Need Help!- Solsylva Dual Lead Screw Table - Suddent Belt Drift Causing Issues

[mlammert]

Hi all,

I have completed my build of the Solsylva Dual Lead Screw Table and have about 40-50 hours of cutting on it... During those 40-50 hours it has worked perfectly, flawlessly and amazing... Very cool machine...

However, all of a sudden the Y axis stepper started stalling...

After HOURS and HOURS of trouble shooting I have come to the conclusion that the belt that turns both lead screws is drifting on the tensioning pulley (grey conduit pulley)... When it drifts too far to the edge of the pulley the belt becomes SO stretched that it is then too tight and causes the stepper to stall...

I am 99% this is the problem and have confirmed this repeatedly...

I have tried EVERYTHING that I can think of to try and correct this... Tore down and rebuilt the whole axis/gantry assembly, re-aligned the whole machine, squared the belt up, squared the tension pulley up, etc...

I have a new belt on order now...

Question(s):

1) Has anyone else run across this issue with the lead screw belt drifting???

2) If so, my main questions are, why would it all of a sudden start drifting after 40-50 hours of flawless operation???

3) And, how the heck did you fix this???

I wish I could find or build some sort of auto-aligning tension pulley... But, I see that as only a band-aid... Again, I would love to figure out why it has started drifting in the first place...

Any similar stories and/or solutions would be GREATLY appreciated!!!

Thank you,
Mark

[CarveOne]

If you or a friend have a lathe, try skimming just enough plastic off the surface of the idler pulley to true up the diameter. If you made it per the Solsylva plans there is probably a small valley between the bulges where the bearings are located. You can lay a straight edge across the idler and see that it is uneven. A sharp lathe bit will cut it nicely. I did this to mine. The belt will move one way or the other a little depending on the direction of rotation but has not given me the problem that you describe so far, and I don't have nearly the run time on my machine as you.

The bolt that the idler pulley is mounted on must be bent in which ever direction it takes to get the belt to run with minimal drifting.

If I ever have this problem on my machine I was thinking that I would make a new idler pulley that is shorter and has washers for flanges that would limit the belt wandering. (If all else fails, cheat.)

Check your gantry to see if it is square with the side rails on both sides in case one side is leading the other. This will cause binding.

CarveOne

[mlammert]

We basically dismantled the entire machine over the weekend and reconstructed and realigned everything...

I am 99.9% sure that the side rails and gantry are square...

Before all this we tried making our own pulley with side walls as you mentioned... This did not work... The belt still drifted and simply bound up when it reached the side walls...

The lathe thing sounds like a good idea...

Before all this we did try bending the pulley bolt to try and compensate for the drift... We can try more...

I am also considering getting an auto-tension pulley from this company:
http://www.econobelt.com/Q460/RFQ/de...nsioner/13.htm

The reason I am thinking about getting one is that for brief moment I thoughts I fixed the belt drift... But, then realized that I had forgotten to tighten up the stepper mount after connecting the belt... When the stepper mount was loose it drifted a little but like an 1/8 of an inch... When I tightened everything up, it started drifting to the edge again and binding...

Thanks for the advise... Off for more troubleshooting...

Mark

[CarveOne]

Oh yes, I had not thought about the stepper pulley alignment could also cause the belt to wander.... Good catch.

CarveOne

[Richster]

Sounds plausible, I agree!

Another thing you could try (which helped mine) is to fix multiple bolts and washers as necessary to each of the three bolts which supports the mount. This ensures they are all the same length, and therefore that the x-stepper is actually parallel to the end plate of the machine your drivevbelt.