Sanding & polishing CNC router work using Dremel attachments

General CNC CNC Routers
1

Hello!

I’m working on a CNC project - etching a Cafe sign from oak. My router did a great job on the etching and cutting, now I’m working on next steps - sanding & cleaning it up, and thinking on how to color the product.

This is the work straight out of the machine

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My main question for this post is a Dremel question - how can I attach the fluffy white felt/cotton attachment? It’s got a tiny hole, and I could not figure out which of my Dremel-provided attachments could grip it.

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I used this nice sander bit, which I’ll admit - I really enjoy, and found relaxing & cathartic to use. I like a smooth, friendly slightly curved edge - and this allowed me to manually smooth edges.

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This is the current state - I’m meeting with the client soon to show it, and get their feedback.

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I bought a few pieces of sandpaper yesterday (150 thru 300 grain) - that was helpful for smoothing the surfaces and edges.

Aside from the Dremel-specific question, I’d love to hear other suggestions on post CNC “finishing” techniques, tips, tricks, "Wish I had known"s etc.

Curious about the bit track-marks - that’s from a 1/16" downcut bit. What’s a good way to smooth those out?

Thanks!

// JRO

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There should be something that looks like a wood screw at the end of a shaft. The screw goes into that hole.

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Got it - thank you @mcdanlj !

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I use these sanding/buffing wheels with EZ lock for this kind of work.

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Are the letters so small that it requires a 1/16 inch endmills? Or did you choose that to get into the small areas? You could use a larger endmill to remove the bulk and then run a profile finishing pass with the smaller one.

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I chose that bit because (1) the small details in the lower letters, (2) I haven’t learned the workflow yet for multi-tool changes using Kiri:Moto.

I’m investing time learning to use FreeCAD - once I have confidence there (specifically: Import SVG text, etch it, cut a shape), I’ll be thinking of how to separate the job operations. Do people usually just have separate G-code files, and run them in sequence - changing bits? I believe that I saw a job organizer in UGS.

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Yes, separate gcode files. Unlike 3D printing where homing the machine is part of the normal gcode sequence, CNC assumes you take responsibility for homing when appropriate. This is part of what makes separate gcode files a workable option here. :smiling_face:

Here’s @stewart describing non-automatic tool changes on Kiri:Moto:

Similarly, FreeCAD Path Workbench has a “Split Output” option in the output tab. Tool change - FreeCAD Forum

Here’s my recipe:

  • Move Z to a safe height
  • Home XY
  • Move to or within the origin-most corner of your stock, set work coordinate zeros
  • Set Z height with first tool at fixed location (e.g. G0 X0 Y0 as long as you have enough surface there to set height against)
  • Run first gcode file
  • Go to same fixed X, Y location, change tool, set Z height in the same way
    • Do not re-home X and Y; that’s not sufficiently repeatable.
    • Leave enough roughing margin that if you disturb X and Y, a re-home in X and Y will probably work. :smiling_face: (Unlikely on screw machines; on belt machines you have to be careful when tightening the collet not to force steppers over a step.)
  • Run second gcode file
  • Rinse, repeat

You can test this cutting air, with bits removed for safety, to make sure you are comfortable with the workflow.

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Thank you for sharing your process @mcdanlj - and the link to the Kiri:Moto thread with @stewart is helpful. Excited to try this out!

// JRO

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