Evaluating Tooling Acceptance Criteria during Overseas Factory Acceptance Testing
Rigorous overseas tooling acceptance demands steady-state thermal runs, single-cavity Cpk validation, complete disassembly wear audits, and escrow-backed signoff.
Cavity Balance
Meaning
Uniformity of plastic melt distribution across all mold impressions during an injection cycle. Maintaining cavity balance ensures that each part produced in a multi-cavity tool reaches identical dimensions and properties simultaneously. This state occurs when pressure and temperature profiles remain consistent across the entire mold face.
Filling Uniformity
Flow fronts must reach the end of each cavity at the same moment to prevent flashing or short shots. If cavity balance is absent, overpacking occurs in the first filled sections while others remain under-filled. High speed cameras or pressure sensors confirm this synchronization during tool qualification.
Thermal Stability
Cooling rates vary if the heat load is not distributed evenly across the mold steel. Because cavity balance influences the thermal history of the polymer, the state of the melt dictates the final shrinkage and crystallinity of the parts. Discrepancies here lead to warping or structural weakness in high precision components.
Large deviations in temperature profile across the manifold create internal stresses that compromise the integrity of the plastic and lead to early part failure in the field.
Production Yield
Success depends on the ability to replicate pilot results at full press speeds. Poorly managed cavity balance increases the scrap rate during mass production as process windows narrow. Corrective actions involve adjusting gate sizes or heater band settings to align the flow across the manifold.