AxiDraw and italic pens

On the back of my text experiments I decided to give italic calligraphy a try. Unlike other calligraphy which requires managing pen pressure, italic calligraphy is done with a simple stub nib (or italic nib) of fixed width. The drawing end is a short line, not a circle. It’s usually held at a 45 degree angle so that both vertical and horizontal lines are wide but a 45 degree line is very thin. It looks beautiful when you draw curves.

Italic calligraphy is a whole art, one of which I am mostly ignorant. But this website has a good introduction to the basics and there’s lots more resources on line. For a pen I am using the Sakura Pigma Calligrapher; their Pigma Microns are my favorite ordinary pens (needle point).

Italic pen nibs need to be held at a specific 45 degree angle to work well, this adapter from AxiDraw makes it possible. Easy to install, although note it’s not compatible with their other pen-holding addon, the one that lets you adjust angles. It took me awhile to understand why they mounted it in the direction shown in the photos. That keeps the pen tip out from under the robot arm, a good thing. However it means you need to place the AxiDraw on the right edge of the page; if you’re used to the AxiDraw being above your design (“on top”) then you need to rotate your images 90 degrees. (This orientation is natural for the AxiDraw; it’s designed for A4 pages in landscape orientation, wider than tall.)

The hardest thing is getting the rotation of the pen correct. You want it positioned so the entire flat line of the nib is in full contact with the page. That’s very fiddly. What I found worked best for me was to set the pen drop height fairly high, like 50%, and position the pen manually and screw it down tight. Then go back and adjust the pen drop to lower, say 40%. That way it won’t ever drop the pen just barely above the paper, particularly if the paper is not entirely flat.

The other thing I learned on my first experience is it works better drawing very slowly, like at 10%. I don’t know if that’s a limitation of the pen I’m using or just a reality. I also suspect it would work better with more pressure, ie a weight attached to the pen itself.

Anyway, after about 15 minutes off fiddling I got some plausible looking things. Here’s a test pattern, also some simple test text. The text is a 10mm high font (with a 2mm wide nib) converted to a stroke font via Hershey Text, using the EMS Readability font. Those simple stroke fonts are a virtue if you’re getting interesting design thanks to the pen nib! The test circles show some ink flow problems I still need to work on. Also I think the font size is a bit too small for the nib.


Made some nice progress.

I figured out how to align the pen more easily. Gently! Let the pen just drop to the page and find its own level. Then don’t overtighten the grip on it, since that will move the pen. It’s still really fiddly though! I also got some mileage from a simple pen-aligment test print.

The 2mm Pigma Calligrapher definitely needs to write slowly. Even 20% speed is too fast; 10% seems OK but very occasionally skips ink. I wonder if that’s a deliberate decision, calligraphy artists tend to draw slowly. Or maybe it’s a requirement of the very wide ink aperture. Anyway it’d be nice if it were faster!

Below, on the left, I made a nice font sample using 10mm sans-serif as my input to Hershey Text and a variety of fonts. All of these look decent, although not are all equally readable. The italic / slanted fonts look better (duh! italic calligraphy is usually written with a slant). The hand script fonts with curves look nicer too. 10mm with a 2mm nib is still too small. On the right is the same image shrunk down 75% (so, 7.5mm?) with a 1mm nib. Looks way, way better.

Anyway this all looks pretty plausible as a basis for fancy looking robot handwriting. I think my next interest is getting some nicer stroke paths for the pen to follow, something more like a real calligrapher would do. I feel this stuff is very well codified by instruction. I should try programming that myself from videos! Or look into digitizing an actual expert’s motions.

In the sample images above, the font for “10mm sans-serif” is EMS Pancake. I included that as a joke but actually it looks pretty good.