good silicone mold practices

Extrusion When part or all of a component is forced from its groove by high continuous or pulsating pressure


Face Seal A sealing system in which the sealing occurs in the axial direction of the seal. If the seal ring were to be placed flat upon a desktop, the seal compression would occur between the top and bottom of the seal

Family Mold A multi-cavity mold where each of the cavities forms one of the component parts of the assembled finished part

Fan Gate This gate is used to help reduce stress concentrations in the gate area by spreading the opening over a wider area. Less warpage of parts can usually be expected by the use of this gate type. Frequently used in large silicone rubber parts

FDA Food & Drug administration

Feather Edge The sharp, thin edge on parts such as wiper seals. Also called a knife edge

Filler A finely divided material used to reinforce or modify elastomer physical properties, impart certain processing properties, or reduce cost. Typical examples are carbon black, clay, calcium carbonates and silica

Fillet A rounded filling of the internal angle between two surfaces of a part

Fin The web of material remaining in holes or openings in a molded part which must be removed for final assembly

Flame Resistance The resistance to burning of material that will not withstand combustion under ordinary conditions

Flash Excess rubber left around a liquid silicone rubber part after molding, due to space between mating mold surfaces; removed by trimming. Sign of poor silicone rubber mold maintenance or design.

Flexural Strength The ability of a material to flex without permanent distortion or breaking

Flow The ability of heated plastic or uncured rubber to travel in the mold and runner systems during the molding process

Flow Line A disturbance in the homogeneous structure of a liquid silicone molded part generally caused when material knitted or blended with itself during the silicone molding operation

Flow Marks Wavy surface appearance of an object silicone molded caused by improper flow of the liquid silicone rubber or plastic into the mold. A mark made by the freezing-in of a visible flow pattern

Fluid A liquid or gas

Fluorocarbon Viton ® DuPont Dow Elastomers, Fluorel TM, 3M Co. Polymer designed to meet the most rigid requirements in oils, solvents, synthetic lubricants and corrosive chemicals, at elevated temperatures

Friction Resistance to motion due to contact of surfaces.

 Friction, Break Out Friction developed during initial or starting motion.

FRP Fiber reinforced plastics

Fused Disposition Modeling Process (FDM) Thermoplastic modeling material is fed into the temperature-controlled FDM extrusion head and heated to a liquid state. The head extrudes and deposits the material in ultra-thin layers onto a fixture-less base

Fixture Block of metal or wood used to maintain the proper shape or to perform secondary operation.


Gamma Radiation Electromagnetic disturbance (photons) emanating from an atomic nucleus. This type of radiation travels in wave form, similar to X-Rays or light, but has a shorter wave length (approx. 1 Ado or 107 mm)

Gasket A static (stationary) sealing device used to retain fluids under pressure or to seal out foreign matter

Gate A silicone injection molding or plastic orifice through which the silicone rubber or plastic enters the cavity

Gate Edge A gate that is cut along one edge of the silicone rubber or plastic mold cavity

Gate Fan Large cross sectional area for feeding plastic into the silicone rubber or plastic cavity. Flow channel tapered from the silicone rubber or plastic runner to the gate

Gate Flash A gate that encompasses entire periphery of the silicone rubber or plastic part. Usually of low sectional thickness in relation to silicone rubber or plastic part

Gate Mark A raised spot or small depression on the surface of a silicone rubber or plastic injection molded part where the gates interface the cavity

Gate Sprue The type of gate in which the liquid silicone rubber or plastic is injected directly from the molding press into the cavity

Gate Underside The orifice found between the \"A\" and \"B\" plate which carries the resin into the cavity in an overlap of the part in such a manner so as to obtain a clean break on the part. Usually found in thermoset molding

Gates the openings in an injection or transfer mold whereby material enters the mold cavity

Geometric Dimensioning & Tolerancing A means of specifying engineering design and drawing requirements with respect to actual function and relationship of part features, it is a technique which properly applied ensures the most economical and effective production of these features

Gland The space in a mechanical system into which a seal is installed. the gland consists of the seal groove and any additional space required to achieve the proper compression of the seal. Care should be taken to distinguish between the terms gland and groove, which are separate but related concepts


Hardness A measurement of the resistance to penetration of a silicone rubber sample by an indenter on a Durometer tester. High values indicate harder materials while low values indicate softer materials.

HDPE High-density polyethylene

HDT Heat-deflection test

Heat deflection temperature The temperature at which a standard plastic test bar deflects 0.010 in. under a load of either 66 or 264 psi

Heat Sealing A method of joining plastic parts or films by simultaneous application of heat and pressure to areas in contact.

