Thermoforming Glossary of Terms

• ABS: Acrylonitrile butadiene styrene is a common thermoplastic used to make light, rigid, molded products such as piping, musical instruments, golf club heads, automotive body parts, wheel covers, enclosures, protective head gear, airsoft BB's and toys.
• Absorption: The amount of radiant energy absorbed by plastic
• Acrylic: is a thermoplastic and transparent plastic. It is sold by the tradenames Plexiglas.
• Advance Engineering has provided a glossary of terms that visitors may find useful
• Air-assist forming: A method of thermoforming in which a flow of air pressure is employed to partially pre-form the sheet immediately. prior to the final pull down onto the mold using vacuum.
• Amorphous polymer: Polymer that has no melting temperature
• Angel hair: Fine fibers caused by improper trimming technique
• Areal draw ratio: The ratio of surface area of the formed part to that of the sheet used to form the part
• Billow: Pre-stretching sheet by inflation with air pressure
• Blank: In forming, a piece of sheet metal stock from which a product is made. Material, produced in cutting dies, that is usually subjected to further press operations. A workpiece that results from a blanking operation. A pre-cut metal shape for a subsequent press operation.
• Blanking: The operation of punching, cutting, or shearing a piece out of stock to a predetermined shape. Die cutting of the outside shape of a part.
• Blend: Physical melt-mixing of two or more polymers
• Carbon Black: A black pigment produced by the incomplete burning of natural gas or oil. It is widely used as a filter, particularly in the rubber industry because it possesses ultra-violet properties.
• Cavity isolator: See Grid
• Chamfer: Bevel
• Chill mark: A mark on the formed part often attributed to contact with a cold mold or plug
• CMM: Coordinate Measuring Machine
• Coefficient of expansion: The fractional change in length (sometimes volume, specified) of a material for a unit change in temperature. Values for plastics range from 0.01 to 0.2 mils/in., C.
• Coefficient of Friction: A number expressing the amount of friction effect.
• Coining: A compressive metal flowing action. A closed-die squeezing operation in which all surfaces of a workpiece are confined or restrained, resulting in a well-defined imprint of the die on the work. A restriking operation used to sharpen or change an existing radius or profile.
• Coining: Localized pressing of heated sheet between two portions of mold
• Compound: Intimate mixture of (a) polymers with all materials necessary for finished product.
• Compound die: Tool used to pierce, form and blank a part at the same time, with one stroke of the press.
• Compression molding: A technique of thermo set molding in which the molding compound is placed in the open mold cavity, mold is closed, and heat and pressure are applied until the material has cured.
• Conduction: Energy transfer by direct solid-to-solid contact
• Contact Techniform Industries today for all your thermoforming needs.
• Contact heating: Heating of sheet by conduction
• Convection: Energy transfer by moving or flowing fluids
• Coordinate Measuring Machine: Accurate three-dimensional electronic ruler used in quality control
• Co-polymer: Polymer with two sets of monomers such, such as HIPS
• Crosshead: A device generally employed in wire coating which is attached to the discharge end of the extruded cylinder, designed to facilitate extruding material at an angle. Normally, this is a 90 degree angle to the longitudinal axis of the screw.
• Cross-linking –Applied to polymer molecules, the setting-up of chemical links between the molecular chains. When extensive, as in most thermosetting resins, cross-linking makes one infusible super-molecule of all the chains.
• Cross-machine direction: At right angles to the extrusion direction; aka transverse direction
• Cut-sheet: Usually heavy-gauge sheet, fed one at a time to a rotary or shuttle thermoformer
• Cutter: Mechanical bit with tip designed to cut specific types of plastics
• Dam: Continuous ridge around mold cavity periphery
• Deep drawing: The fabrication process of flat rolled steel to make drawn parts. The part is mechanically formed through or in a die. The blank diameter is reduced; the blank contracts circumferentially as it is drawn radially inward. Deep drawing is characterized by the production of a parallel-wall cup from a flat blank of sheet metal. The blank may be circular, rectangular, or a more complex shape. The blank is drawn into the die cavity by the action of a punch. Deformation is restricted to the flange areas of the blank. No deformation occurs under the bottom of the punch-the area of the blank that was originally within the die opening. As the punch forms the cup, the amount of material in the flange decreases. Deep drawing is also called cup drawing or radial draw forming. See deep drawing applications.
