Pythagorean Plotter, 4-day Hacking Session

When some of my friends come to town to visit we go see the sites, which is fun. Others though come to town and we spend the entire visit on a hacking session broken up with beer drinking and bad movies. My friend Phil’s is in town for such a visit – and we are doing a 4-day hacking session building a wall plotter. We are calling the plotter Wilbur.

The unique part of our wall plotter is we are building it around industrial suction cups. Our goal is to be able to sneak into a friend’s office, or up to a window, and suction cup the plotter onto the white board or window. The goal is a stealth graffiti system for pranks on friends.

In preparation for Phil hitting town I ordered up some RAM double suction cup mounts, and then CAD modeled up a case coupling the mechanical elements to the stepper motor mounts.


I split the design into two parts so that would bolt together, and to the underlying RAM mount. The electronics are fairly simple, and esp8266 to handle WiFi and computing, and another stepper driver board for handing the motor. Since we are using a counterweighted design all we need to be able to do is control the direction and stepping of each motor, as well as provide pen up / down commands. From those simple pieces we should be able to build a system with very complex output.

The required action shot. Phil soldering. Which reminds me – he’s actually coding while I write this, so I better get back to it.


Finishing the extruder mechanical assembly…

I love long weekends. The rest of the parts I ordered finally showed up Friday, and I was able to finish assembly of the main extruder body. Well “finish” is a bit of a stretch. I’m going to tear it down to machine some of the metal parts, and then re-assemble it – but I’m happy with the design expect to be able to start installing the electronics.

Its nice to see things finally shaped up the way I designed them in SolidWorks.



Its weird, you can make and test incredibly complicated designs in CAD, and these days 3D printers even let you hold versions of the parts as you design them, but most times it is not until I do the physical assembly of the first prototypes that I really feel a sense of accomplishment. There is feeling of transformation from virtual to the real that takes place somewhere during assembly, and it is a transformation that I have been unable to satisfactorily quantify or capture.

As an HCI researcher that elusiveness is a problem I have been chewing on, trying to figure out how to attack for a while now. We are about to see an explosion of virtual and augmented reality technologies release for public consumption – and it seems like understanding what drives that magic transformation will be critical. It is however, not the problem I am working on currently – so back to work.

Hack for using a cheap vise…

A few years ago I got so frustrated picking things up all night, I made one of the most useful tools in my shop. I was using it last night and realized it might be a trick worth passing along.

The problem is that cheaper vises “ratchet” when trying to hold a work piece that does not span the run of the jaws. So when the sides of the vise leave parallel, force gets applied unevenly to the work piece, which means the vise does a horrible job of gripping the work piece.

The solution I used since I was a kid was fairly simple – just put a scrap piece of the same width as the work piece on the other side of the vise. Its fast and work works, but it is generally a pain since you keep one hand one the work piece when loading and unloading the vise, and use the other to work the vise, which means the spacer usually falls through the vise to the floor. When you are cutting a lot of pieces, especially small ones, this means you keep having to pick things up off the floor.


After an evening of repeatedly picking the spacer up off the floor, I routed a small channel in a piece of scrap and glued another piece onto it to act as a lip. This prevents the spacer from falling through the jaws of the vise when loading and unloading the work piece. I did it without thinking as a quick hack, and inadvertently created a tool I use all the time. You only need to make one for each width you commonly use.


This trick makes tasks like cutting a bunch of pins massively faster.

How to build a boat….

I hadn’t seen this quote before and it resonated with me:

“When you want to build a ship, do not begin by gathering wood, cutting boards, and distributing work, but rather awaken within men the desire for the vast and endless sea.”
Antoine de Saint Exupéry