Plasma table homing and limit switches

[landmark573]

I am converting a homemade CNC plasma table to use an Acorn control. I am still unclear how home and limit switches should be configured on a plasma table.

I have mechanical NC HOME switches at -X(axis 1), -Y(axis 2), -Ys(axis 4). The Z(axis 3) doesn't have a HOME switch.
I have mechanical NC LIMIT switches at +X(axis 1), +Y(axis 2, +Ys(axis 4). The Z(axis 3) doesn't have a LIMIT switch.
Z(axis 3) has a mechanical NC floating torch switch but no breakaway mechanism.

I don't have the THC system at this time.

I purchased and installed the Plasma Pro License.

I want to home the table at -XY (lower left corner) and auto square the gantry.

X home is on input 1
Y home is on input 2
Ys home is on input 3
All the LIMIT switches are tied in series and connected to input 4
Floating head is on input 6.

According to the homing setup screen the Z axis will be homed first, then non-paired axis, then paired axis. I do not want Z to home but can't find a way to remove it.

Am I thinking about this setup correctly?

[ShawnM]

If you are going to use auto squaring then you have to follow the instructions in the axis pairing and squaring manual. The setup is very specific with respect to the home switches. Here’s a link if you haven’t read it yet.

https://www.centroidcnc.com/centroid_di ... _guide.pdf

In my opinion LIMIT switches are are waste of time and inputs. Set up the soft limits in the wizard, they work flawlessly.

You can modify the homing macro to not home the Z axis but why? Use one of the many switches you have and add one to the Z axis.

[landmark573]

Thanks Shawn. I did find that manual but couldn't make my way through it at the time. I wasn't planning to buy the Plasma Pro until I was sure the Acorn would work with the HobbyCNC drive and motors I already had. I will go back and read it again.

I do use soft limits with my Acorn CNC mill conversion. I didn't really see any need to home the Z axis since it will use the floating head to find and set the working height of the torch.

[ShawnM]

I think you are missing the point of homing, it has nothing to do with the floating head finding the material surface or working height.

I feel homing the z at the top of travel is necessary for many reasons. Mainly safety so as not to crash the torch or damage the machine or torch itself. Before any rapid move the torch moves up to the z home position at the top of travel to clear and material, clamps, jigs or weights on the material on the table. In fact If I could only home one axis it would be the z axis. To each his own I guess.

[landmark573]

Good points and I do home Z on my mill