An unusual problem

As the title suggests, I have come across an unusual problem with my router.

Occasionally it will change its cutting path mid-run without apparent reason.

I was cutting an a double Archimedian spiral out of 4mm plywood, it ran the first spiral of 5 passes perfectly, then started on the second spiral, it ran one and a half passes on the second spiral Ok, then suddenly shot off at an angle and continued to cut the path from another position. The two paths had be drawn in Illustrator, taken into Aspire 4.5 and calculated there, then exported as a .txt file to run in Mach 3 as a complete path, not separate for each spiral. I stopped the machine and put it down to a glitch without exploring what had happened. I ran the toolpath again in the air, and there as no problem.

A couple of days ago I was machining and lozenge shaped bowl which again I had generated the outline shape in Illustrator, taken it into Aspire to model the bowl, exported it as a roughing cut and as a finishing cut.

I ran the roughing cut without problem, changed tools and started the finishing cut, after 30 seconds or so of the finishing cut, again it displaced and continued cutting the bowl, this time I let it complete and when I returned the tool to zero, the zero x had moved to the right by around 25mm and the zero y had moved down by about 6mm. As the shape was regular, I was able to save the work by running the toolpath again a couple of times, displacing the x axis to take account of the error, then cleaning up by hand after. I ran the path a further 4 or 5 times to correct the bad cut, and each time it ran perfectly without error.

The router and computer are both on a UPS so there should not be any problem caused by power fluctuations etc, but I am at a loss to understand what is happening, I have since run a lot of other toolpaths without problem.

Any help, advice etc. gratefully accepted.

Without giving details of your setup etc. it is difficult for people to diagnose . But I would guess as it could be possibly related to a noise issue. Like a compressor starting up etc.

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Originally Posted by Clive S

Without giving details of your setup etc. it is difficult for people to diagnose . But I would guess as it could be possibly related to a noise issue. Like a compressor starting up etc.

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Thanks for the quick response, I am using a Chinese import 6090 machine with 2.2kw spindle, screw not belt driven, USB controlled motion card, Aspire 4.5 and mach3.

On each occasion there was no external noise source in the workshop, no machines started up or stopped and like I said, the computer and router are both powered through a large UPS to remove surges etc.

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Originally Posted by racerbear02

Thanks for the quick response, I am using a Chinese import 6090 machine with 2.2kw spindle, screw not belt driven, USB controlled motion card, Aspire 4.5 and mach3.

On each occasion there was no external noise source in the workshop, no machines started up or stopped and like I said, the computer and router are both powered through a large UPS to remove surges etc.

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Ok well I now have read your previous posts and see that you are using a usb BOB. Are you using a laptop with it or a PC. How is the BOB being powered (ie via the usb port or through a separate connection? Do you know what the voltage is on the switch mode power supply?

You are missing steps by the sounds of it. This could be Noise, not actual noise in workshop but electrical noise from Spindle or some other device.
But it's more likely a mechanical issue. Lose wires, lose motor connections, worn bearings, sticking or binding axis.

Could be over tuned motors.?

Personaly I would start with checking all wiring connections, separate any signal wires away from power wires.
Next would be mechanical checks, Motor Couplers for slipping, bearings etc for binding.

Next would be making sure it's not your code.!

Then start looking for Noise sources and taking measure to prevent.

Many thanks for the comments, I will now go away and try to shield as much as possible as it would appear from replies here and from other sources that it could well be RF interference causing my problems. I certainly have not been taking excessive cuts on the toolpaths, so hopefully mechanical issues should not be a factor.

Thanks again for the swift response, much appreciated.