RE: Angular axis


Yes, I have taken the gear ration of 72:1 for my rotary table into account in figuring the steps per degree which works out to 80 steps per degree when using 400 steps per revolution on the stepper.  400 x 72 = 28800 / 360 = 80 steps per degree.  A unit of travel on the angular axis is 1 degree therefore steps/unit = 80 which EMC does not seem to like at this time.  I have experimented with different settings and anything less that 1000 steps per degree just does not work well at all.  It seems that it is something to do with a ratio of steps per unit vs steps per revolution on the axis.  Anything less than about 3.5% of the total step count for a revolution of the table, 28800 x .035 = 1008 and EMC just can't handle it.  I am sure it is a granularity issue, it could even be a PID tuning issue.  I just don't know at this point.  What I do know is that I will be doing my 4 axis work using TurboCNC until this gets fixed or I figure out how to configure it.  EMC thinks it is moving the axis at the proper speed based on the display, but is sure as heck isn't
 
John Guenther
Sterling, Virginia
-----Original Message-----
From: emc-at-nist.gov [emc-at-nist.gov]On Behalf Of phil
Sent: Saturday, July 06, 2002 09:52
To: Multiple recipients of list
Subject: Angular axis

I still havent installed bdi onto the laptop just yet, but I've done some tinking, and one question.
Has anyone thought of the gear ratios used in the rotation mechemism, or is that part of the config for axis A?
From what I remember, you can define steps/unit of travel for a linear axis but I havent really heard that in this thread.
If not, then maybe that is part of the problem with the speed, especially if its worm gear driven, 30:1 or larger.
Phil   


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