Glossary of Terms
The words designers of plastic-injection tooling, 3D designers using SolidWorks, tool makers, metal-sheet designers, 3D-printing farms, laser cutters, electrical-erosion cutting tool makers — and the likes — use every day.
Read it as a phrase book: every definition is one or two plain sentences, written for the workshop floor, not for a brochure.
About this glossary
A glossary of terms is a working list of the words a trade uses, each with a plain definition, so customer and supplier mean the same thing when they talk. This one covers toolmaking, mould design, sheet metal and 3D printing, written for the workshop floor and translated into eight languages, alongside real customer questions and what they really meant.
Compiled by Paul Lambourn, toolmaker since 1978.
Last updated 18 September 2026.
What does a toolmaking term mean?
| Term | Category | What it means |
|---|---|---|
| Cavity | Mould & Tooling | The hollow in a mould that shapes the outside of the part. A tool may hold one cavity or many, which sets output per shot. |
| Conformal cooling | Mould & Tooling | Cooling channels that follow the shape of the part, often made by metal additive printing. They cool awkward areas faster and more evenly. |
| Cooling channels | Mould & Tooling | Drilled or milled passages inside the mould for water or oil. Good cooling keeps cycle time down and the part flat. |
| Core | Mould & Tooling | The mould half or insert that forms the inside of a part, such as a bore, a hole or a hollow shape. |
| Draft angle | Mould & Tooling | The slight taper on a moulded wall that lets the part slide out of the tool. Most surfaces use about 1 to 2 degrees. |
| Ejector pin | Mould & Tooling | A pin that pushes the finished part off the core when the mould opens. Pins must not mark or dent a visible face. |
| Ejector plate | Mould & Tooling | The plate that carries the ejector pins. The machine pushes it forward to release the part from the core. |
| Family mould | Mould & Tooling | A tool holding several different parts in one mould. Every part must use the same material, and the cavities are set so each shot makes the numbers needed. |
| Gas-assisted moulding | Mould & Tooling | Injecting nitrogen into the melt so a gas bubble hollows thick sections from inside, which reduces sink marks and clamp force. |
| Gate | Mould & Tooling | The small opening where plastic enters the cavity. Its position and size control flow, weld lines and how easily the part trims. |
| Hardening | Mould & Tooling | Heat treating a tool to make it hard and wear-resistant. It is done after rough machining, because hardened steel is difficult to cut. |
| Hot runner | Mould & Tooling | A mould system that keeps plastic molten in the runner right up to each gate, so there is no runner scrap to recycle. |
| Insert moulding | Mould & Tooling | Placing a metal or plastic insert in the mould before it closes, so the injected plastic forms around it and locks it in place. |
| Lifter | Mould & Tooling | An angled ejector that forms a small undercut and slides or flexes aside as the part is pushed out of the tool. |
| Locating ring | Mould & Tooling | A ring on the back of the mould that centres it on the machine platen, so the nozzle lines up with the sprue. |
| Overmoulding | Mould & Tooling | Moulding a second material over a finished part, usually a soft rubber-like grip over a hard plastic body. |
| Parting line | Mould & Tooling | The line where the two halves of a mould meet. It decides where flash may show and how the part sits in the tool. |
| Runner | Mould & Tooling | The channel that takes melt from the sprue to the gates. Its size and balance decide whether every cavity fills at the same time. |
| Slider | Mould & Tooling | A moving block that forms a feature lying sideways to the mould opening direction and slides clear before the part is ejected. |
| SPI finish | Mould & Tooling | A standard code for mould surface finishes, from a polished gloss to a coarse matt grain. It tells the toolmaker how to finish the cavity. |
| Sprue | Mould & Tooling | The main feed channel that carries molten plastic from the machine nozzle into the mould. It is usually the thickest section. |
| Sprue bush | Mould & Tooling | The hardened bush at the top of the mould that receives the machine nozzle and forms the sprue. It protects the softer plate below. |
| Tool steel H13 | Mould & Tooling | A hot-work tool steel that is hardened after machining. It resists wear and heat, so it suits long runs and abrasive plastics. |
