The Circlon machine and the pen test.

After seeing a video by Robert Howsare, showing what he calleds ”a drawing apparatus” (built out of two turn tables and some wood), I was fascinated. The urge to find out what the design was capable of, was so great that I decided to build one for myself. Mine is built with two stepper motors instead of turn tables. Stepper motors are not as cool as turn tables, but they do give you the opportunity to control the speed and direction very precisely.

One thing that anyone who as ever built a drawing machine realizes, is that to get quality results you need a quality pen. There are millions of pens out there, but after a little trial and error I realized that rollerball pens or pens with gel ink are the best pen types for my machine. Both rollerball and gel ink pens use a water based ink that is less viscous then the oil based ink used in ballpoint pens. The Circlon machine sometimes move very fast, so the pen has to be able to release enough ink to make solid lines even at high speed. Rollerball and gel ink pens will release ink easier then the ballpoint, so they seem to be the best choice. To once and for all try to find the best pen for the Circlon machine, I bought seven pens from and did some testing.

The pens in the pen test are:

Pentel EnerGel

Pilot G-2 07_2

Pilot G-TEC-C 025 2

Pilot G-TEC-C4

Rotring Tikky Rollerpoint

uni-ball eye micro

uni-ball Vision Elite 2



The pens best suited for the drawing machine were the Pentel Energel Deluxe RTX and the Pilot G-2 07. These two pens were the only pens where the line was solid even at very high speeds. For normal hand writing I liked the uni-ball eye micro the best, however all the pens in the test (except the two pilot G-TEC-C models) were great for my style of had writing. Due to the very narrow tips of the G-TEC-C models, the pen has to be held at almost a right angle towards the paper to get good results, and that is not the way I like to write.

I have paid for all the pens used in the test my self and I have no affiliation with the

Pentel Energel Deluxe RTX

The Pentel Energel Deluxe RTX releases a lot of ink, and it does so very quickly. It was the best performer when it came to drawing a continuous line in the drawing machine, regardless of the speed. When left stationary in the drawing machine with the tip out, an ink blot formed around the tip. When it comes to handwriting, it might even be considered a bad ability that that the ink flows so easily. The lines are also a little to thick for my taste.

Pilot G-2 07

Before this pen test, the Pilot G-2 07 was my favorite pen. The one I had ran completely dry while demoing the Circlon machine at  Stockholm Mini Maker Faire. After the G-2 ran out, I switched to a Ballograf ballpoint pen and the results were quite disappointing with ink blotches and more mechanical ware on the paper compared to the gel ink Pilot G-2. The Pilot G-2 was the second best pen to use in the Circlon machine, it produced nice solid lines even at high speed. The only thing that made is slightly inferior to the Pentel Energel Deluxe RTX, was that the line thickness of the G-2 was not as consistent. After trying out all these pens, I now feel that the G-2 releases a little to much ink to be perfect in the machine.

Pilot G-TEC-C25

The Pilot G-TEC-C25 has the thinnest tip of all the pens in the test, and that becomes very evident when you try to write with it. It feels more like you are trying to engrave the paper than writing. You have to hold the tip almost perpendicular to the paper for it to release any ink at all, and that is not my style of writing. When it comes to the Circlon machine, I think it did slightly better then its thicker brother G-TEC-C4 but there are some gaps in the line with the C25 as well.

Pilot G-TEC-C4

While not as thin as the 0.13 mm tip of the C25, the Pilot G-TEC-C4s tip is still to fine for me to write with at a normal angle. This could be a good pen for drawing thin lines with a ruler, but it is not for writing. One use for it would be in the Circlon machine when running very dense patterns that tend to get messy with a thicker tip. However, the fine tip makes it very slow in releasing ink which makes it necessary to run at very slow speeds.

Rotring Tikky Rollerpoint

The Rotring Tikky Rollerpoint has a nice dark black ink which flows very easy. It’s a nice pen to write with but sometimes it feels like the ball at the tip gets a little stuck, this is a very minor thing but I did notice it. At slower speeds I think that this pen could work very well with the Criclon machine, but at high speeds it does not release enough ink to draw a continuous line.

uni-ball eye micro

The uni-ball eye micro is the pen I liked best for writing with. It has a nice black ink and releases enough ink to make nice smooth lines, but not to much to cause ink blots. The tip runs very smoothly against the paper. It was not the best choice to use with the Circlon-machine, but it did ok there as well.

uni-ball Vision Elite

The uni-ball Vision Elite has an ink that is tinted slightly towards grey rather then black. It feels nice to write with, but I preferred the uni-ball eye micro. It did not perform as well as the uni-ball eye micro in the Circlon machine, and there is plenty of gaps in the line where the pen has been moving fast.

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  5. Steve Nash

    Thank you for this article! Do you have any more details (pictures?) of the machine, and how you made it? Thanks!


  6. Alden Hart

    Nice article. Pardon me if I missed this, but can you post the gcode files(s) you used for this test? Perhaps they are not gcode. That is also a possibility. — Thanks



      Thank you, this machine does not use g-code. The pattern that is drawn is dependent on the speed of the motors and the radius of the shaft connected to the motor. The only input parameters are speeds for the motors and direction.



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