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5.2.6 Mechanical Design of Extrusion Screws
5.2.6.1 Torsion
The maximum shear stress Tmax, which occurs at the circumference of the screw root as a
result of the torque MT, is given by [8]
where I? = root radius of the screw.
The maximum feed depth Hmax can be computed from [8]
where
D = diameter
Tzul = allowable shear stress of the screw metal
Example [8]
The maximum feed depth is to be calculated for the following conditions:
D = 150 mm; Mx = 17810 Nm; Tzul = 100 MPa;
Hmax is found from Equation 5.69:
5.2.6.2 Deflection
Lateral Deflection
(5.68)
(5.69)
The lateral deflection of the screw (Figure 5.34) caused by its own weight can be obtained
from [8]
(5.70)