• Density: Weight per unit volume of substance, expressed in grams per cubic centimeter, pounds per cubic foot, etc.
• Density: Weight per unit volume
  Developed blank: A sheet metal blank that yields a finished part without trimming or with the least amount of trimming.
• Diaphragm forming: Stretching heated sheet using an elastic membrane
• Die: Tool with a void or cavity that is precisely fitted to a punch used to solid, molten, or powdered metal primarily because of the shape of the tool itself. Die-casting and powder metallurgy dies are sometimes referred to as molds.
• Die stamping: The general term for a sheet metal part that is formed, shaped, or cut by a die in a press in one or more operations.
• Differential pressure: The difference in the pressure on each side of a sheet
• Dimensional tolerance: Part-to-part variation in local dimension
• Draft: The degree of taper of a side wall or the angle of clearance designed to facilitate removal of parts from a mold.
• Draft: Mold angle from vertical
• Drape forming: Method of forming thermoplastic sheet in which the sheet is clamped into a movable frame, heated and draped over high points of a male mold.
• Draw die: A specific type of form die that basically involves forcing the flat sheet of metal into a die cavity with a punch while holding the workpiece around the cavity to control metal flow.
• Draw down ratio – Ratio of thickness of the die opening to the final thickness of the product.
• Draw ratio: Measure of the extent of sheet stretching; a measure of the area of the sheet after being formed to that before forming
• Drawing: A term used for a variety of forming operations, such as deep drawing a sheet metal blank; redrawing a tubular part; and drawing rod, wire, and tube. The usual drawing process with regard to sheet metal working in a press is a method for producing a cup-like form from a sheet metal disk by holding it firmly between blank holding surfaces to prevent the formation of wrinkles while the punch travel produces the required shape. In metal forming, the stretch rig or compressing of a sheet metal part into a die by a punch to create a 3-dimensional part. The process of cold forming a flat pre-cut metal blank into a hollow vessel without excessive wrinkling, thinning, or fracturing.
• Drum-Buffer-Rope: A production planning technique that helps manufacturers create production schedules that are protected from the adverse effects of "Murphy" events. Learn more about DBR and lean manufacturing at ThermoFab >>
• Dual durometer: combining two dissimilar materials into a single extruded unit. Sometimes called co-extrusion.
• Dunnage: Used to support loads and prop tools and materials up off the ground such as jacks, pipes, and supports for air conditioning and other equipment above the roof of a building.
• Durometer: is one of several ways to indicate the hardness of a material, defined as the material's resistance to permanent indentation. Durometer is typically used as a measure of hardness in polymers, elastomers and rubbers.
• Elastic liquid: A molten polymer that has both fluid and solid characteristics; sometimes called a viscoelastic polymer
• Elastic modulus: See modulus
• 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.
• Elongation: The fractional increase in length of a material stressed in tension.
• Embossing: A process for producing raised or sunken designs or relief in sheet material by means of male and female dies, theoretically with no change in metal thickness or by passing sheet or a strip of metal by passing between rolls of desired pattern. (See patterned or embossed sheet). Examples are letters, ornamental pictures, and ribs for stiffening. Heavy embossing and coining are similar operations.
• Embossing die: A die used for producing embossed designs.
• EMI Shielding: Application of a protective copper substance to protect enclosed electronic products from electromagnetic interference (EMI).
• 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.
• Endothermic foaming agent: A chemical that requires heat to decompose to produce gas for agent foaming. Sodium bicarbonate is a common endothermic foaming agent.
• Energy dome: When energy input to sheet is uniform, temperature at the center of the sheet is higher than at the edges and corners.
• Enthalpy: A thermodynamic measure of the intrinsic heat content of a polymer
• Equilibration: Allowing a sheet to approach uniform temperature throughout, after the heating source is removed
• Exothermic foaming agent: A chemical that gives off heat when decomposing to produce gas for agent foaming. Azodicarbonamide (AZ) is a common endothermic foaming agent.
