ISO 294-4:2018

Overview

ISO 294-4:2018 - Plastics - Injection moulding of test specimens of thermoplastic materials - Part 4: Determination of moulding shrinkage specifies a standardized method to measure moulding shrinkage, post‑moulding shrinkage and total shrinkage of injection‑moulded thermoplastic test specimens in directions parallel and normal to melt flow. The third edition (2018) updates referenced documents and integrates measurement, apparatus and procedural requirements for reproducible shrinkage data used in material comparison, process control and quality assurance.

Key topics and technical requirements

• Scope and definitions: Clear definitions of moulding shrinkage (excludes humidity uptake), post‑moulding shrinkage (includes humidity effects), and total shrinkage.
• Test specimen and mould: Uses a Type D2 ISO mould producing 60 × 60 × 2 mm plates (see ISO 294‑3). Reference marks may be engraved at (4 ± 1) mm from cavity edges; marks should be ≤ 5 µm deep to avoid restricting shrinkage.
• Apparatus:
  • Pressure sensor in the mould is mandatory (cavity pressure measurement).
  • Measuring equipment must resolve dimensions to within 0.02 mm (measure between centre lines, edges or reference marks).
  • Oven required only if post‑moulding shrinkage testing is agreed.
• Injection and pressure control:
  • Recommended cavity pressures at hold: 20, 40, 60, 80 and 100 MPa (intermediate values allowed).
  • Tolerance for cavity pressure: ±5%.
  • Hold pressure and change‑over point must be selected to avoid pressure peaks that exceed hold pressure by more than 10% during the first second after change‑over.
• Procedure elements: Material conditioning, injection moulding parameters, measurement of mould and melt temperatures, specimen handling (cut from runner immediately) and storage at (23 ± 2) °C for 16–24 h before measurement.
• Measurement notes: Include the 0.5 mm gate step when measuring length; ensure jaws of mechanical gauges do not indent specimens.
• Reporting: Expression of results, precision, and test report requirements are specified (see Clauses 6–8).

Applications and users

ISO 294‑4:2018 is used by:

• Polymer materials laboratories and test houses for material comparison (shrinkage behavior).
• Injection‑moulding process engineers for process optimization (melt/mould temperature, hold pressure, change‑over timing).
• Quality engineers and manufacturers for production control and verifying moulding consistency.
• R&D and materials selection teams assessing suitability of thermoplastics for dimensionally accurate parts.

Note: the method measures free shrinkage (maximum unrestricted shrinkage) and is intended for comparison and process insight rather than direct design calculations.

Related standards

• ISO 294‑1:2017 (general principles)
• ISO 294‑3:2002 (small plates / Type D2 mould)
• ISO 2577 (thermosets shrinkage)
• ISO 175 (humidity‑induced dimensional changes)