Hermetic Seal An airtight seal

HIP High-impact polystyrene

HME High-vinyl modified epoxy

HMW High molecular weight

Hob A master model in hardened steel. Also the wearing in of an A&B plate of a silicone injection mold

Honing A machining process that sharpens, enlarges, and smooths material through the use of a fine-grit stone

Hot Runner Manifold Runner less plastic injection molding of a thermoplastic, the melt stays molten until is reaches gate at cavity.

Hot Stamping Engraving operation for marking plastics in which roll leaf is stamped with heated metal dies onto the face of an article by means of felt rolls, ink is applied to type or by means of heat and pressure, type is impressed into the material, leaving the marking compound in the indentation


Impact Resistance Relative susceptibility of plastics or silicone rubber to fracture by shock as indicated by the energy expended by a standard pendulum type impact machine in breaking a standard specimen in one blow

Injection Molding A molding method in which a liquid silicone rubber or plastic material is heated and forced under pressure into the mold cavity

Injection Pressure The pressure on the face of the silicone injecting ram when injecting material into the mold

Injection Tearout A molding defect identified by a hole in the silicone liquid rubber part at varying widths and depths located at the point where the silicone rubber is injected into the cavity area

Insert A term referring to a metal or plastic component, placed (\"inserted\") into a mold cavity prior to the start of the molding cycle, to which rubber or plastic is chemically and/or physically bonded during the molding process

Insert Molding A means of producing a part with two or more materials, the metal, plastic or liquid silicone rubber part is inserted into the mold and plastic or silicone rubber is injected onto to the part attaching by means of mechanical or chemical bond

Internally Lubricated Rubber A silicone rubber formulation containing lubricating materials incompatible with the silicone rubber structure causing it to leach out as a lubricant

ID (Inner Diameter) The innermost (smallest diameter) surface of a circular object, such as a bore or a round seal

Isoprene-acrylonitrite Rubber A low-plasticity copolymer with around 34 per cent ACN.


Jetting A turbulent flow of plastic or silicone rubber accelerating the speed of the melt can be caused by undersized gate or bad mold design

Jig A tool for holding parts of an assembly during the manufacturing process


Knit Line Place or line where two or more flow fronts come together after going around a flow restriction or post

Knock Out (Ejector) Pins Normally pins or blades that, when activated internally to the plastic or liquid injection mold, eject the part from the mold

Knock Out (Ejector) Plate A plate in a plastic or liquid silicone rubber injection mold connects and drives the ejector pins in the plastic or silicone mold


Laminar Flow The flow of a resin in a plastic or liquid silicone rubber 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

Land A shut off surface of a cavity on a plastic or liquid silicone rubber mold by which excess air escapes

LMW Low molecular weight

LDPE Low-density polyethylene

LCP Liquid crystal polymer

LIM Liquid injection molding is injection molding silicone rubber, Casco Bay Molding's specialty

LLDPE Linear low-density polyethylene

LSR Liquid silicone rubber is generally a platinum cured, two-component, low viscosity, heat-curable silicone rubber system delivered in a closed drums or buckets. Casco Bay Molding\'s specialty

L/D Ratio The length over diameter ratio defining a silicone rubber injection or plastic screw

Low Cervix A low cervix is when the cervix sits lower in the vagina, either due to natural menstrual cycle rhythm or a medical condition. Women with a low cervix might want to try the Casco Cup Mini. It is a shorter design and may provide a more secure and comfortable fit during menstruation.


Machine Shot Capacity This is the maximum weight of PS (not silicone rubber) which can be displaced or injected by a single stroke

MBS Methyacrylate-buadiene-styrene

MDPE Medium-density polyethylene

Mechanical Bond A method of physically bonding liquid silicone rubber to inserts through the use of holes, depressions or projections in the insert

Melt Index A measure in grams of plastic material that can be forced through an orifice of 0.0825 inches when subjected to a force of 2160 grams in 10 minutes at 190°C

Memory Ability of a silicone rubber or elastomeric material to return to its original size and shape after deformation

Menstrual Cup A Menstrual Cup is a safe, healthy, and affordable alternative to pads and tampons for menstruating women. Instead of absorbing menstrual blood, menstrual cups are inserted to "collect" it. This allows the menstrual cup to be worn for up to 10-12 hours in-between emptying. They are typically made from USP Healthcare-Grade Class VI Silicone, but there are a few "offenders" produced overseas from inferior materials.Casco Bay Molding produces the Casco Cup & Case, an all-in-one solution to the problem of messy cloth baggies that typically accompany other menstrual cup brands.