• Extruding: The turning up or drawing out of a flange around a hole which has been punched in a previous operation. Also called hole flanging. The punching and flanging of a hole in one operation generating a slug. The cutting or tearing (piercing) and flanging of a hole in one operation without generating a slug.Also called spearing or spear punching.
• Extrusion: A metal forming process which a punch compresses a billet (hot or cold) confined in a container so that the billet material flows through a die in the same direction as the punch.
• Extrusion/forming line: Process where extruder output feeds directly into the thermoformer
• Extrusion: The process of producing sheet
• Fabricate: To work a material into a finished form by machining, forming, or other operation or to create end products by sewing, cutting, sealing or other operation.
• Fabrication: A number of metalworking techniques that allow a part to be assembled from smaller components. Welding, adhesive bonding and fastening by the use of bolts and rivets are the most widely used examples.
• Family mold: A multi-cavity mold where each of the cavities forms one of the component parts of the assembled finished object.
• FEA: Finite Element Analysis, a mathematical method for determining stress distribution when an object is mechanically deformed.
• FEM: Finite Element Method, See FEA
  Female mold: A cavity into which the heated sheet is stretched; also known as a negative mold
• FFS: Form, Fill and Seal; in-line thin-gauge process used in food and medical device packaging \
• Flame retardant resin: A resin which is compounded with certain chemicals to reduce or eliminate its tendency to burn.
• Flammability: Measure of the extent to which a material will support combustion.
• Flange die: Die used to form a flange from a blank.
• Flattening dies: Dies used to flatten sheet metal hems; that is, dies that can flatten a bend by closing it. These dies consist of a top and bottom die with a flat surface that can close one section (flange) to another (hem, seam).
• Flexural Modulus: A measure of the strain imposed in the outermost fibers of a bent specimen.
• Flexural strength: The strength of a material in blending, expressed as the tensile stress of the outermost fibers of a bent test sample at the instant of failure. With plastics, this value is usually higher than the straight tensile strength.
• Floating die: Sie mounted in a die holder or a punch mounted in its holder such a slight amount of motion compensates for tolerance in the die parts, the work, or the press. A die mounted on heavy springs to allow vertical motion in some trimming, shearing, and forming operations.
• Foaming agent: Additive that produces gas during extrusion to produce foamed sheet
• Foaming agents: Chemicals added to plastics and rubbers that generate inert gases on heating, causing resin to assume cellular structure.
• 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.
• Follow die: A progressive die consisting of two or more parts in a single holder; used with a separate lower die to perform more than one operation (such as piercing and blanking) on a part in two or more stations.
• Form: A bend, or the process of bending a metal formed part.
• Form die: A die used to change the shape of a sheet metal blank with minimal plastic flow.
• Formability: The ease with which a metal can be shaped through plastic deformation. Evaluation of the formability of a metal involves measurement of strength, ductility, and the amount of deformation required to cause fracture. The term workability is used interchangeably with formability; however, formability refers to the shaping of sheet metal, while workability refers to shaping materials by bulk forming.
• Formed: A material, metal for this purpose, that has undergone plastic deformation between tools (dies) to obtain the final configuration.
• Forming: Plastic deformation of a billet or a blanked sheet between tools (dies) to obtain the final configuration. Metalforming processes are typically classified as bulk forming and sheet forming. Also referred to as metalworking. Making any change in the shape of a metal piece which does not intentionally reduce the metal thickness and which produces a useful shape.
• Forming die: A die in which the shape of the punch and die is directly reproduced in the metal with little or no metal flow.
• Free surface: The sheet surface that is not in contact with the mold surface
• Gage: The thickness of sheet or the diameter of wire. The various standards are arbitrary and differ with regard to ferrous and non-ferrous products as well as sheet and wire. An aid for visual inspection that enables an inspector to determine more reliably whether the size or contour of a formed part meets dimensional requirements. The ability of a material to under go plastic deformation without fracture. A device used to position work in a die accurately. Another name for a checking fixture which is used to check parts. See gauge.
• Gang-die: A series of dies mounted on a die plate.
