MakerBot Industries

As incredible as RustedRobot’s print of Syvwlch’s printable parametric clock is, a single still photograph just doesn’t do it justice. Two weeks ago there was no such thing as a 3D printed clock. Today you get to watch one in action. Sure, it’s powered by a drill and running a little fast… but this is progress! In the history of the world, there has probably never been a clock that has gone from concept to actuality and run through so many iterations so quickly. Syvwlch has been crunching through versions and derivatives of derivatives of this clock just about as quickly as OpenSCAD can render.

Syvwlch’s work on a printable clock has been one of the most exciting ongoing projects on Thingiverse.  He’s just upload what might be a final version of his work.  This version includes the escapement, pendulum, gears for the seconds, minutes, and hours, and a set of nested concentric gears to provide the corresponding second, minute, and hour movement.  And, let’s not forget he’s made this entire clock parametric in OpenSCAD – in case you need to print up a grandfather clock or a teeny-tiny watch.

As quickly as he’s been developing this project, it hasn’t been without it’s obstacles.  Syvwlch explained some of the benefits to designing such a complex mechanism in OpenSCAD:

There are none of the usual frustrations.  If you made a mistake a few steps back, it’s not a big deal.  I had the math on how to size the thing to fit inside a MakerBot completely wrong.  It took me two minutes to fix it.

As if designing a printable clock weren’t enough, Syvwlch has also set up his OpenSCAD file so that it will kick out STL’s for easy printing on just about any 3D printer AND so that it can show you an animated diagram of how the parts fit together and operate.  I can’t wait to start printing up these parts.

Clockwork Library & Printable Clock Script by syvwlch

Winner of the Pattywac Makerbot United Challenge for collaborative design: makerbot.com/blog/2011/05/16/pattywac-makerbot-united-challenge-winner/ Thank you team! :-) Video of the first ticking powered escapement mechanism:prototribe.net/vidplay/testjig2.html ___________WARNING_________ Several bugs have been fixed since this release, and the current tip-of-the-spear for development is a simplified 2-gear clock with only minutes and seconds. Current development version to be found on git hub here:github.com/syvwlch/Printable-Clock-Project Current version of the 8-Gear Clock (revision D):thingiverse.com/thing:8284 Current bleeding edge development version of the test jig:thingiverse.com/thing:8275 Current repository for the latest version of the clockwork library:thingiverse.com/thing:8155 Thanks to RustedRobot for his continued assistance debugging the clock! ___________WARNING_________ This is both a derivative of the printable clock PoC, and of my escapement library: thingiverse.com/thing:7822 . The involute gear profiles are from the MCAD library. (EDIT: The clock got a mention by Cory Doctorow on boing boing!boingboing.net/2011/04/23/model-files-for-a-wo.html ) I cleaned up the code so it would render faster, moved all the gear work into the library, and created a laidOutToPrint() module to facilitate creating the STLs of the individual parts. I included an optional print volume visualizer, so you can check every part doesn't exceed the printer's capabilities. The assembled() module is still fully animate-able, and I've added colors to help see if everything meshes properly. The clock itself now has clip-on hands, front & back frames, and most importantly, I switched to a different set of gear ratios (3.2, 3, 2.5 & 2.5) which allows for bigger shafts by keeping the ratios small. Assuming an 80x80x80mm printing volume, you now have a bit more than 12mm (almost half an inch!) available for the overall diameter of the shaft, the two sleeves that slide over it and the necessary clearances. I think this configuration is close to final, except for the escapement, which will need fine-tuning... but without re-printing the rest of the clock.

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Printable Clock, Parametric Proof of Concept by syvwlch

Syvwlch has been busy at work on his printable clock over the last week.  He’s produced SEVEN iterations of this design so far.  I’m a huge advocate for posting unfinished or even obsolete designs – the is a perfect example of the benefits.  At any point someone could have jumped in to help out with these designs, the formulas, or contributed code.

Following the evolution of his designs as been very educational for me.  I’ve struggled with how best to design a multi-part mechanical device.  Syvwlch clearly has the right idea – starting with the centermost component – the escapement mechanism – and building outwards upon it.

