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Glossary of Industry Terms


A AXIS: The rotational axis describing motion around the X axis. This movement can be in a clockwise or counterclockwise direction.


AC SERVO: A servomechanism that is powered using an alternating current. AC servos consume less power for better reliability and performance than a DC servo.


AGING: The change of a material with time under defined environmental conditions, leading to improvement or deterioration of properties.

ALLOY: Composite material made up by blending polymers or copolymers with other polymers or elastomers under selected conditions. e.g., styrene-acrylonitrile copolymer resins blended with butadiene-acrvlonitrile rubbers.


ALTERNATING CURRENT (AC): Current that flows in opposite directions at different times. Alternating current can be used to power a servomechanism.

AML (Approved Manufacturer List): A set of approved relationships between manufacturer parts and a company’s internally defined parts. Each relationship links a manufacturer’s part number to an internal part number and results from the R&D team’s identifying the third-party parts that can be used to satisfy the manufacturing demand for the internal part. All approved AML parts for each internal part can share a single inventory bin.


ANNEAL: (1) To heat a molded plastic article to a predetermined temperature and slowly cool it to relieve stresses. (2) To heat steel to a predetermined temperature above the critical range and slowly cool it, to relieve stresses and reduce harness. (Annealing of molded or machined parts may be done dry as in an oven or wet as in a heated tank of mineral oil.)


ANTISTATIC AGENT: Agents which, when added to the molding material or applied on the surface of the molded object, make it less conducting (thus hindering the fixation of dust).


AUTOMATIC MOLD: A mold for injection, compression or transfer molding that repeatedly goes through the entire molding cycle, including ejection, without human assistance.


AUTOMATIC TESTING MACHINES: Technology that uses software to run tests without human involvement. Automatic testing machines find out whether or not a machine is functioning correctly.


AVL (Approved Vendor List): A list of all the vendors or suppliers approved by a company as sources from which to purchase materials.

AXIS: An imaginary straight line or circle used to describe the location or movement of an object in three-dimensional space. The linear axes of the Cartesian coordinate system are the X, Y, and Z axes, and the rotational axes are the A, B, and C axes.

BACK TAPER: Reverse draft used in mold to prevent molded articles from drawing freely. See UNDERCUT.


BACKING PLATE: In mold construction, a plate used as a support for the cavity blocks, guide pins, bushings, etc.


BALLSCEW: A long, threaded device that rotates to move the worktable or cutting tool of a CNC machine. Ballscrews are powered by a motor.


B AXIS: The rotational axis describing motion around the Y axis. This movement can be in a clockwise or counterclockwise direction.


BLEED: (1) To give up color when in contact with water or a solvent. (2) Undesired movement of certain materials in a plastic (e.g. plasticizers in vinyl) to the surface of the finished article or into an adjacent material. Also called "Migration". (3) An escape passage at the parting line of a mold, like a vent but deeper, which allows material to escape or bleed out.


BLISTER: A raised area on the surface of a molding caused by the pressure of gases inside it on its incompletely hardened surface.


BLOOM: A visible exudation or efflorescence on the surface of a plastic. Bloom can be caused by lubricant, plasticizer, etc.


BLOW MOLDING: A method of fabrication of thermoplastic materials in which a parison (hollow tube) is forced into the shape of the mold cavity by internal air pressure. BLUEING OFF — The checking of the accuracy of mold cutoff surfaces by putting a thin coating of Prussian Blue on one-half and checking the blue transfer to the other half.


BOSS: Projection on a plastic part designed to add strength, to facilitate alignment during assembly, to provide for fastenings, etc.


BREATHING: The opening and closing of a mold to allow gases to escape early in the molding cycle. Also called degassing.




BUBBLE: A spherical, internal void of air or other gas trapped within a plastic. See VOID.


BUBBLER: A device inserted into a mold cavity or core, which allows water to flow deep inside the hole into which it is inserted and to discharge through the open end of hole. Uniform cooling of the molds and of isolated mold sections can be achieved in this manner.


BURNED: Showing evidence of thermal decomposition through some discoloration, distortion or localized destruction of the surface of the plastic.


CAD FILES: A system used to create physical designs, usually three-dimensional. Some examples of CAD software are SolidWorks by Dassault Systemes, Pro/ENGINEER by PTC and AutoCAD by Autodesk.


CANNED CYCLES: A predetermined machining sequence used to simplify programming. Canned cycles can be used for common operations such as drilling holes.


CARBON BLACK: A black pigment produced by the incomplete burning of natural gas or oil. Widely used as a filler, particularly in the rubber industry due to its useful ultraviolet protective properties. It is also much used in molding compounds intended for outside weathering applications.


CARTESIAN COORDINATE SYSTEM: A numerical system that describes the location of an object by expressing its distance from a fixed position along three linear axes. The Cartesian coordinate system is used to program machining positions on a CNC machine.


CASE HARDEN: To harden surface of a piece of steel to a relatively shallow depth.


CAST: To form a "plastic" object by pouring a fluid monomer-polymer solution into an open mold where it finishes polymerizing.


CAVITY: Depression in mold, which usually forms the outer surface of the molded part; depending on number of such depressions, molds are designated as a single cavity or multi-cavity.


C AXIS:  The rotational axis describing motion around the Z axis. This movement can be in a clockwise or counterclockwise direction.


CENTER GATED MOLD: An injection or transfer mold wherein the cavity is filled with molding material through a sprue or gate directly into the center of the part.


CHALKING: Dry chalk-like appearance or deposit on the surface of a plastic. See HAZE and BLOOM.