• Gauge: Instrument for measuring, testing, or registering. Numeric scale for metal thickness. See gage.
• Gel: Hard resinous particle in plastic sheet
• Glass Transition Temperature (Tg): The temperature range above which a brittle or tough polymer becomes rubbery
• Grid: A mechanical frame that presses hot sheet against a multi-cavity mold; also known as a cavity isolator or hold-down grid
• H:D: Height-to-diameter ratio; a measure of draw ratio
• Hard tooling: Tooling made for a specific part commonly referred to as dedicated tooling.
• Hardness: The resistance of a plastic material to compression and indentation. Among the most important methods of testing this property are Brinell hardness, Rockwell hardness and shore hardness.
• Heat capacity: A measure of the amount of energy required to raise a polymer’s temperature a specific amount
• Heat deflected temperature: The temperature at which a standard test bar (ASTM D648) deflects 0 010in. under a stated load of either 66 or 264 psi.
• Heat sealing: A method of joining plastic films by simultaneous application of heat and pressure to areas in contact. Heat may be supplied conductively or dielectrically.
• Heat transfer coefficient: A measure of the effectiveness of energy transport between a flowing fluid and a solid surface
• Heavy Gauge Thermoforming: Thermofab provides heavy gauge thermoforming: the thermoforming of plastic enclosures with wall thicknesses ranging from .060-.310 inches. Heavy-gauge thermoforming involves a plastic part that in essence "becomes" the product.
• Heavy-gauge: Commonly, a seet with a thickness greater than 120 mils (0.120 inches or 3 mm)
• High molecular weight polyethylene (HMWPE): is a subset of the thermoplastic polyethylene. HMWPE is a a very tough material, with the highest impact strength of any thermoplastic presently made.
• High-Density Polyethylene (HDPE): is a polyethylene thermoplastic made from petroleum. HDPE is resistant to many different solvents and has a wide variety of applications such as milk jugs, plastic bags and thin gauge packaging trays.
  Hole diameter: Units: mm (SI), inch (Imperial) Minimum hole diameter which can be created by the process. Casting, stamping and molding impose limits on minimum hole size which can be overcome by creating the holes with a secondary process such as drilling or laser cutting.
• Homopolymer: A polymer made from a single monomer, such as PS
• Hot stamping: Engraving operation for marketing plastics in which roll leaf is stamped with heated metal dies onto the face of plastics.
• 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.
• Inclinable press: A press whose main frame may be tilted backward, usually up to a 45° angle to facilitate ejection of parts by gravity through an open back.
  Infrared radiation: Electromagnetic energy transmission at wavelength above visible wavelengths
• Injection mold: Mold into a plasticized material in introduced from an exterior heating cylinder.
  Injection Molding: Process that involves heating plastic pellets or granules until a melt is obtained. The melt is then delivered to a split-die mold where it is allowed to cool into the desired shape. The mold is then opened and the part is ejected, at which time the cycle is repeated. Read about injection molding versus thermoforming
• In-line trimming: In thin gauge, roll-fed forming, trimming that takes place in a separate machine after the thermoforming machine
• In-place trimming: Trimming that takes place while the formed sheet is still within the thermoforming machine
• Inverted die: Die where conventional positions of the male/female members are reversed.
• Ironing: An operation used to increase the length of a tube or cup through reduction of wall thickness and outside diameter, the inner diameter remaining unchanged while the surface is smoothed. Thinning the walls of deep drawn articles by reducing the clearance between punch and die.
• ISO: International Organization of Standardization
  Izod impact test: A test 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.
• K-Resin: a type of plastic made with butadiene.
  Kydex: Durable sheet thermoplastic alloy that can be extruded in a variety of colors/textures
• Line dies: A sequence of stamping dies to perform operations for completing a part.
• Linear draw ratio: The ratio of the length of a line scribed on a formed part to the length of a line scribed on the unformed part
• Linear expansion: Increase in polymer direction on heating
• Loft: Expansion of fiber reinforced sheet during heating
• Low-density polyethylene (LDPE): is a thermoplastic made from oil. LDPE is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various molded laboratory equipment.
