Screwless Heart Gears

by emmett, published

Screwless Heart Gears by emmett Oct 5, 2011

Verified Files


UPDATE: There is a new version of this design which is more reliable to print and easier to assemble. I highly recommend you use it instead: thingiverse.com/thing:243278
At last, here is the much-requested 100% printable heart gears. No more ugly bolt holes! This was designed along the same lines as the screwless cube gears: thingiverse.com/thing:10483, and in fact uses the exact same center block (though the pins are slightly shorter).

UPDATE: If you lack a 3D printer, you can now buy these from CarryTheWhat at etsy.com/shop/CarryTheWhat.

The size has been increased a bit from the previous version to accommodate the printed pins, so it now measures 100mm across when assembled. Since everything is now printable, it should be easy to scale this design up or down as you see fit. At this size it took me ~6 hours of printing time on my TOM.

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I am having the same issue. Anyone have an idea on how to print? I am using a bukobot v.2.

I printed this off on my UP! 3D Printer (2 years old). I did it on the fine print setting (.2) and everything came out perfect. No issues with the pins or assembling the pieces. They all fit together perfect and move great. This was a great Valentines Day gift. Thank you for making it Emmet!

Slic3r complained a lot about the dirty models, but they printed out OK. The pins were too long for me and I had to reprint them scaled down to shorter length(?)

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Print the parts list. The separate files for gears 1, 3, 5, and 7 are just there in case you have a problem with the four gear plate, or if you want them in separate colors. Use multiply to print four of the pin pairs at once.

Plug the short pins into the holes on the small faces of the center block; plug the long pins into the large faces. Slide each gear onto its corresponding pin. I like to start at the top, because it's more obvious how the gears align with each other when you work your way down.

It's always difficult to calibrate a printer to make perfectly fitting bushings, but the good news is if your heart comes out too tight to turn nicely or so loose it's wobbly, all you have to do is make new pins. You can either regenerate them with different parameters from the scad file, or you can just take the existing pin file and stretch it as required in the various axes. This means the big prints won't be ruined by a miscalibration.


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Cammiegrl on Feb 14, 2014 said:

I printed this off on my UP! 3D Printer (2 years old). I did it on the fine print setting (.2) and everything came out perfect. No issues with the pins or assembling the pieces. They all fit together perfect and move great. This was a great Valentines Day gift. Thank you for making it Emmet!

luotinen on Dec 27, 2013 said:

Slic3r complained a lot about the dirty models, but they printed out OK. The pins were too long for me and I had to reprint them scaled down to shorter length(?)

plastkort on Nov 10, 2013 said:

Printed with blue glow PLA but the pins does not seem to fit?, i need to make them slightly smaller ?

epall on Sep 10, 2013 said:

Slic3r is telling me "Warning: The input file contains a hole near edge 94.722260,100.376305,28.111151-94.265778,99.876762,28.801149 (not manifold). You might want to repair it and retry, or to check the resulting G-code before printing anyway." when trying to slice heartcenter.stl, and it comes out with most of the holes pretty well broken. Am I doing something wrong here?

gdahilig on Mar 21, 2014 said:

I am having the same issue. Anyone have an idea on how to print? I am using a bukobot v.2.

ajr1982 on May 8, 2013 said:

Hi. Do the gears require supports if printing with a makerbot replicator 2? Thanks.

holmser on Oct 26, 2013 said:

No it does not.

lookwhatjoeysmaking on Apr 17, 2013 said:

how do you alter the code for a difrent model

emmett on Apr 17, 2013 said:

Learn OpenSCAD, read my .scad file, replace heart.stl with your different model, fix any resulting problems.

lxman on Mar 29, 2013 said:

For those using Rep2, I used whpthomas' pins in his version of this for PLA material http://www.thingiverse.com/thi...

They fit fine.

CoerciveUtopian on Feb 19, 2013 said:

Great model. Very big though. I was happy shrinking it to 50% in x-y-z. The center block gave an "unclosed contours" error but printed just fine.

info2 on Feb 15, 2013 said:

I did not have such a heard time, but required a pliers to put in the pins. This is awesome!

cassetti on Feb 8, 2013 said:

I'm having a hell of a time putting it together. Even after downloading the old version complete STL to see how it fits together, the top piece still feels 'off' to me - seems to hang too high up on the one side. Prints came out perfectly on makerbot replicator. I had it together and it spun freely, but it just didn't seem to take a perfect heart shape like in the photos...

