[rusmannx]

Hey guys.
I converted my mill a year or so ago and have had this problem the whole time, and it is getting worse. My X-axis is only usable for about 6" from center in either direction when above 30ipm (used to be anything above 100ipm). Anything more than that and something is binding and stalling my stepper (570oz direct drive). I am using screws/nuts from linearmotionbearings2008 and used Hoss' DVD for the conversion.

Removing my vise from the table does not help, and I have messed with the gibs (tighten, loosen, curse at) with no improvement. I am specifically wondering if others have had this problem and if so, how you overcame it. I'll also take blind guesses, shots in the dark, etc.

Thanks

[SCzEngrgGroup]

Disconnect the motor, and turn the screw by hand, to move the table end-to-end. If you can feel a difference in the torque required to turn the screw, then you know there's a problem somewhere with the ways, gib, screw alignment, bearings, ballscrew, or nut.

Regards,
Ray L.

[ChrisAttebery]

Have you lubed the screw and ways? Can you see any chips on the screw? I had a similar problem on my machine in one spot and direction. There was a chip that got smashed onto the screw. I cleaned and lubed the screw and I was back in business. I've been using 60ipm for my rapids since then, but I could probably crank them back up if I wanted to.

[rusmannx]

I cleaned and lubed the ways, which it didn't really need and it didn't help. I oiled the screw and that did help a bit. I can pull rapids up to about 100ipm for 5" in either direction from the center of the table. I removed the motor and can definitely tell the screw is harder to turn as the table moves away from center. I am going to pull the whole axis and see if anything looks obvious. Maybe I'll be able to see if something is moving, binding, wearing, etc.

Thanks guys.

UPDATE:

I've been futzing with it all day and have been able to get out to 8" from center up to 100ipm. At no speed can I get beyond 8" from center without loosing steps.

Everything is lubed nicely, gib seem to be just right, bearing preload is good, and the screw is perfectly parallel with the table and no binding.

[Wiggles84]

Could your ball nut be clamped to far the the front or back of the slot?

Seems that could cause the issue your having with it binding as you move away from the center of travel.

Andrew

[ChrisAttebery]

Pull the motor and screw and see how hard it is to move the table on it's own. To me it sounds like maybe the table wasn't ground correctly or something. Maybe there is a burr. You could also try lapping the table to the saddle if there doesn't seem to be any other cause of binding.

At one point I could rapid as high as 330IPM on my machine. I turned it down to 120IPM because I needed more reliability than speed. After I had the problem with the chip stuck on the screw I turned it down to 60IPM, but I think I will turn it back up to 120 when I have time to test it out again. That seems to be a sweet spot for a machine this size.

[rusmannx]

Pull the motor and screw and see how hard it is to move the table on it's own. To me it sounds like maybe the table wasn't ground correctly or something. Maybe there is a burr. You could also try lapping the table to the saddle if there doesn't seem to be any other cause of binding.

I've pulled the motor and the screw does get more difficult to turn near the ends. I've fooled around with how the nut sits in the slot but nothing has really made a difference. When I pulled the table I checked for burs and found none. Lapping may not be a bad idea......

I've never been able to get rapids over 180 on the X, and that is only possible within a couple inches from X0. I'm going to play with it some more over the weekend. I've been putting up with this for to long.

[Wiggles84]

could your table end caps be on the opposite ends than when it came form the factory?

just a "shot in the dark"
Andrew

[wizard]

I've pulled the motor and the screw does get more difficult to turn near the ends. I've fooled around with how the nut sits in the slot but nothing has really made a difference. When I pulled the table I checked for burs and found none. Lapping may not be a bad idea......

I think you missed what Chris was asking for. You need to isolate where the problem is. To do this both the motor and the lead screw need to be taken out of the equation. So you remove the motor and then disconnect the leadscrew. That meas any end support is removed so that the X can be pushed around freely.

Once the X is free to be pushed around you can physically feel any binding that may be there in the ways independent of any lead screw binding. If the X continues to bind when pushed around manually like this then you have issues with the ways. They will need to be scraped back in. Lapping in this case would be a big no no.

If after inspection the X appears to be fine you need to remount the lead screw and then see if the binding returns. The other possibility here is that your nuts and end supports aren't aligned properly. The leadscrew needs to be parallel in both planes with the X axis. If not you will get the types of interference you are indicating where binding occurs in both directions. If you get out a pice of paper and draw an imaginary lead screw "line" slightly out of parallel with another line (the ways) you can see how a leadscrew assembly assembled with the table in the center of the ways would put increasing pressure on the nut until it starts to bind. Usually what happens is that you get some compliance until that is all gone and then the axis quickly binds up. In a perfect would the leadscrew would be absolutely parallel to the planes defined by the axis ways.

I've never been able to get rapids over 180 on the X, and that is only possible within a couple inches from X0. I'm going to play with it some more over the weekend. I've been putting up with this for to long.

Sounds like an assembly problem more and more to me. Even so I'd start right from the beginning and verify that the X ways don't bind at all and then reassemble with the goal of keeping the leadscrew as parallel to the table as possible. If your tooling situation is limited this won't be easy to do. One thing to try is to slide the X axis so that the lead screw mounting plate and the lead screw nut are is close together as possible. In this position the bearings should slide right into the pocket in the mounting plate with no problem. If they don't then you have to address the mis alignment.

[Wiggles84]

Did you ever figure out the issue?

Now that I'm starting to put my machine together, I find that I'm having a similar issue with the table binding at either end. No motors yet, just by hand. Going to take some measurements over pins to see if the table ways are bottle necked.

Might have to look for the thread were someone scraped and\or lapped the ways of their machine.

Andrew

[rusmannx]

Did you ever figure out the issue?

Now that I'm starting to put my machine together, I find that I'm having a similar issue with the table binding at either end. No motors yet, just by hand. Going to take some measurements over pins to see if the table ways are bottle necked.

Might have to look for the thread were someone scraped and\or lapped the ways of their machine.

Andrew

I have not resolved the issue yet as the problem has taken a back burner to some other pressing projects. I intend to keep at it, and will update this thread. I like your idea of measuring between pins, and I think I'll try that too. Let us know what you find.

[Wiggles84]

I have not resolved the issue yet as the problem has taken a back burner to some other pressing projects. I intend to keep at it, and will update this thread. I like your idea of measuring between pins, and I think I'll try that too. Let us know what you find.

I haven't yet taken it apart to check it with pins, but I did pull the Gib and wiped it over some 600 grit paper. found a really high spot about three quarters of the way to the left. I'm sure there will be some flack taken for this, but I put some layout die on the surface and swiped it back and forth a bit to take it down some. seems to have helped some. I also put in the new AC bearings.

I am now able to use a power drill set at the lowest torque setting back and forth (18v Dewalt) . I don't know how that will stack up to a 570 oz stepper. With the way it is set I have less than .001" sag. About 4" from either end the table does ride up about .001" for about .5" and then drops right back down

Andrew