[spletcher1]

Hi Everyone,
I have an NM-135 that has been working great for several years. Recently, the xaxis started making clicking noises and running quite roughly. So much so that it started getting stuck during rapids. I have delayed problems by slowing down the motor acceleration and speed, but I fear it is slowly deteriorating. I swaped out the bearings and the problem remains. So, I think that I will need to change the ballscrew assembly. Has anyone done this? Does anyone have advice for purchasing a replacement...I have contacted Novakon but no answer yet. I am wondering whether I will need to "build it" from scratch with a custom machined ballscrew and nut or whether fitted replacements are available. I am also wondering whether I should upgrade to a better ballscrew given that I have to replace it anyhow.

Thanks in advance for any pointers.

Cheers,
Scott

[SCzEngrgGroup]

I would suggest you disassemble it, and figure out what's *really* wrong. Seems unlikely to me the ballscrew really failed, though it's possible a few of the balls failed, which could be fixed by replacing the balls.

Regards,
Ray L.

[Novakon]

Hello,

Can you send your message again to [email protected]? I have not seen your inquiry about this problem so far. We should be able to take care of this replacement part for you and keep you going.

Regards,
Novakon Team

[spletcher1]

Novakon: Thank you. I just resent my email.

Ray: I disassembled it, and the ballscrew diagnosis was a matter of elimination. When it is disassembled, there is no audible "clicking" when turning by hand, although there is some regular roughness. After cleaning and reassembling I figured the problem was either bearings or ball screw. The bearings are new, so that left the ball screw. I don't know much about the mechanics of those things, so accurately replacing a few balls seemed more challenging than swapping out the whole thing, although maybe that is a little naive. Strangely, I also noticed some runout of the ballscrew when reassmbling. If I loosen the motor screws the clicking goes away and things move smoothly, although obviously I can't run like that. Could it be that the screw itself is bent? I don't know how that could have happened as I don't remember any major crashes.

Thanks again for your insight.

Scott

[hayes]

I know this is an older thread, but I'm having the same issue after recent replacement of the X axis ballscrew and bearings on an NM200. I think the coupler is out of alignment and I need to spend some time getting that aligned and running properly.

OP, did you ever get your machine up and running and resolve the issue?

[Novakon]

If you think there might be a centering problem of the ball screw to the motor mount, you might consider making a centering fixture on a lathe and also making a new motor mount extension plate. The plate can be as little as 1/4" thick. Cut a new motor centering pocket in it and then pin it to the old motor mount. You can use spring pins or similar to hold it in position and just use the original motor bolting holes to fasten the motor down.

There may be other ways also, this is just one suggestion if it is out of alignment.

Regards,
Novakon Team

[hayes]

Novakon,
I have a model of the whole motor mount assembly drawn up. Any chance you have a print I can compare the dimensions against to ensure it's accurate? I plan on drilling and pinning the whole assembly to the table as well.

I indicated the new ball screw yesterday that I recently replaced and was disappointed to find 0.0015" run-out at the journal the coupler attaches to.

[Novakon]

We do have some original factory level drawing of the NM-135 still. There were two versions of the NM-135 from the beginning so if it was from the initial start up production, We don't have anything that could be called accurate. If your mill is gray, We think we can help. Can you sen what you have and we can match up what we have. Most likely we have what you need, but to dig through all of this can be really time consuming.

You referred to the run out at .0015". Are you referring to center to center alignment between the ball screw and motor mount? A good helical coupler will handle this much misalignment and the motor mount usually has a little bit of play in it when you tighten it down.

Regards,
Novakon Team