CHANGEOVER: The process of switching a machine from one part setup to another. CNC machines require very little changeover.


CHROMIUM PLATING: An electrolytic process that deposits a hard film of chromium metal onto working surfaces of other metals where resistance to corrosion, abrasion and/or erosion is needed.


CLAMPING PLATE: A plate fitted to a mold and used to fasten mold to a molding machine.


CLAMPING FORCE: In injection molding and in transfer molding, the pressure which is applied to the mold to keep it closed, in opposition to the fluid pressure of the compressed molding material, within the mold cavity (cavities) and the runner system.


CLOSED-LOOP SYSTEM: A type of control system that automatically changes the output based on the difference between the feedback signal to the input signal. This allows closed-loop systems to correct errors in position.


CM (Contract Manufacturer): A firm hired by a company to manufacture or assemble its product or part of its product.


CNC LATHE: A machine tool that uses computer numerical data to control cutting operations on cylindrical workpieces. On a CNC lathe, the cutting tool moves against the rotating workpiece.


CNC MILL: A machine tool that uses computer numerical data to control cutting operations on flat, square, or rectangular workpieces. On a CNC mill, the cutting tool rotates against a workpiece that is fixed to a worktable.




COLD SLUG: The first material to enter an injection mold. So called because in passing through the sprue orifice it is cooled below the effective molding temperature.


COLD SLUG WELL: Space provided directly opposite the sprue opening in an injection mold to trap the cold slug.




COMPLIANCE: The practice of tracking whether or not a product complies with government-imposed regulations or a company’s self-imposed standards. Some types of compliance requirements are environmental requirements (e.g. RoHS and WEEE) and medical device regulations (e.g. 21 CFR Part 11 and 21 CFR Part 820).


COMPRESSION MOLD: A mold which is open when the material is introduced and which shapes the material by heat and by the pressure of closing.


COMPRESSION MOLDING: A technique of thermoset molding in which the molding compound (generally preheated) is placed in the heated open mold cavity, mold is closed, under pressure (usually in an hydraulic press) causing the material to flow and completely fill the cavity, pressure being held until the material has cured.


COMPRESSION RATIO: In an extruder screw, the ratio of volume available in the first flight at the hopper to the last flight at the end of the screw.


COMPRESSIVE STRENGTH: Crushing load at the failure of a specimen divided by the original sectional area of the specimen.


COMPUTER NUMERICAL CONTROL (CNC): A self-contained system of computers and precision motors that executes program instructions to guide machine tool components and manufacture parts. CNC machines can be either open-loop or closed-loop systems.


CONTINUOUS PATH: A type of CNC control system where cutting can take place as the tool moves from one position to the next. Continuous path systems are usually closed-loop.


CONTOURING: Tool movement along two or more axes at the same time that creates a curved or angled surface. Contouring is possible only in a continuous path system.


CONTROL SYSTEM: A method of tool and part movement in CNC machining. Point-to-point positioning and continuous path are the two main types of control systems.


CONCENTRICITY: Relationship of all inside dimensions to all outside dimensions usually as with diameter expressed in thousandths of an inch TIR (Total Indicator Reading)


COOLING CHANNELS: Channels or passageways located within the body of a mold through which a cooling medium can be circulated to control temperature on the mold surface. May also be used for heating a mold by circulating steam, hot oil or other heated fluid through channels as in molding of the thermosetting and some thermoplastic materials.


COOLING FIXTURE: Block of metal or wood holding the shape of a molded piece which is used to maintain the proper shape or dimensional accuracy of a molding after it is removed from the mold until it is cool enough to retain its shape without further appreciable distortion. Also called: ‘Shrink Fixture’.




CORE: (1) Male element in a die which produces a hole or recess in part. (2) Part of a complex mold that molds undercut parts. Cores are usually withdrawn to one side before the main sections of the mold opens. (Usually called Side Cores.) (3) A channel in a mold for circulation of a heat-transfer medium. Also called "Force."


CORE PIN: Pin used to mold a hole.


CORING: The removal of excess material from the cross section of a molded part to attain a more uniform wall thickness.


CRAZING: Fine cracks which may extend in a network on or under the surface or through a layer of plastic material.


CREEP: The dimensional change with time of a material under load, following the initial instantaneous elastic deformation. Creep at room temperature is sometimes called "Cold Flow".


CROSS SLIDE: The tool-holding component of a lathe that allows tools to approach a workpiece. The cross slide moves along two axes.


CRYSTALLINITY: A state of molecular structure in some resins which denotes uniformity and compactness of the molecular chains forming the polymer. Normally can be attributed to the formation of solid crystals having a definite geometric form.


CURE: To change the physical properties of a material by chemical reaction, which may be condensation, polymerization, or vulcanization: usually accomplished by the action of heat and catalysts along with or in combination with or without pressure.


CURING TEMPERATURE: Temperature at which a cast, molded or extruded product, a resin-impregnated reinforcing material, or adhesive etc., is subjected to curing.


CUTTING TOOL: A device that removes workpiece material in the form of chips. Cutting tools are available in many shapes and sizes.


CYCLE: The complete repeating sequence of operations in a process or part of a process. In molding, the cycle time is the period or elapsed time between a certain point in one cycle and the same point in the next.

DAYLIGHT OPENING: Clearance between two platens of a press in the open position.


DIAPHRAGM GATE: Gate used in molding annular or tubular articles. Gate forms a solid web across the opening of the part.


DC SERVO: A servomechanism that is powered using a direct current. A DC servo is less costly than an AC servo.


DEFLASHING: Covers the range of finishing techniques used to remove the flash (excess, unwanted material) on a plastic molding such as filing, sanding, milling, tumbling, etc.


