A Robot’s Favourite Pen

A test of various pens using a robot

Some people are very picky about their pens. Entire forums exist to discuss the topic of pen superiority. However, it comes down to a personal choice. Some people like gel while others prefer ballpoint.

[Jens] built a drawing robot that produces drawings like the one seen here. It uses several linkages connected to two stepper motors, which give fine control over the pen. With the robot working [Jens] set out to find the best pen for robotic drawing.

Seven pens were tested on the machine, each drawing the same pattern. [Jens] found that gel and rollerball pens work the best on the robot, and started examining the performance of each.

The pens all performed differently, but two winners were chosen to use in the machine. The Pentel Energel Deluxe RTX and the Pilot G-2 07 beat out the competition since they maintained good lines at high speeds.

If you’re looking to build a drawing robot, [Jens]’ research should help you pick the best pen for your application. For inspiration, a video of the robot in action is waiting after the break.

12 thoughts on “A Robot’s Favourite Pen

  1. I’ve made my own pens for my own Roland DXY-990 and the big DPX-3300 at the Bristol Hackspace. Original HP pens, even from sealed packs, have dried up, so I drill out the pen barrels and fit new pens in them. Therefore, I needed to find pens that not only could draw at high speed but also were thin enough to fit in the old HP pen barrels (about 9mm i.d.). I’ve had good results with Pilot V-Ball rollerball pens, and the similar Uni-Ball Eye.

    For a wider, bolder line, I’ve used the Staedtler Triplus felt-tip pens. They draw fast and have slim triangular barrels; the line is bold enough to show up well on video, which helps when I take the plotter to Maker Faires. Also, the Triplus is available as a highlighter pen (green and yellow), which is no larger diameter than the ordinary pens. This allows me to draw in UV-reactive ink (on paper without optical brighteners) and get a plot that glows under a UV torch.

      1. Years ago, I worked at a computer center, where we had a Calcomp drum plotter. We did some experimenting with alternatives to the high priced Calcomp pens. As I recall, there were two types: ball, which looked like shorty ballpoint refills and liquid ink, which looked like Rapidograph technical pens. I don’t remember the results of the tests, it seemed that the ink formula was looser than for regular pens, to improve the flow at high speeds. I do remembert hat we went through a heck of a lot of expensive pens….

      2. Yes, the pen plotter was a precursor to modern bit-mapped colour printers. But at the same time as plotters, we had dot-matrix, teletype, daisy-wheel and line-printers. They couldn’t do graphics, and they couldn’t do colour. For either of those types of output on paper, you needed a plotter. HP made several types, as did Calcomp, Gould, Graphtec, Roland and Versatec. My Roland DXY-990 is from about 1987, as is the big DPX-3300. I also have an HP 7550 of similar age. The Rolands are flat-bed and the HP is a “grit-wheel” type (it moves the paper as well as the pen).

    1. I rigged up a pen for my roland gx-24, Not sure of the maker because it was a refill and random donor barrel but what I do know is that it was gel based and was 0.20mm and worked really well.

  2. Yep, the Pentel Energel is a pretty badass pen when it comes to making smooth lines. Left-handed people, like myself, are big fans, and left-handed people are often described similarly to robots (logical machines), amirite?

  3. G2 at high speed working well doesn’t surprise me. It draws a thick line. It’s a little goopy, though, so probably less ideal for slower drawing. For ball point I really like the uni-ball jet stream, though about 30% of the pens I bought were duds, the other 70% are awesome.

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