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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 08/20/2019 :  09:06:04  Show Profile  Reply with Quote
Discovered we have a 3d printer at the office, and a pretty decent one (Prusa MK3).

First order of business was some jigs for the different sized tubes to be used for the upwrong I'm building for the wife. These ensure the tubes are centered, and the angles for the frame are correct.









Next, I realized I could probably go faster and get more precise and regular joins for some of my common tube joins if I made a mold to get that done.





Next up, an idler cog that will fit a 608 bearing. I'm not sure how well it'll do.



According to this site, (https://www.makeitfrom.com/compare/Acetal-Homopolymer-POM-H/Polylactic-Acid-PLA-Polylactide) many of the characteristics of PLA are fairly similar to POM-H (Delrin) so I think it may be OK. Replacements would be cheap and easy to acquire.

From there, the mind spins. I can make a nice mold/mandrel for doing a replacement head tube (or just the ends) for my NoCom to straighten up the front... Proper jigs for the 50mm main tubes of the recumbent projects would eliminate alignment problems...

Should I stop joining the tubes wet and make molds for those joins, bladder-press CF into them and make custom lugs instead? Would let me add a couple of cm to the frame lengths for the grownups (tube lengths limited by what ships from China, so a free couple CM from a lug = savings of an entire tube, or $25-$50).




--SpiderMonkey

carolina
human power supergeek

USA
1106 Posts

Posted - 08/20/2019 :  11:14:31  Show Profile  Visit carolina's Homepage  Reply with Quote
I wouldn’t know,,,, lugs are beautiful and sure deal. But hysol and gussets held my loweracer square tubes together.. l love the 2 bladder molds i made to make carbon tubes. I hope u make lugs so i can watch:)


I think you could make lug molds with red material if u use Mavcoat release agent. (6 coats per directions).

I wouldn’t know how to layup the carbon with the split mold. Well i do in my square tube bladder mold, should be same for my amateur stage of building. Make 1 lug mold at bb area.
—————
velosRus.com

Edited by - carolina on 08/22/2019 13:21:45
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 08/20/2019 :  11:20:16  Show Profile  Reply with Quote
I will probably run a test soon after I determine just how slippery this PLA plastic is. I don't think epoxy is going to adhere to it very well, which would be helpful. I may just line with thin packing tape as that's worked very well for me too.

Need to see just how thick my CF fabric ends up under bladder compression. I've got a good idea how my carbon fabric responds to being pressed between to slabs of aluminum when I make plate (my cheap, basket-weave-looking 12k fabric turns into "spread tow" and fills out all the gaps perfectly!) but I crank those clamps down pretty well. I won't get the same pressure with an old inner tube pressing outward, but then I probably will just use 3k twill. Measurements suggest it should be about 5 layers = 1mm. OD of current mold is 20mm, want to glue in 17s, so I'll try 7 layers and see how it goes.

Inner tube may be a bit rough for the interior bladder. Did someone here have a tutorial on making bladders from medical tubing + Schraders at one point, or am I hallucinating?

--SpiderMonkey

Edited by - SpiderMonkey on 08/20/2019 11:24:54
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carolina
human power supergeek

USA
1106 Posts

Posted - 08/20/2019 :  12:04:23  Show Profile  Visit carolina's Homepage  Reply with Quote
Inner tube or latex tube (use latex only tube/not rubber) with mclube release (google) on it in side lug split molds. Also u will definitely need Mavcoat (google) Epoxy can do some crazy stuff. But u can make many things with red stuff which is great way into the future. But imo i need the release chemistry.supplies.


Piercanusa.com is custom bladders. Be cool if they had unused lug bladders, u could ask. You may not need these but use latex inner tubes.

Gluing joints:

https://youtu.be/l9x2PjozPus

My bladder mold:

https://youtu.be/WG-dVH3p_7k
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velosRus.com

Edited by - carolina on 08/22/2019 13:30:00
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 08/22/2019 :  15:23:01  Show Profile  Reply with Quote
Annnnd, he discovers that 3-d printers are pretty temperamental and are further out of spec than his own lousy drill-press work, at least in some axes.

Works well for: creating jigs. Half-tubes laid out on x,y axes come in close to drawing.

Works awfully for: creating anything circular in x,y, with long axis along Z. The layers often sag and smear sideways though this can be remedied, counterintuitively, by decreasing resolution (increasing layer thickness) so that the hot head isn't so close to the last layer put down. But even if those layers don't smear, tubular shapes this way are usually > 0.25mm too large.

Printers also have a fun habit of somehow catching part way through the print shifting x or y axis by 0.5mm to 1mm, rendering the part not good enough even for me (which is a pretty lousy part).

