Reasons for softening in the polyurethane part:
1. Mixing ratio incorrect:
Too much resin or hardener can lead to a faulty curing reaction resulting in e.g. in soft spots. Therefore it is very important that the correct mixing ratio is maintained. To ensure this a suitable balance must also be used. The smaller the quantities used the more accurate the balance must be. At best to 0.00 g. The balance should additionally be regularly calibrated.
2. Mixing error:
Inadequate mixing can also lead to softening. Therefore it is important that the components are sufficiently mixed. For systems with appropriate pot life the mixing time should be about 3 minutes. After half of the mixing time the bottom and the wall of the mixing vessel should be stripped with a spatula before mixing is continued. For mixing we recommend a star stirrer.
If you want to use fast casting resins with a certain amount of filler we recommend to split the amount of filler. Weigh all ingredients exactly then mix half of the filler in the resin and the other half in the hardener. Finally the now filled components may be mixed together.