• Machine direction: In the extrusion direction
• Male mold: A mold over which the heated sheet is stretched; also called positive mold
• Manufacturability: The degree to which a product can be efficiently and accurately produced using modem manufacturing methods. See prototype.
• Mark-off: A mark on the formed part that is attributed to contact with plug
• Master die: Universal tool receptacle for holding changeable tool systems.
  Matched die forming: The process of forming sheet between to mold halves, commonly used in foam forming
• MDF: Medium density fiberboard
  Mechanical assemblies: Part combinations attached by mechanical means through hardware
• Mechanical press: A forging press with an inertia flywheel, a crank and clutch, or other mechanical device to operate the ram.
• Melt temperature: The temperature range above which a crystalline polymer changes from a rubbery solid to an elastic liquid
• Metal forming: Solid metal and molten metal process such as casting, forging, stamping and machining.
• Metal Stamping: is a manufacturing process by which sheets or strips of material are punched using a machine press or stamping press to form the sheet. This could be a single stage operation where every stroke of the press produce the desired form on the sheet metal part, or could occur through a series of stages.
• Moat: A continuous groove around mold cavity periphery
• Modulus: The initial slope of the stress-strain curve for a given polymer
• Molding area diagram: Pressure and temperature restrictions overlaid on stress-strain curve for given polymer
• Multiple die: A die used for producing two or more identical parts at one press stroke.
• Neat: Polymers that contain no additives, fillers, or reinforcing fibers
• Negative mold: See Female mold
• Notch sensitivity: The extent to which the sensitivity of a material is increased by the presence of a surface in homogeneity such as a face 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.
• Nylon: is a generic designation for a family of synthetic polymers known generically as polyamides. Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II.
• Orientation: The amount of residual or frozen in strain or stretch in a plastic sheet, usually in a given direction
• Pattern heating: The practice of selectively shielding portions of heaters to achieve a specific energy input pattern on a heating sheet; also called zoned or zonal heating
  Peripheral seal: Region around periphery of twin-sheet part
• PETG: is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber.
• Piercing die: A die which cuts out a slug, which is usually scrap, in sheet or plate material.
• Pigment: Any colorant, usually an insoluble powdered substance used to produce a desired color of hue.
• Pinch trim: Trimming excess material from a drawn part at the bottom of the stroke. Leaves drawn shell without an inside burr, but with an outside burr and a thinned edge.
• Pinch trimming: Trimming the edge of a part by punching or pushing the flange or lip of the part over the cutting edge of a draw or stationary punch.
• Pin-chain: Chain that has spikes or pins regularly spaced along its length to impale or hold thin-gauge sheet
• Plastic Enclosures: Custom plastic exterior cover manufactured by thermoforming, pressure forming, vacuum forming or injection molding. Plastic enclosure surrounds, covers electronic or electromechanical devices used in the medical, industrial or computer industries.
• Plastic extrusion: is a high volume manufacturing process in which raw plastic material is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weather stripping, window frames, adhesive tape and wire insulation.
• Plastic injection molding: is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Molten plastic is injected at high pressure into a mold, which is the inverse of the product's shape.
• Plastic Pressure Forming: Thermoforming technique that involves forcing a heat-softened plastic sheet against a mold, usually female, by introducing compressed air to the backside of the heated sheet.
• Plastic thermoforming: is a manufacturing process for thermoplastic sheet or film. Specifically, it is more of a converting process, where plastic sheet or film is converted into a formed, finished part.
• Plastic Thermoforming: Method of manufacturing plastic parts by preheating a flat sheet of plastic and bringing it into contact with a mold whose shape it takes. Learn More about Plastic Thermoforming
• Plastic Vacuum Forming: Automatic draping of a heat-softened plastic sheet over a female or male mold. Learn More about Vacuum Forming
• Plastic: A mixture of polymers and various additives
• Plasticizer: Chemical agent added to plastic compositions to make softer, more flexible
• Plastics wood composites: A range of materials that resemble wood. It combines the advantages of wood with those of plastic.
• Plug forming: A thermoforming process in which a plug or male mold is used to partially perform the part before forming in completed using vacuum or pressure.
