Torque calculation

[specmario]

It is known some formula for screw torque calculation during extrusion? I'm looking for this for longer time.
Thank you

 

[patprimmer]

It will be a function of motor efficiency times gear ratio if any times amps. The motor manufacturer will need to provide the data for the motor.

All other things being equal, it will be directly proportional to amps.

Regards
Pat
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[specmario]

But I would need something, where temperature, pressure and heat is involved.

 

[patprimmer]

No you won't

Regards
Pat
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[specmario]

But there is difference between torque on empty screw and fully filled, because material is braking rotation of screw, and torque has to be higer. So there has to be involved some material and processing characteristics.

 

[patprimmer]

Your question is so vague it is really hard to know what you mean.

It is to difficult to calculate that way as there are to many variables.

If you are running a twin screw extruder the normal method is to increase feed rate until the amps build to maximum safe amps. That will change with variations in temperature, actual feed rate of each component, raw material molecular weight, moisture content, lubricants present, raw material physical form, the die head, condition of the screens and configurations of screw elements and temperature of raw materials as they are fed into the extruder.

Regards
Pat
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[GilPolymers]

Hi,

At university I had a course where I learned to compute the pressure raise and pressure drop (on the dies) on one extruder along the screw. We were using transport equations to compute the flow in the screw. The equations were divided in three steps, one equation for solids transport, other for solids + melt, and a final one for melt. The screw was considered to be flat.

The screw speed was given by us.

I believe that if you take those equations you will be able to calculate the torque that needs to be applied to make the screw move.

I don't have my notes, but I remember the name of two books that I used on this course and may be helpful for you:

Principles of Polymer Processing by Tadmor & Gogos
Polymer Extrusion by Chris Rauwendaal

To calculate the torque that you have on the drive you will need all the data from the drive - as mentioned.

Hope this can help,

Gil