slaving one axis to another

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02 Jan 2012 20:56 #16220 by boblee
Hi All
Can anyone point me to the part of the manual or manuals that describes how to slave one axis to another ?
I have two screws on my x axis and I need to slave one motor to the other.
I've been doing this for awhile with MACH3 .
I'd like to learn how to use EMC2 because I think it has more to offer .
I've been thru the step coonfiguration wizzard and I've been able to test my Y & Z axis and they work fine.
I haven't been able to test the X axis because I can't figure out how to make both X motors turn at the same time.
Can anybody point me in the right direction or tell me how it's done ?
Any help would be greatly appreciated.
Thanks
Bob

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02 Jan 2012 22:14 #16222 by Rick G
Hello,

You might look here...

linuxcnc.org/docs/html/man/man9/gantrykins.9.html

If you look under sample configurations that come with EMC there is a sample set up for gantry type setup.

Also if you are not going to have seperate homing /limit switches you can just set up a 3 axis and then connect the two pins for the drivers together in software in your hal file.

We can help you set it up either way, the later is simpler.

Rick G

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02 Jan 2012 22:15 #16223 by BigJohnT
I assume you mean your using the Stepconf Wizard... if you have two drives then just duplicate the second step and direction pins to an extra set of I/O pins.

John

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02 Jan 2012 23:27 #16230 by andypugh
boblee wrote:

Hi All
Can anyone point me to the part of the manual or manuals that describes how to slave one axis to another ?

There are (at least) 3 ways to do this.
1) Simply wire the same step and direction pins to both stepper drives (assuming a stepper machine)
2) Do much the same in the HAL file. Where is says
net x-step axis.0.motor-position-cmd => parport.0.pin-XX-out
use
net x-step axis.0.motor-position-cmd => parport.0.pin-XX-out parport.0.pin-YY-out
(and the same for DIR, optionally setting the invert for the second drive direction, if the motors need to run in different directions.
3) Use gantrykins. This allows each side to home separately, but is rather more of a fiddle to use.

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03 Jan 2012 03:57 #16232 by boblee
Thanks Guys
I decided to parallel the outputs on my BoB to the X and A drives until I get more familiar with the software.
I'm not a coder and this is working pretty good right now I don't know if there will be any drawbacks to doing it this way in the future but it's working for now
I don't yet have home or limit switches to worry about yet so this will work for now.
My next step will be to tune my motors.
Thanks for all the help
Bob

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03 Jan 2012 11:25 #16246 by Rick G

I decided to parallel the outputs on my BoB to the X and A drives until I get more familiar with the software.
I'm not a coder and this is working pretty good right now I don't know if there will be any drawbacks to doing it this way in the future but it's working for now
I don't yet have home or limit switches to worry about yet so this will work for now.


That is the way I did my first router with a dos program, worked fine.

With EMC I later switched to connecting the two pins in hal similar to what John and Andy posted, just felt better about doing it in software than combine a parallel port output if I did not have to.

Have fun,

Rick G

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