Rapid Prototyping Glossary P | Attwood Product Development

PA11

Abbreviation for nylon 11.

PA12

Abbreviation for nylon 12.

Pack pressure

Pressure applied after the cavity is initially filled to compensate for cooling shrinkage.

Pack-and-hold

A common processing phrase covering the pressure-controlled stages after fill, when additional material is packed into the cavity and then held until the gate freezes.

Packing phase

The stage immediately after cavity fill when pressure is maintained to compensate for volumetric shrinkage before gate freeze. Also called the pack phase or hold phase, depending on machine terminology.

Pad printing

A process that transfers ink from an etched plate to a part via a silicone pad.

Painting

Applying a liquid coating for colour, protection or both.

Pallet changer

An automated system that swaps one workholding pallet for another to reduce spindle idle time between jobs.

Parameter set

A defined collection of machine settings used for a specific material and process.

Part catcher

A device on a turning centre that catches a finished part after cut-off so it does not drop loose into the machine.

Parting line

The line on a moulded or cast part where the two halves of the tool meet.

Parting off

Also called cut-off; a turning operation that separates the finished part from the remaining bar or billet.

Parting surface

The mating surfaces on the two tool halves that meet at closure and define the parting line. Accurate parting surfaces are essential for sealing, alignment and flash control.

Passivation

A chemical treatment, often for stainless steel, that improves corrosion resistance by enhancing the passive surface layer.

Patternmaker's finish

A manually prepared tool or part finish intended to achieve a clean, visually uniform surface.

PBF

Abbreviation for powder bed fusion.

PC

Polycarbonate; a tough transparent engineering plastic used for impact-resistant prototypes.

Peck drill

A drilling cycle or strategy that retracts repeatedly to break chips and clear swarf from the hole.

PEEK

Polyether ether ketone; a high-performance thermoplastic with excellent heat and chemical resistance.

Peel strength

The force required to peel one bonded material away from another.

PEI

Polyetherimide; a high-temperature engineering plastic, often known by trade names such as Ultem.

Pellet extrusion

A material-extrusion process using plastic pellets rather than filament.

Perimeter shell

The outer walls of an additively manufactured part, surrounding the infill region.

Permanent mould casting

A metal casting process that uses a reusable metal mould rather than a disposable sand or plaster mould.

Permeability

The degree to which a material allows gases or liquids to pass through it.

PETG

Polyethylene terephthalate glycol; a printable thermoplastic known for toughness and ease of processing.

Photopolymer

A light-curable resin used in SLA, DLP, PolyJet and related processes.

Pigmentation

The addition of colourants to a material, coating or printed medium.

Pilot run

A controlled early production run used to prove the process before wider release.

Pin gate

A small circular gate often used in moulding for reduced witness size.

Pin mark

A visible witness left by an ejector pin or contact pin.

Pinch-off

A mould feature that seals or trims material, especially in blow moulding and hollow-part processes.

Pitch

The distance between corresponding points on adjacent screw threads, gear teeth or repeated features; also relevant to tapped and threaded machined parts.

PLA

Polylactic acid; a common, easy-to-print thermoplastic used mainly for visual or light-duty prototypes.

Planing

A machining process that uses linear cutting motion to create or true large flat surfaces.

Plasma treatment

Surface activation using plasma to improve bonding, printing or coating adhesion.

Plaster casting

A casting method using plaster-based mould material, often suited to prototypes, ornaments or smaller metal components.

Plated finish

A finished surface produced by electroplating or electroless deposition.

Platen

The large rigid plate on an injection moulding machine to which the mould halves are mounted. Machines typically have a stationary platen and a moving platen.

PLC

Programmable logic controller; an industrial control system widely used to monitor and regulate machine parameters.

Plug assist thermoforming

Thermoforming in which a plug helps pre-stretch the heated sheet into the mould.

Plunge

A straight axial movement of a tool into material, often used to enter a cut, spot a feature or start a pocketing operation.

PMMA

Polymethyl methacrylate; the polymer more commonly referred to as acrylic.

Pocket milling

A milling operation that removes material from within a closed boundary to form a pocket or cavity.

Polycarbonate

The full material name for PC.

Polyether ether ketone

The full material name for PEEK.

Polyetherimide

The full material name for PEI.

PolyJet

A material-jetting process that deposits and UV-cures tiny droplets of photopolymer.

Polymerisation

The chemical reaction that links monomers into polymer chains or networks.

Polyol

The resin-side reactive component commonly used with an isocyanate in polyurethane and reaction injection moulding chemistry.

Polyoxymethylene

The full polymer name for POM/acetal.

Polypropylene

The full polymer name for PP.

Polypropylene-like resin

A photopolymer formulated to imitate some properties of polypropylene for concept or fit testing.

Polyurethane

PU; a broad family covering cast elastomers, foams, coatings and casting resins.

POM

Polyoxymethylene; the full polymer family name for acetal.

Porosity

Voids or pores within a material, which may be intentional or an undesirable defect.

Post processor

Software that converts CAM toolpaths into machine-specific CNC code suited to a particular control and machine configuration.

Post-curing

Additional UV or thermal curing applied after printing to complete material properties.

Post-processing

Any step performed after the primary manufacturing process, such as support removal, blasting, machining or coating.

Powder ageing

Changes in reusable powder caused by repeated heating, exposure or mixing cycles.

Powder bed fusion

PBF; additive processes that use heat to fuse selected regions of a powder bed layer by layer.

Powder coating

A dry coating process in which charged powder is applied and baked into a durable finish.

Powder recovery

Collecting, sieving and reusing unfused powder from an additive build.

Powder storage bin

The feed bin that stores raw powder beside or above the build area in a powder-bed additive system.

PP

Polypropylene; a versatile thermoplastic used for living hinges, chemical resistance and low-density mouldings.

Pre-production prototype

A late-stage prototype built to closely reflect intended production geometry, material and finish.

Press fit

An assembly fit achieved by forcing slightly oversized and undersized features together.

Pressure die casting

A casting process in which molten metal is injected into a metal die under pressure.

Probe

A measurement device fitted to the machine for picking up datums, checking tools or inspecting features.

Probing

The use of a touch probe or similar system to locate features, set offsets, verify dimensions or automate in-process inspection.

Process capability

A measure of how well a stable manufacturing process can meet specification limits.

Profilometer

An instrument used to measure surface profile and roughness.

Prototype tooling

Tooling created primarily to support prototype or low-volume production rather than full-scale manufacturing.

PSU

Polysulphone; a transparent high-temperature engineering thermoplastic.

PTFE

Polytetrafluoroethylene; a very low-friction, chemically resistant polymer often used for seals and wear parts.

Pull stud

Also called retention knob; the stud fitted to many toolholders so the spindle drawbar can clamp and release them.

Pull-off adhesion

A test of coating or adhesive bond strength measured by pulling normal to the surface.

Purge

Material expelled from a machine to clean the melt path before a new resin or colour is processed.

Purge compound

A specially formulated cleaning material run through the barrel and hot runner to remove residual resin, degraded polymer or colour contamination during changeover.

PVA

Polyvinyl alcohol; a water-soluble support material commonly used alongside FDM or FFF thermoplastics.

PVC

Polyvinyl chloride; a widely used plastic less common in advanced prototyping but relevant in some fabricated products.