Overview
EN ISO 294-4:2019 - Plastics - Injection moulding of test specimens of thermoplastic materials - Part 4: Determination of moulding shrinkage (ISO 294-4:2018) specifies a standardized method to measure moulding shrinkage, post-moulding shrinkage and total shrinkage of injection‑moulded thermoplastic test specimens. The method applies to directions both parallel and normal to melt flow and represents the free (unrestricted) shrinkage that occurs during the hold period. The standard excludes humidity effects from moulding shrinkage (they are treated in post‑moulding shrinkage).
Key topics and requirements
- Scope & definitions: Clear definitions for moulding shrinkage (S), post‑moulding shrinkage (S_P) and total shrinkage (S_T), and related terms such as cavity pressure and cavity pressure at hold (p_CH).
- Test specimens & mould: Uses Type D2 ISO mould producing 60 mm × 60 mm × 2 mm plate specimens (see ISO 294‑3). Guidance on optional reference marks (≈4 ± 1 mm from cavity edges; recommended ≤5 µm depth).
- Apparatus & instrumentation: Requirements for injection moulding equipment, melt and mould temperature measurement, and cavity pressure monitoring near the gate.
- Procedure: Covers conditioning of material, injection‑moulding parameters (melt/mould temperature, injection velocity, hold pressure), measurement of temperatures, specimen treatment after demoulding, and timing for post‑moulding treatments.
- Measurement & calculation: How and where to measure shrinkage (mid‑points of width/length), expression of results in percent (%) and reporting of precision.
- Test reporting: Required information to be included in the test report (procedure parameters, results and conditions).
Practical applications
- Quality control of thermoplastic production - monitor consistency of dimensional behaviour between batches.
- Material comparison - evaluate relative shrinkage behavior when selecting thermoplastics for dimension‑sensitive parts.
- Process development and troubleshooting - assess effects of melt/mould temperature, injection speed and hold pressure on shrinkage.
- Tooling and mould design feedback - provide empirical data on free shrinkage to inform allowance and gate/runners design (note: the standard is not a substitute for detailed component design calculations).
Who should use this standard
- Plastics test laboratories and R&D teams
- Materials and process engineers in injection moulding
- Quality assurance and product engineering groups
- Mould designers and suppliers of test and measurement services
Related standards
- ISO 294‑1 (general principles & multipurpose specimens)
- ISO 294‑3 (small plates; Type D2 mould details)
- ISO 175 (effects of humidity uptake)
- ISO 2577 (shrinkage of thermosets)
Keywords: EN ISO 294-4:2019, moulding shrinkage, injection moulding, thermoplastic test specimens, post-moulding shrinkage, Type D2 mould, shrinkage measurement.