Mach Discussion > General Mach Discussion

Homing Problem - Slave Axis

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joepardy:
I am having a homing problem with a new CNC router.

“Normal” motion (X, Y, Z, & A axis) is working fine.  Jogging works as well.  Homing the Z axis works great.  Homing the Y axis works great.  The problem is during the home operation of the X&A axis (A slaved to X).  Here is what I see happening - per the Alt7 Diagnostic Screen.

I hit the X-Ref button
X & A axis move toward (-) home position
M1Home & M4Home light up (Separate home switches)
X stops A stops
X begins moving away (+) from home switch
X Home switch (M1Home) turns off (M4Home remains on)
X stops moving – X is referenced HOME
A begins moving away (+) from home switch
A Home switch (M4Home) turns off
A continues to move away (+) from home switch until motor “slips” and gantry binds
Finally have to hit “reset” button to stop slipping

IF at this point I then hit A-Ref button …
A begins moving toward (-) home position
A Home switch (M4Home) turns on
A reverses and begins moving away (+) from home switch
A Home switch (M4Home) turns off
A stops moving – A is referenced HOME

In other words, homing seams to work separately – but not together.

Also, when the X&A homing routine fails – Mach 3 no longer recognizes the A axis with regards to standard movement.  In other words, Mach 3 seams to un-slave the A axis from the X axis.  This un-slaving occurs even if the A-Ref button succeeds in homing the A axis.  The only way to resolve this problem is to close Mach3 - and reopen it.

Using Mach3 version 3.042.020
Using a PMDX-132 board
Using Smooth Stepper Driver Beta2_V015ogb
Debounce is set at 2000
X Home on Pin 15
A Home on Pin 13
Y Home & Z Home share Pin 12
All Limit switches share Pin 11

Help! - and Thanks in advance for your input.

Chip:
Hi, Joepardy

Try this in your "Ref All Home" Button's, I had similar Issues with a X, A, dual Axis system awhile back.

DoButton( 24 ) 'Z Home Axis
RefCombination( 9 ) 'X + A Home
DoButton( 23 ) 'Y Home Axis

Hear's some info to review from some Post's.

"Art wrote....> Common problem. When you home , the slaving is disabled till the home is
> done. This is done to auto-square the gantry of such a system, thats why
> the
> lack of slaving when you stop the homing.. The solution is to make the
> homing go in the correct order. This is done by modifying the Homing
> button.. If you open the 1024.set file in the screen designer and double
> click the "Ref All-Home" button, you will see the code is
>
> DoButton( 24 )
> DoButton( 23 )
> DoButton( 22 )
> DoButton( 25 )
>
> This basically calls the Z, then X then Y and A homes. This needs to be
> changed to ..
>
> DoButton( 24 ) ' this homes the Z
> DoButton( 23) ' this homes the Y
> RefCombination( 9 ) ' this will home the X and A at the same time.
>
> RefCombination accepts a number where X = 1 , Y = 2, Z = 4, A = 8, you
> simply add the values of the axis
> you wish to home, so X + A = 9..
>
> The squaring will be automatic and can be adjusted by your settings for
> the home position of the switches..
> Thanks,
> Art
> www.artofcnc.ca

Art also wrote this... and I found the complete "Refcombination" listing here....

"Art wrote....   The home switches, (which may be set to the same input as the limit
switches), are used only for homing. The axis will move to the switch, then
slowly move off.

   The program by default does one at a time, because thats the most usual
combination. YOu CAN move any combination at once by editing the RefAll
buttons script. There is a command called RefCombination( n ) which will ref
any combination of the axi s. N is calcuated by adding the following
numbers..

X - 1
Y - 2
Z - 4
A - 8
B - 16
C - 32

Ref X and Y together would be RefCombination( 3 )

Hope this Helps, Chip

joepardy:
Thanks for the reply Chip.  I saw this solution posted ... tried it ... responed exactly the same.  Sorry, that solution did not work for me. :(

Chip:
Hi, Joepardy

Are you using the "Reversed" settings on you X or A axis.

Looked back at the xml used on the gantry water-jet cutter, We used X and C axises with no "Reversed" on ether axis in Homes & Limits and DoButton( 22 ).

Chip

joepardy:
Chip,

I will check this when I get back to the shop on Monday.  I believe that I have my X axis set Normal and the A axis set for Reversed.  But as I recall, this is the only way I could get the system to travel "normally".  If I set them both Normal or both Reversed, do I need to change some wiring? ???

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