Overview
ISO 2818:2018 - Plastics - Preparation of test specimens by machining - defines general principles and procedures for machining and notching test specimens from compression‑moulded and injection‑moulded plastics, extruded sheets and plates, and finished or semi‑finished plastic products. The standard establishes standardized machining conditions to ensure reproducible specimen preparation for mechanical and physical testing, while recognizing that exact procedures may be set by the material specification or the specific test method.
Key topics and technical requirements
- Scope of specimen types: rectangular bars, notched bars, plates, curvilinear (dumb‑bell) specimens and discs.
- Surface and edge quality: machined surfaces and edges must be free of visible flaws, scratches or imperfections when examined with low‑power magnification (~×5). Rectangular bars must be free of twist and have perpendicular parallel faces.
- Machining processes covered: milling, sawing/cutting (circular or band saw, abrasive discs), cutting disc‑shaped specimens, planing/broaching for finishing or notching, stamping thin sheets, and lathe cutting.
- Tool geometry and machine parameters: definitions and control of tool cutting‑edge geometry, tool radius, number of cutting teeth, cutting speed, feed speed, cutting depth and feed path to achieve reproducible conditions.
- Notching methods: milling or broaching of finished specimens for controlled notch geometry and integrity.
- Inspection and reporting: finished specimens are to be checked against dimensional tolerances and surface quality; test reports should document machining conditions used (tooling, speeds, feeds and any deviations).
- Interplay with other standards: ISO 2818 provides general machining rules and refers to relevant tooling and abrasive standards when applicable.
Practical applications and who uses ISO 2818:2018
- Laboratories and test houses preparing mechanical test specimens (tensile, impact, flexural, hardness) from molded or extruded plastics.
- Material manufacturers specifying reproducible specimen preparation for quality control and product development.
- Standards committees and test method authors referencing uniform machining conditions to reduce variability between laboratories.
- Contract manufacturers and tooling shops producing test coupons or prototype parts that require standardized preparation.
Using ISO 2818 helps reduce variability in test outcomes caused by inconsistent machining, ensuring meaningful, comparable mechanical test results for plastics.
Related standards
Keywords: ISO 2818:2018, plastics test specimens, specimen preparation, machining plastics, milling, sawing, notching, injection‑moulded, compression‑moulded, reproducible machining conditions.