My custom D-Bot
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@phaedrux Thanks for the tips! I've definitely learned some of those the hard way building a couple deltas. I have a nice stash of t-nuts ready to go. I'm holding off on the PC wheels for now, because I have some extra linear rails I might try to see if I can work into it. That's good to know about the Delrin wheels though. I never had that issue on a delta when I was using wheels, but then again, I could see how this would stress them a lot more than a delta. And I definitely picked up bunch of the metal L and T plates, and the 90 degree corner brackets. Parts should start trickling in this week. I'm still waiting on a part for my delta to get here. I held off on installing one of my old extruders because I thought it would get here faster. But I've been pretty busy too, so I still have a lot of parts to print lol.
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Ref the Delrin wheels, I've not seen any sign of wear after many hundreds, if not thousands, of hours of printing and I'm throwing about 2kg of mass on each gantry. We're they the mini wheels or standard?
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@deckingman They were mini V wheels. The edges would eventually leave some black dust on the v slot. Perhaps they were low quality or perhaps over tensioned, but I don't think so. When they were too tight they became stiff to push, I had them still gliding effortlessly. Maybe they didn't match the extrusion profile, but I find that hard to believe as they come from the same source. Who knows. It's not like they fell away to nothing, just had some visible wear.
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I've seen one or two reports from people who have had problems with the mini V wheels. Can't remember the exact nature of those problems but it could well be wear due to the smaller diameter? Or as you say, maybe something to do with not being able to get the correct pre-load. Anyway, for whatever reason, the "standard size" Delrin wheels have been fine for me and my machine.
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I've had Delrin mini V's on my small printer for the last 3 years without any issues thus far. And it has tons of printing hours on it.
I tried running the new harder clear wheels on my large printer but ended up switching that one to Delrin wheels now. The harder wheels transfer vibrations that were showing up in my prints. Also 2 of the harder wheels had chipped at some point during the many hours of printing. I probably got some plastic or who knows what on one of the tracks to cause the damaged wheels.
The Delrin wheels don't transfer the vibrations and aren't as fragile so I'll stick with them. I never tried the larger wheels.
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@timcurtis67 that's interesting you mention vibration transfer. I wonder if I'm not seeing some of that now. At low layer heights I seem to have quite a bit of micro ghosting happening at anything other than a crawl speed.
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@phaedrux said in My custom D-Bot:
@timcurtis67 that's interesting you mention vibration transfer. I wonder if I'm not seeing some of that now. At low layer heights I seem to have quite a bit of micro ghosting happening at anything other than a crawl speed.
If you have a set of the Delrin wheels it's worth trying them. It helped on my large printer.
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@timcurtis67 yeah I still have the set of delrin wheels. I'll have to do some detailed before and after.
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It'd be interesting to see a comparison between the mini V and the "standard" wheels too. That'd probably mean a major re-design though. I think the mini V wheels are about 15mm diameter and the "standard" or non-mini V are about 24mm diameter.
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@deckingman I believe I've seen some mods to use the full size wheels, but I don't have any larger wheels and don't think I'm willing to go that far to test. At that point I might as well go to linear rails.
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@phaedrux said in My custom D-Bot:
@deckingman I believe I've seen some mods to use the full size wheels, but I don't have any larger wheels and don't think I'm willing to go that far to test. At that point I might as well go to linear rails.
Yes they are not cheap when you add in spacers (eccentric and otherwise), bearings, bolts etc. I had a fit when I worked out how much I'd spent on the 40 wheels sets that my machine has! Oh and I wasn't suggesting you try the larger ones - I just meant that it would be interesting to see a comparison.
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I've flat spotted some Delrin wheels. Swapped all 20 to the polycarbonate 'tyres' when I bought a further eight to add a second set of z-axis guides to the front of the machine. Had no problems that I am aware of since.
This was on a core-xy using four wheel guides as per standard build instructions. I think I'd pinched one pair up too tight against the rail.
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That would certainly do it (having them too tight). I have to say that before I started printing my own gantry plates, I bought a couple of OpenBuilds ones and found that even with the eccentric spacers backed fully off, the wheels were too tight on the rails. I got around it by opening up the smaller hole in the gantry plate which gave me a bit more adjustment.
