RE: [CAD_CAM_EDM_DRO] MOTOR SIZE CALCULATION FOR RAPID STOPPING

Hi John

Lets get consistent units and say your moving mass is
about 68 kG.

If your stepper had zero moment of inertia and friction you could
accelerate Force/mass = 15 kN / 68 kG= 220 meters/sec^2.
This is about 22g and does not sound real to me. It would
be half or less considering the steppers moment of inertia
but even that sounds not real.

I suspect the system would be limited by a lot of gearing down
of the stepper to achieve the huge 15 kN linear force. The reflected
inertia looking back into the stepper would go as the square of that
ratio, so my guess would be that the gears and stepper moments would
dominate...The load might be of little or no consequence.

This can all be analyzed by a free program like this:

http://www2.danahermotion.com/about/pr/releases/KOL516_Motioneering430.html

You will need to supply a bit more information such as travel length,
moments of inertia of gears, screws, armature, etc to get an answer.

I'll help run you through it if you want.

Les

Leslie M.Watts
L M Watts Furniture
Tiger Georgia

Main page:
http://www.lmwatts.com
Engineering:
http://www.lmwatts.com/shop.html
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http://www.lmwatts.com/forsale.html
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-----Original Message-----
From: john_glynn57 [mailto:john_glynn57@...]
Sent: Tuesday, August 24, 2004 5:55 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] MOTOR SIZE CALCULATION FOR RAPID STOPPING



I am building a simple grinder with a belt drive and stepper motor
to drive the reciprocating axis which is 150lbs and want to
calculate the maximum speed that I can drive the axis using a 15KN
stepper motor without losing control of the axis due to inertia. Has
anyone got the calculations.

john