LR4 gone super wobbly

LowRider CNC Troubleshooting
1

So I upgraded my MPCNC to a LR4 awhile back. And as I unfortunately tend to do, kind of went dark for a year or so while life tossed other projects at me.

The last few time I used the LR4 was about a year ago and at the time I was starting to get a little frustrated that my cuts were coming out inconsistent from run to run in ways I couldn’t really nail down. I thought it was due to my not using the collet correctly since this was my first go with an ER11 collet and I didn’t realize it was supposed to clip in before tightening the nut.

I haven’t had time to check that hypothesis yet…after my last project it was just too hot to keep working in my garage. I live in Yuma az and for context last week it was 110f in the shade - my garage thermometer saw 114f a few times the last couple of weeks. I have an AC out there - but when it’s this hot it doesn’t do a lot so I don’t even bother trying to use it unless I NEED to be out there. I had hoped to do quite a bit with it last winter - but prepping my old house for rent took way more time than I anticipated and by the time I had that project done and the house rented it was too hot in the garage again.

Well, a few weeks ago on a Saturday morning it was cool enough out I actually did a little bit of bench cleaning and was thinking about firing up the LR4 again. I was looking forward to seeing if correcting my collet would resolve the issues I was having. After I cleared the bench I gave the LR4 a bit of a tug and noticed…oh wow…the carriage is really loose.

I had snugged the idler bearings a few times as it wore in - and with the heat cycles it’s been through I wasn’t really shocked. But when I grabbed the carriage I found it was snug on the rails. What was loose was basically everything else.

So it looks like I’m going to have to go over the whole machine - the strut plate bolts are all loose, the XZ plates are all loose - just…basically everything.

Which has me wondering - what’s my best approach here. I’m sure part of this is due to the expansion/contraction of the temp swings with my machine living in a garage in the desert - my old MPCNC didn’t suffer from this but it was in my old shop which I kept at least somewhat air conditioned.

This is a PLA machine since when I started the rebuild quite a few people assured me they had PLA machines in hot garages with no issues…but I’m kind of nervous now.

I was thinking about taking it off the table and bringing it inside to work on it - but then wondered if snugging everything up inside and then taking it back outside was asking for trouble with the shift from assembling at 75f and then using it at 110f ambient. But…even just snugging things up outside when it’s 110f ambient seems like a less than great idea.

I’m just really surprised at how loose everything suddenly is. It’s almost all nylocs so I assume the nuts haven’t loosened - but that would imply that parts of shrunk which is the opposite of what I’d except in high heat.

So - before I start tackling my machine with a screwdriver snugging everything up and then recalibrating it while dripping in sweat and cursing my self for not just waiting another month or two to work out there…anyone have any thoughts or suggestions?

2

That is a tough one. Have to assume it is heat-related. It has been 100-105 around here but that is not 114. If any sun gets in, that is a machine destroyer for sure. My shop doesn’t have windows, I open it up when I am in there but no sun ever hits any of my machines.

Snug it up and see what happens. See if anything broke.

For the next build you could try petg (pet-cf if you have it in the budget).

3

Yeah, no sun thankfully. Well, there are some windows in the garage door but they’re small and at an odd angle so don’t let any direct light in. Even during the day I need shop lights in there to do anything.

My MPCNC was in PETG and I honestly kind of regretted it…but it was as I’m sure you remember one of your earliest and least rigid designs making it even worse with PETG. I really wanted to do pet-cf this time but had a bunch of good PLA on hand and being in the middle of a home move minimal budget so decided to go with it.

Nothing broke as far as I can tell…just…shocked at how every screw appears to be loose now.

At least it explains why I was getting such random and unrepeatable errors! And why I’d see things like cuts in one direction looking good but cuts in another direction looking like the router was tilted when it cut. It was!

4

So, I’m one of those with OK results with PLA. The outside air temp at home has been up over 100F ten or so times the last month, which means it was up around 110F in my garage. My MPR&P and my small LR4 are fine. I will say that a work colleague took a printed model to a business partner a couple of weeks ago and that thing all but melted in his car over just a lunch hour in full sun. (One of the 100F+ days)

I did do a bit of tightening up on the LR4 this spring as it had started to have a bit of noticeable motion on the core.

