Injection Molding Glossary | Terminology & Definitions | JBRplas

A · B · C · D · E · F · G · H · I · K · L · M · O · P · R · S · T · U · V · W

A

AQL (Acceptable Quality Level): The maximum percentage of defective units that is considered acceptable during random sampling inspection. JBRplas uses ANSI/ASQ Z1.4 Level II, AQL 1.0 for critical dimensions as standard. Learn more →

B

Back pressure: Resistance applied to the screw during plastication (material melting). Higher back pressure improves melt homogeneity and colourant dispersion; excessive back pressure increases cycle time and can degrade heat-sensitive resins.

Bridge tooling: A single-cavity mold built to mirror the gating, cooling, and ejection design of a planned multi-cavity production tool. Used to supply production parts during the 6–8 weeks while the full production tool is being manufactured. Learn more →

C

CAPA (Corrective and Preventive Action): A structured quality process for addressing non-conformances. Corrective action fixes the immediate cause; preventive action ensures it does not recur. JBRplas completes root cause analysis within 48 hours of detection and provides a written CAPA report to the customer. Learn more →

Cavity: The void in a mold that forms the external shape of the molded part. A single-cavity mold produces one part per cycle; a multi-cavity mold produces multiple identical parts per cycle. Cavity count is a primary driver of tooling cost and production rate.

Clamping force: The force (measured in tonnes) that holds the two halves of a mold closed against injection pressure. JBRplas operates presses from 60T to 500T. Required clamping force depends on part projected area and material viscosity.

CMM (Coordinate Measuring Machine): A precision measurement instrument that records 3D coordinates of part or mold surfaces with ±0.002mm accuracy. Used at JBRplas for mold cavity inspection before trial and for First Article dimensional reports. Learn more →

CoC (Certificate of Conformance): A document certifying that a production lot meets the agreed specifications. Issued per shipment and signed by the Quality Manager. Learn more →

Cold runner: A mold feed system where the runner (the channel delivering melt from the sprue to the gate) solidifies with the part and is ejected as waste. Lower tooling cost than hot runner but generates material waste and longer cycle time on multi-cavity tools.

Conformal cooling: Cooling channels machined to follow the 3D contour of the part surface, maintaining uniform distance from the cavity wall. Reduces warpage and cycle time compared to conventional straight-line drilled channels.

Control Plan: A documented quality control procedure listing every inspection point, measurement method, sample size, frequency, and acceptance criteria for a production process. Required for automotive PPAP submissions. Learn more →

Cooling channel: Drilled or machined passages within the mold through which temperature-controlled water or oil circulates to extract heat from the molten plastic. Cooling typically accounts for 60–70% of total cycle time. Learn more →

Core: The mold half or insert that forms the internal surfaces of the part — typically the moving side of the mold that carries the ejection system.

Cpk (Process Capability Index): A statistical measure of how consistently a process produces parts within specification limits. Cpk ≥ 1.33 is the standard minimum for automotive programs; Cpk ≥ 1.67 is considered excellent. Learn more →

Cushion: The small amount of melt left in front of the screw at the end of the injection stroke. Maintains a consistent pressure transfer during the hold phase. Zero cushion (screw bottoms out) results in inconsistent part weight and dimensions.

Cycle time: The total time per molding cycle — injection, pack/hold, cooling, and ejection/mold open-close. Shorter cycle time = lower per-part cost. Typical cycles at JBRplas range from 15 seconds (thin-wall packaging) to 60+ seconds (thick-wall structural parts).

D

DFM (Design for Manufacturability): A systematic review of a part design to identify features that will cause manufacturing problems — insufficient draft, wall thickness variation, un-moldable undercuts, gate witness location — before tooling begins. JBRplas provides a free written DFM report with every quotation. Learn more →

Draft angle: The slight taper (typically 0.5°–3°) applied to vertical part surfaces to allow the part to release from the mold without dragging or scoring. Draft angle requirements increase with texture depth — VDI 27 texture requires minimum 2.5° draft.

E

EDM (Electrical Discharge Machining): A machining process that removes metal using controlled electrical sparks between an electrode and the workpiece. Used for features that cannot be CNC-milled — sharp internal corners, deep ribs, complex 3D contours. Sinker EDM uses a shaped electrode; wire-cut EDM uses a continuously-fed wire. Learn more →

Ejector pin: A cylindrical pin that pushes the solidified part off the core after the mold opens. Pin diameter, quantity, and position are designed to distribute ejection force evenly and avoid cosmetic witness marks on visible surfaces.

F

FAI (First Article Inspection): A complete dimensional verification of the first parts produced by a new or modified mold. Every dimension on the part drawing is measured and recorded. The FAI report is provided to the customer alongside T1 samples for cross-checking. Learn more →

G

Gate: The narrowest point in the melt delivery system where material enters the cavity. Gate type and location affect fill pattern, weld line position, cosmetic quality, and cycle time. Common types include edge gate, tunnel (submarine) gate, fan gate, and valve gate. Learn more →

Glass transition temperature (Tg): The temperature at which an amorphous polymer transitions from a rigid, glassy state to a softer, rubbery state. For semi-crystalline polymers like PP and PA, the practical continuous-use temperature may exceed Tg — but for amorphous polymers like PC and ABS, Tg is the effective service temperature ceiling.

