CTQ
Critical-to-quality characteristics. Dimensions, functions or conditions that must be controlled because they affect assembly, safety, sealing, appearance or use.
Key terms
Cpk
Process capability index. It relates measured process variation to the specification limits of a critical characteristic.
Process window
Range of moulding parameters where the part is acceptable: temperature, pressure, speed, packing and cooling.
Shrinkage
Dimensional reduction of the plastic during cooling. It depends on material, geometry, flow orientation and process conditions.
Warpage
Part deformation after cooling, usually caused by differential shrinkage or non-uniform cooling.
Sink mark
Local surface depression caused by excessive mass, poorly proportioned ribs or insufficient packing.
Gate
Area where molten material enters the mould. It affects flow, weld lines, orientation and visible marks.
Weld line
Area where two flow fronts meet. It can affect strength, sealing or appearance.
Packing
Stage where pressure is maintained to compensate shrinkage during early cooling.
Insert
Machined element forming a cavity or functional area of the prototype mould.
Pre-series
Limited batch before production used to confirm part, process, assembly and acceptance criteria.
Tolerance stack-up
Combined effect of several individual tolerances in an assembly.
DFM
Design for manufacturing: review of geometry, walls, radii, demoulding, ribs and critical zones.
IQ/OQ/PQ
Validation stages used in regulated environments: installation, operation and performance.
Final material
The real or equivalent grade that will be used in production.