1.       Design of worm shaft of the extroder

2.        The worm shaft is the main component of the screw extruder is acted upon by weights of material being processed, pulley and screw thread. In operation, in other to safeguard against bending and tensional stresses, the diameter of the shaft can be determined from the equation given by [Khurmi, & Gupta, 2008] as:

Where, ds is diameter of the screw shaft, T is the torque transmitted by the shaft and  is the yield stress for mild steel.

Design of the screw thread

The worm shaft is essentially a tapered screw conveyor with the volumetric displacement being decreased from the feed end of the barrel to the discharge end. The screw treading system was design as a step up shaft diameter and decreasing screw depth using the expression in the equation below as:

Un = a+(n-1)d (2)

Where, Un is the screw depth at the discharge end, a is the screw depth at the feed end, n is the number of screw turns, and d is the common difference between next successive screw depths.

In my recent experience in designing a single screw extruder, the main design concern is the length of the barrel, the screw design and die, while power sources must be above 16hp to able to have stable flow.