| Tool steel P20 | Mould & Tooling | A pre-hardened mould steel used for many injection tools. It machines well and suits moderate production runs without further heat treatment. |
| Two-shot moulding | Mould & Tooling | Moulding two materials or two colours in one cycle, using a rotating mould or a second injection unit. |
| Undercut | Mould & Tooling | A feature that blocks straight opening of the mould, such as a snap hook or a side hole. It needs a slider, lifter or loose insert. |
| Boss | Part & Product Design | A raised pillar, usually round, that holds a screw or a pressed insert. It is best tied into a wall or a rib. |
| Datum | Part & Product Design | A reference surface or feature that all measurements are taken from. Clear datums stop argument between designer, toolmaker and inspector. |
| Design intent | Part & Product Design | The reason behind each shape and size in a model. It tells the next person which dimensions matter and which may change. |
| DfM | Part & Product Design | Design for manufacture: shaping a part so it can be made easily and cheaply. A DfM review catches problems before the tool is cut. |
| Fillet | Part & Product Design | A rounded inside corner that spreads stress and helps plastic flow. Sharp corners create weak points and are hard to machine. |
| Functional prototype | Part & Product Design | An early part made to test how the design works, not how it looks. It may be printed or machined before a mould is cut. |
| Living hinge | Part & Product Design | A thin, flexible strip of plastic joining two parts so they can bend many times, common in polypropylene lids and boxes. |
| Mould flow analysis | Part & Product Design | A computer simulation of how plastic fills the cavity. It predicts weld lines, air traps and cooling before the steel is cut. |
| Rib | Part & Product Design | A thin raised wall added to stiffen a part without a thick section. Ribs are made thinner than the main wall to avoid sink marks. |
| Snap fit | Part & Product Design | A small hook or lip that bends as two parts push together and then clicks into place, so no screws are needed. |
| Tolerance stack | Part & Product Design | The total of all the small dimensional variations in a chain of parts. It shows whether an assembly still fits in the worst case. |
| Wall thickness | Part & Product Design | The thickness of the plastic wall in a moulded part. Most parts run between about 1.5 mm and 3 mm for even filling. |
| ABS | Plastics & Materials | A tough, easily moulded plastic used for housings, toys and tool cases. It takes paint and glue well but scratches fairly easily. |
| Acetal (POM) | Plastics & Materials | A stiff, low-friction plastic with good dimensional stability. It suits gears, slides and parts that rub against each other. |
| Acrylic (PMMA) | Plastics & Materials | A clear, hard plastic used for windows, lenses and covers. It is more scratch-resistant than polystyrene but can crack under stress. |
| Colour masterbatch | Plastics & Materials | A concentrated colour pellet mixed with natural plastic at the machine. It lets one material run in several colours. |
| Glass-filled nylon | Plastics & Materials | Nylon mixed with short glass fibres for stiffness and heat resistance. It is stronger but more abrasive to the mould. |
| Hygroscopic | Plastics & Materials | A material that absorbs moisture from the air. Nylon and polycarbonate must be dried before moulding or the part shows streaks. |
| Nylon PA66 | Plastics & Materials | A strong, wear-resistant engineering plastic used for gears and clips. It absorbs moisture, so parts can grow slightly after moulding. |
| Polycarbonate (PC) | Plastics & Materials | A very tough, clear plastic that resists impact. It needs drying before moulding and scratches fairly easily. |
| Polyethylene (PE) | Plastics & Materials | A waxy, chemical-resistant plastic made in flexible and stiff grades. It is common for bottles, caps and tanks. |
| Polypropylene (PP) | Plastics & Materials | A light, low-cost plastic that resists fatigue, so it suits lids, containers and packaging. It is the plastic used for most living hinges. |
| PVC | Plastics & Materials | A plastic that can be made rigid or flexible by its additives. Flexible grades are used for cable and hose. |
| Regrind | Plastics & Materials | Sprue and runner material that is ground up and mixed back into virgin plastic. Too much regrind weakens the part. |
| Shrinkage | Plastics & Materials | The amount a moulded part gets smaller as it cools. Toolmakers scale the cavity up so the part ends up the right size. |
