Big CNC as a Plotter

I’m trying to duplicate an existing right & left panel with numerous holes and a slot. I’d like to tryout what I’ve designed to replicate it. So I was thinking that using the big CNC as a plotter would allow me to draw my design first and then check the drawn result against the existing panels before cutting actual wood. Has anyone ever tried that before?

Here is a CAD drawing of my current design to give you an idea of what one panel looks like.

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I’ve got no objections to chucking a magic marker if you like, but it can’t adjust pressure so it could easily mash it too far.

The ER20 collet system can grip cylindrical things up to 1/2" dia

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@dannym, Thanks. Would a spring loaded one work to reduce mashing? Mayne something like this: CNC pen / sharpie holder for plotter by Oscarko - Thingiverse. Also I’d have to put a 4x8 sheet beneath the paper as a smooth surface to draw on. @bwatt

This is a thing that’s done - there are off-the-shelf pen options if you don’t care to make your own, eg: Plotter Pen Bit for CNC Machines - Use Your CNC Machine as a Plotter, Draws in 4 Colors of Permanent Ink - WidgetWorks Unlimited

It’d probably be easiest to tape your paper to as thin a sheet of hardboard as you can find that doesn’t want to bow on you.

I have experimented with something like this. Here’s my first prototype, it uses a spring to apply pressure and was meant for a pencil to be dragged. It’s no good for the spoil board broadly but I have used it to set up X Y reference lines on flat areas of the spoil board. I was planning to make a mini sharpie version in the near future.

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I’d love to use your sharpie version of this.

@lammikecohen, Sweet! Do you have STL or CAD files for what you’ve done. I’ve printed the one from Thingiverse (see third comment above).

and am going to give it a try. I’ve also bought some 36" wide tracing paper for my testing from Amazon (

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@Jon, thanks for the link.

If this is chucked in the spindle, I’d add an arm to contact a static surface so it can’t rotate. The stylus will never be perfectly concentric and it will caster around making squiggles at the start/stop or taking turns

Thanks @dannym, will do.

I designed it in Fusion 360, it’s parametric but a bit of a mess. Will a Fusion file work? If not what file format is best?

I’m a FreeCAD user, and they suggest using STEP file format to transfer from Fusion to it. Is that possible for you? If so, it’s worth a try.

Now that I think about it, you may get better results if the pen does castor. Otherwise you’re limited to using the pen vertically with the point down and that may not work so well

Here’s a step file: Google Drive: Sign-in

This thread makes me want to turn a marker holder

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@Iammikecohen, I just requested access. You should have gotten an email. @bwatt

@dannym, I made an adapter to stabilize the ER20 collet to the collar ring of the router. I haven’t got there to try it out, which I plan to do in a day or so. It’s probably going to need a second pass to make it really fit boh the ring diameter and the space between them, but it’s a start. @bwatt

All this is an experiment to find a solution. I’ve now got a side-pen-mount and want to work with @Iammikecohen’s design for a vertical-pen-mount. More to follow… I’m posting these updates here so there’s a history of what was done for others in the future.

@Iammikecohen, Got the design downloaded. Thank you. Let me use it and 3D print one here. I’ll keep you informed. @bwatt

@Iammikecohen, I have printed the pieces and want to assemble them. I have a potential spring. Your collet is a masterpiece. Do you glue the washer to the open-ended cylinder? Why wasn’t that a single 3D piece?

I assume that to put it together I insert a pencil into the collet and assemble the pencil-collet into the glued washer hole and its cylinder. Next insert the spring into the upper shaft piece followed by the pencil-collet-cylinder to form the overall assembly.

I think the diameter of the open-ended cylinder needs to be larger to fit tighter into the upper shaft piece. It wobbles a little. Also I think the side walls of the pieces should be thicker to handle the stress.

@bwatt watt