LDO Trident POM nut ground down

[JGoz72]

I have had the same issue with my LDO Trident 300, had to replace a few of the POM Nuts now and started keeping a few on hand. For the life of me I can't work out why it's happening.
The mounts have a bit of freedom of movement to allow for lead screw wobble, Starting to suspect the Teflon coating may be rough in sections.

 

[Chopper Rob]

I have had the same issue with my LDO Trident 300, had to replace a few of the POM Nuts now and started keeping a few on hand. For the life of me I can't work out why it's happening.
The mounts have a bit of freedom of movement to allow for lead screw wobble, Starting to suspect the Teflon coating may be rough in sections.

Might be the teflon, or at least something in the leadscrew. LDO is sending jonhi not only a new nut, but they replace the complete motor, so maybe it is not the nut. I still have to contact 3djake and see what they will do.

 

[Yaaj]

Same here. LDO 0.2. Killed the POM nut after 300-400 hours.
But replacing POM nuts is much easier (and cheaper then replacing the motor with its integrated leadscrew.

Was wondering one thing... I run a Nevermore. The Nefvermore spits carbon particles. They are known to be abrasive.

Did you install a Nevermore (or similar ?)

 

[claudermilk]

I've had a Nevermore in my Trident for forever (the printer is nearing 3000 hours print time, lots of it ABS with Nevermore running). As far as I can tell my OG POM nuts are fine. I self-sourced the printer and have the LDO leadscrew motor kit, but before they started putting the coating on.

 

[blinkytheslayer]

I contacted the seller where I bought the kit and they are going to send new pom nuts out, but was going to take a bit to arrive. I didn't want to wait that long so ordered some other replacements off of amazon. Replaced all 3, but the one nut is wearing again. I can see the pom plastic bits that have already worn off.

I have a few theories:
1. It's the lead screw Teflon coating that is not smooth enough
2. I don't have the lock nuts tight enough and it's causing too much movement, and thus wear.
3. Too much z-hop. I'm using the default profile from Orcaslicer, so not sure if too much or too little z-hop. Was set at 0.4mm
4. Bent lead screw. I tried checking it against a straight edge. Didn't seem like it was bent, but tough to tell .
5. Printed parts that hold the lead screws warped in print causing the pom nut not to engage evently/straight.

At least now I have a few more replacements, but not sure what else to do. Seems like this level of wear is excessive. Barely 30 hours of print time on the second set of Lead screw pom nuts and I can already tell the one is highly worn.

Do I need to grease the lead screws? From all I read the POM nut and Teflon coating on the lead screw didn't need it and using the wrong grease/lubricant could cause premature wear. Not sure if it was chemical reaction or something else.

Any suggestions? Can't keep replacing these this often. At this rate, they'll need replacing once a month.

 

[Dave32]

I know you are being methodical and trying to cover all possibilities, but in my opinion, I think you can strike off #3 (" Too much z-hop"). There is no way that 30 hours of print time should wear out those nuts, regardless of how your z-hop is configured.

 

[blinkytheslayer]

I know you are being methodical and trying to cover all possibilities, but in my opinion, I think you can strike off #3 (" Too much z-hop"). There is no way that 30 hours of print time should wear out those nuts, regardless of how your z-hop is configured.

Yeah, wouldn't be my high percentage guess either. But like you said, trying to gather opinions and cover all my bases. I'd rather cross off a bad theory that leave the correct one of the list.

Any bets on the other options?

Easiest to check IMO are 2 and 5 so I'm going to reprint the z carriage left, right, and rear parts.

Have retightened/checked the tightness of the lock nuts already, I'll see if the wear continues to get worse or better. Then probably replace the z carriage parts anyway.

Other than this one issue, I have been loving this printer. It's been making really, really nice prints.

 

[claudermilk]

The lock nuts should actually be loose. That's why they are lock nuts. Tighten them until they are just short of beginning to grab the POM nut. There should be side-to-side movement, but not up-and-down. If they are locked in, it causes binding and that could be why you are seeing the grinding. I first ran into that building my first printer--a Prusa Mini--and it failed the Z axis check. Over tightening caused enough binding to spike the voltage and fail the test; it took me a while to figure that one out at first. I think the Vorons will just power the stepper through the resistance.

 

[blinkytheslayer]

The lock nuts should actually be loose. That's why they are lock nuts. Tighten them until they are just short of beginning to grab the POM nut. There should be side-to-side movement, but not up-and-down. If they are locked in, it causes binding and that could be why you are seeing the grinding. I first ran into that building my first printer--a Prusa Mini--and it failed the Z axis check. Over tightening caused enough binding to spike the voltage and fail the test; it took me a while to figure that one out at first. I think the Vorons will just power the stepper through the resistance.

Okay, so I feel like this could be the issue. How much, or how easy should the side to side play be? I thought I had them setup as you described, loose enough to move side to side (in the x/y direction) but no vertical play (z direction).

From your description here:
"Tighten them until they are just short of beginning to grab the POM nut."

I've tried to get the tightness just right, but I feel like it's either always to loose, or too tight. I don't seem to be able to hit that goldilocks zone. If I have it too loose, it introduces backlash (maybe not right term). and the lead screw will knock back and forth on homing/bed mesh z-motions. I've slowed this down so shouldn't be moving too fast. But faster than normal printing.

