I know this haa been up in the forum before and that are multiple reasons for the X-axis to suddely come out of aligment but I have som data that might help you smart people figure out what the problem is.
I’m currently running a project in thick plywood and the problem of X-axis misalignment seems to happen when I run it at more than 300 mm/min. It happens when I run it at 0.5mm/pass and 350mm/min, but not at 1.0/250.
I would really like to improve my speeds as I’m producing multiple parts and the jobs take several hours to complete. I’m using the 300W/24V spindle.
What should I check first? Excentric nuts, belts or the trim pots on the gshield?
There are too many posts regarding your problem. You may want to search like loosing position - X-Axis problem etc.
If it’s any help I tried running plywood with a 1/8th up cut but at different speeds and feeds cutting 20 teeth cogs, I.e. Lots of X and Y movement.
Looking through my numbers, at 0.5mm per pass, my best cut was at 550 mm/min, but still happily cutting at 1100 mm/min but with a little more tear out.
So I would suggest your first port of call is to check the mechanicals (if sudden change) of eccentrics, belt and check the pulley isn’t loose on the stepper motor shaft (my most common mech problem). Failing that look at bumping the X current pot on the grbl shield up a touch and keep trying.
Hopefully that will sort it 
Cheers
Ian
Thak you Ian and Alan! Thank you for those reference values! I’ll check on these parameters!
I suspect its electronic noise from the spindle causing your problem. Install a pen or sharpie in place of the spindle and run the same file and see if it looses steps
There is lots of data relating to the need to adjust the potentiometers correctly for each axis - if you need a hand with this, please let me know, I’ve done it a few times now.
Don’t overlook the ‘simple’ possible solutions to your problem however…
I was losing position randomly on the x axis and tried dozens of things (all good because I found some other potential problems). The solution to the problem though turned out to be the tiny grub-screws that hold the toothed pulley onto the x axis stepper motor. Undoubtedly due to vibrations, one screw had fallen out and the other wasn’t very tight - this meant that everything worked perfectly through tests & light test cuts, however when starting a long job, the pulley would gradually slip on the shaft - thus losing the correct x position.
When I looked, I also found screws missing from the Z and Y axis…
The way I tested this was to physically hold the machine head (not so tight you’ll damage anything - BE SURE TO KEEP FINGERS AWAY FROM PINCH-POINTS) and send a command to move one axis at a time approx 1". Feel or look at the shaft on the rear of the stepper motor and see if it’s turning (while the head is held stationary). If it’s turning but the head’s not moving, you’ve found the problem.
Solution? I couldn’t find grub-screws that size anywhere (you may have more luck), so I cut down some small stainless screw to re-tghten the pulleys onto the shaft.
All good now…
Hey! I finally got to check this and look, both of the set screws from the X-axis were gone! Hopefully things will improve when I fix this!
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@TorSelden glad to hear your making sawdust again…
Unforunatelly I’ve also narrowed the issues down to the spindle. It sometimes does not start and has to be nudged with wrench to start. It also creeps of course when the spindle is running. It is perfect with out.
Does anyone know if the quiet spindle fits in the same mount as the 300W X-carve spindle?
@TorSelden If your spindle is playing up, contact Inventables though their Help system. Mine too died and Inventables replaced it immediately. In fact they not only replaced it, Inventables even went one better - because I lived on the other side of the world (Australia), and because there was a tiny tiny chance that the unit they sent me could also be faulty, they sent me TWO REPLACEMENT SPINDLES AT NO COST.
As such, I’m now a lifelong customer who’s more than happy to sing their praises. Contact them for help. Then also use them for bits, parts and materials. They’re good, they’re helpful and they’re passionate about Customer Service.
Ultimately however, I’d strongly recommend that you purchase the DeWalt mount (from Inventables) and then buy the new router. It’s many times better than the original spindle and allows you to use the machine in the way that you probably imagined that you’d be able to do.
I had the same problem, I will need to order more little set screws.