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I think I've isolated the source of my micro vibration patterns showing most visibly on lower layer heights. It's hard to get a good picture of it, but it looks almost like ringing patterns, except that it doesn't follow the same edge pattern, it's more distributed and random looking.
Normal ringing pattern:
Vibration ringing pattern:
I have been trying to use the formula provided by @dc42 here to eliminate the ringing. I was able to clear up the X axis, but wasn't able to remove it from the Y axis direction.
Then I started to hear a rather loud cracking sound. What's that sound?
In the video you'll hear what sounds like intermittent snapping plastic. When this started I stopped trying to fix the vibrations and started to find out where the awful sound was coming from. I couldn't see anything broken in the carriage. The wire loom wasn't the source (I took it off).
Then I disconnected the belts and moved the carriage by hand. Movement on the X axis was definitely not smooth. I tested rolling each wheel and discovered that the top wheel was very stiff and when I moved the carriage quickly I could reproduce the sound. I swapped out the top wheel with one of the spares and the sound went away and movement feels smooth again. The bearing of the wheel had exploded and leaked black lubricant
However, the Y axis still has some vibration and I think one or more of the polycarbonate wheel bearings are also failing. I bought a few extra expecting some failures, but didn't expect them this soon.
X before:
X After:
But the Y side always looked something like this:
I'm now torn over whether I should just go back to the delrin wheels and let them deteriorate or get something like the openbuilds delrin wheels. https://openbuildspartstore.com/delrin-mini-v-wheel-kit/ If only they weren't so expensive! 7USD per wheel. The polycarbonate wheels on ali express were 40 for 16$!! Get what you pay for though I suppose.
At least now I know the source of the problem and can fix it.
EDIT: Found a couple more bad bearings. At least it was only one per wheel so I was able to combine the good bearings and reinstall. Who knows how long they will last. Also surprised by the wear on the wheel. The failed wheels were all directly on the tensioner side. I suppose it's possible I had them over tensioned, but it's just an M3 screw finger tightened.
Now to see if the vibrations are gone in the print. The movement definitely feels smoother.
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Oooh, nasty. If it's any help, I've never had any probs like that with the genuine OpenBuilds ones (full size, not the mini). No bearing failures nor any signs of excessive wear. They are expensive though. I think I worked out that with two spaces (some eccentric and some plain) as well as shims, bearings nuts and bolts, they works out on average at about £9.00 a kit. My two X gantries each have 6 wheels (3 per rail but two rails) so that's 12 wheel kits. My Y gantries have 4 each and their are two pairs of Y gantries so that's another 16. Then I have 3 linear guides for the Z axis with 4 wheels per guide so that's another 12 kits making 40 kits in total. So over time, I've spent about £360 on wheels - more than a lot of people spend on a complete printer.
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@deckingman yeah you can definitely blow the bank at the openbuilds store but it does look like good quality kit.
I've replaced all the y axis wheels with delrin now and it's back to smooth. Almost half the wheels feel a little rough and some were very rough and no doubt on their way to the same loud failure.
Quite disappointed by this particular "upgrade". Too good to be true at that price obviously. At least I have the wheels and can replace the bearings. So not a total loss.
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Looks great. I have a heavily modified C-Bot (D-Bot wasn't around when I made it) and I really dig your z-axis leadscrew setup. Nicely done!
My stepper motor website:skysmotor.com
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Oh wow, just catching up. Those came with your PC wheels? Yikes. There are some on Amazon too, but I'm not sure how much better they'd be except probably easier to return if they're a mess, amazon pc wheels 20 pack. $3 and change per wheel might be worth checking out. I almost picked them up, but I'm still interested in the potential to use some of these guide rails I have laying around.
My kit was supposed to show up today, but I got off work today late today, and my wife decided she had somewhere else to be besides at home waiting to sign for my package(joking, of course)... so until tomorrow. I think just about everything else has shown up. I got my delta back up and running, so I'm starting to print parts tonight. I probably won't get to start actually building until this weekend though. -
@rosethia thanks. The z axis definitely took the longest to figure out. Pretty happy with it so far. One thing I might change is getting the idler tensioner plate milled out of metal. It can flex a bit as it is now. It was stiffer in PLA originally but the bolts had a tendency to migrate through and deform it. In PETG it's tougher but has more flex. I'm going to try ASA next. It that doesn't do it, polycarbonate.