DEGASSING: The opening and closing of a mold to allow gases to escape early in the molding cycle. Also called breathing.


DEGRADATION: A deleterious change in the chemical structure of a plastic.


DELAMINTATION: The splitting of a plastic material along the plane of its layers. Physical separation or loss of bond between laminate plies. See LAMINATE.


DENSITY: - Weight per unit volume of a substance expressed in grams per cubic centimeter, pounds per cubic foot, etc.


DEPTH OF CUT: The depth at which the cutting tool penetrates the surface of the workpiece. Depth of cut can be controlled by computer numerical control.


DESSICANT: Substance which can be used for drying purposes because of its affinity for water.


DESTATICIZATION: Treating plastics materials to minimize their accumulation of static electricity, and subsequently the amount of dust picked up by the plastics because of such charges. See ANTISTATIC AGENTS.


DETERIORATION: A permanent change in the physical properties of a plastic evidenced by impairment of these properties.


DIELECTRIC: Insulating material. In radio frequency preheating, dielectric may refer specifically to the material which is being heated.


DIMENSIONAL STABILITY: Ability of a plastic part to retain the precise shape in which it was molded, fabricated or cast.


DIRECT CURRENT (DC): Current that flows in one direction. Direct current can be used to power a servomechanism.


DISCOLORATION: Any change from the original color, often caused by overheating, light exposure irradiation or chemical attack.


DISHED: Showing a symmetrical distortion of a flat or curved section of a plastic object so that as normally viewed it appears concave, or more concave than intended. See—WARP.


DISPERSION: Finely divided particles of a material in suspension in another substance.


DOMED: Showing a symmetrical distortion of a flat or curved section of a plastic object, so that, as normally viewed, it appears convex, or more convex than intended. See—WARP.


DOWEL: Pin used to maintain alignment between two or more parts of a mold.


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


DRAFTING SYSTEMS: Technology that uses a computer to design a product. Computer-aided design software is a form of drafting system.


DRILLS: A metal cutting tool used to penetrate the surface of a workpiece and make a round hole equal to the drill diameter. Automated drills usually use a PTP control system.


DRY COLORING: Method commonly used by fabricators for coloring plastic by tumble blending uncolored particles of the plastic material with selected dyes and pigments.


DRY RUN: A preliminary operation to ensure that the part program will machine workpieces properly. Dry runs are performed without any parts or cutting fluid.


DUROMETER HARDNESS: The hardness of a material as measured by the Shore Durometer.


DWELL: A pause in the application of pressure to a mold made just before the mold is completely closed to allow the escape of gas from the molding material.

EJECTOR PIN: Or ejector sleeve. A rod, pin or sleeve which pushes a molding off of a core or out of a cavity of a mold. It is attached to an ejector bar or plate which can be actuated by the ejector rod(s) of the press or by auxiliary hydraulic or air cylinders.


EJECTOR PIN RETAINER PLATE: Retainer into which ejector pins are assembled.


EJECTOR RETURN PINS: Projections that push the ejector assembly back as the mold closes: also called Safety Pin, and Position Pushbacks.


EJECTOR ROD & BAR: Bar that actuates the ejector assembly when mold is opened.


ELASTICITY: That property of a material by virtue of which it tends to recover its original size and shape after deformation.


ELASTOMER: A material which at room temperature stretches under low stress to at least twice its length and snaps back to the original length upon release of stress. See RUBBER.


ELECTRIC DISCHARGE MACHINING (EDM): A metal working process applicable to mold construction in which controlled sparking is used to erode away the work piece.

ELECTRICAL LOGIC CIRCUITRY: A closed path, usually composed of various devices and wires, through which an electric current follows. Electrical circuitry controlled NC machines before personal computers became common.

ELECTRONIC ASSEMBLY SYSTEMS: Technology that uses automated machines to assemble products. Electronic assembly systems often attach parts using fasteners.

ELECTRONIC TREATING: A method of oxidizing a film of polyethylene to render it printable by passing the film between electrodes and subjecting it to a high voltage corona discharge.

ELECTROPLATING: Deposition of metals on certain plastics and molds for finish.

ELONGATION: The fractional increase in length of a material stressed in tension.

EMBOSSING: Techniques used to create depressions of a specific pattern in plastics film and sheeting. Such embossing in the form of surface patterns on molded part by the treatment of the mold surface by photoengraving or other process.

ENCAPSULATING: Enclosing an article (usually an electronic component or the like) in a closed envelope of plastic, by immersing the object in a casting resin and allowing the resin to polymerize or, if hot, to cool. See POTTING.

ENVIRONMENTAL STRESS CRACKING (ESC): The susceptibility of a thermoplastic article to crack or craze formation under the influence of certain chemicals or aging, or weather and stress.

EXTRUSION: The compacting of a plastic material and the forcing of it through an orifice in more or less continuous fashion.

FABRICATE: To work a material into a finished form by machining, forming, or other operation.

FAMILY MOLD: A multi-cavity mold wherein each of the cavities forms one of the component parts of the assembled finished object. The term often applied to molds wherein parts from different customers are grouped together in one mold for economy of production. Sometimes called "Combination Mold."


FAN GATE: A shallow gate somewhat wider than the runner from which it extends.

FEED: The rate at which the cutting tool and the workpiece move in relation to one another. Feed is typically a linear movement.


FEEDBACK: A return signal that confirms the position of the cutting tool or worktable. Feedback provides information that allows the control system to compare actual position to planned position and signal the motor to move if the positions do not match.


