Why is this happening...again?

[pd417]

At random times on random projects, my machine (NWA Piranha XL) will begin a tool path in the wrong spot and ruin a workpiece. A good example was yesterday, I was making some charcuterie boards for Christmas. The first two toolpaths ran fine (text and graphic and an interior profile). When I ran the toolpath to cut the hole in the top of the board, it cut all the way through and an additional 0.5" into my waste board, even though I had it set to cut 1.02" (board was 1.01"), along with that, the machine started the cut about 2" away. Next, when I ran the toolpath to cut out the piece, my machine started the cut about 1.5" perpendicular from the edge of the workpiece.

This has happened numerous times on various projects. No matter how may times I check and recheck my settings, I can not be confident that the machine will cut correctly. I contacted Next Wave Automation and their only suggestion was to make sure the machine was clean and the threaded drive rods were secure, not much help.

Attached are a couple pics of the issue and a copy of the crv file. If anyone has any ideas, I'll be glad to listen.

[scotttarnor]

I also have a Nextwave Piranha XL and the only time I experience any strange behavior was when I was running a box fan on the same power strip as the CNC, other than that all errors have been self induced. Static electricity and noise from fans and motors have been known to cause some strange issues.
After the strange cuts does the machine return to the original X-Y start position of has that shifted? Are you loosing steps because of your Toolpaths strategy.
To eliminate it is the machine loosing steps you could try changing your Toolpaths a little.
I would slow down the plunge rate of the .25 EM, Piranhas are pretty flimsy. I also use ramps on all my plunge moves and ramps and leads on my profile Toolpaths.

I am interested in what you find to resolve the issue.

[Leo]

Well your speeds and feeds are very conservative.

Do you have any LONG cutters in the spindle?

I wonder if your "Z" axis is hitting at the top of the stroke.
That could cause loosing steps and make things go wonky.
That in itself can cause the hole being too deep.

Do you hear at any time a noise that sounds like gears grinding?

For that matter, any axis over run can be a problem.

Cleaning and lubricating is certainly GREAT advice, not to be minimized or overlooked.

[martin54]

There are all kinds of things that can cause issues both mechanical & electrical & really it's a process of elimination unfortunately, first thing to determine is if the machine is losing steps, have a search on the forum as it's a subject that comes up from time to time & all the things that you will need to check will be listed already.

scotttarnor makes a good point about electrical interference, it's not always the actual CNC machine causing the problem but some other piece of electrical equipment. Personally, I think mechanical problems are generally easier to find, electrical problems seem to have a habit of being a bit more random & more difficult to find

[pd417]

I also have a Nextwave Piranha XL and the only time I experience any strange behavior was when I was running a box fan on the same power strip as the CNC, other than that all errors have been self induced. Static electricity and noise from fans and motors have been known to cause some strange issues.
After the strange cuts does the machine return to the original X-Y start position of has that shifted? Are you loosing steps because of your Toolpaths strategy.
To eliminate it is the machine loosing steps you could try changing your Toolpaths a little.
I would slow down the plunge rate of the .25 EM, Piranhas are pretty flimsy. I also use ramps on all my plunge moves and ramps and leads on my profile Toolpaths.

I am interested in what you find to resolve the issue.

I am running the Piranha on a power strip, but nothing else is plugged into it. I have a ceiling mounted dust collector, but that's on a different circuit along with the shop vac attached to the CNC. I'll try running it with everything else off and see what happens along with slowing the plunge rate on my 0.25" EM.

After each cut, the machine does return to the original X-Y position.

If / when I rectify this, I will let you know.

[pd417]

Well your speeds and feeds are very conservative.

Do you have any LONG cutters in the spindle?

I wonder if your "Z" axis is hitting at the top of the stroke.
That could cause loosing steps and make things go wonky.
That in itself can cause the hole being too deep.

Do you hear at any time a noise that sounds like gears grinding?

For that matter, any axis over run can be a problem.

Cleaning and lubricating is certainly GREAT advice, not to be minimized or overlooked.

Nope, no long cutters, all standard size.
No grinding or strange noises either.
"Z" axis has plenty of top clearance so it's not topping out.

[pd417]

There are all kinds of things that can cause issues both mechanical & electrical & really it's a process of elimination unfortunately, first thing to determine is if the machine is losing steps, have a search on the forum as it's a subject that comes up from time to time & all the things that you will need to check will be listed already.

scotttarnor makes a good point about electrical interference, it's not always the actual CNC machine causing the problem but some other piece of electrical equipment. Personally, I think mechanical problems are generally easier to find, electrical problems seem to have a habit of being a bit more random & more difficult to find

Thanks Martin, I'll look for the thread on losing steps and see if that helps.

I'm really hesitant to do another piece and have a nice piece of teak ruined...again. Frustrating.

[TomWS]

As Scott pointed out, Static electricity will cause strange behaviors and with the humidity levels low at this time of year, it's quite possible static sparks are more likely. Do you have a dust collection system running at the same time and is the hose an anti-static hose (and grounded)?

[adze_cnc]

I am running the Piranha on a power strip, but nothing else is plugged into it.

Sometime last year I watched a video on not plugging powered speakers (for events) into a powerbar. Perhaps similar logic could apply to your machine.

https://kettnercreative.com/speaker/qu ... -speaker/

[TReischl]

......
I'm really hesitant to do another piece and have a nice piece of teak ruined...again. Frustrating.

I really cannot add much to what has already been said, other than:

You might want to run good old cheap big box store pine on your machine until you get this figured out. Figure out some projects that can be made in pine and have at it. Ruining $20+ chunks of wood only adds to the frustration.

[4DThinker]

On my old Shark if I didn't notice and it bumped into a limit (like the end of travel in X or Y direction) the controller would assume it was still advancing in that direction. When it reversed all following coordinates would be off by the amount it wanted to go past the limit of travel. Only resetting X/Y zeros would shift the toolpaths back to where I wanted them.

4D

[Leo]

Lots of guessing - but I'll add one more guess.

How are you loading the g-code?

Do you run from a USB key?
Not a good plan

Do you load onto the control computer hard drive?
Best plan

Is there ANYTHING else running on the control computer?
Screen saver?
Sleep mode?
other software?
email?
ANYTHING?
The control computer should be BARE BONES - with ONLY cnc control software running.

[scotttarnor]

The thing that baffles me the most is the cuts at 9 and 12 o'clock in the cutting board photo and the machine still returning to x y home.
I only have 2 years experience but to cut 2 extra lines in 2 different directions and still make it to x y home means its not a loss of step issue correct ?

[martin54]

+1 on all that Leo has just said

That was my thought, I am wondering if on those cuts the machine was actually stopped & then not returned to the original zero position

[Leo]

On the NWA website there is not a lot of information about the machine. It looks like you need to run from a USB and there is no control computer.

After that happens to your machine - can you jog to the XYZ position that you originally set for the job?
This NEEDS to be done immediately after the incident - no reboot - no tool changes.
It is my guess that your "Z" will be way off.
If NO you cannot jog to XYZ - then you definitely lost steps in "Z" - and that is what your pics look like to me.

If YES you CAN return to XYZ - we need to keep on guessing.