Material degradation is more likely to occur if the shot size is small compared to the injections units maximum shot capacity especially for heat sensitive materials.Īnother problem with large screw diameters are the large shearing forces generated during screw rotation, this can also degrade the material and is likely to lead to reject parts. When small shot sizes are used with large screw diameters, the plastic material spends more time being heated by the barrel heaters compared to large shot sizes. Large screw diameters can cause quality problems due to material degradation. The key to buying a reliable used machine is to find one that has been fully inspected and tested before delivery so that you won’t suffer loss of production due to multiple breakdowns.Ĭlick here to see a case study of how incorrect machine selection can effect part quality Example #2).(opens in a new window) Mistake #2 Selecting Large Screw Diameters. Mistake #1 Buying Used Injection Molding Machines That Don't Work The best way to appreciate the importance of correct plastic injection molding machine selection is to list the most common mistakes made when selecting machines and the effect on part quality and productivity. Common Machine Selection Mistakes And Their Consequences