FEEDBACK DEVICE: A device that sends information back to the controller in a closed-loop system. The feedback device is what allows for slight corrections in position if errors are detected.


FIBER: This term usually refers to thin fibers of glass which are used to reinforce both thermoplastic and thermosetting materials. One-inch long fibers are occasionally used, but the more commonly used fiber lengths are 1/2" and 1/4" or less.


FILLER: An additive to resins for the purpose of improving physical properties (impact resistance, hardness, dimensional stability, etc.), or to reduce cost of resin.


FILLET: A rounded filling of the internal angle between two surfaces.


FINISH: To complete the secondary work on a molded part so that it is ready for use. Operations such as filing, deflashing, buffing, drilling, tapping, degating are commonly called finishing operations. See SURFACE FINISH.


FINISHING: A final metal cutting process that emphasizes tight tolerances and smooth surface finish. Grinding is a finishing technique.

FIXTURE: Means of holding a part during a machining or other operation.

FLASH: Extra plastic attached to a molding along the parting line; under most conditions it would be objectionable and must be removed before the parts are acceptable.

FLASH GATE: Usually a long gate extending from a runner which runs parallel to an edge of a molded part along the flash or parting line of the mold.

FLEXURAL STRENGTH: Ability of a material to flex without permanent distortion or breaking.

FLOW: A qualitative description of the fluidity of a plastic material during the process of molding.

FLOW LINE: A mark on a molded piece made by the meeting of two flow fronts during molding. Also called "Weld Line."

FLOW MARKS: Wavy surface appearance on a molded object caused by improper flow of the material into the mold. See SPLAY MARKS.


FOIL DECORATING: Molding paper, textile, or plastic foils printed with compatible inks directly into a plastic part so that the foil is visible below the surface of the part as integral decoration.



GATE: In injection and transfer molding, the orifice through which the melt enters the cavity.

GLOSS: The shine or luster of the surface of a material. See SURFACE FINISH.

GUIDE PINS: Devices that maintain proper alignment of core and cavity as mold closes. Also called "Leader Pins."

HARDNESS: The resistance of a material to compression and indentation. Among the most important methods of testing this property are Brinell hardness, Rockwell hardness and Shore hardness.

HARDWARE: Any physical or mechanical component. CNC hardware includes the machine control unit, tape readers, and disk drives, depending on the machine vintage.

HAZE: The degree of cloudiness in a plastics material.

HEAT-DISTORTION POINT: The temperature at which a standard test bar deflects 0.010 in. under a stated load of either 66 or 264 psi.


HOT-RUNNER MOLD: A thermoplastic injection mold in which the runners are insulated from the chilled cavities and remain hot so that the center of the runner never cools in normal cycle operation. Runners are not, as is the case usually, ejected with the molded pieces.


HOT/HEATED MANIFOLD MOLD: A thermoplastic injection mold wherein the portion of the mold that contains the runner system has its own heating elements that keep the molding material in a plastic state ready for injection into the cavities from which the manifold is insulated.


HOT-STAMPING: Engraving operation for marking plastics in which roll leaf is stamped with heated metal dies onto the face of the plastics.

HYDRAULIC SERVO: A servomechanism driven by fluids that deliver power to the motor. This type of servo is not powered by electricity.

HYDRAULICS: A system that uses the force of flowing liquids to transmit power. Hydraulics can be used to power a servomechanism.

HYGROSCOPIC: Tending to absorb moisture.

IMPACT STRENGTH: (1) The ability of a material to withstand shock loading. (2) The work done in fracturing, under shock loading, a specified test specimen in a specified manner. (3) Molded plastics are usually given a value on an izod scale. An Izod impact test is designed to determine the resistance of a plastics material to a shock loading, it involves the notching of a specimen, which is then placed in the jaws of the machine and struck with a weighted pendulum.


INJECTION MOLDING: A molding procedure whereby a heat-softened plastic material is forced from a cylinder into a cavity which gives the article the desired shape. Used with both thermoplastic and thermosetting materials.

INJECTION BLOW MOLDING: A blow molding process in which the parison to be blown is formed by injection molding.

INSERT: An integral part of a plastics molding consisting of metal or other material which may be molded into position or may be pressed into the molding after the molding is completed. Also a removable or interchangeable component of the mold.

JETTING: Turbulent flow of resin from an undersized gate or thin section into a thicker mold section, as opposed to laminar flow of material progressing radially from a gate to the extremities of the cavity.

JIG: Means of holding a part and guiding the tool during machining or assembly operation.

KIRKSITE: An alloy of aluminum and zinc used for the construction of blow molds; it imparts high degree of heat conductivity to the mold.



LAMINAR FLOW: Laminar flow of thermoplastic resins in a mold is accompanied by solidification of the layer in contact with the mold surface that acts as an insulating tube through which material flows to fill the remainder of the cavity. This type of flow is essential to duplication of the mold surface.

LAMINATED PLASTICS: A plastics material consisting of superimposed layers of a synthetic resin-impregnated or coated filler which have been bonded together, usually by means of heat and pressure, to form a single piece.

LASER CUTTING: A machining process that uses an intense, focused beam of light to cut materials. Laser cutting is generally a CNC process.

LEAN MANUFACTURING: A manufacturing practice that aims to reduce wasted time, effort or other resources in the production process.

LIGHT-RESISTANCE: The ability of a plastics material to resist fading after exposure to sunlight or ultraviolet light.

LINEAR AXES: Each of three imaginary perpendicular lines that describe movement along a straight line. Linear axes serve as reference points in the Cartesian coordinate system.

