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maximume shear stress on shaft iclude flight

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Topic: maximume shear stress on shaft iclude flight

magnoo
Senior Member

Posts: 6
From:egypt,cairo
Registered: Jan 2006

posted July 31, 2006 05:43 AM

i want to know the calculations of maximume shear stress on the screw , and determine the torque and the power of screw , to know the avilabel motor power and torque .

i have a screw d=30 mm , l= 620 mm , debth in feed section=.11(30+25) , debth in metering section=0.04(30+25), pitch=1*30,clearnce=.2 and the flow rate Q = 8.5 KG/H, we need to run the screw on 100 rpm , i want to know the maximume torque and power on screw to dermine the avilable moror power ...

thank u for your help

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Tom C
Moderator

Posts: 739
From:Brodheadsville, PA USA
Registered: Jun 2001

posted July 31, 2006 09:29 AM

Your output expectation is in range if you are running a more dense resin, and a little high if you are going to run a polyolefin. The L

of 20:1 is short for most materials.

Typically the motor power needs are not calculated in the way you described.

In an extrusion process the worse case power need is about 0.25 kw-hr/kg. Factor in about 25% extra power.

I say you need about a 3kw motor if you gear it for 100RPM, 6kw if you gear it for 200 screw RPM and so on.

One thing to be concerned about is screw strength. From the motor and gearing ratios you can develop the maximum applied screw torque. There are formulas available to determine shaft torque carrying ability which should consider the screw root as the shaft diameter.

Screw simulation software is available to help calulate all these parameters because of the complexity.

------------------
Best Regards,

Tom Cunningham

www.ExtrusionTechnicalServices.com

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