The plasticizing feedscrew is the heart of any injection molding or extrusion machine. These machines are designed to convert plastic pellets or powders into sellable products. As feedscrews begin to wear, this conversion process is negatively affected. Maintaining the feedscrew in a like-new condition assures process consistency, lowest conversion cost and the highest level of good (sellable) production.
Process effects of wear
| Injection Molding | Extrusion |
|---|---|
| Increase in plasticizing time | Drop in output rate |
| Increase melt temperature | Increased melt temperature |
| Degradation products | Gel formation |
| Shot inconsistency | Extruder surging |
Examples
| LCP injection molding | HDPE pipe extrusion |
|---|---|
| Maximum wear allowable .018” (.45 mm) | 120 days operation |
| Nitrided steel life: 300,000 shots | C83 hard facing, .090” (2.2 mm) wear |
| Tool steel life: 1,500,000 shots | 1,250,000 lbs |
| XC1000 life: 4,000,000 shots | XC1000 coating, .010” (.125 mm) wear 1.550,000 lbs |
Intangible costs are difficult to calculate but often represent a multiple many times the cost of coating a feedscrew in terms of lost productivity and profit. Overall production consistency and repeatability are the benefits from a feedscrew in like-new condition over a longer service life.
PDF Example Low Rate 20 LB hr PDF Example High Rate 3000 LB hr