Mismatch Unequal cross-sectional match between the two mold halves, seen in silicone injection molded parts.

MMA Methyl methacrylate monomer

Modulus Tensile stress at specific elongation, normally 100% elongation for silicone elastomers

Modulus of Elasticity One of several measurements of stiffness or resistance to deformation, but often incorrectly used to indicate specifically static tension modulus

Moisture Marks or Welds Marks on the finished part that are caused from moisture in the resin and look like weld lines except they may be in the wrong areas for weld lines

Mold Typically made from steel for liquid silicone tooling, article is produced by injecting silicone into machined cavity

Mold Base Mold frame that holds mold cavities

Mold Cavity Hollow space of the mold within which the liquid silicone rubber is injected and cured to the desired finished product form

Mold Finish The surface finish of the silicone injection mold which imparts the desired surface quality to the finished molded silicone product

Mold Marks Slight irregularities in the surface of molded articles caused by mold machining marks, or damage to the mold itself

Mold Shrinkage The difference in dimension, expressed in inches per inch, between a silicone part and the steel cavity in which it was injection silicone molded, when both are measured while at room temperature

Mold: Three Plate Integral moving plates in a conventional silicone injection mold, containing the cavities and allowing the injection point or gate to feed directly into the part

MOQ Minimum Order Quantity

MSDS Material safety data sheet

MUD Set MUD stands for Master Unit Die. A MUD set is a purchased universal injection mold base which reduces injection mold fabrication cost. Great for short runs, quick overturn and repair.

MW Molecular weight


Neoprene (GR-M) A DuPont Dow Elastomers polymer of chloroprene which is prepared from coal, salt and limestone, not injection molded

Nitrile Or Buna-N, The most commonly used elastomer for O-Rings because of its resistance to petroleum fluids, its good physical properties, and its useful temperature range

Non-fill An unintentional void or absence of material in the liquid silicone rubber part

Nominal Dimension The mean dimension of a liquid silicone injection molded article, from which small dimensional (plus and minus) deviations are allowed as manufacturing tolerances

Nozzle The hollow cored metal nose of a liquid silicone injection screw and barrel that seats off against an LSR mold


O-Ring A doughnut-shaped object that functions as a seal, blocking the passage of liquids or gases, by being compressed between the two mating surfaces comprising the walls of the cavity into which the ring is installed

Off-register Misalignment of mold halves causing out-of-round O-Ring or part cross section

Oil Resistant Ability of liquid silicone or natural rubber to resist swelling and other detrimental effects of exposure to various oils

Orange Peel A surface finish on a liquid silicone molded part that is rough and splotchy

Original Equipment Manufacturer (OEM) A company who makes components that are used in other products

Oscillating Seal Most commonly used in faucet valves, in this application the inner or outer member of the gland moves in an arc around the axis of a shaft. Movement is limited to a few turns in one direction and a few turns in the return direction (i.e. faucet on, faucet off)

Outgassing A phenomenon wherein a substance (i.e. silicone or natural rubber) spontaneously releases volatile constituents in the form of vapors or gases normally during curing process with liquid silicone rubber.

Overflow A designed escape reservoir for liquid silicone rubber, used to insure mold cavity fill and also allowance for excess compound, generally frowned upon because part requires post molding trimming

OD, Outer Diameter The outermost, largest, surface of a circular object, such as a shaft or a round seal. the term OD is frequently used to indicate both the circumferential surface itself as well as the measured diameter of that surface

Ozone Resistance Ability to withstand the deteriorating effect of ozone, which generally causes cracking


PA Polyamide (nylon)

Pack Out The filling of the liquid silicone mold cavity or cavities as full as possible without causing undue stress on the silicone mold or causing flash to appear on the finished parts

PAI Polyamide-imide

PAN Polyacrylonitrile

PB Polybutylene

Parting line The witness line on the surface of a silicone molded part corresponding to the location where the LSR mold plates were in contact

PBT Polybutylene terephthalate

PBTP Polybutylene terephthalate

PC Polycarbonate

PCTFE Polychlorotrifluoroethylene

PE Polyethylene

PEC Polyphenylene ether copolymer

PEEK Polyetherether ketone

PEH Polyphenylene ether homopolymer

PEI Polyetherimide

PEO Polyethylene oxide

Permanent Set The deformation remaining in a liquid silicone rubber specimen following both stress and relaxation over a period of time

Permeability The rate at which liquid or gas, under pressure, passes through a solid material by diffusion and solution. In silicone rubber terminology: the rate of gas flow, expressed in atmospheric cubic centimeters per second, through an elastomeric material, one centimeter square and one centimeter thick