I guess as with all tools, I need to learn what it can and can't do, and just use it however it can help.

--SpiderMonkey
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alevand
human power expert

USA
3541 Posts

Posted - 08/22/2019 :  15:28:46  Show Profile  Visit alevand's Homepage  Reply with Quote
PLA is too brittle for an idler, use nylon or bridge nylon. Follow instructions on removing water from the nylon filament, You'll get a much nicer part, or else it will have steam bubbles.

If you want thinner layers use a smaller nozzle.

C:
Tony Levand

Edited by - alevand on 08/22/2019 15:35:58
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carolina
human power supergeek

USA
1106 Posts

Posted - 08/23/2019 :  18:58:06  Show Profile  Visit carolina's Homepage  Reply with Quote
Non geek here: listen to what he says about 3D printing. Maybe you guys can explain it. He mentions using resin making the wheels.

https://youtu.be/a19QPG3MiQo
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velosRus.com
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 08/27/2019 :  14:40:42  Show Profile  Reply with Quote
Upped my design skills a little too by learning basics of Fusion 360. I get nicer, more precise plans than drawing by hand, and a lot faster. Quick export to 3d printer for mockup isn't bad either.

Upwrong dropouts nearly figured out. Just needed to move the m5 holes a bit further out to avoid bumping with fenders, racks, etc.





Even managed to get that drive side derailer hanger completely within the Shimano specs.

--SpiderMonkey

Edited by - SpiderMonkey on 08/27/2019 14:42:57
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strayray
Warren

USA
13 Posts

Posted - 08/27/2019 :  16:08:34  Show Profile  Reply with Quote
If you mean Z as the up direction, ovalized x-y circles on the XY axis is usually a sign of some slack in the motion system. Usually in slack belts, sometimes in other loose hardware. (The MK3 autocalibrates out-of-square XY, and X & Y steps/mm should have been correctly set at the factory.) You can check Prusa forums or their web site for instructions on adjustment, and other tips.

3D printing, and design for printing are definitely skills. The good news is many of the issues can be overcome. Bad news is that it takes learning and effort, and not all advice on the web is good.

quote:
Originally posted by SpiderMonkey

Works awfully for: creating anything circular in x,y, with long axis along Z.
--SpiderMonkey

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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 08/27/2019 :  17:17:59  Show Profile  Reply with Quote
The smearing/ovalization is random and only occurs at the highest resolutions, so I think it's the heating issue, and I don't know if that can be fixed without tweaking printhead moving settings or something else. When I print at 0.2mm resolution I get better results. I get the odd x-axis shift now and then when the machine skips and the next layers are all off by half a mm or so, but not too often.

Still, circles or holes printed vertically are rarely very close to spec. A 6mm hole will typically be 5.6mm or so. A 22mm bore printed vertically will be about 21.5mm. A 22mm bore printed horizontally (half a pipe concavity) will be much closer to that 22mm, within about 0.2mm or so.

The belts seem right. The machine is kept in good working order by one of my colleague's who's really into this stuff. I just don't think it's capable of doing finer work than that.

That's OK. I think the biggest hurdle is figuring out what it's good for, and using it appropriately.

The jigs should work well, and I should be able to make cutting patterns and other fixtures that will be a big help. Got an idea on my run for making a 3d printed "dish stick" that improves on the one I use now (3 overturned coffee mugs and a pile of coins). I'll make 3 blocks and a little central jack that will be more precise and simpler to use than the mugs and coins.

--SpiderMonkey
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strayray
Warren

USA
13 Posts

Posted - 08/28/2019 :  06:46:46  Show Profile  Reply with Quote
>A 6mm hole will typically be 5.6mm or so.

Hot filament wants to contract as it cools, so it tends to pull in a bit on inside curves like small holes. Reaming to size is good for accuracy. and it smooths out the bore.

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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 08/29/2019 :  09:17:52  Show Profile  Reply with Quote
I'm finding that, yup. I need a lesson on reaming to size. Drill bit push-through isn't so accurate sometimes. I'm working within the limitations of my knowledge and experience and skills, plus my tools, for now. I got some ideas on my run the other day (when they all come to me) for making much more precise jig fixtures as well, including some proper BB centering cones, a fixture to hold them, and better v-block fixtures that should align nice and square, and stay put better than the hand-"machined" aluminum ones I did prior.



My little dishing jackstand/feeler came out OK -- at least at test size. Those are stock printed M16 threads,2mm. It's a bit rough, but works as intendted for setting the distance/height.