| Sink mark | Plastics & Materials | A shallow dip on a moulded surface above a thick section. It happens because the thick plastic shrinks after the skin sets. |
| TPE | Plastics & Materials | A rubber-like plastic that can be moulded like any other thermoplastic. It is used for soft grips, seals and flexible tabs. |
| Warpage | Plastics & Materials | Bending or twisting of a moulded part caused by uneven cooling or flow. It is corrected by cooling layout, gate position and packing. |
| Weld line | Plastics & Materials | A faint line where two flow fronts meet in the cavity. It is weaker than the surrounding plastic and may show through a gloss finish. |
| Assembly mate | CAD & SolidWorks | A rule that fixes how two components sit together, such as a coincident face or a concentric hole. Mates let the assembly be moved like the real thing. |
| Configuration | CAD & SolidWorks | A saved set of model values inside one file, used for different sizes or versions of the same part. |
| Drawing | CAD & SolidWorks | A 2D sheet made from a 3D model, carrying views, dimensions and tolerances for the workshop. |
| Exploded view | CAD & SolidWorks | An assembly picture with the parts pulled apart along their assembly paths. It shows how the product goes together. |
| Extrude | CAD & SolidWorks | The CAD feature that pushes a sketch along a straight line to make a solid. A cut-extrude removes material instead. |
| Interference check | CAD & SolidWorks | A CAD test that finds parts that overlap or clash when assembled. Finding a clash on screen is cheaper than finding it in steel. |
| Parametric model | CAD & SolidWorks | A model driven by dimensions and relationships rather than fixed geometry. Changing one value updates the whole design. |
| Reference geometry | CAD & SolidWorks | Planes, axes and points created to build from or measure against. They are the invisible scaffolding that keeps a model tidy. |
| Revolve | CAD & SolidWorks | The CAD feature that spins a sketch around an axis to make a round solid, useful for nozzles, bushes and shafts. |
| Sketch | CAD & SolidWorks | A 2D outline, drawn on a plane or a face, that drives a 3D feature. A fully defined sketch has every line fixed by dimensions or relations, so nothing moves. |
| SolidWorks | CAD & SolidWorks | The 3D CAD program used here for most product and tool design. Models are built as history trees of sketches and features. |
| Surface modelling | CAD & SolidWorks | Building shapes from thin skins instead of solid blocks, used for smooth, styled or complex forms. |
| 5-axis machining | CAM & Machining | Machining on a machine that moves the cutter and the work together on five axes, three straight and two rotary. Complex shapes are then cut in one setup. |
| CAM | CAM & Machining | Computer-aided manufacturing: software that turns a 3D model into machine instructions. It plans how each shape is cut. |
| Climb milling | CAM & Machining | Cutting so the cutter tooth bites into the material at its thickest point. It gives a better finish and longer tool life. |
| Cutter compensation | CAM & Machining | A control setting that shifts the toolpath sideways by the cutter radius, so one program suits a re-ground tool. |
| Cutting speed and feed | CAM & Machining | How fast the cutter edge moves and how fast it advances. Wrong values burn the tool or break it. |
| Finishing pass | CAM & Machining | The final light cuts that bring the surface to size and finish. Cuts are lighter than in roughing, with a small depth and stepover to hold the finish. |
| G-code | CAM & Machining | The plain text instruction list a machine control reads, holding coordinates, feeds and speeds for every move. |
| Post-processor | CAM & Machining | A translator that turns a generic CAM toolpath into the G-code one specific machine control understands. |
| Roughing pass | CAM & Machining | The first heavy cuts that remove most of the waste material, leaving a small allowance for the finishing pass. |
| Stepover | CAM & Machining | The sideways distance between two passes of the cutter. A small stepover gives a better finish but takes longer. |
| Toolpath | CAM & Machining | The path a cutting tool follows, with depth, stepover and feed. The toolpath decides finish, tool load and machining time. |
| Workholding | CAM & Machining | The vice, clamps or fixture that holds the workpiece while it is cut. Weak holding causes chatter and scrap parts. |
| Die spotting | Toolroom & Machining | Coating one half of a die with blue and closing it on the other to find the high spots. A fitter then stones those marks down until the faces touch evenly. |
