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.
Runner Balance
Meaning
Design requirement where the flow path of plastic melt ensures equal pressure and time to every cavity in a mold. Achieving runner balance means that the molten material travels the same distance and encounters identical resistance regardless of which cavity it enters. This is typically accomplished through symmetrical branch layouts or adjusted channel diameters.
Flow Synchronization
Geometry dictates how the material cools and shears as it moves from the sprue to the gate. If runner balance is not maintained, some cavities will fill faster than others, leading to inconsistent part weights. Engineers use rheological software to model these flows before the mold is cut into steel.
Waste Reduction
Symmetrical layouts often require more material than branched designs but offer better process control. Because runner balance stabilizes the injection pressure, it allows for a wider processing window and fewer rejected parts. Naturally balanced runners use identical path lengths to ensure the melt arrives at each gate in the same state.
Correction Method
Technicians may trim gate land lengths or change runner diameters during the sampling phase to fine-tune the delivery. Precision is required. Once runner balance is verified through a short-shot study, the process remains stable for the life of the tool.
Consistent delivery is the foundation of high-volume manufacturing success. This verification step prevents the need for manual sorting of parts downstream and ensures that automated assembly systems receive components with uniform dimensions.