As the price of materials spikes, blow molding companies are looking for ways to reduce their costs. Many managers may not be aware of the advantages of extrusion blow molding. Compared to injection molding, extrusion blow molding offers unique opportunities to save valuable materials.
About Extrusion Blow Molding (EBM)
In the EBM process, the machine extrudes plastic pellets into a parison, which is a hollow tube. The plastic leaves the head though a female die and a male pin. Then the machine clamps the parison between the halves of the mold, and a blow needle sends air in. That forces the parison to the mold walls where it solidifies into the right shape. The top and bottom of the container have a flash, which is extra material that the machine trims, grinds, and sends back to the extruder. The reused material is the regrind.
Sometimes, you do not always have a consistent level of regrind. Operators may increase the regrind percentage of the extrusion blow molding machine to get rid of the excess. But this can make your parisons longer and wider, which may change the position of vital program points.
In the end, your containers may be inaccurate. One strategy is to stretch parison sections over more than needed. With this method, they can make a usable part, even if the parison is a different length. But that means they may make heavier parts than they need to.
Reducing the Parison Length
You should make sure that your material handlers can deal with regrind upsurges and calibrate gravimetric systems. You might consider putting some tail flash with the right length, so operators can check if the parison length is correct.
When using multi-cavity systems, many operators do not try hard enough to adjust the parison length. It takes patience and skill to get each parison to extrude from the head to the right length. Your workers should make slight mechanical adjustments. Each time, they need to stop the machine, which many operators do not want to do for fear of reducing production.
If you are not producing much at once, you may not want to spend time on this. But for longer production runs, the savings can add up.
It is a good idea to give your setup staff enough time to adjust the parison length properly. If the extrusion program has thick sections, let them tighten them up. Some companies have programmers that only offer 20 to 25 points during a cycle. For larger bottles, you should go with 64 points.
Having the right extrusion blow molding machine manufacturer as a partner is key to succeed in your initiative to reduce material usage. Pet All Manufacturing, Inc. offers state-of-the-art equipment to help boost your efficiency while saving material.