Blow molding HDPE bottles is a challenging task when blowing products that must be consistent with a mated closure. Before any SuperQuad caps are shipped to a new customer, a survey is taken by Blackhawk engineers. The survey includes assessing blow molding conditions and equipment. Before a conversion, our engineers bring in sample neck finishes to a potential new customer’s facility and blow sample bottles. The blow molding documentation gathered by the engineer is crucial. This information is the basis for determining how to cut the neck finish tooling to produce bottles that conform to the customer’s current blow molding specifications. These parameters will be re-checked when the production neck finishes are installed during the installation. Because the neck finish tooling was designed based on these initial blow molding parameters recorded during the survey, it is crucial to maintain these settings. Bottle problems will occur if major setting changes occur. The SuperQuad cap and STS capping system allows a wider range of deviation in bottle neck specification than any other cap or capping system, but problems may still occur. We will just touch on some of the common problems.

Resin change

If a new resin supplier is brought in before or after a conversion Blackhawk should be notified. The new/current tooling may or may not work after the resin change. HDPE has a wide range of shrink factors from supplier to supplier. Due to the shrink, the bottle may not shrink enough or may shrink too much leaving the marriage between closure and bottle out of specification. This problem may result in capping problems and leakers. During the testing of a new resin, Blackhawk should be contacted so that we can work with our customer to see if this pending change will require new neck tooling.

Cycle time

The cycle time is set to blow the best quality bottle for the given parameters. If the cycle time is changed, the volume of the body and neck finish will change. This cycle time change will create a problem between the marriage of the cap and bottle resulting in capping and sealing issues. The change in cycle time should be communicated to a Blackhawk Field Engineer. They can evaluate if this cycle time change will require new tooling even if it does not require new tooling it will allow our engineers to update the original information on the survey.

The next bulletin will contain more blow molding information to help better understand the blow molding process.