Bent ACME lead screw...scared straight?

Hi All-

Has anyone successfully straightened a bent ACME lead screw? Mine is obviously warped and introduces errors as it wobbles around. It would even bind up when I was using a Nema 17 motor. My new 23 will power through it, but once again…Bummer errors

This looks like a pretty hefty piece, and I obviously can’t nick it up, so I don’t have a ton of ideas except a table saw top and a rubber mallet. That might do it, ya never know.

Any ideas are super welcome.

Ah man, the ex got the 20 ton hydraulic press in the divorce! Why did I keep the KitchenAid?!? :wink:

I have a good size vice and I will try this. Nothing to lose really. Cause then I just default to Bob’s suggestion. $$ Pony up.

Thanks for the ideas Angus!

What size acme?
Mine were bent slightly but the way I designed my plates it corrects the problem for the most part. Unless the bend is reeeeal bad.

Of thats the case don’t bother.
Inventables swapped my z rod twice and it’s still bent. Even though the bend was not that bad by mine it didn’t affect things much.

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C-Beam. And I really like the C-Beam! Because it is all slots I can add attachments very easily. Like mister or arm supports for a dust boot.

I actually just did a mod to it so I can get a huge travel out of it.

I will post more details soon.

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Will check soon. I get minimum 5" of z travel.
My x lift is to the point that I have about 1/4" space from collet to wasteboard at the lowest and 4.5 stick out to lowest point of undercarriage.

I don’t think screw is bent. Usually bents on flat end which is going into Bearing. You can nicely hammer it to straight out.
Mine was the same, requested replacement couple years ago, new one came worst. I attached to drill from other side and punished that with brass hammer until turns perfect.

Thanks for the ideas…I will try looking at the ends first.

Thanks @BillBlades, I haven’t tried using the table saw as reference yet. That was my plan, thinking that it’s machined flat, it might be a good indicator as to what’s going on.

I’m going to pull it out today and see what I get. I’m definitely getting wobble on the final bit end.

@Phantomm This is interesting…do you have any links to how this mod is done?

Once again, thanks all

@BillBlades Oh yeah, I could see it not going well for table or screw! This is going to be an interesting process, that’s for sure. Thanks for the ideas!

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Well, very good news here. I took everything apart today and I think what was happening was a poorly installed Delrin nut. The lead screw was just fine. I think I put all of that together without making sure everything was really square. So, after completely rebuilding the Z axis - carefully - everything is great.

One thing I noticed that was interesting was that when I remounted the Delrin nut, if I tightened it much at all, the lead screw started to bind. The Delrin must flex enough to bind up the screw. Something for new builders to look out for! Tighten, but don’t jam down on it.

Now, this is making me wonder if I shouldn’t have bothered adding a more powerful Nema 23 up there this past weekend. Is it overkill? Are others doing this? Cause I’d be happy to put the 17 back, get one more 23 and upgrade my Y axis. Thoughts?

Thanks again to everyone for your input.

You are not alone with that experience. Should be worth mentioning in the building instructions :slight_smile:

I would get a Nema23 for sure. I had a super smooth delrin block and Nema17 on mine ( type) and my Z would drop from the weight of the axis alone when unpowered. I could also easily overpower the Nema17 causing Z to loose step. Last thing I had against the 17 was that it got blistering hot during long carves. (water would boil on motor surface)
Nema 23 on Z would be a good investment IMHO. Be aware of max motor length for Z.

@HaldorLonningdal I was thinking it would be smart to add to the instructions too. It’s kind of a big deal. It was part of the reason my 17 was binding, for sure.

Good deal, I’ll leave the 23 there. It’s in place and working very nicely. Guess you can’t have enough power really.

Thanks for the thoughts!

I measured about 6.5" of travel.


I will open a new topic with it soon.

Stock but modded.

It’s not how high it goes, it’s about lowest point of that assembly and your waste board distance.
Measure the distance from your Waste board to that two holed aluminum brackets bottom end. That thick material you can carve.
Edit; I saw on enlarged picture. You can carve 2 1/4" material with this configuration.

I have a custom lift on my gantry since I’m using a screw drive mod pack.
But it clears nearly 3.5".
Before the lift I lost almost .5" because of the thick plate on bottom.

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Is there any way you can lift that mod a little higher. You can slide your router down as necessary if you can.

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I did that. And the way it installs makes it easy to adjust the c beam height and resquare it.

That’s fine. All I can see is you’re wasting about 3/4" between that bottom plate and your original Gantry.