PES Polyethersulfone

PET Polyethylene terephthalate

PETG Glycol-modified PET

PETP Polyethylene terephthalate

PETP Polyethylene terephthalate

PF Phenyl-formaldehyde

PFA Perfluoroalkoxy (resin)

PH Determines the concentration of either an acid or a base

PI Polyimide

PIB Polyisobutylene

Plasticize To soften a silicone rubber by making it plastic, less viscous or moldable, either by means of a plasticizer or the application of heat

Plasticizer A chemical agent added to the rubber compound batch mix to soften the elastomer for processing, as well as to improve physical properties of the compound product (i.e., increase elongation, reduce harness, improve tack)

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

Plate Stripper A plate that strips a liquid silicone molded piece from core pins or force plugs. The stripper-plate is set into operation by the opening of the mold

Platens The mounting plates of a press to which the entire mold assembly is bolted

Platen: Movable The large back platen of an silicone injection molding machine to which the back half of the mold is secured during operation. The platen is moved horizontally or vertically by either a hydraulic ram or a toggle mechanism

Platen: Stationary The large front plate of an silicone injection molding machine to which the front plate of the mold is secured during operation

PMMA Polymethyl methacrylate

PMS Paramethylstyrene

PMT Polymethylpentene

Polymer A material formed by joining together many (poly) individual units (mer) of one or more monomers; synonymous with elastomer

Post Cure The process of baking or autoclaving silicone parts after molding. This process is used to improve the heat and compression set resistance of specific elastomers- like silicone and fluorocarbons.

PP Polypropylene

PPAP (Part Production Approval Process) Our ability, as product supplier, to meet requirements determined by our customers through continued process documentation and analysis. See PPAP link for more information.

PPO Polyphenylene oxide

PPS Polyphenylene sulfide

Pressure Injection The pressure on the face of the injection ram at which molding silicone rubber is injected into a mold, liquid silicone rubber generally uses much lower injection pressures when compared with plastic injection

PS Polystyrene

PTFE Polytetrafluoroethylene

PU Polyurethane

Purging Cleaning one color or type of liquid silicone rubber from the cylinder of an injection molding machine by forcing it out with the new color of LSR

PVC Polyvinyl chloride

PVDF Polyvinylidene Fluoride

PVF Polyvinyl Fluorid


QS 9000 Quality System model, used in conjunction with the ISO 9000 standard, for the automotive industry

Quench Bath The cooling medium used to quench molten thermoplastic materials to the solid state

Quick Cast An SLA build style that produces a thin shell with a honeycombed interior. This method is used mostly for investment castings when the SLA model will be used as a sacrificial mold


Radial Seal Compression is applied perpendicular to the seal center-line

Rapid Prototyping Fabrication of a physical, three-dimensional part of arbitrary shape directly from a numerical description, typically a CAD model, by a quick, highly automated and totally flexible process.

Reciprocating Seal Seals used in moving piston and rod situations

Regrind A process that finely grinds plastic part runners and rejected parts

Relative Humidity The ratio of the quantity of water vapor actually present in the atmosphere, to the greatest amount possible at a given temperature

Resilience The capability of returning to original size and shape after deformation

RF Radio Frequency

Rockwell Hardness A standard method for measuring the hardness of metals. The hardness is expressed as a number related to the depth of residual penetration of a steel ball or diamond cone after a minor load of 10 kilograms has been applied to hold the penetrate in position, designated by letters varying from "A" to "H" the "B" and "C" scales are most commonly in use.

Rotary Seal Seals for rotating shafts, with the turning shaft protruding through the I.D. (hole) of the O-ring

RTV Molding A procedure where a part is molded in a silicone mold to reproduce up to twenty urethane parts

Rubber A common name for both naturally occurring and synthetically made elastomers like liquid silicone rubber

Rubber: Natural A natural product of the juices of certain tropical plants (latex), improved through heat treating with sulfur (vulcanization)

Rubber: Synthetic Man-made elastomers such as Nitrile, Fluorocarbon, Silicone and liquid Silicone rubber

Runner The channel that connects the sprue with the gate for transferring the molten liquid silicone rubber to the cavities


SAN Styrene-acrylonitrile

SBR Styrene-butadiene (rubber)

Seal Off A feature on two liquid silicone mold halves or cavity inserts seal off the cavity with the exception of the silicone injection gate and air venting ports

Seal Any device used to prevent the passage of a fluid, liquid or fine particles

Shore A A hardness scale used to measure the hardness of molded silicone rubber. The Shore A scale is most effectively used to measure liquid silicone rubber with a hardness from 10 to 95 Shore A

