Removing Flash While Blow Molding Plastic

When performing a blow molding plastic extrusion process, a preform is thrust out. The top and bottom are pressed to remove the excess and then blown into the shape of the hollow space. The excess plastic that is squeezed off the top and bottom of the mold’s cavity is called flash.

Minimizing Flash in the Process

Post-molding is when the flash is removed. Removal of flash can be mechanical or manual. These types of operations can damage the parts. It is important to minimize flash to make quality parts.

In the design of a plastic container, the importance of controlling flash has an impact on the part. The container’s size and shape determines how much flash will form during manufacture. As an example, a bottle with a trigger sprayer forms a neck to the side, which will make more flash than a centered neck bottle.

How Flash Impacts the Product

Both appearance and functionality of the container will be impacted by flash. The visual appeal of parts that have the flash methodically removed is far greater than that of parts with ragged and excessive flash. Also, if there is too much flash at the closure to a container or bottle, an improper fit can prevent closing.

Regular Maintenance of Blow Molds is Important

It is very important that regular maintenance of blow molds is done when large areas of flash are required. The flash can be neatly removed by having a raised pinch-off. When a mold has a worn pinch-off, the result will be unacceptable parts. Regular inspections should be done on the mold and the parts to be sure that any excess flash is removed.