ASTM D955

ASTM D955 is the ASTM standard that covers the Standard Test Method of Measuring Shrinkage from Mold Dimensions of Thermoplastics. It provides a consistent way to evaluate how thermoplastic parts change in size after molding, which is important for product fit, tooling decisions, and dimensional control. By using a defined test method, manufacturers and laboratories can compare results more reliably and support quality-related decisions for molded plastic components.

What is ASTM D955?

ASTM D955 is a test method focused on measuring shrinkage from mold dimensions in thermoplastics. In practical terms, it helps users determine how much a molded item differs from the dimensions of the mold after processing and cooling. This type of measurement is commonly used when dimensional accuracy matters and when molded parts must meet expected size targets. The standard is useful for establishing a repeatable testing approach for thermoplastic materials and molded specimens.

Where is ASTM D955 used?

This standard is commonly used in laboratories, plastics processing operations, and quality control environments that work with molded thermoplastic parts. It is especially relevant when mold design, part dimensions, and post-molding shrinkage need to be evaluated together. ASTM D955 may also be used during material qualification, process validation, or supplier acceptance checks where consistent measurement of molded shrinkage supports better engineering decisions and more predictable production outcomes.

Why is ASTM D955 important?

ASTM D955 matters because shrinkage can affect whether a molded thermoplastic part meets dimensional requirements after manufacture. A standardized test method helps reduce uncertainty, supports repeatable results, and makes it easier to compare data across materials, molds, or production runs. For procurement, testing, and quality control teams, it can help verify product performance, reduce fit issues, and support more confident decisions about compliance and process stability.

• Measures shrinkage from mold dimensions
• Applies to thermoplastic materials
• Supports dimensional evaluation of molded parts
• Useful for quality control and material comparison
• Helps improve repeatability in testing