| Hand fitting | Toolroom & Machining | Shaping and finishing a tool by hand with a file, a stone or a scraper, where a machine cannot reach or where a few micrometres decide the fit. |
| Jig borer | Toolroom & Machining | A precision boring machine that places holes from fixed coordinates, so a die plate's guide pillars and bushes line up within 0.005 mm. |
| Lathe | Toolroom & Machining | A machine that turns work between centres or in a chuck while a single-point tool shaves the outside diameter to size. |
| Machining centre | Toolroom & Machining | A computer-controlled milling machine with a tool changer, so it drills, taps and mills a part without an operator swapping cutters. |
| Surface grinder | Toolroom & Machining | A grinder that travels a spinning abrasive wheel across flat work held on a magnetic chuck, holding flatness and thickness to a few micrometres. |
| Tempering | Toolroom & Machining | Reheating a hardened tool to a lower temperature to trade a little hardness for toughness, so it will not crack in service. It eases the stress left by rough machining. |
| Tool steel D2 | Toolroom & Machining | A cold-work tool steel rich in chromium and carbon, hardened through to 58–62 HRC. It stands up to abrasive work but is less tough than S7. |
| Tool tryout | Toolroom & Machining | The bench check of a new tool before it reaches the machine: halves spotted, shut-offs fitted and slides run by hand, so the first machine trial starts from a tool that closes and moves correctly. |
| Vertical miller | Toolroom & Machining | A manual milling machine with a vertical spindle that cuts flat faces, slots and pockets one job at a time. Its table carries a vice or clamps. |
| Copper tungsten | EDM & Electrical Erosion | A dense copper-tungsten alloy used for fine EDM electrodes, where wear must be low and detail fine. |
| Dielectric fluid | EDM & Electrical Erosion | The oil or de-ionised water that fills the spark gap, flushing debris away and helping control the spark. |
| EDM | EDM & Electrical Erosion | Electrical discharge machining: removing metal with controlled electric sparks between an electrode and the workpiece. |
| EDM finish | EDM & Electrical Erosion | The spark-textured surface left by EDM. Coarse settings cut fast and leave a rough matt, while fine settings take much longer and leave a smoother surface. |
| Electrode | EDM & Electrical Erosion | The shaped copper, graphite or copper-tungsten tool that burns the wanted shape into the work during EDM. |
| Electrode wear | EDM & Electrical Erosion | The amount the electrode is eaten away while burning. It is allowed for so several cavities come out the same size. |
| Graphite electrode | EDM & Electrical Erosion | A graphite electrode used for rough burning, where a lot of metal has to come out. Graphite is low-cost, machines fast and wears slowly on coarse settings. |
| Orbiting | EDM & Electrical Erosion | Moving the electrode in a small circle while burning, so debris is flushed and the cavity is opened evenly. |
| Sinker EDM | EDM & Electrical Erosion | EDM that burns a shaped electrode down into the work to make a pocket, a corner or a deep rib. |
| Spark gap | EDM & Electrical Erosion | The small gap between electrode and work where the sparks jump. Toolmakers allow for it so the burnt pocket ends up to size. |
| Wire EDM | EDM & Electrical Erosion | EDM that cuts with a thin moving wire, like a band saw made of sparks. It cuts hard steel very accurately. |
| Assist gas | Laser Cutting | Oxygen, nitrogen or air blown through the cut. It clears molten metal and, with oxygen, adds heat to the cut. |
| CO2 laser | Laser Cutting | A gas laser that suits wood, acrylic, plastics and also mild steel. It is used a lot for non-metal cutting. |
| Dross | Laser Cutting | Hard metal slag stuck to the underside of a laser-cut edge. It is removed by deburring or by a better cutting setting. |
| Fibre laser | Laser Cutting | A laser that makes its beam inside a glass fibre. It cuts steel, stainless and aluminium quickly with modest power. |
| Focal point | Laser Cutting | The point where the laser beam is narrowest and its energy is most concentrated. Its position above or below the surface changes the cut. |
| Heat-affected zone | Laser Cutting | The thin layer of metal beside the cut whose structure is changed by heat. It matters on hardened or stressed parts. |
| Kerf | Laser Cutting | The narrow gap of material removed by the cut. It is typically a few tenths of a millimetre and must be allowed for. |
