Blow Molding Bottles - Part 2

Posted by: developer
Jan 2013

Blow molding HDPE bottles is a challenging task when blowing products that must be consistent with a mated closure. This is the second installment in blow molding bottle issues when changing settings in the blow molding process.

Gram Weight

The Blackhawk engineer will sample the neck tooling to evaluate the correct size for production neck tooling. The gram weight is crucial. If this parameter is changed, bottle neck specifications can be compromised. If the bottle gram weight goes up and the additional material is in the bottle neck, the bottle neck finish will shrink more. More material, more heat more shrink. If the bottle gram weight is decreased in the same area, this may compromise the bottle neck by not trimming, collapsing under the filler valves or not capping due to distorted neck finishes. If a gram weight is going to be changed by a significant amount, please inform the Blackhawk field engineer.

Air and Water Pressure Gauges

The Air & Water pressure gauges on the blow molding machine are very important and need to be in working order. If these gauges are not functioning properly they need to be replaced. Blackhawk Engineers record this information to determine how to cut the neck tooling. If the information is recorded and the gauge readings are erroneous, interpreting this information will result in cutting the production neck tooling wrong resulting in bottle neck finishes out of specifications. This will result in a destitute union between the bottle neck finish and the closure.


Temperature is very important and needs to be stabilized to maintain proper bottle volumes and dimensions. Defective or old heating components and obstructed cooling channels in the bottle molds are a few reasons why temperatures may fluctuate. If the temperature fluctuates, the bottle volume and dimensions may be inaccurate. The results can be too much or too little product in the bottle and once again a poor marriage between the bottle and the cap.

Blow Molding Bottles

Keeping the major variables in check will allow the blow molder to maintain consistent and better quality bottle. This result will see fewer returns from customers.