H

HDT (Heat Deflection Temperature): The temperature at which a standard test bar deflects 0.25mm under a specified load (typically 1.8 MPa). Used to compare the short-term thermal performance of different resins. Not the same as continuous service temperature. Learn more →

Hot runner: A mold feed system where the runner is heated and the melt remains molten between shots. Only the part (and a small gate vestige) solidifies — there is no runner waste. Higher tooling cost than cold runner but lower material waste, faster cycles, and better cosmetic quality. Brands used at JBRplas: Yudo, Mold-Masters, Husky, Synventive. Learn more →

HRC (Rockwell Hardness): A measure of steel hardness. Mold steels at JBRplas range from P20 at 28–34 HRC (general purpose) to H13 and S136 at 48–52 HRC (hardened production tooling, abrasive or corrosive resins). Higher HRC = greater wear resistance but higher machining cost.

Hygroscopic: Describes a resin that absorbs moisture from ambient air. PA (nylon) is strongly hygroscopic and can absorb 1–3% moisture by weight; PC, ABS, and PBT are also hygroscopic. All hygroscopic resins must be adequately dried before molding or the moisture turns to steam during injection, causing splay marks, voids, and reduced mechanical properties.

I

Injection speed: The rate at which the screw moves forward during the injection phase, measured in mm/s. Faster injection improves surface finish and thin-wall fill but increases shear heating and the risk of burn marks if venting is inadequate.

Insert molding: A process where a pre-formed component — typically a metal bushing, threaded insert, or electrical contact — is placed into the mold before injection so the plastic encapsulates or bonds to it during molding. P20 steel minimum required due to insert loading complexity.

IQ/OQ/PQ (Installation/Operational/Performance Qualification): A three-stage validation protocol used in medical device manufacturing. IQ verifies correct equipment installation; OQ verifies it operates within parameters; PQ verifies it consistently produces conforming product. Required for ISO 13485 programs. Learn more →

K

Kanban: A pull-based inventory replenishment system. JBRplas holds a finished goods buffer and ships on customer call-off — the customer releases orders as needed rather than committing to a fixed schedule. Suitable for programs with steady monthly demand.

L

Lifter: A mold component that moves at an angle during ejection to release an internal undercut. Mounted on the ejector plate; rises and tilts simultaneously as the plate advances. Used for internal snap features, latch details, and threaded sections.

M

Masterbatch: A concentrated mixture of pigment or additive dispersed in a carrier resin. Added in small percentages (typically 1–5%) to natural-colour base resin at the press hopper to achieve the target colour. Allows colour changes on a single base resin supply. Learn more →

MFI / MFR (Melt Flow Index / Melt Flow Rate): The mass of polymer (in grams) that flows through a standard capillary in 10 minutes at a specified temperature and load. Higher MFI = more fluid melt = easier to fill thin sections. Lower MFI = higher melt strength = better for extrusion blow molding.

Melt temperature: The actual temperature of the molten plastic as it enters the mold — distinct from the barrel set temperature. Measured by an air-shot probe. Melt temperature affects viscosity, fill behaviour, material degradation risk, and surface finish.

MOQ (Minimum Order Quantity): The smallest production quantity a supplier will accept. JBRplas has no formal MOQ; we regularly produce batches from 500 pieces for prototyping and validation. Production economics favour volumes above 10,000 pieces per year.

O

Overmolding: A process where a second material is molded over a previously molded substrate — typically a soft TPE or TPU over a rigid PC or ABS part. Used for soft-touch grips, seals, and wearable device bands. At JBRplas, low volume overmolding is done via insert-overmold or two-step molding. Learn more →

P

P20: A pre-hardened mold steel (28–34 HRC) used for general-purpose production tooling. Suitable for non-abrasive, non-corrosive resins — ABS, PP, PS, unfilled PC. Typical shot life: 300,000–500,000. The most common steel grade for medium-volume production molds. Learn more →

Parting line: The plane where the two mold halves meet. The parting line leaves a visible witness line on the part. Parting line position is a critical DFM decision — it affects part appearance, flash control, venting, and tooling cost.

PFMEA (Process Failure Mode and Effects Analysis): A structured analysis that identifies every potential failure mode in a manufacturing process, assesses severity/occurrence/detection ratings, and defines preventive actions. Required for automotive PPAP submissions. Learn more →

PPAP (Production Part Approval Process): A standardized 18-element documentation package used in the automotive supply chain to validate that production parts meet specification. Level 3 is the most comprehensive level. JBRplas provides PPAP Level 3 for automotive customers. Learn more →

Purging: The process of flushing one material or colour out of the injection barrel before introducing the next. Performed between colour changes or material switches. A commercial purging compound is used to accelerate the process and reduce transition waste.