Short shot A condition where there is insufficient liquid silicone rubber is introduced into a LSR mold cavity to completely fill the cavity, resulting in a partially formed part

Shot The complete amount of silicone rubber required to fill all silicone mold cavities completely

Shot Capacity The maximum weight of liquid silicone rubber which an injection machine can inject with one forward motion of the screw

Shrinkage The ratio between a mold cavity size and the size of a product molded in that cavity

Single Cavity Mold A silicone injection mold having only one cavity and producing only one finished part per cycle

Sink Marks A shallow depression or dimple on the surface of a finished plastic part due to shrinkage or low fill of the cavity, much less prevalent in liquid silicone rubber parts

Sliding Core A pin on a mold that automatically retracts when the mold opens

SMA Styrene maleic anhydride

SPC (Statistical Process Control) Methods of controlling our processes to prevent defects from being made

Specific Gravity The ratio of the mass of a unit volume of a material to that of the same volume of water at a specified temperature

Spiral Twist A type of seal failure resulting from a twisting action that strains or ruptures the rubber

Splay Marks Marks or droplet-type imperfections found on the surface of the finished parts that may be caused by the spraying of the melt through the gates and into the cool cavity

Sprue The primary feed channel that runs from the outer face of a silicone injection mold to the mold runner and gates

Sprue Bushing A hardened steel insert in the silicone injection mold that accepts the silicone molding machine nozzle and provides an opening for transferring the silicone or molten plastic

SPS Syndiotactic Polystyrene, High heat resistant thermoplastic material with crystalline structure. Generally glass filled. Used in under hood-automotive or other high heat applications i.e. sterilization cassettes and electrical connectors. Casco Bay Molding has extensive experience injection molding and ultrasonically welding SPS.

Static Seal A seal that, except for pulsations caused by cycle pressure, does not move in its environment

Static Mixer A helix like device that mixes two liquids by redirecting the flow path into each other repeatedly, common with RTV Silicone and some liquid silicone rubber applications

Statistical Process Control (SPC) The use of statistical techniques on processes and their output to establish process stability and increase capabilities

Strain Deformation caused by an applied stress

Stress Force per original cross section that is applied to a specimen

Stress Relaxation Decreasing stress with constant strain over a given time interval or viscoelastic response

Stripper Plate A plate that strips a molded plastic or liquid silicone rubber part from core pins

Sublimation The direct conversion of a substance from solid state to vapor or gas state

Submarine Gate Tunnel gate, a type of edge gate where the opening from the runner into the mold is located below the mold parting line

Suck Back A method of decompressing a molds runner system by retracting the screw on a plastic or silicone injection molding machine

Steel Safe Add Plastic = Removing Steel, Removing Plastic = Adding Steel (welding or inserting). When it comes to mold-making, you can always cut more metal away - making your plastic part larger, walls thicknesses wider, etc. - but adding metal back to the mold - removing walls, thinning features, etc.-  can be extremely costly, and often times not possible.

Stereolithography (SLA) This form of 3D-printing utilizes a UV laser to cure photo-reactive liquid resin layer by layer into a solid form pre-defined by a 3D modeling file.

Selective Laser Sintering (SLS)','2014-09-23 14:20:07','2014-09-23 18:12:00','selective-laser-sintering-sls-2','This method of rapid prototyping utilizes a laser to soften a powdered material, (typically metal),  and binding it together into a form pre-defined by a 3D-model.

(321,'Plastic Jet Printing','2014-09-23 14:21:08','2014-09-23 14:27:36','plastic-jet-printing','This process involves melting a solid plastic and extruding it layer by layer until the 3D -model is formed. In more complicated shapes, sometimes a soluble plastic is also extruded as a support piece, these can either be defined by the designer, or automatically rendered in the 3D modeling program..

(322,'Color Jet Printing ','2014-09-23 14:21:39','2014-09-23 18:14:28','color-jet-printing','This system involves two main components, the core and the binder. It begins with a layer of the core laid out on the building platform, and then the binder is ejected from inkjet printer heads. This effectively bonds and sets the material, while adding the color.


USP Medical Grade Class VI For a material to be considered USP Class VI, it must pass a series of tests performed by the material supplier to determine the amount of irritation the material causes. These tests are:

  • Acute System Toxicity Test: Oral, dermal, and inhalation.
  • Intracutaneous Test: Exposed tissues are subject to contact with the material in question.
  • Implantation Test: Samples of the material are implanted into a living animal for 5 days.\n\nBased on the result of these tests, the material is assigned a class between I and VI, (VI being the strictest & least irritating).

More detailed information can be found here.