Precision Blow Moulding:

1. This blow moulding application will work for both 2 stage and single stage processes.

2. The chamber with an accurate hole is moulded in the injection moulding stage to form the pre-form.

3. The top of the chamber is kept cold during the remainder of the process, ensuring that this area is kept constant and hence preventing the stretching of material in this area.

4. The pre-form is designed with a thicker section at the bottom of the side wall.

5. The heat profile along the wall of the pre-form is critical. The thick
area in the side wall at the base will be hottest, so that when the stretch
rod moves down, the material is taken from this side wall area.
During blowing this area will need to be heated correctly in order to form as projected.

6. A vital point for both single and 2 stage processes is the stretch rod, as it must seal on the hole. With the single stage process this is easily done as the pre-form is moulded around the stretch rod during the injection phase.
In the 2 stage process, the pre-form must be located such that the stretch rod seals on the hole. This can be done by accurate positioning or a sealing mechanism. This will ensure that the stretch rod seals the hole thus allowing the high pressure air to blow the heated pre-form.

7.  In this step the chamber is released. This can be done with a static base to the blow mould, which moves down before the blow mould opens so to release the chamber or with the use of a bottom stretch \ push rod to meet the upper stretch rod which would clamp the base of the pre-form to seal.

8. Finally, to achieve the moulded chamber, the neck form will open to allow the retraction of the mould cores.