Screw manufacturer

Spare parts for common components such as heaters for barrels, transfer lines, and dies, thermocouples, pressure transducers, drive belts, and fuses should be kept in stock. Since the goal is to keep the line operational at all times, keeping these low-cost but necessary components in stock can reduce the amount of downtime due to simple failures. For operations where the resin is abrasive or corrosive, a spare screw should be kept in stock. As the screw wears in the extruder and the performance decreases beyond an economic limit, then the screw should be replaced with the spare screw and the worn screw should be sent to a screw manufacturer for refurbishment. 

An identical screw was ordered with the correct flight clearance. As soon as the screw was delivered, the screw was installed in the extruder. Soon after startup, the extruder was discharging at a temperature near 220 °C at the base rate of 130 kg/h. Next the rate was slowly increased to 180 kg/h. The discharge temperature increased to about 224 °C. Higher rates are likely possible. The worn screw was sent back to the screw manufacturer for refurbishment. This screw was then stored as the spare screw. 

LT must be greater than LE plus any pointed portion of the screw otherwise, the screw would bottom in the hole and 1) make it impossible to tighten the joint and 2) could split the plastic. If the hole will be tapped (rare today), LT must be deep enough to permit a run-out for the tap. For self-tapping screws, the difference between LT and LE depends on the selected screw. In either case, the designer must use the recommendations for proper hole dimensions from the screw manufacturer s charts. 

Fig. 1. Non-collapsable threaded inserts for assembly after moulding. (Courtesy of The Precision Screw Manufacturing Co Ltd.)...

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