| Characteristics |
- As with pinholes, these fine cracks on the painted surface are caused by solvent attack, and this phenomenon is often seen in acrylic painting. These cracks generally occur near gates and at edges in particular."
(picture: Acrylic paint)
|
| Cause |
This problem often occurs at areas close to gates with molding defects such as gate flash, flow marks, or jetting; furthermore, these factors are difficult to eliminate even by annealing. |
| Countermeasures |
- Selection of a less aggressive solvent
- Modification of the paint and solvent mixture ratios
- Annealing (at between 60deg.C and 70deg.C for 20 to 60 minutes)
- Raising of the cylinder temperature and die temperature.
- Lower the injection pressure (holding pressure) and increase the injection speed
* Generally speaking, the addition of retarder is not a good means of
treating chemical cracks. |
