Smaller way to clamp 3d prints to shafts - Page 1
Forum section: electronics / general

author: Infraviolet
author_rank: Super Contributor
timestamp: September 08, 2024, 04:17:06 pm
content: I've found a really nice solution for mounting printed parts on to motor shafts (D shafts or even fully round shafts) in the 2mm diameter to 10mm diameter range. It takes torque pretty well, but is a bit bulky. Does anyone have any idea how I might do the same thing within a much smaller space?My present solution, see the image for a CAD diagram, takes about 18mm of length along the shaft, and needs a surrounding area of a diameter around 30mm. It will easily take 10s of kg*cm for a 6mm D shaft, and happily take (haven't tested to the limit for this one) many kg*cm for a round 3mm shaft.Grub screw based systems, where a nut sits in a hex shaped gap in the plastic and gets pushed outward against the plastic as you tighten a screw through them to clamp against the shaft, are a lot less rugged due to the deformation (and likely creep over time to) they cause to the plastic. My design's both-sided clamping action is much stronger.But have you any ideas how I could make it, or some other equivalently strong clamping design, smaller?Where 3mm round shafts are concerned, I'd really like something that could fit within that tiny gear, or the little conical region behind it, on the end of the one in the diagram. But that gear is only 1mm tooth-tip-to-tooth-tip, and has only 5.8mm diameter in the area within the dedendums. The gear is only 7mm in length, and the cone behind only gives an extra 4mm of length with a 19mm diameter.I can 3d print any shape from plastic. I've got all the nut and bolt sizes one can likely need, I could also order more 2d lasercut metal pieces (4mm or other thickneses) but would rather not as it was fairly costly to get a big batch of those I show in the design and am already using in all and any projects where I need to clamp a print to an axle shaft. I don't presently have any means available to make custom made metal pieces which are anything other than 2d lasercut type shapes.Thanks

author: Benta
author_rank: Super Contributor
timestamp: September 08, 2024, 08:57:46 pm
content: M5 bolts for a 3 mm shaft? Crikey!

author: langwadt
author_rank: Super Contributor
timestamp: September 08, 2024, 09:37:00 pm
content: Quote from: Benta on September 08, 2024, 08:57:46 pmand M2.5, and 4mm steel, none of it makes any sense

author: Smokey
author_rank: Super Contributor
timestamp: September 08, 2024, 09:43:41 pm
content: If you just 3D print the "metal shaft" then you won't need to clamp anything.. and you get more 3D printed parts, which is always better right? I guess you could 3D print all the screws and nuts and plates too. If you 3D print the screwdriver you can assemble your 3D prints with 3D prints!Seriously though, that thing getting clamped to the "metal shaft" looks like a nightmare to 3D print with all the holes and unsupported surfaces.

author: Infraviolet
author_rank: Super Contributor
timestamp: September 08, 2024, 10:42:09 pm
content: M5 and 4mm steel is overkill for a 3mm shaft, but I initially designed this for 6mm D as my sweet spot. The M2.5's do a less stressful job, they just give further connection between the steel plates, which are already clamping the shaft and partly touching the plastic, and the plastic. For a 6mm D shaft giving 10s of kg*cm this is not overkill, at those torque levels 1.5mm clamping plates will bend out of shape and plastic against a D shaft is utterly destroyed. But right now I've a 3mm round shaft to clamp, and this was the best thing I had to hand.A printed shaft isn't an option, the 3mm shaft is a motor shaft, I can't just replace that with a printed one. And a 3mm diameter 3d printed shaft, where Z is along the shaft's length, will easily break under even tiny torque loads.As holes and unsupported surfaces go, this prints without need for any support except around that flat area outside the cone near the gear. There are holes in it which print unsupported just find, the overhangs are sloped. It is not printed in the orientation shwon in the diagram, it is printed with the gear at the bottom and the clamping area at the top. It genuinely works pretty well, my trouble is making something as good but smaller, maybe not so necessary for the 6mm sweet spot but the size is excessive when dealing with small gears on 3mm shafts.

author: shabaz
author_rank: Frequent Contributor
timestamp: September 08, 2024, 11:10:57 pm
content: Hi,One technique that works very well, is to use aspur gear(either metal or plastic; they are available for shaft diameters down to 2 mm usually) and drill a few holes on the face of it (as if it were an arm on a hobby servo motor for instance), for screwing onto whatever you wish to attach. Then, the gear is attached to the shaft, and although there may be a grub screw, it's not essential; instead glue can be used; either epoxy glue, or for the nylon gears, there is a liquid (I forget the name) that is water-thin that is painted into the bore, left to dry, and then superglue is applied.This works great for circular and D-shaped shafts.If the aim is to connect shaft-to-shaft, then that link offers couplings too; sometimes good to decouple slightly with (say) silicone tube, or belt etc., rather than bolt the shaft to the load.

author: Benta
author_rank: Super Contributor
timestamp: September 08, 2024, 11:18:43 pm
content: The exit shafts from motors are generally short. so there are not that many options.The preferred ones (ranked in order of strength/size/performance) are:Shrink fit (steel only).Collet (steel or brass)Grub screw (preferably with a ground shaft flat)None of these are 3D-printable, I know.Personally, I'd design a shrink-fit "interface adapter" that fits your needs, and can be drilled out and turned down to the shaft diameter in question.That can then connect to any "3D-thingy."

author: Smokey
author_rank: Super Contributor
timestamp: September 08, 2024, 11:29:05 pm
content: Quote from: Infraviolet on September 08, 2024, 10:42:09 pmohh.. what if you 3D printed the motor too! You can 3D print the magnets and 3D print the coils! 3D printed bearings!heh. sorry. I'm done. I promise. (the design actually looks fine)

author: thm_w
author_rank: Super Contributor
timestamp: September 09, 2024, 08:21:05 pm
content: These and loctite:https://www.aliexpress.us/item/3256805347888672.htmlhttps://www.aliexpress.us/item/2251832671159446.htmlYou might have to file some flats on the shaft depending on torque.