Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

12 Shot Rubber Band Gun

by Isaac_e93 May 4, 2017
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Printed this great model today with the single shot trigger. I'm suffering the same issue as others have (firing multiple bands in one go), I'm going to check if I can remedy this by upscaling the cog. Also I did file down the pins and noticed that my cog and trigger where a little lose on the pin. I made some little spacers to remedy this and center the cog and trigger.

I'll let you guys know how the upscale went.

can u share a link to the bolts you used because all the ones i find are different to the hexagon looking ones on the gun

I think the hex side is meant to hold the nut.

When will this rubber band gun be finished?

I've read all the comments about problems people have had, and I think I might be able to help those who make this in the future

  1. The cog is NOT symmetrical: the top of the teeth bend slightly. I tried it both ways, and found that I got very reliable triggering when the teeth slant forwards (i.e., makes it easier for the rubber band to slide off). When I had it the other way, I got lots of multiple triggers when using the single-shot tirgger.

  2. The nuts will not fit, not matter what. On two of the holes I tried enlarging the hole with an Xacto knife. Big mistake. The nuts eventually ended up down in the infill area. It still worked, but doesn't look professional. On the other two holes I put the nut in place, lightly heated the nut with a soldering iron, and then pushed it down into the plastic (I used PLA for my print). That worked great and is definitely the way to go.

  3. The trigger pin is too large for the trigger hole, but you most definitely DO want a snug fit. I spent 2-3 minutes sanding the pin to get it to just barely go in. I very briefly started to use a rat tail file on the trigger hole, but stopped almost immediately after I realized there is very little plastic around that hole, and I was going to make it weak. Sanding the fat part of the trigger pin is definitely the way to go.

  4. I had a huge amount of trouble printing the two body halves on my Ender-3. The problem is that, because the holes on both halves are recessed, and because you HAVE to enable supports in order to print the trigger guard, the printer has to also create supports for these tiny holes. Because there is so little plastic put down on these tiny support islands, getting the initial support layer for those sub-millimeter support to stick was next to impossible. It took about half a dozen attempts, but I finally found some Cura settings that let me make it work. The key settings were:

Initial layer height: 2x layer height (I printed 0.16 mm layer height, so the initial height was 0.32 mm).
Print thin walls: Checked (probably not needed, but I figured that these supports were so small, the slicer might skip them)
Retraction distance: 3mm (default is 5mm)
Retraction speeds (all three of them): 25 (default is 40)
Retraction extra prime amount: 0.064 (default is 0). I think this was the key setting. It causes over-extrusion for a moment after a travel
Minimum extrusion distance window: 3mm (default is 5mm) Cura help says to set this equal to Retraction Distance.
Support speed 60 mm/s (default is 120). This was to give the Ender more time to extrude when doing the little supports.
Initial layer speed: 20 mm/s (default is 30).
Initial layer travel speed: 40mm/s (default is 60)
Skirt/brim speed: 20mm/s (default is 30). I think this got change automatically. It doesn't really matter
Regular fan speed at height: 0.32 (default is 0.2). This is designed to keep those tiny islands sticking to the bed
Generate support: Checked (mandatory)

  1. I used 10% infill for the body. I would definitely recommend using more infill, probably 25% would be better. I used 100% infill for the pins, cog, and band holder, and I printed them in a second color.

I think there is something really wrong with this model. The nut holes are too small, the shafts to thick and the triggers have different hole sizes?!

The cog shaft does not fit into the hole of the cog. Do I have a wrong calibrated printer or is it because of the files?

nice print, but much to tight tolarences, can't get the axes to fit every thing has to be manualy filed and glued

Do you think instead of using screws and bolts you could use glue

Comments deleted.

Filing down the inhibitor worked for me. I went a little to far so it's fully automatic, but I'll print a trigger again and work it out. Yes my shafts were too thick to fit down the cog and trigger but I drilled them out a bit at a time till I got a snug fit. Great model. I'll be trying this out scaled down also but I'll mod the design to take the nuts and bolts I have to hand. Thanks dude. Great idea

Comments deleted.

Can you make it have a burst feature or auto ?

Can you add a magazine that holds rubber bands ?

What can cause the problem that with the single shot trigger, the gun fires all the rubber bands loaded to it?

i had same problem. I guess if scale the trigger longer may be able to stop at next shot.

Comments deleted.