CoerciveUtopian on Feb 19, 2013 said:

The top piece is symmetric across the top bumps of the heart. I had this problem too but I noticed that one end has 1 gear and the other has two. Try rotating it 180 degrees and see if that fits better.

jrdetoro on Feb 15, 2013 said:

I have the same problem :(

notwebsafe on Jan 5, 2013 said:

Very cool. I found the original pins too large to fit; the pins from http://www.thingiverse.com/thi... fit better but were too loose. I found that scaling those pins 90% in x only (using netfabb) was perfect.

GreatScottTechnology on Dec 28, 2012 said:

Only way to get those pins in was to lube them up, but boy once I did it was smooth sailing

Dynamic on Jan 26, 2013 said:

using what ?

DanielJABailey on Dec 27, 2012 said:

I am having trouble with the scad file. I have downloaded the latest version of openscad, I have the heart.stl file, the pins.scad file and the involute_gears.scad file. Yet it still crashes every time I try to run it.

DanielJABailey on Dec 25, 2012 said:

This is awesome, I'm printing one for a friend, I have the hub, the pins and two of the gears printed so far, the third gear is on its way. My printer isn't fantastic but with some careful filing and reaming the parts fit together like a jigsaw puzzle.

casentim on Dec 23, 2012 said:

Had a little trouble printing the pointy edges of the gears because of curling. Printing at 180 C with just two outlines in sequence; loops-infill-perimeter worked out pretty good. This way the fill and outline get to cool before being fused together by the loops.

The pins fit perfectly. Everything snaps right in. Just squeezed them together a bit before inserting to make them more flexible.

Printed in galaxy blue and mother of pearl. Very happy with the results!

lazerusrm on Dec 14, 2012 said:

Printed pins are almost a waste. ugh all of that and the gears just pop out / dont fit right. i've printed 6 different sets of pins trying to get something that works. why arent the pins round? or roundish? It looks cool, but thats all you can do is look at it

mortinus on Dec 22, 2012 said:

Hi lazerusrm! I'd be glad to help you troubleshoot your printer! Hit me up and I'm sure we can your printer tuned. I've been working with 3D printers professionally for about 2 years now.

emmett on Dec 14, 2012 said:

 The pins are round, with flats sides just large enough to make them stick to the platform so they'll print. Many people have printed these and they've worked, so have you checked your printer? Sometimes a loose belt or something causes problems.

sailwings on Dec 7, 2012 said:

Made one yesterday for my wife's birthday!  All parts printed out okay, but it was very difficult to insert the pins (requiring a lot of force) - is it normal?  I finally had to sand them down a little bit to put them in. 

emmett on Dec 7, 2012 said:

Yeah, the pins were always a pain. I finally just updated tbuser's pin library; I should probably update these files using the V3 pins one of these days...

on Sep 20, 2012 said:

WOW!  We made Popular Science.  All credit goes to Emmett for the heart design, I just made the holder, but, 


njkl44 on Aug 5, 2012 said:

So I was going to start assembling this and there is really no way that the pins are going to fit into the holes of any part. Also even if they did how do I know the top of the center part to put the top of the heart on?

HappyDemon527 on Oct 6, 2012 said:

Hey, I had the same thing and this might be too late but i was trying to compile the scad file with openscad and it kept crashing, sooo... i remade the stl with the dimensions I needed you can download the stl here. It worked for me and i hope it works for everyone out there too. http://www.thingiverse.com/thi...

Mortimer on Aug 5, 2012 said:

I keep getting the tips of the gear teeth curling up when it's printing. Eventually they curl up and in enough that there's no material for the next layer to hold on to and it starts drooping over the edge. I've tried varying the extruder temperature, print speed, layer height, and extruder steps per mm. Nothing I've tried has shown any significant difference one way or the other. What am I missing here?

apexio on Oct 9, 2012 said:

25 aborted attempts later: I believe the problem is there's not enough time for each layer to cool before the extruder comes back for another pass, causing hot layers to stick together and pull up.  My solution is to print at least two parts at a time, on each side of the build table.  This gives each layer ~20 seconds of extra cooling time.

apexio on Oct 9, 2012 said:

 Exact same problem... I've tried to print gear 1 about 10 times now.  The first 1mm is fine, after that the tips curl up and it all goes to hell.

njkl44 on Aug 5, 2012 said:

yeah same here but i just had to push them down with my finger and it came out alright

mmmlinux on Jun 9, 2012 said:

i was trying to print this, but i ran in to a problem of slic3r complaining about the center piece. i ran it through netfabb, and it stopped complaining but it didnt print correctly. see attached image.