LINEAR SCALE: A type of feedback device that relies on the size of an electrical current to convey the position or distance on a CNC machine. A linear scale is one of the most accurate feedback devices.

LOT: The number of parts made with a particular tooling setup. A lot is composed of identical or similar parts or materials.

MACHINE CONTROL UNIT (MCU): A small, powerful computer that controls and operates a CNC machine. The MCU is also known as the controller and interprets the numerical data in the part program to guide machine movement.

MACHINING CENTER: A sophisticated CNC mill that can perform multiple machining operations, including milling and various hole-making operations, in the same setup with a variety of tools. Machining centers usually use a continuous path control system.

MADE-TO-SPEC: Describes an item that is made to a company’s specifications internally or by a supplier.


MANUFACTURING COST: Includes quality-related costs, direct and indirect labor, equipment repair and maintenance, other manufacturing support and overhead, and other costs directly associated with manufacturing operations.

MANUFACTURING CYCLE TIME: The time of actual production from the moment a customer order arrives on the plant floor to the completion of all product manufacturing, assembly, and testing.

MATTE FINISH: A type of dull non-reflective finish. See SURFACE FINISH.

MELT INDEX: The amount, in grams, of a thermoplastic resin which can be forced through a 0.0825 inch orifice when subjected to 2160 grams force in 10 minutes at 190°C.

MELT STRENGTH: The strength of the plastic while in the molten state.

METERING SCREW: An extrusion screw which has a shallow constant depth and constant pitch section over, usually the last 3 to 4 flights.


MICA: Any of a group of mineral silicates crystallizing in monoclinic forms that readily separate into very thin leaves. Used as a filler for plastics molding materials.


MODULUS OF ELASTICITY: The ratio of stress to strain in a material that is elastically deformed.


MOLDING MATERIAL: Plastic material in varying stages of granulation often comprising resin, filler, pigments, plasticizers and other ingredients, ready for use in the molding operation. Also called "Molding Compound' or ‘Powder."


MOLDING PRESSURE: The pressure applied directly or indirectly on the compound to allow the complete transformation to a solid dense part.

MOLDING SHRINKAGE: The difference in dimensions, expressed in inches per inch, between a molding and the mold cavity in which it was molded, both the mold and the molding being at normal room temperature when measured. Also called "Mold Shrinkage", or "Shrinkage", and "Contraction".

MOLD RELEASE: A lubricant used to coat a mold cavity to prevent the molded piece from sticking to it, and thus to facilitate its removal from the mold. Also called "Release Agent."

MOLD SEAM: A line formed by mold construction such as removable members in cavity, cam slides, etc. (Not to be confused with mold parting line).

MOLECULAR WEIGHT: The sum of the atomic masses of the elements forming the molecule.

MONOMER: A relatively simple compound which can react to form a polymer.

MOVABLE PLATEN: The moving platen of an injection or compression molding machine to which half of the mold is secured during operation. This platen is moved either by a hydraulic ram or a toggle mechanism.

MYLAR TAPE: A thin, yet strong polyester film that was used to transmit programs to numerically controlled machines. Programs executed on mylar tape had to be rewound after each use.

NOTCH SENSITIVITY: The extent to which the sensitivity of a material to fracture is increased by the presence of a surface in homogeneity such as a notch, a sudden change in section, a crack, or a scratch. Low notch sensitivity is usually associated with ductile materials, and high notch sensitivity with brittle materials.

NOZZLE: The hollow cored metal nose screwed into the extrusion end of (a) the heating cylinder of an injection machine, or (b) a transfer chamber where this is a separate structure.

NUMERICAL CONTROL (NC): A system that guides machine tool components and manufactures parts using electrical logic circuitry to execute program instructions punched into paper or mylar tape. NC was the precursor to CNC.

OEM: Original equipment manufacturer.

OLEFINS: A group of unsaturated hydrocarbons of the general formula CnH2n, and named after the corresponding paraffins by the addition of "ene" or "ylene to the stem. Examples are ethylene and propylene.

ORIENTATION: The alignment of the crystalline structure in polymeric materials so as to produce a highly uniform structure. Can be accomplished by cold drawing or stretching during fabrication.

OUT-OF-ROUND: Non uniform radius or diameter.

OPEN-LOOP SYSTEM: A type of control system that uses only an input signal to actuate an output. There is no automatic feedback to adjust the process, so adjustments must be made manually by the operator.

OPTICAL ENCODER: A type of feedback device that records light reflections during the machining process. The optical encoder then converts those reflections into feedback signals.

OPTICAL SENSORS: A type of sensor that detects the presence of an object through the use of a beam of light. Optical sensors are used by optical encoders.

ORIGIN: The fixed, central point in a coordinate system. The origin has a numerical value of zero.

PAPER TAPE: A way of transmitting programs to numerically controlled machines. Program executed on paper tape had to be rewound after each use.

PART PROGRAM: A series of alphanumerical instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece. Multiple part programs can be stored in a CNC at one time.

PARTING LINE: Mark on a molding or casting where halves of mold met in closing.

PART NAME: A unique name assigned to a part.

PART NUMBER: A unique numerical value assigned to a part.For more information see the following articles: Part Numbering Schemes—Intelligent vs. Non-Intelligent and Part number system: How to get started.


PERFORM: A pill, tablet, or biscuit used in thermoset molding. Material measured by volume, the bulk factor of powder reduced by pressure all in the interest of efficiency and accuracy.

PERMANENT SET: The increase in length expressed in a percentage of the original length, by which an elastic material fails to return to original length after being stressed for a standard period of time.