I may have to work in an adjustment mechanism for my jig v-blocks using the same bits. As imprecise as it might be, it could be better than undoing the upright extrusion L-brackets and re-tightening every time I need to adjust the height a millimeter. Of course, a couple sheets of paper in the V-block works OK for that and is simplest.

--SpiderMonkey
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Balor
recumbent guru

Russia
750 Posts

Posted - 09/09/2019 :  07:52:26  Show Profile  Reply with Quote
Shouldn't slicers be smart enough to compensate for thermal expansion/shrinkage by now? Gotta find out.

P.S.
Ouch, this is actually much harder than I've thought, and would likely require a FEA package built-in into the slicer or model would have to be 'prewarped' on design stage according to a complex physical model.

It seems that 'print once, measure, compensate, print again' is the way to go for now...

Edited by - Balor on 09/09/2019 08:26:24
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 09/09/2019 :  20:25:16  Show Profile  Reply with Quote
Most of my actual fabrication now is being done (horrors!) on the DF I'm making my wife. (http://www.crazyguyonabike.com/doc/22203)

Printing improved jigs and molds and fixtures still for more upcoming recumbent work. I don't have too many more booms to make, but this will make tacking them SO MUCH EASIER.





I'll make the same for my handlebar joins. I've got one knocked out for the seat join that I need to make about 20x, but I'm going to make a new mold (smoother curves) and attempt to make that corner a single-piece lug. If I can get the ID near 17mm (my seat tube diameter) it will save me a bunch of time, and even some money.



I've got my dish stick (made from a piece of leftover square aluminum tube that I used to make a frame alignment tool a few months back) about done as well, with a few 3d printed bits.

--SpiderMonkey

Edited by - SpiderMonkey on 09/09/2019 20:35:44
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Balor
recumbent guru

Russia
750 Posts

Posted - 09/10/2019 :  13:08:04  Show Profile  Reply with Quote
That's great! Can you point out at some materials you've found particularly educational when it comes to 3D desing, or maybe even make a few hints yourself?
So far I find that tinkercad maxes out my ability to model in 3d, and using 3d printed jigs with carbon tubes will REALLY come in handy in my next project.
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Balor
recumbent guru

Russia
750 Posts

Posted - 09/10/2019 :  13:20:06  Show Profile  Reply with Quote
By the way, by using a 46mm id carbon tube (it has to be very smooth though... or you can print the mandrel and make it yourself using carbon sleeves) and using a interlock BB like this:
https://www.aliexpress.com/item/32899151818.html
You can get rid of aluminium insert in the frame (which is prone to delamination sometimes, due to thermal expansion coefficient mismatch), and save some weight.
I've heard that such a system indeed eliminates creaking and allow the cups to be pressed directly into carbon.
I'll try to do it myself.
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 09/10/2019 :  19:37:45  Show Profile  Reply with Quote
My 50mm tubes are supposed to be 46mm ID. They're pretty close. They're a lot closer than I could print and mold. But I'll stick with bonded in aluminum. I've got a lot of CF over aluminum in the stable, and I've never had a problem with any of it. (Fork ands, BB shells.) The one time I froze an aluminum mandrel inside a CF tube (and it had separator film) and swapped it back and forth between hot and ice water to try to get it to loosen up, it gave me plenty of confidence that CF over glass over knurled aluminum in epoxy isn't likely to loosen up in my use.

I've had problems with black CF just heating up so much it heats up the steel screws holding stuff and they loosen. I park black CF in the shade all the time as a result.

Listening to the Fancy Boys and their Incredible Creaking $6,000 Carbon Upwrongs on the trail means I'm not a fan of any press-fit BB systems, and even less so considering the crankset hoops I'd have to jump through to work with that product. I have more than half a dozen cranksets sitting around already for british threaded BB shells.

If I didn't maybe I'd experiment.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 09/10/2019 :  19:49:29  Show Profile  Reply with Quote
quote:
Originally posted by Balor

That's great! Can you point out at some materials you've found particularly educational when it comes to 3D desing, or maybe even make a few hints yourself?
So far I find that tinkercad maxes out my ability to model in 3d, and using 3d printed jigs with carbon tubes will REALLY come in handy in my next project.



I watched a couple of youtube videos by a guy named Lars about Fusion 360, then I just dove in and started making stuff. I use Fusion, export the components as STLs, slice them in Prusa slicer, and I print at 0.15 or 0.20mm layers.

You can insert McMaster-Carr parts right info fusion, so, for instance, when I needed to quick design a rotating piece of jig for my aluminum extrusion jig, I could just grab a couple of lengths of the extrusion I bought from them and work up my part right there on the same stock:



That might not be news to the engineers and machinists here, but it was a cool thing for me to get using. Those extrusion pieces are the ones I'm using, so I just built that rotating fixture (circled) and I'll print it in 2 pieces tomorrow, and it'll be pre-drilled to go together with M5s. I tap the PLA, making the pilot holes 4.25. It taps well and holds just fine for these purposes.