Writing it out now, that might be pointing to too much friction between the lead screw and nut. So maybe the lead screw is bent or my parts are warped causing uneven pressure on the pom nut.

In either case, i'm reprinting the parts. Will report back when i've got more data.

PS. I appreciate the feedback/comments! Keep 'em comin'

 

[Chopper Rob]

I do run a nevermore, it came (at least the parts) with the kit. I think the printer ran for about 200 hours of the total 300 with the nevermore.
If the nevermore is an isssue, LDO should not have included it in the kit. I have the "official' carbon pellets in the nevermore,

About the POM nuts, In my case these were not fully tightened, they were loose enough that there was some horizontal movement, it was mentioned in the manual to do this.
I also removed the other 2 POM nuts and they look fine.

 

[claudermilk]

Well...I'm running a Nevermore too. I doubt that's the issue.

Have you tried just running the POM nut up and down the length of the lead screw without anything attached? Does it run the length of the thread smoothly?

 

[Yaaj]

The nut alone runs smoothly.
The same dust is appearing on the leadscrew after 20 hours or so...
Definitely not carbon : the Nevermore is perfectly clean.

 

[claudermilk]

I can only think there's something mechanically off there. My LDO V0.2 is at about 230 hours, and the leadscrew is clean. With the motor off, I can easily move the bed up and down.

 

[Yaaj]

Nothing's mechanically wrong. Believe me. And this thing prints a perfect sub 15mn benchy.
Wasn't the leadscrew replaced with a uncoated one, and the nut with a PEEK one (v0.2 S1 rev A+) ? Read this somewhere, maybe Discord.

 

[JGoz72]

Had to replace another one the other day so I did all 3 while I was going, one was close to failure (Front Right) one was starting to go that way (Rear) one was in pretty good condition (Front Left)

I did enquire on the ldo_motors channel on discord and got this advice from The Technical Ace, which I did on reinstalling everything so I will see how long this set lasts.

"Loosen the screws fastening the joints to the railings (one railing at a time), gently shake the bed, retighten screws. Follow the process throughout for all motors and test motion.
Note: I’m not talking about the screws that secure the joints to the bed frame. I am talking about the 4 screws that fasten the joint to the linear rail. Total of 12 screws all together. 4 per rail."

Cleaned the the leadscrews up and noticed there seems to be some build up of what appears to be a coating in the threads of the Teflon lead screws.

 

[Yaaj]

On the 0.2, the screws were loose...
The problem is elsewhere. Not speaking of the PTFE coating (poor surface finish) ! Looks like a pan (shot a few macros to be sure).
Replaced the nut + AB nut, and stress tested it : z-hop 0.4 mm ; they failed after 40 hours !!! (jam)

Currently testing something different : new nut + AB nut (same batch as the previous one), + a washer and a wave washer (spring) under the screw heads. Tightened the screws all way down, then unscrewed 1/2 turn, giving a preloaded 0.25 mm axial play without radial constraint (just some light friction).
Also, instead of reusing the stock spring, I installed a spring from a brass kit. Thinner wire, longer, much weaker.
z-hop 0.2 instead of 0.4. Prints perfectly, no backlash issue. No powder build up after 25 hours. So far so good... Still didn't have to readjust the z offset.

This being said, this printer will get a belted Z ASAP. I'm done with leadscrews.

[EDIT] maybe we could help the nut sliding sideways against the Z joint, with some silicone grease (on the nut upper flat, NOT on the threads !)

Wave washer :

 

[claudermilk]

Cleaned the the leadscrews up and noticed there seems to be some build up of what appears to be a coating in the threads of the Teflon lead screws.

Yeah, that surface looks rough. My uncoated ones don't look like that at all. That picture makes me suspect the lead screw is acting like sandpaper and grinding down the nuts. I'd send that in to LDO and see what they have to say, looks like bad parts to me.

 

[Yaaj]

 

[guptaxpn]

On the 0.2, the screws were loose...
The problem is elsewhere. Not speaking of the PTFE coating (poor surface finish) ! Looks like a pan (shot a few macros to be sure).
Replaced the nut + AB nut, and stress tested it : z-hop 0.4 mm ; they failed after 40 hours !!! (jam)

Currently testing something different : new nut + AB nut (same batch as the previous one), + a washer and a wave washer (spring) under the screw heads. Tightened the screws all way down, then unscrewed 1/2 turn, giving a preloaded 0.25 mm axial play without radial constraint (just some light friction).
Also, instead of reusing the stock spring, I installed a spring from a brass kit. Thinner wire, longer, much weaker.
z-hop 0.2 instead of 0.4. Prints perfectly, no backlash issue. No powder build up after 25 hours. So far so good... Still didn't have to readjust the z offset.

This being said, this printer will get a belted Z ASAP. I'm done with leadscrews.

[EDIT] maybe we could help the nut sliding sideways against the Z joint, with some silicone grease (on the nut upper flat, NOT on the threads !)

Wave washer :
View attachment 4638

I can't believe I've never heard of a wave washer. Neat!