PINPOINT GATE: A restricted orifice through which molten resin flows into a mold cavity. Also called "Restricted Gate".

PITCH: The distance from any point on the flight of a screw line to the corresponding point on an adjacent flight, measured parallel to the axis of the screw line or threading.

PLASTIC: Natural and synthetic material and chemicals that can be transformed into a solid, as either or both heat and pressure is applied.

PLASTIC DEFORMATION: A change in dimensions of an object under load that is not recovered when the load is removed: opposed to elastic deformation.

PLASTIC TOOLING: Tools e.g. dies, jigs, fixtures, etc., for the metal forming trades constructed of plastics, generally laminates or casting materials.

PLASTICITY: - A property of plastics which allows the material to be deformed continuously and permanently without rupture upon the application of a force that exceeds the yield value of the material.

PLASTICIZE: To soften a material and make it plastic or moldable, either by means of a plasticizer or the application of heat.

PLASTICIZER: A material incorporated in a plastic to increase its workability and its flexibility or distensibility normally used in thermoplastics.

PLASTISOLS: Mixtures of vinyl resins and plasticizers which can be molded: cast, or converted to continuous films by the application of heat.

PLATENS: The mounting plates of a press on which the mold halves are attached.

PLUNGER: That part of a transfer or injection press that applies pressure on the unmelted plastic material to push it into the chamber, which in turn forces plastic melt at the front of the chamber out through the nozzle. See RAM.

POINT-TO-POINT POSITIONING (PTP): A type of CNC control system where no cutting takes place during the movement of the tool from one position to the next. PTP systems are usually open-loop.

POLYMER: A high-molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the MER: e.g., polyethylene, rubber, cellulose. Synthetic polymers are formed by addition or condensation polymerization of monomers. If two or more monomers are involved, a copolymer is obtained. Some polymers are elastomers, some plastics.

POLYMERIZATION: A chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular weight is a multiple of that of the original substance. When two or more monomers are involved, the process is called copolymerization or heteropolymerization.

POTTING: Similar to ENCAPSULATING, except that steps are taken to ensure complete penetration of all the voids in the object before the resin polymerizes.

PREHEATING: The heating of a compound prior to molding or casting in order to facilitate the operation, reduce cycle, and improve product.

PREMIX: A molding compound prepared prior to and apart from the molding operations and containing all components required for molding: resin, reinforcement fillers, catalysts, release agents, and other compounds.

PRESSURE FORMING: A thermoforming process wherein pressure is used to push the sheet to be formed against the mold surface as opposed to using a vacuum to suck the sheet flat against the mold.

PRODUCT-DEVELOPMENT CYCLE: Often called time to market, this is the period from when design/development work begins to the time that the final product is available for purchase.

PROTOTYPE MOLD: A simplified mold construction often made from a light metal casting alloy or from an epoxy resin in order to obtain information for the final mold and/or part design.

PUNCH PRESSES: A machine with a stationary base and an upper arm that moves along a vertical axis to shear, bend, or form sheet metal. Punch presses often use computer numerical data to control machine movements.

PUNCHING: A shearing operation that creates an open hole in sheet metal by separating an interior section. Punching can be performed using a punch press.

PURGING: Cleaning one color or type of material from the cylinder of an injection molding machine or extruder by forcing it out with the new color or material to be used in subsequent production. Purging materials are also available.

RAM: The press member that enters the cavity block and exerts pressure on the molding compound designated as the "top force" or "bottom force" by position in the assembly.

RAM TRAVEL: Distance ram moves when operating a complete molding cycle.

RECIPROCATING SCREW: A combination injection and plasticizing unit in which an extrusion device with a reciprocating screw is used to plasticize the material. Injection of material into a mold can take place by direct extrusion into the mold, or by reciprocating the screw as an injection plunger, or by a combination of the two. When the screw serves as an injection plunger, this unit acts as a holding, measuring, and injection chamber.

REINFORCED MOLDING COMPOUND: A material reinforced with special fillers to meet specific requirements (glass, carbon, etc.)

REINFORCEMENT: A strong inert material bound into a plastic to improve its strength, stiffness, and impact resistance. Reinforcements are usually long fibers of glass, sisal, cotton, etc. — in woven or non-woven form.


RESIN: Any of a class of solid or semi-solid organic products of natural or synthetic origin, generally of high molecular weight with no definite melting point. Most resins are polymers.

RETAINER PLATE: The plate on which demountable pieces, such as mold cavities, ejector pins, guide pins, and bushings are mounted during molding: usually drilled for water lines.

RIB: A reinforcing member of a fabricated or molded part.

ROCKWELL HARDNESS: A common method of testing material for resistance to indentation in which a diamond or steel ball, under pressure, is used to pierce the test specimen.

ROTARY RESOLVER: A type of feedback device that records the ballscrew rotations of a CNC machine. The rotary resolver then sends electronic signals back to the CNC control to indicate position or speed.

ROTATIONAL AXES: Each of three imaginary circles that describe rotation around a linear axis. The A axis rotates around the X axis, the B axis rotates around the Y axis, and the C axis rotates around the Z axis.

RUBBER: - An elastomer capable of rapid elastic recovery after being stretched to at least twice its length at temperatures from 0 to 150°F at any humidity.

RUNNER: - In an injection or transfer mold, the channel that connects the sprue with the gate to the cavity.

RUNNER SYSTEM: - The term usually applied to all the material in the form of sprues, runners and gates which lead material from the nozzle of an injection machine or the pot of a transfer mold to the mold cavity.