• Plug or Plug Assist: A mechanical device used to aid or assist sheet stretching prior to total contact with the mold
• Plug-and-ring: Method of sheet forming in which a plug, functioning as a male mold, is forced into a heated plastic sheet help in place by a clamping ring.
• Polybutylene: A polymer prepared by the polymerization of butane as the sole monomer.
• Polycarbonates: are a particular group of thermoplastic polymers. They are easily worked, molded, and thermoformed; as such, these plastics are very widely used in the modern chemical industry.
• Polyethylene (low, medium and high density): is a thermoplastic commodity heavily used in consumer products (notably the plastic shopping bag). Over 60 million tons of the material is produced worldwide every year.
• Polypropylene: is a thermoplastic polymer, made by the chemical industry and used in a wide variety of applications, including packaging, textiles, stationery, plastic parts, reusable containers of various types and more.
• Polystyrene (HIPS): is one of the most widely used kinds of plastic. It is used, for example, in disposable cutlery, plastic models, CD and DVD cases, and smoke detector housings. Products made from foamed polystyrene are nearly ubiquitous, for example packing materials, insulation, and foam beverage cups.
• Polyurethane: Polyurethane products have many uses for example: used for moldings which include door frames, columns, balusters, window headers, pediments, medallions and rosettes to name a few.
• Polyurethane Resins: A family of resins produced by reacting diisocyanate with organic compounds containing two or more active hydrogens to form polymers having free isocyanate groups. These groups, under the influence of heat or certain catalysts, will react with each other, or with water, glycols, ECT. to form a thermosetting material.
• Positive mold: See Male mold
• Press: A machine having a stationary bed or anvil and a slide (ram or hammer) which has a controlled reciprocating motion toward and away from the bed surface and at right angle to it. The slide is guided in the frame of the machine to give a definite path of motion.
• Press forming: Any sheet metal forming operation performed with tooling by means of a mechanical press or hydraulic press.
• Press tool (metal stamping die): A piece of precision-made, mass production, tooling used to cut, bend and shape metal components from flat, strip, coil or sheet material. The components produced could range in size from car roof panels, door skins or bonnets, to small clockwork gears in mechanical watches and timepieces.
• Pressure forming: Commonly, differential pressure across the sheet in excess of 30 lbs/in2, (0.2 MPa or 2 atm)
• Progression: The precise linear travel of the stock strip at each press stroke and is equal to the interstation distance. Also called pitch, advance, or feed.
• Progressive die: A die with two or more stations arranged in line for performing two or more operations on a part one operation usually being performed at each station. The parts are connected by a carrier strip until final parting or cutoff operation.
• Progressive die stampings: is a metalworking method that can encompass punching, coining, bending and several other ways of modifying metal raw material, combined with an automatic feeding system.
• Progressive forming: Sequential forming at consecutive stations with a single die or separate dies.
• Progressive tool: Die using multiple stations or operations to produce a variety of options. Can incorporate piercing, forming, extruding and drawing, and is usually applied to high quantity production runs.
• Prototype: First part of a design which is made to test tolerance capability, tooling concepts and manufacturability.
• 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-and-die: A trimming assembly for thin-gauge forming
• Pusher: See Plug
• PVC (rigid and flexible): Polyvinyl chloride is a widely used thermoplastic polymer. As a hard plastic, it is used as vinyl siding, magnetic stripe cards, window profiles etc. It can be made softer and more flexible by the addition of plasticizers, the most widely-used being phthalates. In this form, it is used to make flexible hoses and tubing, flooring, to roofing membranes, and electrical cable insulation.
• Radiation: Electromagnetic energy transfer or interchange between hot and cold surfaces
• Reflector: A shaped surface that refocuses radiant energy from a round heater
• Replication: Faithful imaging of the mold surface by the hot formed sheet
• Residual stress: Frozen-in orientation in sheet
• Resistance Projection Weld (RPW): See projection weld.
• Resistance Spot Welding (RSW): Melting and joining action of two adjoining metal surfaces created by the thermal reaction of the metal to the flow of an electrical current forming a weld nugget.