| Laser cutting | Laser Cutting | Cutting sheet by melting a narrow line with a focused beam. It gives accurate edges with little finishing work. |
| Nesting | Laser Cutting | Arranging parts on a sheet so as little metal as possible is wasted. Good nesting lowers the cost of each part. |
| Pierce point | Laser Cutting | The spot where the beam first burns through the sheet before cutting starts. It is usually placed off the part outline. |
| Tube laser | Laser Cutting | A laser machine that also rotates the work, so round and square tube is cut and mitred accurately. |
| Bend allowance | Sheet Metal | The length of the neutral axis running around a bend, added to the flat pattern so the folded part comes out the right size. |
| Bend radius | Sheet Metal | The inside radius formed by the press brake tooling. A radius that is too tight cracks the metal. |
| Bend relief | Sheet Metal | A small cut or notch at the end of a bend line that stops the metal tearing when it is folded. |
| Blank | Sheet Metal | The flat piece of sheet cut to the unfolded shape of a part, before bending and forming. |
| Deburr | Sheet Metal | Removing the sharp edge or burr left by cutting, by hand, in a tumbler or on a machine. |
| Flat pattern | Sheet Metal | The developed shape of a bent part, laid out flat. It is what the laser or the punch actually cuts. |
| Hem | Sheet Metal | A folded-over edge of sheet metal. It hides a sharp edge and stiffens the part. |
| K-factor | Sheet Metal | The number that describes where the neutral line sits inside a bend, used to calculate the flat length. |
| Powder coating | Sheet Metal | Spraying electrostatically charged powder paint onto metal and baking it to a hard, even finish. |
| Press brake | Sheet Metal | The machine with a punch and a V-block die that bends sheet metal to an angle. |
| Punch and die | Sheet Metal | The matching male and female tooling that cuts or forms sheet metal in a press. |
| Sheet metal | Sheet Metal | Metal supplied in flat sheets, usually from 0.5 mm to 6 mm thick, formed into parts by cutting and bending. |
| TIG welding | Sheet Metal | Tungsten inert gas welding, using a tungsten electrode and a hand-fed filler rod. It gives clean seams on sheet and tube. |
| Annealing | 3D Printing & Additive | Heating a printed part and cooling it slowly to reduce internal stress and improve its strength. |
| Build plate adhesion | 3D Printing & Additive | Flat rings or pads printed around the base, or glue on the bed, so the first layer sticks and the part does not curl off. |
| FDM | 3D Printing & Additive | Fused deposition modelling: printing by laying down melted plastic filament, one thin layer at a time. |
| Infill | 3D Printing & Additive | The internal pattern inside a printed part, given as a percentage. More infill makes a stronger, heavier part. |
| Layer height | 3D Printing & Additive | The thickness of each printed layer, often 0.1 mm to 0.3 mm. Thin layers look smoother but take longer. |
| MJF | 3D Printing & Additive | Multi-jet fusion: printing by sweeping a fusing agent and heat across a powder bed, faster than single-laser SLS. |
| Nozzle diameter | 3D Printing & Additive | The size of the FDM nozzle opening, often 0.4 mm. A bigger nozzle prints faster but with less fine detail. |
| Print orientation | 3D Printing & Additive | How a part is placed on the build plate. It decides strength, support, surface finish and print time. |
| Resin curing | 3D Printing & Additive | Washing uncured resin off a resin print and exposing it to ultraviolet light to finish the reaction. |
| SLA | 3D Printing & Additive | Stereolithography: printing that hardens liquid resin into solid layers with light. Laser machines trace each layer, and screen machines flash a whole layer at once. |
| SLS | 3D Printing & Additive | Selective laser sintering: fusing plastic powder with a laser, so no supports are needed and strong parts are possible. |
| Support | 3D Printing & Additive | Extra printed material that holds overhangs up during printing and is broken or dissolved away afterwards. |
| Anodising | Finishing & Surface Treatment | An electrochemical treatment that thickens the natural oxide layer on aluminium into a hard, coloured or clear skin. The coating resists corrosion and can accept dyes. |
| Diamond paste | Finishing & Surface Treatment | An abrasive paste, graded in microns, used on a soft lap or a felt wheel to polish mould steel. Going from coarse to fine grades builds a mirror that releases cleanly. |
| Dry-film lubricant | Finishing & Surface Treatment | A baked-on coating of a solid lubricant such as molybdenum disulphide that keeps moving parts sliding. It suits threads and slides where an oil film would be washed away. |
