ISO 294-4 Test Standard Explained

Mold Shrinkage - ISO 294-4

This standard covers the measurement of specimen shrinkage for injection and compression molding. Data for mold shrinkage should be used for material comparison. Actual mold shrinkage values are highly dependant on part geometry, mold configuration, and processing conditions.

Mold Shrinkage Specimen

Mold shrinkage for many materials differs for flow and transverse (or across flow) directions. Flow direction is taken as the direction the molten material is traveling when it exits the gate and enters the mold. Mold shrinkage is expressed as a percent change in dimension of a specimen in relation to mold dimensions.

Measurement Orientation

Mold shrinkage in the flow direction is calculated by:
S_Flow = 100 * (L_M - L_S) / L_M
where L_M is the length of the test section of the mold cavity and L_S is the corresponding length of the test specimen after it has cooled.

Mold shrinkage in the transverse direction is calculated by:
S_Transverse = 100 * (W_M - W_S) / W_{M M} is the width of the test section of the mold cavity and W_S is the corresponding width of the test specimen after it has cooled.

Similar Standards:

• ASTM D955

Property information for specific grades of resin are available in the Prospector Plastics Database.