While researching H-bot and CoreXY printer designs, I came across a video of a guy who strapped on a pen to the XY gantry to test the kinematics.
I found a couple other videos of people doing the same thing, but what they weren’t doing was lifting the pen to avoid it from writing during travel moves. I knew that Slic3r had Z lift settings under the retraction section and decided to try implementing it to create some cleaner drawings.
Here is my first print.
Here is how I set up Slic3r for pen plotting. The important settings here are Perimeters and Bottom Solid Layers. The number of perimeters will affect the thickness of the outlines generated. The Bottom Solid Layers should be set to 1 if you want solid infill, or set to 0 if you want sparse infill.
If Bottom Solid Layers is set to 0, the infill will be defined by the Fill Density, Fill Pattern, and Fill Angle. Depending on the image you can play around with the Solid Infill Threshold Area to create some interesting effects. More on that later. Ensure that Only Retract When Crossing Perimeters is unchecked. This will force Z lifting to be activated for all moves.Don’t worry about changing the settings under Speed for Print Moves. Instead set the First Layer Speed to the desired speed. When this setting is defined it overrides the other speed settings for all move types. The tooltip states, “If expressed as absolute value in mm/s this speed will be applied to all the print moves of the first layer, regardless of their type.”By changing the First Layer Extrusion Width the spacing between lines can be varied. This will depend on the writing utensil used. If set too low, the lines will overlap with each other. This wastes time and has the potential to oversaturate the paper and cause it to warp. If set too low, there will be white space between the lines. This might be desired, but if solid infill is the goal, getting this setting right is important and requires a little bit of testing.This is where we define the pen lifting. Set the Retraction Length to any positive number to activate retraction. The value for Lift Z should be minimized to speed up the print. This requires some testing to see how little lifting can be done while still preventing the writing utensil from marking the page during moves. Minimum Travel after Retraction should be set to 0 to ensure Z lifting occurs for all moves.As far as what to draw, I started off by using OpenSCAD to export STLs from dxf files I found online. This method worked well for most of the dxf files.
Some files on the other hand did not load properly in OpenSCAD. Some of the files failed to produce anything, others had random lines running across them. One of these, an image of a car, led me discover a trick for producing some interesting effects. By setting the Solid Infill Threshold Area to non-zero, the smaller areas of the image were filled in solid while the larger areas were filled with the Hilbert Curve pattern. This actually happened by accident and confused me at first.