Turning Your CNC Machine into a Pen Plotter

Gareth Branwyn

Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and "lazy person's memoir," called Borg Like Me.

4024 Articles

By Gareth Branwyn

Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and "lazy person's memoir," called Borg Like Me.

4024 Articles

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My friend Andy Holtin, an amazing maker and an art professor at American University, sent me the details of a simple jig that he bodged together to turn his ShopBot into a pen plotter. While adapting plotter pens to CNC routers is not uncommon, I like the adapter he made (originally to hold a rotary tool) and how he made a secondary pen adapter to fit inside.

About the adapters, Andy writes:

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This is a pretty common adaptation. A lot of people just pop a pen into the chuck and draw, but the nicer plotter adapters have some kind of spring or gravity driven plunger to keep the pen in contact with the paper, as surfaces are always a tiny bit irregular.

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A couple of years ago, I made this little wooden Dremel mount so that I could clamp it onto my router body and run the Dremel as the business end instead. I just disabled the router, pulled out the collet, and it was pretty easy to trick the machine into zeroing at the Dremel bit’s position. I’ve used this setup for fine engraving, PCBs, and things like that. I didn’t have a vacuum table for my ShopBot, and taping or clamping PCBs is pretty ridiculous, so I also made a mini vacuum table for the Dremel adapter as well.

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I have a some projects coming up where I need some good CNC drawings, so I figured it was time to rig up a plotter. Since I already had the Dremel adapter mount, I thought I’d use that rather that designing something new to fit in the router collet. You can see the drawing tip much more clearly in the wooden mount than when it’s up under the router. I happened to have a chunk of plastic from a previous belt-drive project that fit perfectly into the Dremel mount. In fact, all of the other parts in the holder are recycled bits from other projects, so it was pretty quick to knock this together in the studio. So far, it’s working great!

Have you created any specialty jigs or adapters for your CNC machine? If so, please tell us about them in the comments.