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Author Topic: Motor tuning 4th axis  (Read 5796 times)

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Motor tuning 4th axis
« on: January 18, 2008, 06:40:24 AM »
After searching the message board,  I still can not find info on how to tell my 4th (A) axis motor to move steps per revolution instead of steps per inch. Does the motor tuning window have a place to do this? I am trying to make a small camshaft. Can anyone help?
Danny
Re: Motor tuning 4th axis
« Reply #1 on: January 18, 2008, 07:35:01 AM »
In Mach, theres a checkbox in config>general config.  You will see a checkbox that says A-angular,B-angular ect.. I'm sure one of these will need to be checked to enable steps per revolution for a 4th axis.
Re: Motor tuning 4th axis
« Reply #2 on: January 18, 2008, 07:50:05 AM »
If you can determine the pulses per degree of rotation, can you just put that value into the "Pulses Per" and not change from linear to angular ?
If so..what is the purpose of angular ?
Possibly to loop when 360 degrees is hit ?
RC

Overlooked it earlier..............

« Last Edit: January 18, 2008, 07:56:38 AM by Overloaded »
Re: Motor tuning 4th axis
« Reply #3 on: January 18, 2008, 08:19:57 AM »
The box was checked.
I don't see a "pulses per". In the motor tuning box, it has "steps per" but that is the number of steps per inch. I don't think the step pulse and dir pulse values in the motor tuning boxes are relevant with Geckos (10us).   I'm actually not hooked it up on machine yet, but I'm trying understand the setup for degrees per step.
2000steps/360 degrees = 5.55555555... degrees per step? I will test and see?
Thanks
Re: Motor tuning 4th axis
« Reply #4 on: January 18, 2008, 08:40:50 AM »
You're right.. "Steps" per is per whatever unit you are using, in the case of angular, it's usually degrees.
However many steps your motor needs to index 1 degree goes in the box.
If there is no gear reduction, 2000steps per rev. won't yeild very good resolution. 1 step would = 5.55555555 like you say.
RC
« Last Edit: January 18, 2008, 08:42:43 AM by Overloaded »

Offline Chip

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Re: Motor tuning 4th axis
« Reply #5 on: January 18, 2008, 08:42:19 AM »
Hi, Danny

To setup 4th axis in deg. mode, Example: Stepper 200 steps X rot. table ratio 72 to 1 is 14400 steps for 1 full turn of table.

Then deg's 360\14400 = 40 steps per deg, Enter 40 in Steps Per.

Entering 360 in A axis G-code will give you 1 full turn.

Hope this helps, Chip

Offline jimpinder

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Re: Motor tuning 4th axis
« Reply #6 on: January 18, 2008, 02:00:40 PM »
Hairball - I think you will have got the idea by now - but - the computer is not the slightest bit interested in what units or measurement you are working in - inches, feet, degrees, radians, etc.

All it wants to know is - when you put in a command (say starting from 0,0) g0 x1 to move the x axis by one unit, how many pulses must it  put out to the motor to move the axis the required distance. This works identically on all the axis - how many pulses does the computer put out to move the axis by one unit.

Clearly - when writing G code, YOU must then know what units you are talking about and always use the same units.

The computer assumes you are going to program the machine in inches or millimeters (but you could use finger widths if you wanted) and asks for this first - but the computer is not bothered. All it needs to know this for is when it converts from g20 to g21 and back, for altering all the offsets. (As pointed out, it does not alter rotary axis)

For a rotary axis you could program it  in any measurement you liked - for example, running a rotary table, on a job which required a similar machining at 10 degree intervals, you might program the computer to put out the correct number of pulses to move the table 10 degrees at a time (remembering in the G Code that 10 degrees is 1 unit) and instead of using g0a36, use g0 a1 etc.

So what you need to do is work out the drive to your axis.  How many steps per revolution of the motor (a) how many revs of the motor per 1 unit moved (b) and the number of steps per unit is (a*b)
Not me driving the engine - I'm better looking.
Re: Motor tuning 4th axis
« Reply #7 on: January 19, 2008, 10:24:25 AM »
Thanks,
Test concurred. You guys are the best. Mach 3 secrets are fading fast!
Hairball