R

Regrind: Ground-up material from previously molded parts, runners, or sprues that is blended with virgin resin at a controlled percentage. Reduces material cost but can degrade mechanical properties and colour consistency if the percentage is too high or the material has been heat-degraded.

Runner: The channel that delivers melt from the sprue to the gate(s). See also cold runner, hot runner. Runner diameter is sized to balance adequate flow against material waste — typically 4–8mm for most engineering resins at JBRplas.

S

Shot weight: The total mass of material injected per cycle — part weight plus cold runner weight (if applicable). Press selection requires that shot weight falls within 20–80% of the press barrel capacity for consistent melt quality.

Shrinkage: The reduction in part dimensions as it cools from melt temperature to ambient. Material-specific and influenced by wall thickness, mold temperature, and process parameters. Tooling cavities are machined oversized by the predicted shrinkage percentage so the part cools to the target dimension. Learn more →

Slide: A mold component that moves perpendicular to the mold opening direction to release an external undercut — a hole, slot, or recess in the side of a part. Slides are cam-actuated by the mold opening stroke. Adding a slide increases tooling cost by 15–30% per slide.

SPI finish: A surface finish standard defined by the Society of the Plastics Industry. Ranges from A1 (diamond polish, Ra 0.012μm) to D1 (dry blast, Ra 0.80μm). SPI B1 (600-grit stone, Ra 0.10μm) is the most commonly specified finish for cosmetic visible surfaces. Learn more →

SPC (Statistical Process Control): A quality method that uses statistical analysis of measured dimensions to detect process drift before it produces out-of-spec parts. JBRplas monitors critical dimensions on a sampling basis (typically every 50–100 shots) and plots Cpk. Learn more →

Sprue: The primary channel through which melt enters the mold from the injection barrel nozzle. In a cold runner system, the sprue solidifies with the runner and is ejected as waste. In a hot runner system, the sprue bushing is heated — no sprue waste.

Stripper plate: An ejection method that uses a full-circumference plate to push the part off the core, rather than individual ejector pins. Produces no pin witness marks and is preferred for cosmetic parts, thin-wall parts, and transparent parts where pin marks would be visible.

Submarine gate: A gate type where the melt enters the cavity through an angled tunnel below the parting line. The gate shears off automatically during ejection — no manual degating required. Gate witness is hidden on a non-visible surface. Common in high-cavitation tooling.

T

T1 / T2 / TF: T1 = first trial shots from a new mold, used to verify part dimensions and mold function. T2 = second trial after modifications, typically a dimensional adjustment or surface finish refinement. TF = final trial before production release. JBRplas provides a full FAI report with T1 samples. Learn more →

Thermoplastic: A polymer that can be repeatedly melted and solidified by heating and cooling. All injection molding resins at JBRplas are thermoplastics — ABS, PC, PP, PA, POM, PEEK, etc. Contrast with thermoset.

Thermoset: A polymer that undergoes an irreversible chemical reaction during molding and cannot be re-melted. Not processed by JBRplas. Examples: epoxy, phenolic, silicone rubber, unsaturated polyester (SMC/BMC).

2K molding (Two-shot molding): A process where two different materials or colours are injected into the same mold in sequence, producing a single integrated part. Requires a dedicated 2K injection press with two injection units or a rotary platen. At JBRplas, low-volume multi-material parts are typically produced via insert-overmold rather than dedicated 2K tooling.

U

Undercut: Any part feature that prevents the part from being ejected straight out of the mold — a hole, slot, recess, or protrusion not aligned with the mold opening direction. Undercuts are released by slides (external) or lifters (internal). Each undercut adds tooling cost; DFM review prioritizes undercut elimination where design permits. Learn more →

V

Valve gate: A hot runner nozzle with a mechanically actuated pin that opens and closes the gate orifice. Produces a flush gate vestige (<0.2mm high) versus the small protruding nub of an open hot tip. Used for cosmetic parts, medical enclosures, and optical surfaces. Learn more →

VDI texture: A surface texture standard (Verein Deutscher Ingenieure) commonly used in European mold specifications. VDI 12 (finest) through VDI 45 (coarsest). Deeper VDI textures require increased draft angles. Learn more →

Venting: Shallow channels (typically 0.01–0.03mm deep) machined into the parting line to allow air and volatiles to escape during injection. Inadequate venting causes burn marks (dieseling), short shots, and poor weld line strength. FR and high-temperature resins require more aggressive venting.

W

Wire-cut EDM: A precision machining process that uses a continuously-fed brass or zinc-coated wire electrode to cut through hardened steel with ±0.003mm accuracy. Used for shut-off surfaces, precision apertures, ejector pin holes, and features that cannot be achieved by CNC milling. Learn more →

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