SCREW PLASTICATING INJECTION MOLDING: A technique in which the plastic is converted from pellets to a viscose melt by means of an extruder screw which is an integral part of the molding machine. Machines are either single stage (in which plastication and injection are done in the same cylinder) or double stage in which the material is plasticated in one cylinder and then fed to a second for injection into a mold.

SEGREGATION: A separation of components in a molded article usually denoted by wavy lines and color striations in thermoplastics. In thermosets, usually meaning segregation of resin and filler on surface.

SELF-EXTINGUISHING: The term applied to a flammable material that will cease burning when the source of heat is removed. Usually expressed in time elapsed.

SEMI-AUTOMATIC MOLDING MACHINE: A molding machine in which only part of the operation is controlled by the direct action of a human. The automatic part of the operation is controlled by the machine according to a predetermined program.

SERVOMECHANISM (SERVO): A special servomotor used in closed-loop CNC machines that adjusts the position of machining based on feedback. Servos are powered using electricity or hydraulics.

SERVOMOTOR: A motor in a CNC machine that powers movement of the machine tool. A servomotor rotates the ballscrew, causing the table of a mill or the slides of a lathe to move.

SHELF LIFE: An expression to describe the time a molding compound can be stored without losing any of its original physical or molding properties.

SHORE HARDNESS: A method of determining the hardness of a plastic material using a scleroscope. This device consists of a small conical hammer fitted with a diamond point and acting in a glass tube. The hammer is made to strike the material under test and the degree of rebound is noted on a graduated scale. Generally the harder the material the greater will be the rebound.

SHORT SHOT: A molded part produced when the mold has not been filled completely.

SHOT: The yield from one complete molding cycle, including cull, runner, and flash.

SHOT CAPACITY: The maximum weight of material which a machine can produce from one forward motion of the plunger or screw.



SIDE CORING OR SIDE DRAW PINS: Projections 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.

SIGNAL: A message sent electronically. An open-loop system signals the motor to move, and a closed-loop system signals the motor to start and to adjust its position based on a feedback signal.

SILK SCREEN PRINTING: This printing method, in its basic form, involves laying a pattern of an insoluble material, in outline, on a finely woven fabric, so that when ink is drawn across it, it is able to pass through the screen only in the desired areas. Also called "Screen Process Decorating".

SILICONE: Chemical derived from silica used in molding as a release agent and general lubricant.

SINK MARK: A depression or dimple on the surface of an injection molded part due to collapsing of the surface following local internal shrinkage after the gate seals. May also be caused by a short shot.

SINTERING: In forming articles from fusible powders (e.g. nylon), the process of holding the pressed-powder article at a temperature just below its melting point for about 1/2 hour. Particles are fused (sintered) together, but the mass as a whole does not melt.

SMART MANUFACTURING: Aims to reduce manufacturing costs from the perspective of real-time energy management, energy productivity, and process energy efficiency. Initiatives will create a networked data driven process platform that combines innovative modeling and simulation and advanced sensing and control. Integrates efficiency intelligence in real-time across an entire production operation with primary emphasis on minimizing energy and material use; particularly relevant for energy-intensive manufacturing sectors.

SOFTWARE: The machine programs and instructions that control the computer hardware functions and operations. CNC software includes the part program or a canned cycle.

SOLVENT: Any substance, usually a liquid, which dissolves other substances.

SPECIFIC GRAVITY: The density (mass per unit volume) of any material divided by that of water.

SPEED: The rate at which the machine spindle rotates. The spindle speed affects how fast the cutting tool or workpiece moves at the point of contact.

SPIDER GATE: Multi-gating of a part through a system of radial runners from the sprue.

SPIN WELDING: A process of fusing two objects together by forcing them together while one of the pair is spinning, until frictional heat melts the interface. Spinning is then stopped and pressure held until they are frozen together.

SPLAY MARKS: Lines found in part after molding, usually due to flow of material in mold.

SPRUE: Feed opening provided in the injection or transfer mold; also the slug formed at this hole.

SPRUE-BUSHING: A hardened steel insert in an injection mold which contains the tapered sprue hold and has a suitable seat for the nozzle of the injection cylinder.

SPRUE GATE: A passageway through which molten resin flows from the nozzle to the mold cavity.

SPRUE LOCK OR PULLER: In injection molding, a portion of the plastic composition which is held in the cold slug well by an undercut; used to pull the sprue out of the bushing as the mold is opened. The sprue lock itself is pushed out of the mold by an ejector pin. When the undercut occurs on the cavity block retainer plate, this pin is called the Sprue Ejector Pin.

STABILIZER: An ingredient used in the formulation of some plastics to assist in maintaining the physical and chemical properties of the compounded materials at their initial values throughout the processing and service life of the material.

STAMPING: A metalworking process that involves forming or separating sheet metal into parts with the use of dies and punches. Stamping can be performed using a punch press.

STATIONARY PLATEN: The plate of an injection or compression molding machine to which the front plate of the mold is secured during operation. This platen does not move during normal operation.


STEPPER MOTOR: A servomotor that generates steps from electronic pulses that move the tool and the worktable. Stepper motors are used in open-loop systems.


STRIATION: A separation of colors resulting in a linear effect of color variation.

STRIPPER-PLATE: A plate that strips a molded piece from core pins or core, the stripper-plate is set into operation by the opening of the mold.

SUBMARINE GATE: A type of edge gate where the opening from the runner into the mold is located below the parting line or mold surface as opposed to conventional edge gating where the opening is machined into the surface of the mold. With submarine gates, the part is broken from the runner system on ejection from the mold.

SURFACE FINISH: Finish of molded product.

