Surface Melt Fracture Onset Limits in Polyolefin Profile Extrusion
Surface melt fracture limits in polyolefin profile extrusion are governed by critical wall shear stress thresholds between 0.08 and 0.14 MPa at the die exit.
ISO 4287
Meaning
Geometrical product specifications define the terms, definitions, and parameters used to evaluate surface texture by profiling methods. This standard, designated as iso 4287, outlines the mathematics behind roughness, waviness, and primary profiles. It provides a common language for manufacturers and quality control engineers across the globe.
Surface Parameters
Amplitude parameters such as arithmetic mean deviation and maximum height are defined to quantify the heights and depths of surface peaks and valleys. These numbers help determine whether a machined part will perform correctly in high-friction environments. The specification ensures that measurements remain consistent regardless of the measuring equipment used.
Metrology Tool
Stylus instruments are used to trace the physical peaks and valleys of a component’s surface to generate a profile line. This data is then filtered according to the standard’s guidelines to separate roughness from waviness. Using the wrong filter can lead to inaccurate roughness reports and the rejection of good parts.
This step is critical before launching full-scale production.
Calibration Standard
Reference specimens with known surface profiles are measured regularly to verify the accuracy of the stylus instrument. These tests prevent drift and ensure the measurement process remains stable. Regular calibration is required to maintain quality certifications.