My spindle dropped to the bottom of the Z axis

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My spindle dropped to the bottom of the Z axis

Postby supernat » Thu Aug 10, 2017 8:19 pm

Hey everyone, I just had a problem I haven't experienced before, but this is my first double sided 3D model cut with V9. I ran through a roughing pass for the top side which cut the wood down to half way through the work area okay, then I switched bits, exported the Finish toolpaths which all looked good, all were above the middle of the work area. I then ran the finish, and it was almost done, all the way to the last cut, so I stepped away for a few seconds, only to hear a change in pitch with turned into a grinding, come back in to find the work piece blown to the side, spindle cutting away my spoil board and then into the aluminum table, Z axis was at the very bottom. I went back in the software to double check, and there was no point where the Z axis ever went even close to that. I am using an Axiom AR8 Pro, just wondering if anyone else has experienced something crazy like this??? It ruined the workpiece and probably the bit, I haven't turned the machine back on yet to pull it up out of the table...
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Re: My spindle dropped to the bottom of the Z axis

Postby sharkcutup » Thu Aug 10, 2017 8:44 pm

After switching bits you did re-set 'z' zero, right? I ask because you do not mention it.

Anytime bits are changed the 'z' axis needs to be set again.

Or was everything set and cutting correctly and it suddenly went haywire?

I am at a lose if it just went haywire.

I have had this happen but it was due to my error in which I had not re-set zero on the changing of a bit or a calculated mathematical error in the depth setting within the V-Carve software. Of course now with this type of thing happening I am now very cautious when changing bits and/or setting depths within the V-Carve software.

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Re: My spindle dropped to the bottom of the Z axis

Postby Bob Reda » Thu Aug 10, 2017 9:04 pm

It could of done that if the hold down failed and the wood went flying

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Re: My spindle dropped to the bottom of the Z axis

Postby 4DThinker » Thu Aug 10, 2017 9:27 pm

The only time I've seen my CNC suddenly take off in an un-programmed direction was due to a static discharge. Is your CNC frame grounded? Were you running a dust collector?
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Re: My spindle dropped to the bottom of the Z axis

Postby supernat » Fri Aug 11, 2017 12:08 am

Yep, I set the Z value appropriately after switching the bit. It ran through and cut almost the entire toolpath which has just maybe 1/2" Z variance, then drops. I actually just tested it again without a bit in it and without the dust collector running. It drops in Z way below where it should around the 92,000'ish line number. I think I'll have to send it in to Vectric as a bug report, because the software shows the Z staying where it should, the simulation looks good, but the program that is generated tore down into my table at this point. I was just curious if anyone else had seen this. It's a fairly complex cut (i.e. that's a lot of lines) with a single bit and almost makes it to the end when it's like the bottom just drops out. :(

In the image, you can see it looks like it's making a profile cut around the outside of the sword on the right side here, but I do not have a profile cut in this toolpath or even on this side of the piece, it's just supposed to continue cutting at pretty much the same depth level to give some additional offset (boundary offset set to 0.2 inches) , then I flip the piece over and do the profile cut from the other side.

Also, I did get some kind of "Inertia Position Error" (or something like that) on the A11 controller the first time it failed. That could have been because it tore the piece out though I guess.

20170810_175817.jpg
Shows where the bit just digs down into the piece at the wrong depth.
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Re: My spindle dropped to the bottom of the Z axis

Postby 4DThinker » Fri Aug 11, 2017 1:14 am

If you have been using a file that was carried to the CNC on a thumb drive, the g-code file might have been corrupted when you pulled the drive out of your PC.
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Re: My spindle dropped to the bottom of the Z axis

Postby IslaWW » Fri Aug 11, 2017 1:17 am

Any chance the bit came loose in the collet?
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Re: My spindle dropped to the bottom of the Z axis

Postby Rcnewcomb » Fri Aug 11, 2017 2:07 am

because the software shows the Z staying where it should, the simulation looks good, but the program that is generated tore down into my table at this point

If the preview is correct then it is not a Vectric software issue.

