Will, I cannot get any more tension out of them. I’ve actually broken a belt clip and striped others trying to get them tight.
Is it possible they are too tight?
Yes, too tight can cause problems as well, esp. if you’ve bent a motor shaft.
Let us know at support@carbide3d.com and we’ll get this sorted out.
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So you might try to make 3 squares and cut them and see if the squares are consistent. If they are consistent then you might need to calibrate your settings. If the squares are inconsistent then you are looking at a mechanical problem.
@gdon_2003 I cut one more because currently work held there is only the possibility for two additionally tests.
All measurements within .05-.1mm of the prior cut. Is that consistent?
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Possibility of grub screw working it’s way loose on stepper motor.
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Since it was not mentioned in this thread yet, here’s the ultimate how-to for proper belt tensioning:
120-140Hz is my new motto.
And then, inspect your v-wheels very closely for integrity (do they still look round and smooth), and then I would say loosen all v-wheels and re-fasten the eccentrics such that the wheels don’t slip anymore…but just barely. Too-tight vwheels can do strange things, if some of the other threads are any indication.
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All grubs are as snug as that tiny Allen key can get them.
All of my belts sound like this. https://www.dropbox.com/s/puc9s5wa7rixcoi/IMG_2579.MOV?dl=0
This is after replacing one V-wheel that looked a little questionable… I think more than anything it cleaned up the pocket of the cut (minor Z fluctuation due to buildup).
@WillAdams support has been contacted. No response yet.
@Julien it seem like the biggest problem is the circle that seems to be stretched larger in the NW to SE direction? evidenced there on the Diamond that is .15mm larger on the NE side vs. the SW side.
Hopefully someone will be able to respond presently.
Since they were the only thing which changed, my inclination would be a bad set of belts.
Other things to check:
- endmill stickout/deflection
- feeds and speeds for this material and climb/conventional cut and whether or no the endmill is getting pulled in
Perhaps leave a roughing clearance and take a finishing pass?
Should all of them have a GT2 stamp on them? presently only one does… don’t know at what lengths they stamp.
Compressed PVC is pretty soft; it sort of cuts like butter… I can try a 1/4" instead of 1/8" but my feeling is that a larger bit just hides the issue vs solves it right?
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@WillAdams heres a 1/4" bit it’s about the same all over. Is there anything we can do right now based on these results? I’m behind on jobs and need to get moving. Let keep in mind that while I visually couldn’t see a problem before with oval holes it doesn’t mean that the machine wasn’t off .05-.1mm on this test (I’ve never run it before). Caveat #2 my Wixey brand digital calipers are probably accurate to about .05mm.
Shouldn’t this test should be performed twice per test, once at the extreme right side of the x-axis and again at the extreme left side of the x-axis.
The z would be irrelevant unless you measure that dimension also (which I would) the x should not matter in placement, (only 1 belt)
but with the Y movement having 2 belts shouldn’t both sides should be tested.?
Earlier I had suggested you run the test multiple times. If you are getting consistent results on each test then your mechanics are good and you need to calibrate your machine for your belts. So even though you are getting minor deviations it seems that you need to calibrate your steps. You will have to look on the forum for the parameters to do that. Just write down your original settings in case you need to revert back to them.
If you get widely different results each time then you would have a mechanical issue.
So if you feel the results are consistent then change your calibration, see belt stretch calibration on the forum.
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Yep,
As Guy says, if your measurements are consistent then it’s the $100 and $101 you want to update to match these belts, see the ebook
https://shapeokoenthusiasts.gitbook.io/shapeoko-cnc-a-to-z/x-y-z-calibration
It’s probably worth using the phone app belt frequency measurements to get all three of your belts about the same (matching the Y tensions is definitely worth it) in a sensible range and then do the steps / mm calibration.
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Ran the video while listening on the Gates Carbon Drive app and it consistently shows 148 - 151 Hz.
From what @Julien suggests, they might be a bit tight.
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In person, when I can get that app to trigger a reading I get ~128-133Hz.
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Sounds like that’s in the range.
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So help me understand something here… I’ve cut some pockets ~6" apart in the shape of a right triangle; measured them with my calipers and determined my X and Y adjustments are exactly the same:
$100=39.9121574
$101=39.9121574
I haven’t yet cut another Diamond,Square,Circle… but because my circles were ovals I was expecting to have to adjust more in one dimension then the other to get to the expected distances between pockets?
If the belts are evenly tensioned/stretched then the circles being ovals should be a matter of backlash, usual culprits for that are pulley set screws.
To add to what @WillAdams mentioned above, the shape may be oval from backlash because you have 2 belts dividing the backlash/elasticity on one axis (Y) versus the same forces on a single belt in the other axis (X), thus 2 times more movement in X than in Y due to belt elasticity or backlash (making an oval)…
Feel free to correct me if I mislabeled something, I am only a shapeoko apprentice…
EDIT: As @LiamN points out, there are other factors my mental sandbox didn’t take into account, that are involved, that result in both the X- and Y- axes being pretty balanced, so disregard the above (explained in the link he posted in the next post). Also, thank you Liam for being gentle with your correction 
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In general the X and Y movements are quite well balanced.
Yes, the Y has two motors and two belts, but it also has twice the rolling resistance from twice as many V wheels. All other things being equal this results in fairly similar performance, on average, across the working area of the machine. There’s a lot more detail to it for those who are interested
If it was my machine, I’d back off the V Wheel tensions on X and Y, then re-tension them all until just the point where, with one finger, you can’t quite turn the lower V wheel. One finger, no gripping and twisting the V Wheel or it’s easy to reach backlash and broken V-Wheel inducing levels of pre-load.
As always, check the set-screws on the motor pulleys, after a while you can hear and feel the little ‘clonk’ as the pulley slips back and forth around the flat.
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