SURFACE TREATING: Any method of treating a material so as to alter the surface and render it receptive to inks, paints, lacquers, and adhesives such as chemical, flame, and electronic treating.

TAB GATED: A small removable tab of approximately the same thickness as the mold item, usually located perpendicular to the molded part. The tab is used as a site for edge gate location, usually on items with large flat areas.

TAPPING: Cutting threads in the walls of a circular hole.

TENSILE STRENGTH: The pulling stress, in psi, required to break a given specimen. Area used in computing strength is usually the original, rather than the necked-down area.

THERMAL CONDUCTIVITY: Ability of a material to conduct heat; physical constant for quantity of heat that passes through unit cube of a substance in unit of time when difference in temperature of two faces is 1°.


THERMAL STRESS CRACKING (TSC): Crazing and cracking of some thermoplastic resins which results from over-exposure to elevated temperatures.

THERMOPLASTIC: (a.) Capable of being repeatedly softened by heat and hardened by cooling — (n.) A material that will repeatedly soften when heated and harden when cooled. Typical of the thermoplastic family are the styrene polymers and copolymers, acrylics, cellulosics, polyethylenes, polypropylene, vinyls, nylons, and the various fluorocarbon materials.

THERMOSET: A material that will undergo or has undergone a chemical reaction by the action of heat and pressure, catalysts, ultra-violet light, etc., leading to a relatively infusible state. Typical of the plastics in the thermosetting family are the aminos (melamine and urea), most polyesters, alkyds, epoxies, and phenolics.

THREAD PLUG OR RING OR CORE: A part of a mold that shapes a thread and must be unscrewed from the finished piece.

TIE BARS: Bars which provide structural rigidity to the clamping mechanism of a press often used to guide platen movement.

TIGHT TOLERANCE: If you want a technical answer, a product’s tolerance is defined by the maximum acceptable level of deviation from its specification, measurements or standards. Basically, this means that products with tight tolerances have extremely strict design parameters. If those parameters are deviated from even slightly, the product becomes useless and it has to be manufactured again from scratch.

TOGGLE ACTION: A mechanism which exerts pressure developed by the application of force on a knee joint. It is used as a method of closing presses and also serves to apply pressure at the same time.

TOLERANCE: A specified allowance for deviations in weighing, measuring, etc., or for deviations from the standard dimensions or weight.

TOOLPATH: A series of program blocks that describes the movement of a single cutting tool. Canned cycle toolpaths are evaluated using dry runs.

TOTAL QUALITY MANAGEMENT: A company-wide approach to improving quality and customer satisfaction–including fast response and service, as well as product.


TURNING CENTER: A sophisticated CNC lathe that can also perform a variety of drilling and milling operations all at the same location. Turning centers usually use a continuous path control system.

TURRET: A lathe component that holds a number of cutting tools. Turrets rotate to place tools in cutting position.

TURRET PUNCH PRESS: A CNC punch press with an open frame and a turret containing multiple punches. A turret press is used to perform a variety of punching and shearing operations.

ULTRASONIC SEALING/BONDING: A sealing method in which sealing is accomplished through the application of vibratory mechanical pressure at ultrasonic frequencies (20 to 40 kc.). Electrical energy is converted to ultrasonic vibrations through the use of either a magnetostrictive or piezoelectric transducer. The vibratory pressures at the interface in the sealing area develop localized heat losses which melt the plastic surfaces affecting the seal.

ULTRASONIC INSERTION: The inserting of a metal insert into a thermoplastic part by the application of vibratory mechanical pressure at ultrasonic frequencies.

UNDERCUT: (a.) Having a protrusion or indentation that impedes withdrawal from a two-piece, rigid mold. Flexible materials can be ejected intact even with slight undercuts. (n.) Any such protrusion or indentation; depends also on design of mold.

UNIT MOLD: Mold designed for quick changing interchangeable cavity parts.

UV STABALIZER (ULTRAVIOLET): Any chemical compound which, when admixed with a thermoplastic resin, selectively absorbs UV rays. 

VACUUM METALIZING: Process in which surfaces are thinly coated with metal by exposing them to the vapor of metal that has been evaporated under vacuum (one millionth of normal atmospheric pressure.)

VENT: In a mold, a shallow channel or minute hole cut in the cavity to allow air to escape as the material enters.

VERTICAL FLASH RING: The clearance between the core and the vertical wall of the cavity in a positive or semi-positive mold; also the ring of excess material which escapes from the cavity into this clearance space.

VOID: A void or bubble occurring in the center of a heavy thermoplastic part usually caused by excessive shrinkage.


WARPAGE: Dimensional distortion in a plastic object after molding.

WATER ABSORPTION: The ability of a thermoplastic material to absorb water from an environment.




WELDING: Joining thermoplastic pieces by one of several heat-softening processes: Butt fusion, spin welding, ultrasonic, and hot gas are several methods.

WORKPIECE: A part that is in the process of being manufactured. A workpiece may be a complete product in itself or one component of a product consisting of many parts.

WORKTABLE: The component of a CNC mill that supports the workpiece and any work-holding devices during machining. The worktable can remain fixed or move.


X AXIS: The linear axis representing coordinate positions along a line parallel to the longest edge of the worktable. The X axis usually runs left-to-right.


Y AXIS: The linear axis representing coordinate positions along a line parallel to the shortest edge of the worktable. The Y axis usually runs back and forth.

YIELD VALUE: The lowest stress at which a material undergoes plastic deformation. Below this stress, the material is elastic; above it, viscous.


Z AXIS: The linear axis representing coordinate positions along a line parallel to the spindle and perpendicular to the worktable. The Z axis usually runs up and down.

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