As you may have learned on our YouTube channel, Unsharpen is currently running a number of tests in order to find out how far a pen can write. So far we’ve been doing the test using a a number of different of SVG files which are paired with an Axidraw pen plotter — essentially a drawing robot — in order to scientifically test the distance a pen can write.
Of course pens can last a very long time — up to 6000 meters are claimed by refills like the Fisher Space Pen PR4 — so the testing can take a huge amount of time, even with a robot!
The SVG files (or G-code in some cases) used by the plotters are essentially complex patterns of lines. While pen plotters can yield incredibly cool works of art, we’ll be using them to maximize how much and how quickly a pen can draw in a given area. Our pen plotter is A4 size, but others get much larger, for instance A3, A2, or even A0.
Our original test file was a page of Lorem Ipsum text. This had the strength of being an accurate and understandable writing assignment to give the plotter. The motion of the pen largely simulated a real-life writing sample, which was our primary concern in the initial test. Unfortunately each page took about 75 minutes to write, and some pens would last for over 15 pages (or 50 in the case of a ballpoint). The pages are not contiguous, so a manual change would need to be made every page, limiting throughput to (at the very most) 16 pages per day.
Each page was about 250 feet (76 meters) of text, as measured by the writing distance of the pen. Because words are short and have multiple breaks, the pen would need to lift up and down thousands of times per document, yielding a writing output of just 3.33 feet/minute at a standard 50% writing speed and 75% pen up/down speed.
It was quickly clear that writing text was not a good way to test a pen’s writing distance because of the complexity of the patter. Instead we’ve moved the distance testing to drawing lines, which are much faster, can allow the plotter to move from 50% to 100% of it’s potential speed, and means the plotter spends almost no time with the pen raised (essentially wasted time while the plotter repositions the pen).
In order to improve the writing test file — the current test version’s name is Lines3.svg — I’m using vpype in order to optimize the file. This isn’t a set of words, but rather a tight grid of lines which an maximize the amount of ink used on each piece of paper.
All tests will be at Writing Speed 50%, Pen Up/Down Speed 75% unless otherwise noted.
Lines3
- Estimated print time: 2:11:43 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 512.253 m
- Total movement distance: 1024.149 m
- Feet/min: 3.85
Lines3 Linesort
“Sort lines to minimize the pen-up travel distance.”
- Estimated print time: 1:37:15 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
- Feet/min: 5.28
Lines3 Linesort Two-Opt
“Further optimization using the two-opt algorithm can be enabled using the –two-opt option”
- Estimated print time: 1:37:15 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
- Feet/min: 5.28
No effect from moving to the –two-opt algorithm.
Lines3 Line Merge
“Merge lines whose endings and starts overlap or are very close.”
- Estimated print time: 1:44:11 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 57.819 m
- Total movement distance: 569.715 m
- Feet/min: 4.92
Lines3 Line Merge & Line Sort
“Note: to further optimize the plotting time, consider using linemerge before linesort.”
- Estimated print time: 1:37:15 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
- Feet/min: 5.28
No effect past line sort.
Lines3 Multi-pass
For maximizing ink usage on a given piece of paper, not distance traveled per minute.
“Add multiple passes to each line”
- Estimated print time: 5:47:22 (Hours, minutes, seconds)
- Length of path to draw: 1535.688 m
- Pen-up travel distance: 512.253 m
- Total movement distance: 2047.941 m
- Feet/min: 4.44
Note that this has the added advantage of being able to cover huge amount of distance with no intervention, but it will be impossible to note where the pen stops writing because lines are written over more than once. This would only be useful for getting a ton of ink out of a ballpoint when yo know the writing distance is over 1500 meters.
There is also the issue of if the writing ball (the ink put down on the page) is affected by the pen writing over ink not normal paper. This would certainly skew the test yielding Multi-pass impractical for our purposes.
Lines3 Linesort – Normal Speed, Maximum Acceleration
50% Drawing Speed, 75% Pen Up/Down Speed, Maximum Acceleration
- Estimated print time: 1:33:27 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
- Feet/min: 5.28
Saves 4 minutes from Linesort.
Lines3 Linesort – Maximum Speed, Normal Acceleration
100% Drawing Speed, 100% Pen Up/Down Speed, Standard Acceleration
- Estimated print time: 1:01:25 (Hours, minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
Saves about 36 minutes vs. normal print speeds.
Lines3 Linesort – Maximum Speed, Maximum Acceleration
100% Drawing Speed, 100% Pen Up/Down Speed, Maximum Acceleration
- Estimated print time: 54:17 (Minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
Saves an additional 7 minutes from high print speeds or about 40 minutes from normal print speeds.
Lines3 Linesort – Over 100% Speed, Maximum Acceleration
110% Drawing Speed, 110% Pen Up/Down Speed, Maximum Acceleration
- Estimated print time: 51:06 (Minutes, seconds)
- Length of path to draw: 511.896 m
- Pen-up travel distance: 0.963 m
- Total movement distance: 512.859 m
Saves an additional 3 minutes from high print speeds or about 43 minutes from normal print speeds.
And that’s all for now! Subscribe to our Youtube channel so you don’t miss future pen tests! If you know a lot about pen plotters or pen distance testing, please do reach out via email!