Plan for Shrinkage Before Specifying Case Fit
ARM describes how cooling and draft influence dimensional stability. Lid fit, liner clearance and gasket contact should be checked on molded samples.
The association guide explains that a rotomolded part changes size as it cools and that uneven cooling can distort shape. Draft angles help remove the part from the mold without excessive force. Material, geometry and processing all affect the final dimension.
Fit is a system property
A lid, liner and seal must work together on the actual molded part. A nominal CAD dimension cannot show all process variation. Prototype assembly should therefore assess opening, closing and contact around the perimeter, especially after material or color changes.
- Identify fit-critical dimensions and how they will be measured.
- Review sample parts after cooling, before final approval.
- Include the complete gasket, liner and hardware configuration in fit checks.
The cover is an illustrative CASEROVA carrier photo; it is not an example of a fit failure or an ARM specimen.
Source: Association of Rotational Molders — Draft Angles, Shrinkage & Warpage