| Electroplating | Finishing & Surface Treatment | Depositing a thin metal layer onto a part using an electric current in a chemical bath, such as chromium onto steel. It adds corrosion resistance, hardness or a bright decorative face. |
| Glass bead blasting | Finishing & Surface Treatment | Shooting fine glass spheres at metal under air pressure to give a clean, dull, uniform surface. It strips rust and old paint without cutting the base metal, and it is coarser than wet honing. |
| Gloss level | Finishing & Surface Treatment | How shiny a moulded surface reads, measured by bouncing light off it in gloss units. A high gloss needs a polished, scratch-free cavity; a low gloss hides blemishes. |
| Laser marking | Finishing & Surface Treatment | Using a focused laser beam to burn a dark, permanent code or logo into a surface. It survives washing and wear better than an ink print, without cutting into the part. |
| PVD coating | Finishing & Surface Treatment | A vacuum deposition process that bonds a thin, very hard layer, often titanium nitride, onto a tool. It cuts friction and wear so forming dies and moulds last longer. |
| Texture etching | Finishing & Surface Treatment | A pattern etched into a mould cavity with acid, so every moulded part carries that grain on its face. It hides minor tool marks and gives a grip that gloss cannot. |
| Vapour honing | Finishing & Surface Treatment | A wet-blast finish that fires a fine slurry of glass beads and water at a part, giving a soft, even satin. It is gentler than dry blasting, so it suits thin sections and moulded finishes. |
| Calibration | Metrology & Quality | Checking a measuring tool against a known standard and recording the result, so its readings can be trusted. |
| CMM | Metrology & Quality | Coordinate measuring machine: a probe that touches points on a part and reports its real size and position in three dimensions. |
| Cpk | Metrology & Quality | A capability index showing whether a process comfortably fits inside the tolerance. Higher is better, and 1.33 is common. |
| First article inspection | Metrology & Quality | Checking the first part from a new tool or process against the drawing, before full production starts. |
| Go/no-go gauge | Metrology & Quality | A simple hardened gauge with a good end and a bad end, used on the shop floor to check a size quickly. |
| Inspection report | Metrology & Quality | A written record of the measured features of a part, with the drawing tolerance printed beside each reading. |
| Micrometer | Metrology & Quality | A precision hand tool with a screw spindle that measures small sizes to a thousandth of a millimetre. Not to be confused with the micrometre (µm), a unit of length. |
| Non-conformance | Metrology & Quality | A part or process that does not meet the drawing. It is written up, quarantined and decided on before it ships. |
| PPAP | Metrology & Quality | Production part approval process: the documentation pack that shows a supplier's part and process are capable. |
| Surface roughness Ra | Metrology & Quality | A measure of how rough a surface is: the average height of the tiny peaks and valleys, in micrometres. Mould finishes and sealing faces often carry an Ra limit. |
| Tolerance | Metrology & Quality | The allowed amount a dimension may vary, such as plus or minus 0.05 mm. Tighter tolerance costs more to hold. |
| Clamp force | Production & Injection | The force holding the mould closed against injection pressure, measured in tonnes. Too little lets the tool open and flash. |
| Cooling time | Production & Injection | The part of the cycle when the plastic is left to solidify enough to be ejected without being damaged. |
| Cycle time | Production & Injection | The time from one shot to the next, often 20 to 60 seconds for small parts. Shorter cycles make cheaper parts. |
| Degating | Production & Injection | Cutting or breaking a part away from its runner and gate, by hand, by robot or in a trimming fixture. |
| Flash | Production & Injection | Thin unwanted plastic squeezed out at the parting line or around a pin. It is trimmed off or prevented by better clamping. |
| Holding pressure | Production & Injection | The pressure kept on the melt after the cavity is filled, to pack out shrinkage while the gate is still open. |
| Injection moulding | Production & Injection | Making parts by forcing melted plastic into a closed steel mould, letting it cool and ejecting the solid part. |
