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Author Topic: DC Motor as Rotational axis  (Read 3757 times)

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Offline jr_82

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DC Motor as Rotational axis
« on: March 28, 2011, 12:21:41 AM »
I have a DC motor that I would like to run as a 4th axis Rotational. This is not for speed. It is to rotate stock.  It has a gear box with a 660 to 1 ratio.  nice and slow.  How do I get Mach to run it as an axis? the motor has 3 wires one for each direction of movement and another that does nothing. I assume it is another ground of some sort.

Junior

Offline Tweakie.CNC

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Re: DC Motor as Rotational axis
« Reply #1 on: March 28, 2011, 03:53:28 AM »
Hi JR,

I know nothing of lathes but the rotating headstock is fitted with a slotted disk which interrupts the beam from an optical sensor. This pulse is then fed into Mach to  measure RPM and is used for synchronizing threading etc. A similar system is used for spindle speed control on a mill.
You may need to do a bit of searching but there are details of spindle setups on the forum.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Hood

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Re: DC Motor as Rotational axis
« Reply #2 on: March 28, 2011, 06:10:54 AM »
To run it as an axis you will need to have control over it with a servo drive, that will require you have an encoder on it as well.
If simply wanting to use it as a spindle, ie no sync between other axis then a relay would likely be all you need to operate it via Mach.
Hood

Offline jr_82

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Re: DC Motor as Rotational axis
« Reply #3 on: March 28, 2011, 09:06:25 AM »
Like the relay that is on my board, that just turns on and off a spindle?
JR
Junior

Offline jr_82

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Re: DC Motor as Rotational axis
« Reply #4 on: March 28, 2011, 09:08:37 AM »
I still need it to move to certain positions ie, 0 180 90 270 degree, will I have a reading in the dro? for the angle. 
Junior

Offline Hood

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Re: DC Motor as Rotational axis
« Reply #5 on: March 28, 2011, 09:49:24 AM »
If you need to use it as a true axis then you will need to add an encoder and get a suitable drive to control direction and speed.
Hood

Offline jr_82

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Re: DC Motor as Rotational axis
« Reply #6 on: March 28, 2011, 10:43:19 AM »
with a relay can I tell it how far to move.
Junior

Offline Hood

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Re: DC Motor as Rotational axis
« Reply #7 on: March 28, 2011, 10:49:02 AM »
No, the relay was mentioned just because you said "one for each direction of movement" about the two wires. So I was thinking if you had a double pole double throw relay you could reverse the direction. You would not have any control over it except you could vary the supply voltage to control the speed and reverse the direction.
For positioning as you would such as with an axis you would need proper control over it by turning the DC motor  into basically a servo  and that is where the encoder and drive would be required.
Hood

Offline jr_82

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Re: DC Motor as Rotational axis
« Reply #8 on: March 28, 2011, 11:37:34 AM »
OK thanks!
Junior
Re: DC Motor as Rotational axis
« Reply #9 on: March 28, 2011, 11:14:21 PM »
If you need infinite positioning, then you need a motor controller.  If you just need 0, 90, 180 and 270 degrees, you can use 4 limit switches.  Turn on the motor with a relay and watch for the correct switch to trip.