There are 4 different types of blow molding that use material such as HDPE, PVC, PET, PP and others::
1. Extrusion blow molding
1.1. Continuous extrusion blow molding
1.2. Reciprocating screw extrusion blow molding
2. Injection stretch blow molding
2.1. Single stage injection stretch blow molding
2.2 Reheat stretch blow molding
3. Injection blow molding
4. Rotational blow molding
There are 4 different types of blow molding that use material such as HDPE, PVC, PET, PP and others::
First we want to have a mold built that we can still tweak, i.e. we want the neck to be made material safe or smaller than we would expect it to be taking shrinkage into account. To save time we want all flash areas, i.e. areas that are cut away on the mold, to be wider than your mold maker wants them to be. At least that is my experience. I hate to send a mold back just to get the bottom flash area enlarged by 1", what a waste of time. It does not cost much to go to the maximum right away and then you will not have any problems.
Our head tooling, blow pin tips, cutting knife are of course all ready by the time the mold is in and a machine is available. We have 100 psi water pressure on the machine with the water at 50 to 55º F. Assuming that the head tooling is right, now run the machine until either one of these conditions occurs:
* Bottom or neck flash sticks. Examine mold drawing if cooling channels are optimal.
* Body wall shrinks to concave shape. If your mold maker has the capability, the mold can be compensated for this shrinkage: A grid pattern is drawn on the bottles and each point of the matrix is measured in depth. This information is then fed to a machining center that cuts the mold deeper by the same amounts. If this is not posible or too costly, you have to experiment with different cycle times and let the bottles sit for 2 days at 50% humidity to observe shrinkage before you make a final decision.