Z axis malfunction...cuts in the air

[dbmdesign]

Hi, all.  I'm a middle school Tech/Design teacher, first time posting, and appreciate your help troubleshooting this: (using Axiom AR 8 Pro and VcarvePro 8.5)

Z axis stopped working properly.  I have successfully run files from Vcarve Pro software for years
1. (saving files as .mmg type onto a flash drive), and
2. successfully mounted material,
3. setting X, Y ["XY-0" key on controller],
4. then plugging in puck and pressing "On/Off" & "Menu" keys simultaneously [bit goes down and lightly touches puck and recalculates Z axis as expected],
5. I run a file from the flashdrive per instructions and machine starts
** BUT NOW it runs X, Y & Z in the air as if that were the Z starting position (?!). 

This started after the pandemic in 2021, even with student files that I succesfully ran that same week.  Nothing changed with the code or the process in setting it up or transfering data.  I've tried running files that were previously successful to no avail, and I've tried creating new basic files to just test carving simple profiles, also with no success.  The X & Y axes seem to be moving correctly for the toolpaths, but the Z axis remains in the air.  

Any ideas?  I'd appreciate it.  

Thanks.

- Danny

[grossmsj]

How far up in the air above the cutting surface? Is it always at the same height?
If you look at the Z value when it is cutting, is it zero or something higher?
If you set Z0 using 'the paper method', does it cut correctly?
Don't you have a Tool Set button on your controller? I'm not familiar with the key combination you're using.
I'm wondering if the value for the puck is correct.

[dbmdesign]

So I tried following manufacturer's instructions for "Step" down onto paper and using "Z-0" key, and that worked in running the file where it didn't before.

My biggest question, if anyone has an answer, is Why, after no unsuccessful cuts for years, would the CNC not work as it had, requiring some different method for setting Z?

I don't get it.

I appreciate everyone's help with this.

[Bob]

It's easy to accidentally set the safe z too high.If it's too high, the gantry will hit the top of travel and lose steps. This will cause the machine to make "air" cuts. So check the Clearance (Z1), and Z Gap above material.
Bob

[grossmsj]

I've had settings in my Siemens VFD change. I NEVER mess with the VFD, and yet when I did go in (with instructions from Axiom) I reset a value and the problem was solved. You could have had some error crop up in a stored parameter as a consequence of an electrical glitch.
But most of the time it's us doing something we didn't recognize had unforeseen consequences.

[Bob]

Dbmdesign,
It's been four days now. Have you made any progress with your problem?
Another thought...Did you change the Z zero position?  It's another easy way to accidently get an air cut.

Remember, these settings are also changed when you import another person's files. 

Bob

[dbmdesign]

Bob, your screenshots of Z positions and depths are helpful. I wish I knew what a proper setting was for Home Position Z Gap. Is it supposed to be .5 inches?

I'll check the Z Zero Position when I get back to work, but wanted to thank you for following up with my situation.

All the best,

- Danny

[Bob]

Danny, a home position Z gap of .5 is kind of small because I was working on a thick project and didn't have much gantry clearance. After you check your Z zero position, and if that is not the problem, it would be a good idea to call Axiom. They provide excellent support.
Bob

[dbmdesign]

In response to anyone searching this thread in the future (and in Thanks to anyone who responded), when on a call with Axiom's troubleshooting dept. we realized that the Z-motor Coupling was broken. It was supposed to have a red plastic piece in between the two metal pieces that connect the motor to the axle below it. Mine was just open in the middle, but I don't remember seeing any broken red pieces on the cutting board.

I ordered the new coupling ($40-ish), installed it, and so far running files has been working as intended.

Thanks everyone.

[eagle55]

Danny,
I'm just curious. Could you manually zero the z axis with the puck? Seems like if the coupling was broken you wouldn't have any z-axis movement at all. Just trying to understand the symptoms for future reference.

Roger