Just like the other said, the 2 shafts are fitting in the gun case but are too thick to fit in the cog and the trigger. With a knife, sandpaper and some force I got the cog and cogshaft to fit. Still working on the other.

The auto trigger hole is super tiny. Nothing fits in there.

Great design, thanks

I do not recommend printing. The rubber gun, despite the properly selected trigger, shoots more rubber bands at a time. the rotor knob has a bad reverse step for charging.

Hey mate, All the mechanics of this gun will work as it's supposed to if it is printed right, there is a small amount of fine tuning and possibly fileing of components if they don't work correctly (this may happen if the printer didn't print components properly).

Alternatively, feel free to remix this design!


Looking good so far! But be sure to use supports! Lol I forgot about the trigger guard... haha :) will be printing again soon!

or do i have to print all the parts out

Judging by the fact that he says "the fully assembled one is an example and not printable," you'll have to print each piece.

will the gun thats printed fully assembled work

you know maybe you can scale it ?

I don't get it.

The 2 shafts are fitting in the gun case but are too thick to fit in the cog and the trigger.

do i have to drill the cog and the trigger with bigger holes?

Hey mate,

You can drill out the shaft to fit the cog and trigger for better fitment, and is recommended that you have a tight fit (or glue) the cog to its shaft and the trigger to its shaft so that the solid bodies rotate on the gun frame.

Isaac, this is a great design. Printed wonderfully, the kids love it. Thank you for sharing your work!

Thanks mate! I'm glad that you guys love it! :)

Could you tell me what pen you used? All my "Common" pens are too big.

I can't recommend a brand of pen but a general click out and click in pen's spring should do the trick. :)

I've successfully printed all details. But trigger guard doesn't look good (plz see attached). Did I miss something?

did you try printing with supports? it may help the stringing issue, otherwise I could only put this issue down to printer settings / incorrect g code conversion.

yep, actually this is my second print and i've never heard about support. now i know :) thank you for the tip and great model.
maybe you can add a note in summary about support, i'm not the first person who makes this fail.

Thanks mate, I certainly will! glad I could help.

Woohoo! I'm no. 2,000 to collect!
Thanks for the share Isaac_e93, congrats!

Thank You very much! I hope you enjoy the printed product!

I had to scale x and y up to 110% to get the mentioned m3 bolt and nut size. Printed on a cr-10.

Im glad it worked for you after sorting out the small issues :)

Is that a bag of chocolate coins in the background of the first picture?

You bet it is!! Haha

Because chocolate :-) I'm printing your design right now. Looking forward to shoot those bastards at work :-)

Nice design. I had to reduce it to 95% to fit my bed and then drill the screw holes a bit and heat the nuts to sink them in, but it mostly worked. The only issue I have is I can't load more than 6 shots with the single shot trigger. Don't know if it's the design or my resize that is causing the problem.

what is it doing when you try to add more rubber bands? are they slipping off or are the gears not responding properly?

The gear won't turn to allow more to be loaded. I'm going to try filing the trigger a bit when I get the chance and see if that helps.

are the rubber bands really tight? Im not too sure whats causing that, file the components down to make everything rotate around each other easily and it might help :)

i had to scale the trigger down to 99% to get a proper 1 shot trigger overall its a proper toy

Can this be printed at say 75% scale? the body is too large to fit on my print bed.

You need to slice whatever won't fit. I had to slice each frame section into thirds to get it to fit because my printer has low quality far up, but slice it in half and you should be fine.

i havnt tested scaling with it yet, but i dont see why not. :)

If printed in ABS the Cog and the single shot trigger should be printed in about 102% otherwise it doesn't stop after one shot

I printed in PLA and found I also had to scale the trigger up by 102% in order to get single shot, at 100% it would single shot one or 2 then auto the rest all in one trigger pull. There was no need to scale the cog, just the trigger.

Is the trigger and cog supposed to be tightly fit on the shafts (and the shafts rotate in the body), or the other way around?

I haven't fully assembled the gun yet, but the single shot trigger doesn't seem to interact correctly with the cog, the cog can't rotate past the inhibitor (no idea if that's the right word) pin on the trigger when the trigger is not depressed, so the cog basically can't rotate at all. I imagine I must be doing something wrong.

yes the trigger is supposed to be tightly fit or glued onto the shaft, and the shaft rotate on the body.

its a close fit to get the cog rotating properly, try file down the inhibitor until the cog can just rotate past it when the trigger is not pressed.