2 hours into the carve and the Z axis decides it would like to be .4 inch lower than the rest of the model. This has never happened to me before but I read about this type of problem often, on the forum.
Sad reality is the saddest reality…
I’d send a few pics to show the carnage, but darned if I can figure out how.
Time to move on… 
You should be able to drag and drop a photo into a post.
It was looking good. How big is the piece?
This happened to me a few times when I first started out. Sometimes after running the same Gcode successfully. I still don’t know what happened.
Now you can strategically mess it up some more, pour some green resin in, and redo the carve.
It’s hard to tell in the pics, but this is carved onto a dome (like a shield) that is 10 inch round and just over an inch high. It’s destined for the wall of shame…
Thanks for the response,
Wg
That looks fantastic @W.g shame it failed when it did. I had some early cuts go down in the Z direction, but haven’t had that happen in a very long time.
The two things I would check are the tightness of the Z axis coupling and the tightness of the bit itself. I can only guess that the bit was well engaged with the wood when the Z axis was being raised, holding itself there and then plunging further in on the next downward movement.
As I said, my issue went away, but for all I know it was due to my own mistakes at the time, since the issue hasn’t come back. When it was happening, it was on one particular project, and it happened repeatedly, which is why I feel like something (for me) must have been loose that I later tightened.
When you do get things sorted, be sure to post - we would love to see the results!
I use foam insulation board for a test piece. It comes in various thicknesses. Saves expensive wood and it can be run much faster. My 2 cents worth.
Thanks, I will check the whole Z mechanism over.
Appreciate the feedback,
Wg
The foam is a great tip, thank you. A question about it though, just how messy is it to carve?
Wg
I tried again on some 2 x material. same thing in about the same spot. i changed the carve order - so the center carved first with no issues. Then most of the first ring went well ,UNTIL!!
Everything is secure on the Z axis (seemingly). I am going to loosen the backlash screw a bit, in case that was binding. There is plenty of room above the workpiece for Z travel (I had an issue with that before).
The carve preview is a beauty, with everything being as it should be. Any other suggestions are sure appreciated.
Thanks again for the support,
Wg
To adjust the anti-backlash block I would back the screw out until you can feel the play when you try to move the Z axis up and down by grabbing the the plate that the anti-backlash nut is mounted on. You should be able to feel and maybe hear the play when it is loose. Then tighten it just enough to make that go away. Just figured I’d throw out how I adjust mine.
Good luck, that’s going to be a beautiful piece when you get sorted!
Edit: Not sure if you have a MK1 or MK2. If you have a MK1 make sure the two pulleys on top of the Z axis are tight and that the belt is tight. If you have a MK2 then I believe there is a coupler to check on the Z axis. Any slippage there could cause loss of Z position.
Are you using any other power tools while it is carving? Turning on/off anything?
Thank you, I have done all those things as suggested. Running another try now, this tim with son poplar I had laying around.
I won’t finish tonight, but tomorrow look for an update…
Wg
The only thing other than lights on during the carve is the 1HP dust collector, on a separate circuit.
Check tomorrow, I’ll finish the third try in the AM sometime.
I sure do appreciate you and the others helping me to get this dialed in - very frustrating.
Wg
I use Vectric desktop and UGS (Universal Gcode Sender) to design and machine my projects.
Wg
@W.g While it certainly looks like a hardware issue, it may be worthwhile to post the .crv file for people to analyze.
In the walnut version, it looks to be very deep, top to bottom. Can you be hitting the limits of Z travel?
Any luck getting past that same spot?
Maybe try gSender?
DC-Calendar_bySandyEggoCNC_DXF.zip (2.9 MB)
The .crv file is too big for this format. However you can open the attached zip to see what I’m working with. I am carving this file onto a domed shape.
The Z travel has plenty of room on top and on bottom, unless there is some freak move that is sending Z extremely far in one direction or another.
Thanks Grant for your help,
Wg
Yep roughly the same spot in the carve. I’m making another attempt today and will slow the feed WAYYY down so I can observe it closely.
As far as gSender goes, I’m not comfortable using that program - I’m old and set in my ways!
I’ll post the resulting carve later…
Thanks for your input, all of the help is greatly appreciated,
Wg
