Desmopan articles can be demolded more easily if the surface of the mold cavity is grained or sandblasted. This gives significantly better results than a smooth or polished surface. We therefore strongly recommend that the roughness should correspond to spark erosion textures 27 to 33.
Coating of mold sufaces:
Mold surfaces can be coated to facilitate demolding. The coefficient of static friction during the demolding operation is an indication of the force required for demolding. On an internal test rig the PVD coatings TiN and TiCN exhibited the lowest coefficients of static friction and should therefore tend to have a positive effect on the demolding of Desmopan (see following diagram).However experience shows that the coatings do not always produce the desired effect, and that in some cases no improvement results. It is therefore advisable to think very carefully before deciding to use a coating.
When demolding Desmopan® and Texin™, a rough cavity surface is an advantage – such as a surface that complies with VDE 3400 (Ref. 24-33). This gives the lowest demolding forces by comparison with other types of surface roughness or coatings.
Mold drafts should be at least 5°, particularly for components made of soft Desmopan® or Texin™ grades. (Fig.16)
Fig. 16: Demolding drafts
For TPU, the surfaces of the ejectors should be as large as possible to avoid any deformation of the finished article (Fig. 17).
Fig. 17: Ejectors
The high elasticity of Desmopan® and Texin™ allows the demolding of undercuts and hollow articles. Blow moldings can be blown off the core using compressed air (Fig. 18).
Fig. 18: Blowing off blow moldings by the use compressed air