LDO Trident POM nut ground down

[jonhi]

After 600 hours my Trident met a major failure with the POM nuts, where one got ground down until it completely lost the grip:

This "shouldn't happen", but there were at least two others who reported the same issue in Discord so I thought I'll start a discussion here about it.

Maybe there's something that's misaligned, but I have no idea what that could be or how to check it. The nuts holding the nuts should be loose (my were a little loose, but I don't know how loose is enough). Another option is that there's an issue with the parts that came in the LDO kit?

Thinking back, the flakes started showing up soon after I started using the printer, but I didn't think it'd be something serious.

I haven't dissembled it yet, but I've ordered replacement nuts I'll try when they show up.

 

[vinnycordeiro]

I disagree with the "this shouldn't happen" statement. POM nuts are a consumable, they need to be replaced from time to time. There's no escape from that, friction is unavoidable. It's also a matter of priority: it's cheaper to replace the nut than the leadscrew, that's why the nut is made of a softer material.

Now, what may need to be discussed is the time it took to reach this point. 600 hours seems to me a little bit too early, so you may need to revise the mounting and maybe also make changes on the Z hop configuration on your slicer.

 

[jonhi]

Alright.

I found one potential issue, with the mount not being completely flush against the extrusions/cover:

Could something like this be the cause?

I noticed that the pom wasn't ground evenly:

With one side having clearly visible threads, and on the other they're almost completely gone.
Could a slightly slanted z screw cause something like this perhaps?

and maybe also make changes on the Z hop configuration on your slicer.

I honestly have no clue what to do with Z hop, I think I've just left as default (from the superslicer profile referenced from the voron docs). What kind of setting could maybe cause something like this?

 

[majic79]

Set "lift Z" to 0 - that effectively disables Z-hop. As for the Nut failing - very annoying, but better than wrecking the leadscrews. Have you got any burrs/damage on the leadscrews? That could contribute to an early failure as POM is so soft it could start grinding with just a bit of dirt - keeping them clean helps here. But looking at the damage, it's likely that there's some stress coming in and pushing the nut somewhere. Expansion in the bed + loose Z rail/carriage fixing? Do any of the other nuts look damaged?

 

[Sanity Agathion]

Wasn't there some recall or replacement of teflon coated motors from some early batch due to them wearing out these nuts prematurely? If you can, contact somebody from LDO and ask about it.

 

[claudermilk]

Something is very not right with alignment on that printer. I'm at 2800 hours on my original POM nuts (self-sourced, not LDO). My worst issue is the dang thin squeals when making rapid vertical moves like for parking.

 

[jonhi]

I've sent an email to 3DJake (where i bought the kit) and asked them to contact LDO for me (dunno where else i should turn?). I'll see what they come back with.

I haven't seen any wear on the leadscrews and the other POM nuts seem fine.

 

[jonhi]

I heard back from 3DJake and LDO is sending a new "teflon-coated leadscrew Z motor with a stainless leadscrew and PEEK POM nut".

But it's shipping from China so it's around 4 weeks of waiting time. In the meantime I'll try to find a new nut that fits the screws.

 

[Dave32]

In the meantime I'll try to find a new nut that fits the screws.

Presuming they aren't "special" for some unknown reason, there are tons of them on Amazon.

(I generally would recommend buying from one of the 3D printing companies who supports the community instead, but it sounds like this is a temporary/throwaway solution until your new parts arrive... )

 

[jonhi]

(I generally would recommend buying from one of the 3D printing companies who supports the community instead, but it sounds like this is a temporary/throwaway solution until your new parts arrive... )

I did order this nut: https://3do.eu/coupler/1129-t8-pom-nut-lead-8mm-pitch2mm.html ... But it didn't fit.

Looking at it more, I think I need a "Tr8*4-2p (2 starts)" nut, which I found here: https://www.electrokit.com/leadscrew-nut-pom-tr84 (good because it's a Swedish company with fast shipping to me). But I haven't received it yet so I dunno.

It was surprisingly difficult to find the correct nut for the leadscrew, or maybe I'm just bad.

 

[Dave32]

How about Amazon ASIN B07RKXWDSG?
"Befenybay 6PCS Diameter 8mm Black TR8x2 Lead Screw Nut for CNC and 3D Printer Parts (Size: Tr8x2)"

//edit: (or one of the alternate thread start versions in that same listing...)

 

[majic79]

Is there any reason not to use a brass nut?

 

[jonhi]

Is there any reason not to use a brass nut?

Yes, I do think that if you use a brass nut with these leadscrews then the screws will gradually get destroyed.

So I'd have to replace all Z motors if I want to go with the brass option, but that's quite expensive compared to replacing the POM nuts.

 

[majic79]

I disagree - brass is a softer material than steel, so the brass will wear out first. Second, you do need to lubricate, but as it's in an enclosure, you're not going to get significant dust build up (I'm at around 300 hours on my trident, and no sign of dust or wear).

I'm not sure where your reasoning comes from - is there a reason why you think it would cause higher wear?

 

[Dave32]

I disagree - brass is a softer material than steel, so the brass will wear out first.

It's not brass on steel. The leadscrews are Teflon coated.

 

[majic79]

Ok, fair enough brass is going to damage a teflon coating. But this just feeds back into the other question, which is about making sure the right lubrication is used. I would also question the sanity of a teflon coated leadscrew and POM nut, Vs a simpler brass nut and straight steel/stainless steel screw. Brass is going to be much more wear resistant than a teflon/POM combination, and without coating the leadscrews, your saving money on fabrication and avoiding potential issues with the wrong lubrication being used (brass/steel is going to be much more forgiving on choice)

 

[Dave32]

I don't have the data, but I would presume it is more about friction (particularly, stiction, and its impact on the ability to make fine movements) rather than wear resistance, cost, or longevity.

 

[majic79]

It would be interesting to measure that and do some comparison

 

[blinkytheslayer]

This just happened on my LDO Trident 300mm^3 I built last month. Barely 100 hours on it. worried it failing may have bent the lead screw. Contacted the seller and ordered some replacements from amazon. couldn't find any of the right sized ones on any of the Canadian 3d printer companies.

 

[Chopper Rob]

Have the same issue on a LDO Trident 300 with around 300 hours of printing.