Printable Clock, Parametric Proof of Concept by syvwlch

Another proof of concept along the way to a WORKING printable clock. A working clock would, for example, have a case. :-) Aside from such petty concerns, this clock is complete, in that we have a power source (a drum to wind a string and weight), a whole gear train (5/3/2/2/5/3/2/2), a Graham escapement, a (token) pendulum and three hands mounted on concentric shafts to show the time. It is fully parametric, animate-able, and about as modular as I could make it within the current constraints of OpenSCAD (recursion would be nice for the eight gears in the gear train!). The code uses three different types of gear wheels, each able to support any level of nested concentric shafts if needed for support or to run clock hands: 1. A drum with an outer gear along one rim, 2. A pinion wheel with a gear supporting a smaller gear, 3. An escapement wheel supporting a smaller gear. It also automatically positions them relative to each other, ensures that they mesh properly and rotates them according to the correct gear ratios to support animation and to check the design. It uses the involute gear script from the MCAD library, and my own escapement library. I intend to move as much of the script into another library at some later date, and like in some of my previous scripts, to provide both the current assembled() module and a handy laidOutToPrint() module. Lastly, the modular nature of this PoC should allow for separate tweaking of the various components of the clock until they all work, without having to print an entire clock every time. (EDIT: fixed a bug, kindly pointed out by DaveD, and uploaded a fixed version of the OpenSCAD script, along with an exploded version of the STL and a JPEG of same.)

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Rubber-Band Escapement Test Jig by syvwlch

I’ve been really hoping someone would design a printable clock for a while now.  I need hope no longer!

Syvwlch has been long absent and long missed from Thingiverse.  After a sabbatical of about two years, he’s back and posting parts for a printable clock.  He’s making copious use of math, science, and OpenSCAD in the process.  I’d also point out that in the span of about 24 hours he went from just one component to three in three versions – and I can’t wait to see what’s next!  Click through to his offerings and leave a comment of encouragement or some feedback on how these parts printed for you.

Rubber-Band Escapement Test Jig - Maker Block Edition by syvwlch

Maker Block asked if there was a way to have fewer, larger teeth on the escapement wheel, and thanks to the power of parametric design in OpenSCAD, the answer was a resounding yes! With the larger teeth, this should be much easier to print. (EDIT: added a beefier, thicker version, slightly smaller so the pendulum fits inside the build platform. Duncha love parametric designs?)

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Broken gears are a sign of progress

I originally called this “Project RoboSpider,” but I’ve decided “Clockwork Spider” is significantly cooler.  Once I had printed the original “RoboSpider” parts, I noticed a few problems.  I’m hoping that someone else might be able to make use of the lessons I learn in designing and printing this multi-part mechanism.

1. Don’t make parts too thin. The parts I printed tended to be designed too thin.  If you are designing a multi-part mechanism, don’t skimp on plastic and make the parts unnecessarily thin or small.  My original gears and cogs were 2mm thick.  The problem was that it was easy enough for the teeth in one gear to simply miss the other thin gear.  My new design uses gears that are 5mm thick and they never miss one another.
2. Don’t use vertically printed snap parts. I printed all the parts using a vertical resolution of 0.25.  Dave Durant was right, this is basically a sweet spot for printing.  It’s quick enough that I’m not waiting forever for parts, the resolution is high enough that it looks pretty amazing, and layers close together enough delamination just isn’t an issue. ¹  All of the gears were designed with prongs so that they could be snap-fit to the chassis.  My first attempt at these failed because the prongs were so incredibly thin they couldn’t be printed.  My second attempt failed because the prongs just snapped off as they were flexed to go through the hole in the chassis.
3. Don’t reinvent the wheel… or gear.  The gears in my original designs were very very home brew, and it showed.  I just created a flat cylinder and extended a bunch of small cubes off the edge.  You can build a gear such as this easily in OpenSCAD, but using the “module” command makes it SOOoooooOOOOOooo much easier. ²   However, there was a lot of trial and error for me in getting the length, width, and space between the gear teeth properly proportioned.  For my second revision, I designed the gears over from scratch using MCAD, Greg Frost’s Involute Spur Gear Script, and cbiffle’s Spur Gear Fitter Script to create gears that meshed well.  Yes, it is more work to learn how to incorporate others’ works in your own, but you also get to benefit from their knowledge, experience, and expertise.  You’ll also save time by not having to print a bunch of crappy gears that don’t work. 
4. Ask for help.Thingiverse citizen Dna responded to my call for a rubber band powered motor with his Rubber Band Ratchet Engine.  My second revision benefited from Dna’s comments and input, as well as from getting to modify my designs to work with an alpha version of his rubber band engine.  And, last but not least, for creating this super sweet video of a variation on the clockwork spider in action:

What lessons do you have for others creating multi-part mechanisms?

1. Dave Durant: “You can go down to tweaking it by 0.25 if you want but any more than that is overkill, IMO. Other variables (ambient temperature, filament inconsistencies, how well X/Y rods are oiled, etc) can effect the print more than tweaking that much. If you can get it to 0.25, you’re going to be really happy with the prints.” [↩]
2. What’s that?  I haven’t covered modules in OpenSCAD?  Don’t worry – they’re easy and actually a lot of fun. [↩]