peteGSX

Wow looks like a lot of effort went into that! I'm just starting out at the moment and have only got a very basic layout on my bench just to get DCC sorted and to test my narrow gauge conversion efforts. I'm also designing some narrow gauge stuff based on what we run locally here in my home town of Brisbane in Australia. Here's a couple of happy snaps of the prints with the 0.4mm nozzle. As you can see, not perfect, but no deformation top to bottom that I can see, but a bit too much stringing. I'll attempt to clean these up over the weekend and see how they look for functionality. Oh, and I moved to the square hole for the axle hub on the driven gears as suggested by Geert as I thought that was a great idea. Edit: Actually, a little deformation on closer inspection, but certainly much better than any previous efforts.

Yeah that certainly would work. My backup plan if I can't get this to work is to narrow the existing gears, but my hope was not to do that so I could always revert back to standard gauge if I needed to. I don't have a photo but I printed all the gears and axle hubs again last night with the 0.4mm nozzle with 0.12mm layer height, a faster speed of 50mm/s, and again the lower 50 degree bed temperature. I'm very surprised at the results! I don't see any obvious deformation of the teeth on either the top or bottom which is a fantastic result. They need a bit of post-processing with a knife as I got a reasonable amount of stringing, but that could also simply be because I stayed with the default 50mm/s speed rather than slowing it down. I'll have a closer look when I get some time tonight, but it looks far more promising than any of the 0.2mm nozzle prints which is very interesting.

That's very interesting to see! I'm certainly not expecting these to be as long lasting as brass gears or anything like that, and given I'm modeling in N scale I expect the freight to be relatively light. These gears are actually for converting an N scale locomotive to run on Z scale track for a narrow gauge railway. Interestingly enough I printed a second set on the weekend with my newly saved small gear profile containing all those settings I mentioned earlier, and while the large idler gear came out well, the two driven gears again showed some deformity with the side on the build plate being a slightly larger diameter. I can't find what I did with my original tests using the 0.4mm nozzle, but I don't recall noticing this issue with those, so I'm thinking I might try with the larger nozzle again and see if that makes any difference. As an aside, I've contemplated taking the easy path out and looking for somewhere to buy small gears, but there's nowhere locally here I can find in Australia that has them narrow enough, and the only alternative seems to be buying bulk lots of 50 to 200 from China, of which maybe 10% will be useful to me which is a bit wasteful (and shipping from China at the moment seems to be taking a couple of months!).

That's an interesting point actually. The larger idler gear will be fine as the teeth do all the work and the axle is just to spin on, but the smaller driven gears will be driving the wheels, so slippage would be a problem. I've yet to see how they turn out for longevity, but the gears they're replacing are plastic, and I've seen many comments during Google searches that PLA lasts surprisingly well in low stress gear applications. With what I'm doing, I'd consider it low stress, but time will tell.

Ah yeah that makes good sense! I did end up getting a set of gears I'm very happy with after all that, and my final settings are what I posted above but with the minimum layer time extended to 40 seconds. The other thing I ended up changing was the bed temperature, which I lowered from 60 degrees to 50 degrees. This seems to have solved the problem for me and while I'm not at the point of testing the gears for use yet, they certainly seem to mesh well and appear to be the right dimensions. To answer your elephant's foot query, no, I haven't seen that with any of my other prints. I revisit bed levelling often and am confident it's set correctly. Thanks for the tip!

Success! Well, I believe at least good enough for what I need anyway but not perfect. Using the Ultra Quality Cura profile (0.08mm layer height) and the 0.2mm nozzle I ended up making these modifications: Infill density 100% Infill pattern Concentric Print, initial layer, and skirt speed 20mm/s Minimum layer time 35 seconds Skirt for adhesion I think they're good enough to use, so I'll print the axle hubs next to glue in and see how that goes. The big things seemed to be a combination of the slow speed and extra cooling time. I suspected the initial layers were staying too hot, allowing the layers on top to compress them and spread them out instead of maintaining the correct shape. I still have no clue why printing with supports and the axle hub in place causes the opposite issue but as long as I can print the hubs separately and glue them in it's a non-issue for me. Thanks for the help!

Haha cheers! Scrolling through the settings in Cura makes my brain hurt, but it's always good to know another helpful one 😁 I'm doing the brim print now with the 10 layers at 10mm/s, concentric infill, etc. but will give brim distance a shot as well.

Yeah ok, makes sense. All the Googling I've done for 3D printed gears is larger stuff, and I knew I'd be pushing the friendship trying to get small gears printed, but I'll keep trying and persevere. The raft and slow print is a no-go, it just finished and still has the narrower base. Looks like a brim is the way to go, so I'll try that again tomorrow with the slower speed initial layers and see how that goes. If it means a bit of post-processing trimming pain I'll cope. The brim has most definitely given the best results so far and the ones I did earlier today are almost useable.

The straight on the bed print literally just finished, and while it's not as bad as it was, they're still bevelled. Printing with the brim is by far the best result so far, and yeah I agree I reckon trimming is going to be an issue. Sounds like a good idea on the more, slower layers. At the moment I've just set initial and print speed to 20mm/s, but I might do initial at 10 and do that for the first 10 layers and I might try a raft again instead of the brim. I'm feeling a little more hopeful now though, so thanks a heap!

Ok so today I grabbed a gear test print off Thingiverse, scaled it to 20% of it's original size, and no bevel/taper issues to be seen. Looking at the fact that those gears are on a reasonably thick bed, I tried a brim instead of the skirt or raft, and much better! I did slow the print speed to 20mm/s as well. I'm trying again now just straight on the bed with a skirt and no brim at 20mm/s, and I've also been able to make the gears a little wider which may or may not help.

One more go tonight. I kept the slicer settings as above but just added a raft. Reverted to the original behaviour of the inverted bevel I had first up, so no improvement there.

Hahaha if only my goal was to print bevel gears! 😁 I'll keep fiddling as well and see if anything makes an improvement. Your support comments did make sense to me, but I'm still pretty new to 3D printing and have been focused on larger items so far, so this finer printing is all new. Keen to learn and improve though!

Ok, the Meshmixer supports didn't work. The issue was just as bad (if not worse), and given they're tree supports, one gear actually didn't make it through the print and got knocked off so I guess they were a bit too weak (I reduced post and tip size). Anyway, I gave direct on the bed a try this evening after ditching the axle supports altogether and enlarging the centre hole so I could print them separately and glue them in. Unfortunately now it seems that the bottom side of the teeth is now printing larger than the top side teeth. This is with the 0.2mm nozzle, initial layer 1.12mm and layers set to 0.08mm. I set infill to 100% also. The bed was still hot when I took the photo so I haven't taken them off yet.

Yep, cool, that is definitely on my experimenting list for the long weekend! I've also got one ready to go using Meshmixer supports as well which I'll try this afternoon after work. I'm more than happy to do all the heavy lifting, after all this is my problem that needs solving 🙂

Ok, tried the extra support settings with 0.2mm nozzle and 0.1mm layers. The quality is awesome! Unfortunately, the problem persists despite the obvious extra support around the base of the gears. Off to work shortly but you've kicked my brain into gear here with some other potential ways to support those teeth, as well as trying without the hubs, flat on the bed. I'll keep experimenting and will report back.