• Roll-fed: Thin-gauge sheet, fed continuously into the thermoformer
• Rotary press: Heavy-gauge thermoforming machine in which sheet is conveyed from station to station in a carrousel fashion
• Router: A device for trimming heavy-gauge parts
• Sag: Distortion of a sheet, under its own weight, while heating
• Secondary Operations: Addition of inserts, mesh, and other features to custom plastic enclosures. ThermoFab's revolutionary process puts more detail in the original part reducing the requirement for secondary operations.
• Set temperature: The temperature below which a part can be removed from the mold without appreciable distortion
• 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.
• Shrinkage: Temperature-dependent volumetric change in the polymer
  Shuttle press: Heavy-gauge thermoforming machine in which sheet or oven move in a to-and-from fashion
• Silk screening: (Screen Printing) is a printing technique that uses a woven mesh to support an ink blocking stencil. The attached stencil forms open areas of mesh that transfer ink as a sharp-edged image onto a substrate. A roller or squeegee is moved across the screen stencil forcing or pumping ink past the threads of the woven mesh in the open areas.
• Skeleton: Trim in thin-gauge forming
• Soak time: See Equilibrium
• Specific Gravity: The density(mass per unit volume) of any material divided by the water at a standard temperature, usually 4 degrees C. Since water’s density is nearly 1.00 g./cc, density in g./cc and specific gravity are nearly numerically equal.
• Specific heat: See Heat capacity
• Specific volume: Volume per unit weight; reciprocal of density
• Spring-back: Elastic recovery of sheet after forming forces are removed
• Steel rule die: Sharpened metal band used in compression cutting
• Stiffness: The product of polymer modulus and part geometry
• Strain: Stretch; the polymer’s response to applied stress
• Stress: Applied load or force on a sheet, per projected area
• Stretch Forming: A plastic sheet forming technique in which the heated thermoplastic sheet is stretched over a mold and subsequently cooled.
• Surge tank: The tank between the vacuum pump and the mold assembly to allow near-uniform differential pressure to be applied to the sheet during forming
• Syntac: See syntactic foam
• Syntactic foam: A mixture of sintered inorganic or organic foam spheres and plastic matrix, commonly epoxy or polyurethane, used for plugs, fixtures, and prototype molds, sometimes referred to as syntac
• Tab: An uncut portion or a trimmed part, used to retain the part in its web in thin-gauge
• Tapping: Operation to create internal threads by either cutting or forming.
• 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.
• Terpolymer: A polymer with three sets of monomers, such as ABS
• Thermal conductivity: Measure of time-independent energy transmission through a material
• Thermal diffusivity: A material property measure of the rate of energy transmission
• Thermal Expansion Coefficient: The fractional change in length (sometimes volume, specified) of a material for a unit change in temperature. Values for plastics range from 0.01 to 0.2 mils/in, degrees C.
• Thermoforming: is a manufacturing process for thermoplastic sheet or film. Specifically, it is more of a converting process, where plastic sheet or film is converted into a formed, finished part. The sheet or film is heated in an oven to its forming temperature, then stretched into or onto a mold and cooled.
• Thermoforming window: Temperature range over which sheet is sufficiently soft to allow stretching
• Thermoplastic: 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 thermoplastics family are the styrene polymers and copolymers, acrylics, cellulosics, polyethylenes, vinyls, nylons, and the various fluorocarbons materials.
• Thermoplastics: Two-dimensional organic molecules that can be reprocessed
• Thermoset: A material the will undergo or has undergone a chemical reaction by the action of hear, catalysts, ultra-violet light, etc. Leading to a relatively in fusible state. Typical of the plastics in the thermosetting family are the aminos (melamine and urea), most polyesters, alkyds, epoxies, and phonemics.
• Thermosets: Three-dimensional organic molecules that cannot be reprocessed
• Thick-gauge: See Heavy-gauge
• Thin Gauge Thermoforming: When you hear thin gauge: think thin plastic packaging. We can't create thin gauge packaging here at ThermoFab because the typical thickness of thin-gauge ranges from .005-.030 inches. Read more about heavy gauge thermoforming vs. thin gauge>>
• Thin-gauge: Commonly, sheet thickness less than 60 mils, (0.060 in or 1.5 mm)
  TIG weld (Tungsten Inert Gas): TIG is short for Gas Tungsten Arc Welding (GTAW). In the TIG welding process, an arc is formed between a non-consumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool. TIG is most commonly used in high quality, high precision, welding applications.