Some questions for you if you’re willing to explore:

  • What are your strut plates made of? (My smaller LR4 has my mostly printed PLA strut plates and extra braces as a result.) One notable difference from a lot of machines to mine is that with all of that PLA, the CTEs are much more similar than say an aluminum strut plate or even the tightbond painted MDF that I’ve also had on a LR4 that I had in my garage for a while.
  • When you say good PLA, what brand, type, and color?
  • Do you see any notable plastic deformation on the braces? Places to look are around the clamp circumference at the tubes, and around the screw holes in the clamp section.
  • Where in AZ? The temp ramp rates in the deep desert are way more aggressive than say in Flagstaff… Ramp rates on the cooldown cycle are just as stressing. One (not really a) benefit of my garage is although it gets hot, the heating and cooling cycles are somewhat slow. Nice for me if I get up early as I can work in there, but hell from about 10AM till about midnight.

Edit- It looks like from your other thread that you have a bunch of white parts. I wonder if all that titanium dioxide is a factor in your situation?
Edit2- oh that looks like Zen parts, not LR4 parts.

5

Yeah, this summer is pretty rough already. I’m a little north of you, near Phoenix. I’m dripping water into a mud puddle and the chickens hang out in it all day long.

My last place wasn’t air conditioned, and I built several mpcncs and lowriders. Pla was alright for the first one except the stepper mounts. Then I used petg, extra walls, no problems. I built a printer and another cnc with abs parts. Honestly, the difference always seems very subtle to me, and i think material rigidity is important, but not as important as careful construction. Friend of mine out here did have a heavy spindle on his and the parts just sagged out of shape. That was wild.

All that to say, parts tend to break in strange hidden places. I agree, look for busted pieces, maybe some bolts that didn’t get tightened or got tightened too much. Depending on the inconsistency, you know, grub screws :neutral_face:

If you have to reprint, pick something good for the heat, add a perimeter or two.

Edit, after rereading your post, I’m leaning more towards deformed pieces. It sendt like all of a sudden because it’s just the next time you looked at it, but it’s been out there absorbing heat all day every day. Warms up, gets soft, sags under the weight of the machine. Next day heats up again, sags a bit more. @tgm022861 you still in here?

6

Yeah, I am still lurking in the shadows. All this talk of Lowriders and desert heat is bringing back fond memories. And some not so fond memories as well…

7

Always happy to explore :smiley:

My strut plates are hardboard - I had it on hand and and my old MPCNC was able to handle it (My old MPCNC was really oversized but I mostly used it for cutting foam board so the lack of ridgidity wasn’t much of an issue…cutting stronger materials though very much was an issue and ply was pushing it’s limit so the hardboard was the best option at the time.)

The PLA was actually a mix from a couple of sources - The core and strut plate braces were in a reddish brown I had originally built to print a hovalin for my late wife before realizing the neck wouldn’t fit on my printer. Most of the rest was brown green and red from Hatchbox. I tried to focus on using the atomic filament on any larger more critical parts and the hatchbox on smaller less critical spots.

No noticeable plastic deformation - was one of the first things I looked for and have been watching for.

I’m in Yuma - south of CA and east of Mexico :smiley: It’s HOT here. Monday when I came home my car was showing 120f ambient and my shaded back patio thermometer was 113. And that was after the hottest part of the day. My garage seems to top out around 110f thankfully. The machine is against the east wall which stays the coolest - the west wall is big and gets hit hard by the sun all afternoon. One of the things I dislike about the house is that the water main comes up through that wall and just bakes all afternoon. When I get home I have to let the water run for about 10 minutes (thanks to a new lower flow faucet) before I can even put my hands in it - this is my cold water shortly after turning it on:

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It’s actually cooler to run my hot water sometimes!

And yes - no white parts on my LR4 - the zen is all white but the LR4 doesn’t have any.

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The orange router clamps are PETG as is the dust shoe. The ligher brown of the core and the braces is the really nice Atomic filament. The darker brown of the YZ’s is I believe Hatchbox…the Dark green is Atomic, the red is all hatchbox I’m pretty sure.

I’ve also kept it on blocks when not using it so the weight is supported and it’s less likely to have anything deform.

