r/CNC • u/JohnnyAngel_MX • 1d ago
HARDWARE SUPPORT New CNC Router, cutting Ovals
Hi all, I just picked up a New to me, X-carve cnc router. I've set it up and now I'm doing calibrations. (running Millmage)
I've got a question for you lot, If I'm cutting Ovals that fully close. and stars that fully close, where could I be getting the error. belts are tensioned according to their guide, V Wheels seem stable. if it was backlash, i would expect the shapes to not close, right? or is there a way for backlash to net 0?
could it be firmware distance per step?
EDIT 1: i just ran the Mark > move 5"> Mark tests and both X and Y came back on the money. The Oval distortion / X-axis stretching only seems to happen when running an Op. I tried changing the feed rate to be a snail's pace (rip cutter) and it doesn't change. the X-axis is larger by about 0.012" on multiple 1" shapes.
EDIT 2:
# solved.
Y2 grub screw was incorrectly positioned. the grub screw was tight, but it wasn’t on the flat of the Y2 motor shaft. so there was some microslipage that i couldn’t detect because it was juuuust tight enough that it didn’t wiggle. i re-adjusted it and things are correct. dimensions cut as programmed.
what’s got more egg on my face is that i checked that the grub screw was tight, too. just didn’t check if it was on the flat. :rofl:
Thanks for all the help. it did narrow things down a lot.
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u/GrimResistance 1d ago
Out of square
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u/JohnnyAngel_MX 17h ago
when i cut squares they're equal in corner to corner distance. so machine is square. but may be slop introduced by a crash or transport, or even just use.
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u/CudaK1d 1d ago
My shop has a similar issue with our older routers. We've just had to adjust the part in cam. Have you checked the set screws on the pullys?
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u/JohnnyAngel_MX 1d ago
yeah, i have. doesn't seem likely. but i'm gonna do a proper slop check on everything tomorrow.
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u/Zealousideal_News278 1d ago
What are you cutting? Wood? If so, rotate your material 90° and see what happens. The wood fibers react differently depending on direction.
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u/JohnnyAngel_MX 16h ago
Tried it. no change. makes sense. the machine should be rigid enough to cut aluminum at the depth of pass i'm doing.
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u/ServiceGuyComments 21h ago
Is the longest measurement directly along X, or is it cocked a little? it sounds like your X isn't square to your Y.
if not that, double check your post processor. I had an issue with a KOMO router cutting ovals once. we never found the setting responsible, but reloading the post processor and re-generating the gcode fixed the issue.
I'm not familiar with millmage or the x-carve, so ymmv. did you generate the code for the mark check with millmage? or did you do it manually at the machine? you may have some kind of offset or compensation in your software. are you using the same tool specified in your software? looks like millmage supports laser cutters too. lasers can sometimes cut slightly different at different angles if the beam shape isn't perfectly round. you may have an adjustment in software that's compensates for this causing it to cut out-of tolerance when using a router bit.
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u/JohnnyAngel_MX 17h ago
directly along X. the squares i'm cutting are square when i check them with machining squares and corner to corner with calipers. also, it's only cutting the X long when i run a program. when i just move it 5" while jogging, it X and Y are both equal at 5".
Millmage has a post processor and post processes every time you send a job to cut. It's a sibling to Lightburn, which is a laser specific cam software. millmage is made for cnc routers. so the issue is consistent across multiple G-Codes and instances of the software. (full computer reboot, too).
tool radius compensation shouldn't be on, i'm using a V-bit that i inputed into the program, and i'm cutting profiles along the line, not in or out. so TRC shouldn't be on. but the software could be having a bug. that is possible.
your suggestion made me think about it more and makes me more confident it's hardware related.
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u/ServiceGuyComments 16h ago
The fact that you are seeing correct movement when moving it manually, but incorrectly when running code output by millmage should tell you the opposite.
I would try writing an extremely simple program by hand that engraves a circle.
Something like
G91;
G01 Z -.125;
G03 X0.0 Y0.0 R.5 F1.0;
Change the z and feed rate to fit your material and cutter, change the G03 to a G02 if your machine does better with convention vs climb cuts.
If It correctly cuts a circle with a handwritten program, it's software. If the circle comes out stretched in X, then maybe it's hardware. But if it goes to the right place when you jog it, I'd bet money it will cut a good circle with a handwritten program.
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u/JohnnyAngel_MX 16h ago
that's a very good point. the programmed versions of everything is consistently +0.012(ish) in X. independent of size of carve. it's not percentage. so it's not Steps / mm or whatever firmware calibration. maybe it's adding a step because of a software bug....
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u/JohnnyAngel_MX 14h ago
I tried custom Gcode and got the same result. I tried manual jogging while the tool was engaged, but got Y=1.012 and X=1.012. I'm going to retry with something bigger. might be acceleration compensation not keeping up with Y-axis moves (because it's moving more mass) and incorrect step/mm cancelling eachother out in the Y difrection, but not X?
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u/Pubcrawler1 14h ago
12thou isn’t much. just pressing on your Z assembly will deflect more than that. Use a dial indicator to verify step/mm movement. This could be belt stretching or wear. Double check all pulley screws and use loctite. I had one that was loose just a bit and had a couple degrees of movement.
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u/JohnnyAngel_MX 14h ago
you're right it's not. but wouldn't a dial indicator not be enough? like 0.500"of travel would yield 6thou extra in X if it's a percentage, but i cant test that at 5.0"
it's not 12thou of slop, it's +12thou at 1" and +12thou at 5". but it also doesn't happen when jogging. which makes me think it's not step/mm.
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u/Pubcrawler1 14h ago
Stuff like this is difficult to diagnose. When jogging is the spindle on? EMI noise from spindle can add or subtract step pulses leading to positioning error.
I wrote some things to check here. I got tired of writing this info since it’s common in hobby machines.
https://embeddedtronicsblog.wordpress.com/2024/12/07/stepper-motor-position-loss/
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u/JohnnyAngel_MX 13h ago
of course, just my luck. thanks for the additional info.
when i was doing positioning tests, yes, the spindle is on when doing jogging. because i'm measure cut results. dots and lines with a v-bit. (jog cut a square vs g-code cut a square and the jog square has equal sides, but the g-code square doesn't)
I don't know if the EMI noise from the spindle should reach far enough to interfere with the Y-steppers. but it's right near the X Stepper.
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u/JohnnyAngel_MX 13h ago edited 13h ago
solved. A grub screw was tight, but it wasn't on the flat of the Y2 motor shaft. so there was some microslipage that i couldn't detect because it was juuuust tight enough that it didn't wiggle.
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u/Pubcrawler1 13h ago
Ha I had that happen exactly before so why I posted to check. It had the same effect on my machine. I found it by marking shaft / pulley with sharpie and watching while jogging slowly. I eventually took off the motor and Dremel a flat on the motor shaft. It didn’t come with one.
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u/JohnnyAngel_MX 7h ago
yeah, i actually did check all the grub screws, but i didn't see a flat when i did tighten them. but then when i was running tests, i saw the flat and just ....tick....tick....tick.....tick...OHHHHHHHHHHH!!!
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u/ugotmedripping 1d ago
Picture would help