| Melt temperature | Production & Injection | The temperature of the plastic as it leaves the machine nozzle, often set between 200 °C and 300 °C. |
| Mould temperature | Production & Injection | The temperature the tool is held at by its cooling circuit. It controls gloss, shrinkage and cycle time. |
| Short shot | Production & Injection | A part that is not completely filled because the plastic froze too early or there was too little pressure. |
| Shot | Production & Injection | One complete injection cycle, together with the parts and runner it produces. The cavity count sets parts per shot. |
| T1 trial | Production & Injection | The first run of a new mould on the machine, used to check filling, size and defects before adjustments are made. |
| Blow moulding | Blow Moulding | Making a hollow plastic part by inflating a hot tube or a heated preform inside a closed mould until it takes the shape of the cavity. Bottles, jerry cans and tanks are made this way. |
| Blow pin | Blow Moulding | The hollow pin that enters the neck of the parison and lets compressed air in, usually between 0.2 and 1 MPa. It also forms and sizes the neck opening. |
| Blow ratio | Blow Moulding | The widest moulded diameter divided by the diameter of the parison or preform. A high ratio thins the walls steeply, so the design spreads the stretch over as much of the part as it can. |
| Calibration jig | Blow Moulding | A cooled sizing sleeve or jig that holds the hot neck or mouth of a blown part to its exact size while the plastic sets, so the thread stays round and fits. |
| Die head | Blow Moulding | The tool at the end of the extruder that shapes the molten tube and sets how thick its wall is. Adjusting the die gap moves material to where the container needs it. |
| Extrusion blow moulding | Blow Moulding | An extruder pushes a continuous tube of melt down through a die head, and each mould clamps the tube, inflates it and cools it. It suits containers from about one litre upwards. |
| Parison | Blow Moulding | The hot tube of plastic that hangs down between the two open halves of a blow mould. The mould clamps it shut and compressed air inflates it against the cavity walls. |
| Pinch-off | Blow Moulding | The welded seam where the sharp edges of the mould squeeze the parison shut at the top and bottom. The width of those lands decides whether the seam holds pressure. |
| Preform | Blow Moulding | A small injection-moulded tube that already carries its finished neck and thread. It is made first, then reheated, stretched and blown into the final bottle. |
| Stretch blow moulding | Blow Moulding | Blowing a reheated preform while a rod stretches it lengthways, so the plastic molecules line up and the bottle gains strength with a thin, even wall. |
| Fettling | Casting & Foundry | Cleaning up a raw casting: cutting off gates and risers, grinding away flash, knocking out sand and dressing the surface before any machining allowance is cut away. |
| Gravity die casting | Casting & Foundry | Pouring molten metal into a reusable metal mould under gravity alone, with no pressure behind it. It gives a finer surface and grain than sand and suits aluminium parts in thousands. |
| High-pressure die casting | Casting & Foundry | Forcing molten metal into a hardened steel die at high speed and pressure on a locked machine. It makes accurate thin-walled parts quickly, but the tooling cost is high. |
| Investment casting | Casting & Foundry | Also called lost-wax casting: a wax pattern is coated in ceramic, the wax is melted out, and metal is poured into the empty shell. It gives fine detail and needs little machining. |
| Pattern | Casting & Foundry | The wooden, plastic or metal copy of the part that is packed in the sand. It is made oversize for shrinkage and shaped with draught so it lifts out cleanly. |
| Porosity | Casting & Foundry | Small gas holes or shrinkage voids trapped inside cast metal. They weaken the section and can leak under pressure, so a casting is specified with a porosity limit. |
| Riser | Casting & Foundry | A reservoir of molten metal, also called a feeder, that keeps feeding the casting as it shrinks. Placed correctly it keeps the last shrinkage void out of the part. |
| Sand casting | Casting & Foundry | Molten metal is poured into a cavity shaped in packed sand, and the sand is broken away once the metal has set. It suits iron, steel and aluminium in small or very large batches. |
| Sand core | Casting & Foundry | A shaped sand insert placed in the mould to form a hollow inside the casting, such as a water passage or a bore. It is broken out after the metal has set. |
