CNC Shark Problem: Toolpath Shift/Jump

[PCDude]

I tested the machine with no wood and the router off again and it did shift on the X-Axis and made the motor made the sound it makes when you jog to the limit of the machine when it its the edge of the guide rail and support gantry.

I took apart the whole machine and looked for any mechanical damage and there was no damage or signs of slippage on the couplings that connect the screw rod and motor. I checked the screw guide for damage and there was none. I reinspected the wiring to the controller and moved it around. I ran the same project when it jumped again and it didn't do it with 5 full runs of the project. I created a test tool path that incorporated many lines of travel for the X-Axis to take so I can see if it would replicate the problem again.

The issue is gone now after taking it apart and putting it back together. I didn't see anything that would have caused the problem, but the problem has been solved.

[PCDude]

I replicated the problem and pinpointed the issue. I confirmed the cause of the problem.

Previous posts of the problem, cause, and solution in this thread regarding the Screw Rod / Stepper Motor Coupling are accurate and I appreciate the input that lead to me replicating the problem and confirming the issue.

Solution for future reference for other CNC Shark Owners:

Problem: Intermittent Toolpath Shift/Jump

Cause: Mechanical, Screw Rod / Stepper Motor Coupling slipping due to loose torx screws, cutting dense material at high a feed rate, and jogging the CNC Machine to its limit causing the motors to put excessive force on the coupling torx screws and the screw rod guide.

Solution: Disconnect Stepper Motor from CNC Machine Frame (Unscrew mounting screws), Disconnect the screw rod guide (The black threaded plastic piece that connects to the gantry) and inspect for damage, Use a torx bit that fits the torx screws in the coupling and unscrew the screws enough to remove the coupling from the stepper motor shaft and the screw rod end without removing the screws themselves, Inspect screw rod end and stepper motor end that slips into the coupling for damage (Precaution), Reinstall the coupling on the stepper motor and tighten the screw until properly seated half way in the coupling on the flat part of the stepper motor shaft, Reinstall the screw rod in the coupling and tighten the screw until properly seated on the flat part of the screw rod end (Make sure that the screw rod end is completely inside the coupling where the flat end barely sticks out to ensure that the lip is past the screw and will not cause slippage), Reinstall Stepper Motor back onto the CNC Machine Frame. Complete, repeat steps for other motors where suspected slipping occurs.

Ways to avoid this problem:

1. Slow down feed rate for cutting dense material
2. Avoid jogging the machine to its limit
3. Ensure all screws in couplings are tight when first initially putting together the CNC Machine
4. Visually inspect couplings before starting projects or by scheduled maintenance
5. Make sure clamps are not going to be in the way of the router, as this can cause damage to the router bit, clamp, screw rod guide (strip the threads) and cause the couplings to slip (The screws will scrape the motor shaft and/or screw rod end causing it to slip or the screw will shear)
6. Make sure cutting depth is not too deep for the router bit you are using otherwise the bit will go too deep and not be able to cut to move back and forth on the X/Y axis. This will either break the router bit, damage the router, ruin the project, move the project, damage screw rod guide (strip the threads), and cause the couplings to slip (The screws will scrape the motor shaft and/or screw rod end causing it to slip or the screw will shear)

Basically make sure that nothing will cause excessive force on the motors, couplings, and screw rod guides.

There might be other causes for this issue that I do not know of, and therefore I cannot test for other causes since my machine is now working 100%.

Thanks.

[Wilderness Sign]

Hi All!
I wanted to post that I have fixed my problem with the x-axid re-centering in the middle of a carve. I called rockler and then subsequently called next wave. The gentleman atnext wave suggested that this could simply be a maintenance problem. I think we can all agree that specifics are not available for on-going maintenance (at purchase time), but, Jim suggested that the T-nuts and spiral bar need to be lubricated often. To lubricate, only use Dupont Silicon Teflon Spray. Although I was not thinking this was my fix, I was convinced it was an electrical problem, IT WORKED! I was proved wrong. So far so good, I have been using it for a couple weeks with no problems.

[AJR]

Good catch on the couplings, also keep an eye on your warrantee period, my problem turned out to be bad fets on the drive board from Xylotex, problem occured 2 weeks before my warrantee was up. They fixed it and now all is good.

[flytrader]

Wow!

I have the same issue.

I stall in the "X" movement and then jump an inch.

This issue happened enough randomly on X, Y, or Z, for me to start pre running tool-paths on pink foam first and if it ran fine before I would trust it to wood.

This process only raised my odds slightly because sometimes it still jumped on the project.

I think my issue may be from Norton which is demanding to be updated.

I turned Norton off and the program ran fine.

I am not confident that Norton is the sole cause however, I will be updating it before I run another project on the shark.

I have nearly ruined a project that had cost hundreds of dollars and many days of continuous running.

I am glad that wood is so forgiving with some sanding.

I salvaged what I had and the project should be delivered to the customer this week.

I am glad the tool paths are complete all I have to do now is glue and collect the payment.

I had many scary moments with the shark.

I would like to know more about what may be causing the shark to have a mind of its own.

Ed

[ca8920]

Having the same problems with my new SD100. I called both the Customer Service number for Nextwave and the Tech Support number for Nextwave today leaving a message requesting help at both numbers and didn't get a return call from either. Not a happy camper. I have found a broken plastic cap that covers the electrical connection for the Z axis motor. The factory apparently screwed the screws in too tight cracking the plastic but I can't believe that is causing the problems. I'll try tipping the gantry up and looking at the Y motor and rails tomorrow. Again, not a happy camper, it's a two week old CNC.