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

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

3. 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

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

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

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

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

8. Design For Manufacturing – Plastics Extrusion

9. Design For Manufacturing – Plastics Extrusion

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

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

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

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

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

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

16. Differential shrinkage: the root cause for warping
Filled versus unfilled materials

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

18. 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

19. 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