Printing coarse threads

Hi. I’m wondering if anyone here has any experience printing threaded bolts and holes. Using Fusion 360, I’ve created a few prints using their Thread Tool, but they always seem to bind up. I asked over at the Autodesk forum, and they suggested that FDM printers don’t have the tolerances to do it.

I kind of question that statement given how coarse a thread I’d accept. Has anyone done it?

You have to have a really well calibrated printer, but it is certanly possible. I’ve printed several myself. There are dozens printable models available for that.

Since ABS is malleable, I find that printed threads conforms too the mated metal nut or bolt. Never used an ABS nut and ABS bolt/screw… I suspect you’ll want a bit of play in the threads… maybe .25mm or a more generic1.5x(layer height).

In most projects, I’ll tap the hole or just use the screw to cut its own thread.

If you call Makerbot and request a sample of a print from one of their fdm machines they will send out a sample nut and bolt, so yes it s/ be do-able on a TAZ.

I have not used Fusion for threads but I know if you use the thread tool in Inventor it does not actually create the threads in the model. You just get a plain hole that seems to be the tap drill diameter. You can tap the hole after it prints. If you want to print the threads you have to create a helix and build the threads in the model. And yes you do have to allow for print O.D. usually being a bit bigger and I.D. being a bit smaller than design dia. I have not tried with smaller threads. I don’t think it could work that well on say 1/4-20 but like I said I have not tried it. It worked well for a 1" dia. bolt and nut I made just for fun. It also worked well on a 3/4-5 acme thread I used on a project.

Chuck

I made threads for a project, they were about 30mm in diameter and around 4 or 5 mm in pitch. I modeled the bolt, subtracted it from the nut, and scaled the nut up 4% and they worked well. Also, the threads did not come to a point, but rather a 1mm or so flat. hth

I haven’t made threads in either program mentioned, but I have gotten them to work with fine in freeCAD. As others have said, you need to account for side ooze from your nozzle – if you make a screw, then directly subtract that from a nut, the nut could be a nozzle diameter smaller, and the screw a nozzle diameter wider and they’ll never fit.

Here’s a picture of one I did. The tap is too narrow in the points, but I guess that wears off easily the first time it is screwed together because I never noticed a problem.
bolt.png
Anyway, I’m a little embarrassed by how messy my freeCAD file is looking at it now, but the screw does work on a lulzbot mini in both ABS and PLA. Totally not a model of perfection but rather, merely a demonstration of one method to get a screw: http://www.thingiverse.com/thing:948098

To make thread In freeCAD you make a sketch of your thread shape and sweep it on a helix (check the frenet box), then fill the thread with a cylinder. Be careful though, If the threads ever intersect as they travel the helix, the part won’t be usable for cuts – imagine the thread as a triangle, if the bases of triangles intersect, the part will be broken, so leave a gap between them either by reducing the length of the base, or increasing the pitch.