• Tool: A tangible instrumentality having a surface portion which is designed and intended to engage or react against work with sufficient force to effect an operation of the class type. A core, mandrel, anvil, or the like, which may be "passive" in the sense of supplying only reaction force is included in this definition. The tool may be either transitory or enduring. It may be destroyed in a single use.
• Tooling cost: Units: Currency (UK£, US$ etc.). The tooling cost is the cost of the tooling (that is, molds, die, jigs and fixtures) which are totally dedicated to the production of a single product. This cost must be pro-rated over the number of products produced in the production run. Processes with high tooling costs have high economic batch-sizes.
• TPR (Thermoplastic Rubber): Thermoplastic elastomers, sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties. Used in applications such as shoe soles, snowmobile tracks, catheters and in adhesives.
• Transfer die: Variation of a progressive die where the part is transferred from station to station by a mechanical system. Mainly used where the part has to be free from the strip to allow operations to be performed in a free state.
• Transfer press: A press having an integral mechanism for transfer and control of the workpiece.
• Translucent: Descriptive of a material or substance capable of transmitting some light, but not clear enough to be seen through.
• Transparent: Descriptive of a material or substance capable of a high degree of light transmission, e.g. glass. Some polypropylene films and acrylic moldings are outstanding in this respect.
• Trapped sheet forming: Conduction heating of sheet
• Trim: That portion of the formed sheet that is not part of the final product
• Tumbling: Cleaning articles by rotating them in a cylinder with cleaning materials.
  Turnover device: A device to turn over a part between production operations. Sometimes called a turnover.
• UHMW: also known as high-modulus polyethylene (HMPE) or high-performance polyethylene (HPPE) is a subset of the thermoplastic polyethylene. A very tough material, with the highest impact strength of any thermoplastic presently made.
• Ultimate Sealing: A film sealing method in which sealing is accomplished through the application of vibratory mechanical pressure at ultrasonic frequencies. Electrical energy is converted to ultrasonic vibrations through the use of either a magnetostrictive or piezoelectric transducer. The vibratory pressures at the film interface in the sealing area develop localized heat losses which melt the plastic surfaces affecting the seal.
• Ultimate Strength: Term used to describe the maximum unit stress a material will withstand when subjected to an applied load in a compression, tension or shear test.
• UV stabilizer: Any chemical compound which, when mixed with a thermoplastic resin, selectively absorbs UV rays.
• Vacuum forming: commonly known as vacuforming, is a simplified version of thermoforming, whereby a sheet of plastic is heated to a forming temperature, stretched onto or into a single-surface mold; held against mold by applying vacuum between the mold surface and sheet.
• Vacuum hole: See Vent Hole
• Vent hole: Small diameter hole drilled through mold surface to allow exhaustion of cavity air; also called vacuum hole
• View factor: A measure of the fraction of radiant interchange that occurs between primary heaters and energy absorbers
• Virgin polymer: Unprocessed polymer
• Watt density: Heater output in W/in2 or kW/m2
• Wavelength: A measure of the nature of incident electromagnetic radiation
• Web: In forming, a fold of plastic that cannot be stretched flat against a mold surface
• Web: Trim in thin-gauge thermoforming
• Weld nut: Internally threaded hardware designed to be spot or projection welded onto sheet metal parts.
• Weld stud: Externally threaded hardware in various lengths in headed and head-less version, welded in place.
• Welding: Welding is a process for joining similar metals. Welding joins metals by melting and fusing the base metals being joined and the filler metal applied. Welding employs pinpointed, localized heat input. Most welding involves ferrous-based metals such as steel and stainless steel. Welding covers a temperature range of 1500° F: 3000° F. Weld joints are usually stronger than, or as strong as, the base metals being joined. Typically, welding is used for forging, blacksmithing, oil pipelines, and food equipment applications.
• Zoned heating: See Pattern heating
  

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