MANUFACTURING – INJECTION MOULDING & PLATIC CALCULATOR
Warpage Shrinkage Diff
A precise tool.
What is the Warpage Shrinkage Diff & How does it work?
Differential shrinkage occurs when the polymer contracts at different rates along the flow and transverse directions during cooling, leading to internal stresses that manifest as warpage.
The linear shrinkage percentages, typically denoted S_f for the flow direction and S_t for the transverse direction, are measured from molded test coupons and are influenced by material grade, mold temperature, and cooling time.
By relating the shrinkage differential to part geometry and material stiffness, engineers can estimate the resulting angular deviation (warpage) and take corrective actions such as adjusting gate location or mold temperature.
\theta = \frac{(S_f – S_t) \cdot L}{t \cdot E}
S_f = flow direction shrinkage (%); S_t = transverse shrinkage (%); L = distance from gate (mm); t = part thickness (mm); E = Young’s modulus (MPa); \theta = warpage angle (degrees)
Parameters
Result
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Frequently Asked Questions
What is warpage shrinkage difference?
Warpage shrinkage difference is the variation in shrinkage rates between the flow and transverse directions of a molded part, leading to internal stresses that cause warpage.
How do material grade, mold temperature, and cooling time affect differential shrinkage?
Material grade affects the polymer’s inherent properties, mold temperature influences how quickly the polymer cools, and cooling time impacts the extent of contraction, all of which contribute to differential shrinkage.
What are S_f and S_t in the context of warpage shrinkage?
S_f represents linear shrinkage percentage in the flow direction, while S_t denotes linear shrinkage percentage in the transverse direction.
How does part geometry relate to differential shrinkage?
Part geometry affects how internal stresses from differential shrinkage are distributed, influencing the extent and pattern of warpage.
Why is material stiffness important in relation to warpage shrinkage?
Material stiffness determines how easily a part deforms under stress; higher stiffness can lead to more pronounced warpage due to internal stresses from differential shrinkage.
Results are for informational purposes only and do not constitute professional advice.