You can further verify this by looking in the generated toolpath file for any like where the Z is instructed to move too deep.
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Re: My spindle dropped to the bottom of the Z axis

Postby supernat » Fri Aug 11, 2017 4:05 am

Thanks for the suggestions guys. I created gcode and viewed in an online browser, then compared to the Axiom code being created in notepad, and they jived okay, so I don't think it's the post processor. However, I noticed that the Z position is around -27, then it commands Z to a value of 4mm about 20 commands later, then 2 command lines later a value of -27mm again. I'm not savvy enough to know if that is a bad thing, seems that the hardware will only finish processing one command before it goes to the next command.

When I started the file on my CNC just before this, I hit the error condition. The Z axis goes up a short ways but nowhere near the limit, and then starts squalling because it's unable to move for some reason, and the position sensors keep on counting, so it causes it to think it moved up to a Z value of 4 while the actual Z axis wasn't moving. Then it moves down to a Z of -27mm which is actually much lower now and into my board. It's interesting, because I killed the run right at the point that it started squalling, and I can manually move the Z axis up and down with no issues, never had a problem with that. It seems to only do it because the Z4 and Z-27 commands are very close together in the gcode, but that shouldn't matter? I'll have to run this by Axiom I guess. I'm not even sure why it's moving up to Z4 to be honest, all the material it is cutting at that time is around Z-27. Probably just something I don't fully understand yet.
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Re: My spindle dropped to the bottom of the Z axis

Postby Martin Reid » Fri Aug 11, 2017 2:01 pm

Dear 'Supernat'

This is not a unique problem there are other posts around that may help...

for example DMcDonald... viewtopic.php?f=35&t=27270&p=199730&hilit=limit+switch#p199730

As for me, the one time we had this issue (Shopbot PRS Alpha). It was a Z axis limit switch issue which shut down the machine and while the spindle was running down gravity pulled it down into the bed.

Best of luck, I'll keep watching to see if you get to the bottom of it.

Sincerely and in good faith
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Re: My spindle dropped to the bottom of the Z axis

Postby garylmast » Fri Aug 11, 2017 2:04 pm

Because I use a large spindle and problems I had with stepper motors holding the Z-Axis, I bought my latest CNC with oversized servo motors instead of stepper motors. I used it for a while with no problems, but when I powered the equipment back on, after I shut it down, the spindle dropped several inches, driving the mill through the spoil board, into the bed. Opening the control panel, the Z-Axis controller showed an error. The manufacture had me switch cables to the A-Axis controller, but didn’t solve the problem. Turns out, I have to power the machine on first then open Mach 3, making sure it connects to the controller board. If I open Mach 3 first, with the power off on the machine, then power on, the spindle with drop and the controller will error out. Obviously the equipment needs to shake hands with the Mach 3, so I have to go through that ritual every time I power on.

You may try to unplug your cable from your computer then reconnect it to see if your software shakes hands with the CNC controller board. Gary
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Re: My spindle dropped to the bottom of the Z axis

Postby mick40 » Sat Aug 12, 2017 1:53 pm

This happened to me on two occasions. The Z axis motor was failing. Replaced, problem solved.

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Re: My spindle dropped to the bottom of the Z axis

Postby supernat » Sun Aug 13, 2017 12:14 am

Thanks Mick. I hope that's not the case, because this unit is barely a month old. And it only does it in this exact same position of the file every time, never when manually moving it. However, I have contacted Axiom, I'm sure they'll have to work this out. If anyone's curious though, because it's difficult to explain in words, I made a video: https://vimeo.com/229422960
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Re: My spindle dropped to the bottom of the Z axis

Postby garylmast » Sun Aug 13, 2017 1:07 pm

Because my spindles weighs the same as a small truck, it drops 10 times faster than what your showed in the video, but it was doing the exact same thing. My machine was only a few days old when this happen. It sure sounds like the Z-motor controller problems. I haven't replaced it yet, because if go through the startup procedures I mentioned and when I hear the spindle click, and know it connected, then it works. I will probably eventually have to replace it. Gary
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Re: My spindle dropped to the bottom of the Z axis

Postby ger21 » Sun Aug 13, 2017 1:32 pm

OK, so the stepper is stalling when it's lifting the Z axis, so the Z axis is always lower than the controller thinks it is. IT also appears that it only stalls during rapid moves?

It could be that the Z acceleration is set too high, or there's some binding on the Z axis when moving up.

The issue is not that your Z axis is dropping, but that it's not moving up.
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