Principle of the process Structure/Configuration Process modeling Defects/quality control Design For Manufacturing (DFM) Process variation

Shaping Processes For Plastics - Extrusion Die configurations and extruded products Extruded product depends on the shape of die Solid profiles

Die configurations and extruded products The main quality problem is related to die swell. There are several methods to overcome the die swell a. Increase die opening length b. A draw operation follows the extrusion c. For non-round shape, a correction is needed. Correction Desired shape

Die configurations and extruded products Defects in Extrusion – melt fracture Turbulence flow at the entrance of the die

Die configurations and extruded products Defects in Extrusion – sharkskin or bambooing Friction between die and extrudate

Principle of the process Structure/Configuration Process modeling Defects/quality control Design For Manufacturing (DFM) Process variation

Design For Manufacturing – Plastics Extrusion Shrinkage is a root cause. In the figure below, there are three common types of problems

Design For Manufacturing – Plastics Extrusion

Design For Manufacturing – Plastics Extrusion

Design For Manufacturing – Plastics Extrusion DFM guideline – wall thickness:

Design For Manufacturing – Plastics Extrusion DFM guideline – wall thickness:

Design For Manufacturing – Plastics Extrusion DFM guideline – wall thickness:

Design For Manufacturing – Plastics Extrusion DFM guideline – sink marks:

Design For Manufacturing – Plastics Extrusion DFM guideline – hole location:

Design For Manufacturing – Plastics Extrusion DFM guideline – hole location:

Differential shrinkage: the root cause for warping Fillled versus unfilled materials

Differential shrinkage: the root cause for warping Non-uniform mold cooling across the part thickness

Differential shrinkage: the root cause for warping Part geometry asymmetry or curvature” The poor cooling of the mold wall on the ribbed side causes a slower cooling of the material on that one side, which can lead to part warpage

Differential shrinkage: the root cause for warping Part thickness variation: Larger volumetric shrinkage due to the high crystallization level in the slow cooling areas (e.g., the thick sections) leads to differential shrinkage and thus part warpage