I am sorry to hear about the issues you are having, and can only imagine how frustrating this is, especially given the time you and Onefinity support have put into troubleshooting. Your guess of a faulty ball screw nut was one of my guesses as well. Did Onefinity have you do anything to confirm or dismiss this as a possible cause of some of your CNC’s issues?
OF support has been responsive but not resolution yet. They got back to me right away today when I let them know of my continued issues.
In the meantime, I have taken the X off again, as well as the Y steppers. The right Y bearing block is much more difficult to move than the left one. I believe this is the main issue. I am guessing a bad ball nut as the machine does not lock up in the same spot every time.
A replacement Right Side Y assembly would be appreciated.
while I’ve been waiting to hear back from OF, I decided to measure my rail diameter. My right side top Y rail is .001” larger than my left side top Y. I used a Starrett outside mic to measure. Curious to know how much tolerance the linear bearings allow for. If anyone wants to compare, my right side top Y rail measures 1.378”
Just doing a quick McMaster check, their 35MM linear motion shaft has a upper tolerance limit of 1.377”. Of course, I don’t know where OF gets their linear shafting from nor do I know their tolerance limits or surface finish requirements.
I was curious so do a really quick search of some related tolerances, and for the precision I am guessing we have on our CNCs, 0.001+" seems to be common for both shaft and linear bearings.
On a hunch, I loosened the two mounting screws that hold the ball nut to my right Y bearing block (the black machined part that the X rail sits on). What a difference! The bearing block is much quieter and way easier to move than ever. Loosened about 1/4 turn and it slides along the rails nicely. Either the ball screw is bent or the ball nut mating faces are not machined parallel to each other. I will investigate more as I try to get my machine reliably running.
If you take the mounting screws off completely, then rotate the ball screw nut out all the way, your eye may be able to spot any ‘wobble’ or clearance differences as it emerges from the hole in the mounting block.
So far, OF wants more video, more typing, more EMI issue. I’ve taken every single thing off the machine and it is bare stock. The X rail has been removed 3 times, I’ve been more than patient.
What I’ve found so far:
X rail is off, steppers on Y are off, slide block is very difficult to move by hand on the right side, left side moves nicely, if I loosen the two bolts that hold the ball nut in, the right slider moves very nicely. When tightened back down, it binds up again.
OF asked for videos of Y running without X and I’ve given that to them. Now they say that both sides look like they run the same?!? That was never the issue! It locks up from time to time and causes carve failures.
Ugh.
Did you have a chance to try my suggestion? Did you see a ‘wobble’ in the face of the mounting plate as you rotated the ball screw nut out of the hole in the offending Y axis mounting block? If you have a set of feeler gauges, you could see if there is a big difference in space between the back of the ball screw nut mounting face and the front of the Y axis block. Linear bearings would need to be loosened and pushed back a bit for this test.
I was going to try your suggestion but could not. The right side ball nut is so tight in its mount that it won’t easily come out. It has to be tapped out. I was able to verify that .015” shim under the outside edge makes it slide better.
I am not a machinist, but that seems like a fair amount, especially since the force is acting over a relatively short ball screw nut.
OF has come through and I believe my issue will be fixed!
OF tech has been very responsive, even on Sunday!
Thanks OF
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What was your final diagnosis. Having a similar issue. Losing xy Orgin during carve. When carve ends even sits at diffrent position than when started
The ball nut on the right side Y slider locked up from time to time. It was causing failures similar to what you spoke of in your post.
An easy way to check if this is your issue it to remove the x rail and pull both steppers off of each Y. This will allow you to more clearly feel if there is binding. If there is binding on one side, loosen the two bolts that hold the ball nut to the slider. Just a 1/4 turn was all I needed to feel a huge difference. I suppose it goes without saying that the machine needs to be squarely installed on a flat surface.
I hvd earlier thought that the take up nut on the ball screw was “self tightening” but this does not seem to be the case.
Curious to know, was your issue only showing up only with parallel tool paths?
So I have only had this issue in my last 2 attempts. 3d carve. The roughing is 200ipm along the Y axis. The one causing the problem is the finish Raster at 400ipm but it appears to be close to the outer part of carve.
Cesar,
When your carve fails, do you hear a “grinding” noise from the machine? After it fails and prior to powering down or restarting, will Y move all the way forward or does it stop short?
My X axis has been binding at unexpected times and it throws off the X-home so the cut is destroyed. I get grinding noises and metal binding noises. I’ve calibrated the set screws that hold the silicone gears in the ball screw nut with various results, but eventually each ends with X binding and shifting the X-home.
I think my ball screw nut for X needs to be replaced. It does make a bit of a grinding noise and if I isolate on the X-screw it does not turn as freely as the two Ys.
A month ago I installed the 80mm spindle; would the added weight damage the bearings in the ball screw nut?
If I upgrade to the 50mm rails will this be a better solution for my 80mm spindle? Perhaps the 35mm components are not up to snuff for 80mm?
It sounds like you have your issue nailed down. I’m not sure about the spindle however.
Have you tried removing the stepper and loosening the two bolts that hold the ball nut in place? Doing that was how my issue was nailed down.
What do you mean by “removing the stepper?” I should know that 
The stepper mother that drives the ball screw on the axis you’re having trouble with.
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That’s disturbing - LOL