Extrusion Minimum Runs Measured in Tonnes Rather than Pieces
Extrusion runs are quoted in tonnes because start-up scrap, thermal equilibration, and bulk resin compounding operate as continuous mass processes.
Linear Density Tolerance
Meaning
Permissible range of mass per unit length for an extruded profile or fiber. This specification ensures that the product meets both functional strength requirements and commercial weight agreements. Monitoring linear density tolerance allows manufacturers to control material usage and detect process drift before parts fall out of specification.
Sourcing Economics
Material costs are often the largest component of the total part price in high volume extrusion. When a process runs at the upper end of the linear density tolerance, the factory is essentially giving away resin. Reducing the variation allows the plant to target the lower end of the range without failing mechanical tests.
Quality Measurement
Weighing a fixed length of the profile at regular intervals is the standard method for verification. If the measured value exceeds the linear density tolerance, it often points to an issue with the feeder or a change in the melt temperature. Ultrasonic gauges can provide continuous non-destructive monitoring of this variable.
Structural Integrity
Variations in the weight per meter can affect the stiffness and impact resistance of the final assembly. Architects and engineers rely on a tight linear density tolerance to ensure that the profiles behave predictably under load. Products that fall below the limit may fail to support the necessary glazing or hardware.