PrototypeAsia on Jul 13, 2012 said:

I'm also getting the same problem, thanks for the new part. This one is currently printing and so far no issues to report.

Salted on Jun 10, 2012 said:

Its a problem with the geometry, too many duplicate vertices. I've fixed it and test printed with Slic3r 0.8.2. You can find the fixed center piece here.


emmett on Jun 9, 2012 said:

Well, perhaps you've found a bug in Slic3r. I use skeinforge, and it has plenty of bugs too, but it usually does okay with this shape.

CrazyJaw on May 1, 2012 said:

Printed a full version, and is loved by every one ive shown it to. My much mocked printer is finally getting some cred thanks to this guy.

I would love to scale this down to a roughly keychain sized version, print a bunch and give them out to everyone (burning man gifts, cuties at a bar, etc). Would it be feasible to just use the simple scaling function in replicatorg, or would some openscad trickery be better?

emmett on May 1, 2012 said:

Thanks, always glad to help a fellow printer get some cred. It looks like someone had a similar idea: http://www.thingiverse.com/thi.... It sounds like making it keychain sized is possible, but may require some tweaking; they have a discussion going.

Anonymous on Apr 6, 2012 said:

Printed most of this with Helsinki Hacklab's printer "Torsti" during Reaktori youth event and finished it off at the lab. Great conversation piece and printer demo :)

catzpaw164 on Apr 5, 2012 said:

I just printed and assembled this...it is AWESOME ! !

michelefaini on Mar 30, 2012 said:

I did it for one of my friends and we used it in this music video!


emmett on Mar 30, 2012 said:

That's awesome, thanks for sharing!

shadowjig on Mar 14, 2012 said:

Whenever I open the scad file it crashes OpenSCAD. Has anyone else had the same experience?

emmett on Mar 14, 2012 said:

Hmm, does it crash when you open the file, compile or render? Do you have all the libraries and external STLs it calls? It takes a very long time to render, so I recommend only compiling at first. Just because it hangs on render for ten minutes doesn't necessarily mean it's crashed.

wcraigtrader on Feb 22, 2012 said:

I printed this for my wife for Hallmark Day, and she loved it. Thanks for sharing this with the community.

toybuilder on Feb 15, 2012 said:

This is neat! I wanted to get it done for V-day for my wife, but my printer's not done with its shakedowns, so I have only been able to print 5, 7, and then with more futzing 1, and 3. The overhanging plus the curling at the tips on gear 2 is my next challenge!

I've been working on this for most evenings the past week, and I finally had to tell my wife that I couldn't get this present done in time -- but I showed her this Thingiverse page, and she thought it was the coolest thing!

Looking forward to completing this one!

MangoT21 on Feb 14, 2012 said:

Maybe someone smarter than I can create some sort of way for the rest of us to input ANY model into something and get screwless pieces out :)

THAT would be awesome!

emmett on Feb 14, 2012 said:

Actually, the OpenSCAD file is designed with a base module that you put whatever shape you want in to make a different design. Several derivatives have already been made by different people: http://www.thingiverse.com/tag...

You may have to learn a little bit of OpenSCAD, but not too much for a relatively small change like this.

Svpernova09 on Feb 14, 2012 said:

Just wanted to share, one of our hackerspace members printed this and it came out looking good: http://www.midsouthmakers.org/...

UechiMike on Feb 12, 2012 said:

Having difficulty with Gear 6 - I'm getting some layer separation near the top (see picture below. Otherwise the gears print perfect. I tried 1 shell 0% infill and 2 shells 0% infill with similar results...actually the 1 shell setting came out better. Any suggestions? What should I be printing with for settings on these? Would going faster/slower help? I'm printing with a ToM with a HBP.

Glitch3DModels on Feb 13, 2012 said:

I had better results with 30% infill than 20%. On the 20% infill print I watched the top surface sag into the holes between the infill. 30% had a better finish but still not perfect. Needs more infill or more skins/shells to be perfect.

See link for more details.

UechiMike on Feb 12, 2012 said:

I have similar problems on Gear 8. Not sure what to do.

Charles on Jan 28, 2012 said:

Help!!!!! I printed all the pieces, but can't figure out how to put it together. To say that I'm not good at puzzles would be an understatement. Can someone point out which piece goes where? thanks!

