Testing New Pens with a Pen Plotter

David HookCircuit Scribe News

Pages filled with conductive ink laid down with a pen plotter

We’re doing something fun here at Circuit Scribe Central: Testing new pen designs.

You might ask how in the world we’d test how long a pen will write and whether the quality of its line holds up after many pages. Being makerspace nerds, we looked around our office and our eyes alighted on a pen plotter. Perfect, we thought, we’ll get the pen-drawing robot to do our tests for us!

For the uninitiated a pen plotter holds a pen and draws designs you “print” by moving the pen in the X axis (left-and-right), and moving the paper in the Y axis (front-and-back). It can also lift the pen off the paper at will. (The amazing thing is that they usually have a cutting mode where you can insert an X-acto-like knife and cut out shapes, even circles and intricate lines. We’re just using pens, though, in our Silhouette SD plotter.)

Photo of a Pen Plotter

Pen plotting robot – go to work!

We fired up the pen plotter, created a document that is an entire sheet of horizontal lines, and hit “print.” The machine worked great.

Testing Line Length and Resistance

Since we’re comparing our existing conductive ink pens with a couple new pen designs, we wanted to test all of them together and compare. We used the paper our workbooks are printed on because we know exactly how much electrical resistance to expect with this paper.

We’re basically testing three things:

  1. How many pages will each pen write? Based on the length of the lines in our print file (which is 560 lines per page at 19.8 cm, or 7.8 inches, per horizontal line), we can tell how many meters each pen will draw before running out.
  2. How does the quality of the line hold up page after page?
  3. What is the conductivity of the ink with each pen? We see a typical resistance of 1 ohm per centimeter with our existing pen on regular paper, so how do the new designs hold up?

How Did Each Pen Write?

As you can see from the movie above, the pen plotter draws horizontal lines until a sheet is full of ink. We loaded up our paper and tried the existing Circuit Scribe pen. Since each page has 560 lines at 19.8 cm, one page is about 110 meters of ink. The regular pen wrote more than 300 meters.

Pages covered with Circuit Scribe conductive ink

Pages filled with Circuit Scribe ink.

We tried out our new circuit drawing pen designs. The ink flowed differently from the new ones. One of them filled five pages for more than 500 meters of conductive ink! It was also interesting to see how the first page printed by each pen looks completely silver, while the last couple of pages had much less ink coverage.

Once we had all the sheets drawn, we tested the electrical conductivity of the conductive silver ink pen with a very sensitive 4-point meter that tests ohms per square. (“Ohms per square what?” you ask? That’s a trickier question to answer than you’d think.)

It’s still early days for our pen-design experiments, but we’re happy with how the new pens performed, and we also liked the way the pen plotter let us do this experiment without getting Carpal Tunnel Syndrome by drawing hundreds of meters by hand.

Ohms per square 4 point meter

The ohms per square four point meter