The jigs really are the best thing I've made. These made it simple (and it likely would have been impossible without them) to put together my wife's upwrong on the kitchen island with no swear words.





--SpiderMonkey

Edited by - SpiderMonkey on 09/10/2019 19:50:57
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 09/12/2019 :  07:45:15  Show Profile  Reply with Quote
Finished the disk stick made with a hunk of scrap aluminum tube and some 3-d printed parts.







--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 09/13/2019 :  20:46:50  Show Profile  Reply with Quote
Getting the hang of this 3d printing thing. I needed a little rotating v-block to help support the wife's upwrong frame for tacking on the chainstays and seatstays. This little 2-part design I made was quick and easy and works really well.



This BB shell holder is sturdy enough, but it's PITA to thread the rod through the cones, crews, shell, ends, etc. Next time (if I get ambitious and print another version) I'll slot the hole and print a block closure for it that just snugs down with an M5.



--SpiderMonkey

Edited by - SpiderMonkey on 09/13/2019 20:47:05
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strayray
Warren

USA
13 Posts

Posted - 09/17/2019 :  20:13:25  Show Profile  Reply with Quote
Looks like you're putting that 3D printer to great use!
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 09/19/2019 :  08:46:40  Show Profile  Reply with Quote
I have made dozens of designs for tooling, so it's been a good learning process. I'm going to try a couple bearing drifts next. Those are usually expensive, and I never have the ones I need. I think solid plastic would be plenty good for pressing into hubs, etc.

I've got some improved bike jig bits printing right now, lolz.

--SpiderMonkey
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Balor
recumbent guru

Russia
750 Posts

Posted - 10/07/2019 :  06:39:18  Show Profile  Reply with Quote
Next step in 3D printer assisted composite manufacturing :)
https://www.sciencedirect.com/science/article/pii/S2214860419302039

Seems extremely cool if you ask me. I don't think you even need to design any means to inflate the bladder - Just print it "airtight" using close tolerances to inner geometry (plus composite layers) and put it under vaccuum.
You will not get very high compression this way, but I don't think that is really important for a homebuild - still tons better than hand layup.
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 10/07/2019 :  06:54:53  Show Profile  Reply with Quote
Interesting. I'm getting closer to done with the wife's upright bike, and then back to the homebuilt recumbent(s). I need to test my inner lug molds. I bought a yard of unidirectional and a yard of 45-degree biaxial to go with some plain weave to make these.

I've got some 22mm x 19mm ID handlebar stock coming, with a 19mm mold for making join lugs to be one of the first tests.

The biggest savings for me will be if my lug mold works for seat making corners. I'd have to make up to a dozen hand joins per seat with a 2 x 45 degree turn, which is a PITA. Lugs from this will hopefully be faster, stronger, and a lot easier. I need to find a skinny inner tube, though. The diameters on those ends are 15mm OD.

I need to stop at REI. They've got a busy cycling shop and they've been happy to let me root through their box of popped inner tubes to find salvageable ones for this kind of thing. Re-use before recycle and all that.



--SpiderMonkey
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Balor
recumbent guru

Russia
750 Posts

Posted - 10/07/2019 :  07:18:07  Show Profile  Reply with Quote
That's where 3d printed bladders may come in handy. If you wrap it PE bags first - fully reusable as well. TPU filament is relatively expensive, but not by much.
You may leave the bladder to be cure inside the mould though, it should *really* add some vibration damping to the part (vibration damping properly of carbon is massively overblown if you ask me) at expense of some weight (and having to print more bladders).

Edited by - Balor on 10/07/2019 07:24:24
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SpiderMonkey
recumbent guru

USA
569 Posts

Posted - 10/08/2019 :  08:03:45  Show Profile  Reply with Quote
Wondering how to get a good valve seal on the end of one. Maybe just Gorilla Glue a valve in the end. Probably a better idea for a mold that doesn't get smaller at the ends.

For straight stuff, forgetting about air, thickening it up, and squeezing it at the ends with a couple washers on a long screw should do the trick to push it outward. (IRRC That's how Garrie H. does custom head-tubes, headset-ready.)

Prusa (the printer I've got access too) recommends shore 90-ish filament, so fairly stiff.

Didn't realize until you prodded me that one could print custom elastomers for seat mounting, etc. to try to take out a little road buzz. I'll have to tuck that away for the future.

--SpiderMonkey
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