Polargraph / Drawbot Pen Holder

I have been playing with Drawing robots / Polargraphs for a few months now, first inspired by my friend Matt Venn’s Energy Monitor: http://www.mattvenn.net/2011/09/19/polargraph-energy-monitoring/

and later Sandy Noble’s Polargraph: http://www.polargraph.co.uk/

Like many projects, I have ended up making many revisions / versions of my drawbots. First, there was David, then Derek, then Doris, Delilah is the latest, and next up is Deirdre [can you spot a theme?].

There are many problems/issues/obstacles/characterful niggles that one comes across when building a drawing robot. I won’t list them here – take a look through the polargraph forums, or have a go at making your own to find out!

One challenge is the pen holder:

  • must hold pen securely enough for drawing
  • nice if can change pen easily
  • needs to also hold servo to lift pen
  • detachable from holding wires for transportability
  • place to attach weight


Early experiments by Matthew and Sandy addressed some of these problems, but often included extra / hard to find parts, or more expensive parts, etc. Then Sandy (I think) came across Mr Drew’s pen holder (name of a drawbot by Darcy Whyte of mambohead.com ) and put it up on his own site.

There are pros and cons to different designs of pen holder / gondola – I was keen to address some of the cons of the holders I have been using and seeing how my own changes affected performance / usability.

Bigup Darcy and mambohead for sharing their Mr Drew pen holder! I can’t find the original file link, but Sandy has it up on his google code hosting (sketchup file) here:


I downloaded this file, converted it to dxf for my laser cutter and made one up. After getting a spring from an old printer in my junk store, I had a nice, easy-to-swap-your-pen, pen holder. Sweet!

After a bit of use I had a few thoughts of design improvements [in my eyes] and decided to make a few changes.

It is entirely possible/likely that I didn’t assemble the parts as intended (I used ~60% of the parts in the MrDrew file) but I had a working holder. From that base I tried:


  • extend string hooks for easier stringing/de-stringing
  • reduce number of components
  • modify sprung arm to clear spacers
  • modify pen holder to include servo holder
  • extend weight attachment position
  • widen pen space to allow larger pens to be held
  • extended lever handles on sprung jaws


You can download my design here:


All files above are shared under a Creative Commons Attribution ShareAlike 3.0 Unported license – for more details see the Creative Commons website.

Other hardware

In addition to the laser cut parts (I used 3mm sheet stock), you will also need:
  • 2x M3 40mm machine screws
  • 2x M3 16mm machine screws
  • 4x M3 nuts
  • 10x M3 nylon washers (optional)
  • 1x small spring
  • 1x micro servo
  • drawbot, pen, etc etc


Big nice to Matt Venn, Sandy Noble and the many other drawbot / polargraph people doing lovely things.

UPDATE - fatter pens

My first revised version could hold Sharpies but I got hold of some fatter markers that I wanted to try, so I did some more tweaks and have two other versions available – one that can take pens up to ~20mm in diameter and another that can take up to ~28mm diameter (pretty chunky markers).

Grab the files here:



3 thoughts on “Polargraph / Drawbot Pen Holder

  1. Pingback: Another drawing robot gondola design

  2. TeamTeamUSA

    Hi Stuart,

    Nice work with the FAT & FATTER Mr Stu gondolas! :)

    I laid them out on P1, Ponoko’s smallest material size, so people like me without a laser cutter can use them with our polargraphs.

    I also created a derivative that incorporates a yoke to mechanically press down on the pen body to create tilt and induce ink flow. You can see them here: http://www.ponoko.com/showroom/TeamTeamUSA/product-plans/free

    I was unsure under which license you made your designs available, so I selected the BY-NC-SA license (http://creativecommons.org/licenses/by-nc-sa/2.0/) for mine; hope that’s all right.

    I hope you don’t mind. If you do, I’ll gladly remove them. If you’re OK with it, then at some point I’d like to put them on Thingiverse too as 3D printable versions.


    =m i l e s=

    1. Stuart Post author

      Hey Miles,

      nice work on the updates, and thanks for the props! Looks like I hadn’t quite implemented my sharing template when I did the fat pen updates!

      If you’re interested – here’s a link to the layout / sharing template- if you’d like to use it!


      More than happy with your choice of license. I tend to go for sharealike 3.0 unported but.. i’m not fussy ;)

      Cheers + keep up the good work yourself :)


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