| Shrinkage allowance | Casting & Foundry | The extra size built into the pattern or die because liquid metal contracts as it cools and sets. Aluminium shrinks about 1.3 per cent, so a metre-long casting would finish short without it. |
| Amortisation | Business & Trade | Spreading the one-off tooling cost across the number of parts ordered, so each part carries a share. |
| Deposit | Business & Trade | Money paid before work starts, covering materials and the early stages of a tool or a production order. |
| Lead time | Business & Trade | The time from a confirmed order to delivery. Tooling lead times run in weeks and are quoted separately. |
| MOQ | Business & Trade | Minimum order quantity: the smallest batch a supplier will make, because setting up the machine costs the same. |
| NDA | Business & Trade | A non-disclosure agreement: a signed promise not to share the customer's design or drawings with anyone else. |
| NRE | Business & Trade | Non-recurring engineering: the one-off design and development work charged before production begins. |
| Part cost | Business & Trade | The price of one moulded part once the tool exists. It falls as quantity rises because the tool cost is spread. |
| Patent | Business & Trade | A legal right, granted by a patent office, that stops others making a new invention for a set time. A search before tooling shows whether a design may infringe. |
| Prototype versus production | Business & Trade | A prototype is one or a few parts made to prove the idea works. A production part is made to the final drawing, in quantity, on tooling built to last. |
| Quotation | Business & Trade | A written offer to supply a part or a tool at a stated price, quantity and lead time. |
| Sole sourcing | Business & Trade | Buying a part from one supplier only. It simplifies control but leaves the buyer exposed if that supplier stops. |
| Tooling cost | Business & Trade | The one-off cost of designing and building the mould. It is paid once, before any parts can be made. |
Injection, blow moulding or casting?
The route is set by the part and the quantity. Injection moulding suits solid parts in large numbers. Blow moulding suits hollow containers. Casting suits metal parts in small or very large batches. The tooling cost is paid once, so the route you pick depends on how many parts you need.
| Route | How the part is formed | Choose it when |
|---|---|---|
| Injection moulding | Melted plastic is pushed into a closed steel mould under high pressure, then cooled and ejected as a solid part. | The part is solid, detailed and needed in large numbers, so the one-off tooling cost is spread across many parts. |
| Blow moulding | A hot tube is clamped in a closed mould and inflated with air to take the shape of the cavity. | The part is a hollow container, such as a bottle, jerry can or tank, from about one litre upwards. |
| Casting | Molten metal is poured into a mould or forced into a steel die, then left to set. | The part is metal and the quantity is small or very large, where casting suits the batch. |
Frequently asked questions
What is a glossary of terms?
A glossary of terms is a working list of the words a trade uses, each with a plain definition, so customer and supplier mean the same thing when they talk. This one covers toolmaking, mould design, sheet metal and 3D printing, written for the workshop floor and translated into eight languages.
How many terms does this glossary cover, and in which languages?
It defines 201 toolmaking and mould-design terms in 8 languages, alongside real customer questions decoded — what the caller asked, what they really meant, and what it means for the professional.
Should my part be injection moulded, blow moulded, or cast?
The route is set by the part and the quantity. Injection moulding suits solid parts in large numbers. Blow moulding suits hollow containers such as bottles and tanks. Casting suits metal parts in small or very large batches. The tooling cost is paid once, so the route depends on how many parts you need.
Who compiled this glossary?
It was compiled by Paul Lambourn, an industrial designer and toolmaker who has worked in toolmaking since 1978. The definitions are one or two plain sentences each, written for the workshop floor rather than for a brochure.
Where are the Customers Talks?
The Customers Talks now have their own page: Talks, in the menu. Every one started as a real phone call, and the table shows what the customer asked, what the customer really meant, and what that means for the professional. To ask your own question, write to paul.lambourn1@gmail.com.