Charles on Jan 28, 2012 said:

nevermind, finally figured it out! really nice model, thanks

Anonymous on Jan 27, 2012 said:

;) ;) ;) ;) ;) ;) :) ;)
amp;gt;:o =-X *DONT_KNOW* ;)

on Jan 23, 2012 said:

Hi - I created this thing, http://www.thingiverse.com/thi... as a stand for your item. I imported your Exploitable Heart shape as an STL into OpenSCAD, subtracted it from a tapered cylinder, and then added a small cutout for the bottom tip of the heart. I think it shows off the heart nicely, it's stable, and it self-aligns when you set the heart into it.

Davidmmeyers on Dec 28, 2011 said:

Hi Emmett. I guess I am a wannabe 3d printer. So fascinated by these gear box and heart. I am also a newly to thingiverse. Do you or others print for others? Sell your things? Is that done? I don't want to be asking inappropriate questions. Thanks for your help.

emmett on Dec 28, 2011 said:

Thanks, I don't have time to print these as a business, but lucky for you someone else does. I just added a link in the description where you can buy a copy.

Anonymous on Dec 10, 2011 said:

Great "Thing" ... am happily printing for my wife! One (or rather, two) small problems: when I try and slice the heart pins and heart centre, I get a "non-Manifold" error. Any ideas on how to fix?

Many thanks

Anonymous on Dec 12, 2011 said:

I got them fixed on iMaterialize's www.STLFIX.COM website. They now slice with Slic3r, and are printing as I type.

I will put the two "fixed" STLs on a website to make them available.

Anonymous on Nov 15, 2011 said:

hey are your cad files compatible with autodesk inverter?

emmett on Nov 15, 2011 said:

OpenSCAD is it's own language, so .scad files are just text files. The STLs should be importable to just about anything, but I'm not sure how easy it'll be to work with them in autodesk. I'd recommend trying OpenSCAD: it's pretty simple, free, and can do most things.

ajferna on Nov 7, 2011 said:

This is so beautiful! sadly i dont own a 3D computer, could i buy a plastic heart from you?

emmett on Nov 7, 2011 said:

Thank you, I've actually gotten this question a lot. I'm not really in the business of selling my designs. I have started thinking about putting some of my designs on Shapeways, http://www.shapeways.com/, so people like yourself could order them. Would that be interesting to you?

lars0 on Nov 3, 2011 said:

I cannot figure out how the heck to stop the gear teeth from curling up on me. :(

My build platform is cranked up to 130 and I have checked to make sure my heiight is good. Any advice?

Landru on Nov 4, 2011 said:

It's because the print is too warm. Print more than 1 at a time and it will help a lot.

emmett on Nov 4, 2011 said:

It is a tricky print. If it's peeling off the build platform, try changing the z to squish the first layer. If the warping is happening higher up, I find blowing the prints a little can bring them back into line. A lot of it is also calibration; low width / thickness tends to work better (~1.4).

MeHoo on Nov 2, 2011 said:

This was fun. I think my little gears show an issue with my .15 layer height profile.. the border/infill gaps. Not quite sure what to tweak for that.. hmm. Anyhoo, I didn't actually expect the gears to work, but they do. They work great. Thanks! :)

emmett on Nov 2, 2011 said:

Beautiful print! What gaps are you referring to?

on Oct 31, 2011 said:

Could you make some "heartless screw gears"? :-P

Max on Oct 25, 2011 said:

Wowza! Some time ago I printed "with screws" version of the heart gears, and so now I clearly need to print this one as well.

rhmorrison on Oct 6, 2011 said:

Where is the file "heart.stl"?

It is needed to compile the scad file.

emmett on Oct 6, 2011 said:

The heart shape is here: http://www.thingiverse.com/thi..., but you'll also need some other scad files. I believe everything you need to compile is listed in my scad file.

rhmorrison on Oct 6, 2011 said:


Now all we need is to get dougc314 to motorize it!! 8-)

Zh4x0r on Jan 24, 2012 said:

I beat him to the punch! http://www.thingiverse.com/thi...

tbuser on Oct 5, 2011 said:


Architect on Oct 5, 2011 said:

Dude! Sweet!

schmarty on Oct 5, 2011 said:


emmett on Oct 5, 2011 said:

In case you're having trouble visualizing what happens when you spin this around, here's an animation:

CarryTheWhat on Apr 5, 2012 said:

Hey! Do you mind if I use this GIF on my Etsy?