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### Author Topic: Homing slaved axis with a common switch  (Read 3985 times)

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#### rrc1962

• 673
##### Homing slaved axis with a common switch
« on: November 07, 2010, 01:17:49 AM »
My current setup consists on a gantry with both sides driven through a drive shaft with one motor.  There are limit/home switches on all three axes.  They are all NC switches and connected in series.  Homing and limit functions work well and as expected.  I'm thinking about losing the drive shaft and going to 2 motors, so I'll have A slaved to X.  Ideally, I'd want to just add another switch to the A side of the gantry and wire it in series with all the others.  Will this work properly for homing the slaved axis or are two independent home switches needed?  What I'm after is for the gantry to square when it is homed.

One problem I can see is if X and A are homed together and the gantry is close to square,  X could hit first then A could hit before X has had a chance to back off it's switch... Or would A stop when the X switch makes contact, wait for X to back off then continue?  I'm low on inputs, so trying to figure out if this will work before making any machine changes...and trying to avoid the low tech method of squaring (Turning off machine and pushing the gantry against hard stops.)

Thanks

#### Greolt

• 956
##### Re: Homing slaved axis with a common switch
« Reply #1 on: November 07, 2010, 02:03:46 AM »
For slaved axis homing you must have the two relevant home switches on separate inputs.

Greg

#### rrc1962

• 673
##### Re: Homing slaved axis with a common switch
« Reply #2 on: November 07, 2010, 08:57:00 AM »
So could I just keep what I have, which is XYZ home and limits on one switch and just add an A home/limit on the other side of the gantry on it's own input?  That would separate the A switch from the rest of them.  That should work, right?  problem is that I only have one unused input, so I can't separate all of the home inputs.

Thanks

#### Fastest1

• 920
• Houston, TX
##### Re: Homing slaved axis with a common switch
« Reply #3 on: November 07, 2010, 09:39:11 AM »
You also have a change on the general logic configuration page, I think. Home Slave Master Axis needs to be checked. But I dont think the switches would work like you have it set up and just add 1 switch on another pin. Seems like it would put the gangtry well out of rack while homing. I could definitely be wrong.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)

#### ger21

• 6,287
##### Re: Homing slaved axis with a common switch
« Reply #4 on: November 07, 2010, 09:46:46 AM »
I could definitely be wrong.

Sorry, but you are.

Home Slave with Master should only be checked if using ONE Switch for two separate motors.

And yes, it should work if you just add one switch (with it's own input) to your existing setup. You may need to separate the XA homing from the Y (and Z), though. You'll need to test to be sure, although it should work fine as is.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

#### rrc1962

• 673
##### Re: Homing slaved axis with a common switch
« Reply #5 on: November 07, 2010, 11:07:11 AM »
Cool.   I figured I'd need change the referencing code to something like this...

DoButton( 24 )
DoButton( 23)
RefCombination( 9 )

#### ger21

• 6,287
##### Re: Homing slaved axis with a common switch
« Reply #6 on: November 07, 2010, 02:32:14 PM »
Yes, homing the others first should work.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html