When I first started 3D printing I actually did some tests on various brands of PLA to see how they’d hold up in our heat. I purposefully left a couple of prints in my car and was pretty shocked by the results. I found that as expected they more or less turned to putty sitting in a vehicle on a hot Yuma summer day. But…if it didn’t touch them - most didn’t actually deform (unless they were a shape that could sag where something wasn’t supported) one of them was a small box and a version sitting with the opening up didn’t really deform while a version with the opening down the bottom sagged. That was just the first day though.

What really surprised me was what happened the second day.

The second day even in the heat of the day they felt almost as stiff as they did when cool. I wasn’t able to press my finger into them like I could on that first day. I ended up concluding that I basically annealed them that first day in the heat and they had recrystallized into a stronger form afterwards.

My gut instinct was that it would likely be plastic deformation - but most of the spots I’m finding loose just don’t seem to back that up. Like the strut plate screws and the Beam to YZ bolts - The bolts are still snug in the plastic parts - no apparent sagging or elongation in the holes. But the bolts are just spinning in there really loose. I’m pretty sure I had them snug when I first assembled it…but maybe it’s been loose all along and I just hadn’t noticed.

I did tend to err on the side of snug but not too snug since when I built my first MPCNC I broke some parts over tightening bolts. But I’m also pretty sure I hadn’t left anything actually loose like it is now. Though I do see in the instructions Ryan says “Snug…don’t crush. It is very easy to leave them a bit light and check them again later.” so maybe I just took that advice a little too far :smiley:

8

To be fair I wouldn’t say it happened all at once.

I was chasing cut quality issues the last half dozen or so times I used it and starting to get frustrated. Running the same gcode twice and getting different results was really discouraging as nothing was obviously off. But now I’m thinking maybe things had been too loose and just got worse with some use and I didn’t notice in my frustration.

Walking away for a few months and coming back the looseness was obvious. In the heat of the moment upset at another cut that didn’t go the way I expected I could see myself missing it.

I’ve been hoping to cut a new case for my modular synth and it’s going to have to be accurate since there are mounting holes that need to match some 3D printed parts fairly closely. So I was cutting a lot of little boxes as tests - but one box would come out great - then the next all the cuts would be slanted in different directions like the router was crooked in a different direction on each axis…but when I’d try to tram it things would look good. So it makes sense that if things were loose it would be shifting around on me.

The first few times I had issues it was the core idlers needing adjusting as it wore in. What I was seeing was similar - but the core was snug on the rails so I was confused where else it could be coming from. I think the beam to plate connections being loose has been the big problem and I just didn’t find it until I gave things a bit different of a shake this time to look for looseness.

At some point I’ll probably reprint in PETG or splurge on PETGCF - but given how long it took me to finally upgrade my MPCNC it’s highly likely I’ll just keep it going as is until something actually breaks :smiley:

9

The recommended high temp filament is PET-CF. Different stuff from PETG-CF, and much more suitable for the machine. It’s not only higher temp compatible, it’s more rigid than PLA.

Fascinating. I wonder how hot the car interior got on the first day. 120F ambient should see above 150F interior temps. Nasty. Now you have me wanting to do some experiments with annealing PLA.

10

It was about 10 years ago so I don’t remember the specifics now. But it was July and temps were up there.

I’ve baked “car cookies” several times just setting the baking sheet on my dash in the morning and enjoyed them by lunch with my co-workers :smiley: They don’t get as brown as in a real oven but they definitely bake. Unfortunately the smell doen’t last more than an hour or two after :grin:

I’ve played with annealing PLA a few times and it does seem to have potential - the big issue is preventing deformation during the process. I think it CNC Kitchen did some experiments with putting prints in sand or salt while annealing them - and it mostly worked but the sand got embedded in the prints in the process.

A few of the pieces I had tested were off the original MPCNC - I think some of the corner tube clamp pieces IIRC. They were printed with enough walls and were dense enough that they didn’t really deform - even though on the first day I was able to push my finger into one them like really stiff silly putty. But as long as they just sat there with no pressure on them they held their shape and the next day even the one I left a thumbprint in I couldn’t deform any further.

Far from scientific I know…but it was still a fun little experiment.

And noted that PET-CF is the recommendation not PETG-CF :+1: