← Projects

I turned a CNC router into a drawing machine.

When my former boss gave me a small CNC router, I wanted to make something with it immediately. I couldn't justify buying wood or metal to machine. So I asked whether I could teach it to draw.

The converted CNC pen plotter beside one of its completed drawings
Photos and actual test resultsSwipe or use the arrows · 7 images
The converted CNC pen-plotter
The converted CNC pen-plotter
Printed fixture for raising and lowering the pen
Printed fixture for raising and lowering the pen
Early drawings before Z-axis control was integrated
Early drawings before Z-axis control was integrated
Example of an image prepared for plotting
Example of an image prepared for plotting
Repeatability experiments with the drawing toolpath
Repeatability experiments with the drawing toolpath
Additional behind-the-scenes image from the original machine build
Additional behind-the-scenes image from the original machine build
Details of the drawings before adding pen-lift control
Details of the drawings before adding pen-lift control
Watch the CNC machine draw.

Actual test footage from my original posts.

Open on TikTok

Watch CNC pen-plotter video 1 Watch CNC pen-plotter video 2 Watch CNC pen-plotter video 3
Read the full build logExpand ↓

Make use of the machine you already have

  • I had experience operating industrial CNC equipment. This little router was a different opportunity: I could change the machine itself. Instead of keeping the original spindle use-case, I replaced the cutting task with drawing on paper.
  • That meant I didn't need expensive machining stock to get useful results. I needed a pen that moved precisely and lifted when it was supposed to.

Lesson: A limitation can point you toward a cheaper—and more interesting—first experiment.

Building the missing motion

  • I wired the X and Y stepper motors to controllers and used a spare laptop power supply. For the third movement, I designed a small 3D-printed mechanism using a servo and rack-and-pinion arrangement to raise and lower the pen.
  • Some geometries were too flexible or unnecessarily complicated. I iterated toward something that would actuate reliably and was quick to print, rather than chasing machine-tool accuracy for a proof of concept.

Lesson: Use just enough precision and stiffness for the outcome you're trying to prove.

Turning an image into physical motion

  • A picture isn't automatically a path the machine understands. I wrote software to take SVG curves, approximate them with line segments, transform them into coordinates and scale them to the page.
  • It connected design, mathematics and embedded control into one tangible result: a drawing made by a machine I'd repurposed myself.

Lesson: When you can explain each transformation from input to outcome, you understand the system much better.

How I'd present this project now

  • I wouldn't lead with a long list of programming languages. I'd show the before-and-after: here was a router I couldn't afford to use as intended, here's the motion I added, and here's the actual artwork.
  • That evidence says more about problem solving than any generic line about being 'passionate about robotics'.

What this really cost

  • A previous employer gave me the small CNC router, which changed the economics entirely. I already had the basic machine, and I powered the steppers with an old laptop supply. That is different from claiming anyone could replicate the full system for free.
  • The incremental build centered on stepper drivers, a servo and the small 3D-printed pen-lift mechanism. I never published a dated receipt-level BOM for those purchases, so the cost is best described as low additional materials expenditure rather than a precise price.
  • The key saving came from changing the project goal: drawing on paper meant I could test motion control without buying machining stock and tooling for a router I otherwise could not use.

Lesson: Always identify what you already owned, borrowed or received free before giving a project budget.

← All projects