Pen-plotting for the Hack a Day/Adafruit Trinket Contest


On October 21 the Hack a Day blog announced a contest where readers can slap the blog’s logo on something and win Trinkets that were supplied by Adafruit Industries. There were twenty 41 Trinkets to give away in this contest and preference was given to both the smallest and largest of the entries. The deadline was November 1st and being the busy college student that I was with not much time on my hands, I decided to just sit back and watch the entries roll in.

At around 9pm on October 31, with only three hours left in this contest, I suddenly got the urge to enter. Not a minute later I came up with a very simplistic idea for a universal pen plotter based off my 3D printer and the software I normally use with it.


I started by zip-tying a kluged pen to my RepRapPro Huxley because I didn’t have time to print a pen holder. This pen involved using the lower half of a Pilot G-2 and its ink cartridge as well as a rubber band and a small length of tape. The rubber band was used to give this ink cartridge a consistent pressure on the bed when the Z axis was at its lowest (i.e drawing). This gave me about 8mm of travel to act as a kind of buffer when working with an arbitrary Z offset.

From this I went over to the computer and started to figure out how I could get this thing to plot. I toyed around with RepRap pen-plotting some time ago, but never actually got something, well, plotted. Back then I was trying to use dedicated Python software but I never got very far with any of it.

Under this mild last-minute pressure I came up with the crazy simple idea where I’d take the SVG version of the HaD logo and extrude it in 3D slightly to give it an overall height of about 0.15mm. From there I’d take it to Slic3r under a new config and send the resulting g-code to my printer to watch the awesomeness unfold.

I was very pleased with the results and decided to see how small I could plot this logo. The smallest “dot” you saw above is roughly 0.47mm across; that’s pretty amazing when you consider how much ink bleeds. Reviewing the file this was plotted from, the two smallest logos were reduced to only a handful of polygons before they were sliced. The smallest of these two had very little left on the outer wrenches and therefore only a measly round dot of ink remains where the skull should be.

Nonetheless, I learned a lot from all this, and at 10pm, an hour after I started, I sent my entry to Hack a Day for review.  The results of the contest are still pending. I am happy to announce that I, along with 40 other great entries, won an Adafruit Trinket!

If this this project still intrigues you, here is some uncut video of one of the larger Hack a Day logo pen-plots being printed at a fairly high speed.

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