Trouble Shooting

• Often seen in urethane painting, this phenomenon is characterized by the appearance of small holes on the painted surface, and it is also known as "cratering.
  (picture:Urethane paint)

• Inclusion of air

Pinholes can be caused when air bubbles trapped in the paint film expand during drying and break through the surface. Furthermore, this phenomenon is not dependent on the substrate, and it occurs often in high-temperature, high-humidity environments; with thick application of paint; when there is insufficient setting time; and when the speed of thinner evaporation during drying is high.

• Modification of the painting environment
• Lengthening of the setting time
• Reduction of the paint's viscosity
• Slowing of the thinner evaporation speed

• Residual strain

When the plastic substrate contains residual stress, the material is attacked by the paint's solvent and fine cracking occurs. The solvent penetrates into these cracks, and when this then evaporates during the drying process, the resulting vapor bursts through the surface of the painted film.

• Selection of a less aggressive solvent
• Modification of the paint and solvent mixture ratios
• Annealing of the unpainted component (at between 60deg.C and 70deg.C for 20 to 60 minutes)
• Raising of the cylinder temperature and die temperature
• Lowering of the injection pressure and raising of the injection speed