Using the Longmill as a sanding robot

I can’t currently afford a drum sander so I’m trying to get creative with time management.

Has anyone tried using the Longmill with a random orbit sander to make a sanding robot? The software side is easy, a surfacing program with a 5" bit set to slow speed.

I have some ideas for a mounting bracket including some that I have come across online, but was looking for some neutral input from this community.


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@mid_al Welcome back, Michael.

Without getting into whether this is a good idea, if you have not seem this video, it may give you some thoughts. Good luck.

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Thanks! I have seen that video and am designing something similar. The part that is stumping me is how to attach it to the z axis sub-assembly.

@mid_al You could consider attaching it to the router mount. Remove the front piece of the router mount, and use the 2 x 5mm holes in the mount to hold your new bracket. PLEASE note, I am not recommending this. I have no idea of the forces you will be applying to the router mount and how they could affect the linear guides of the Z axis or any of the other moving parts. I merely throw it out there for consideration.

I prefer to do my orbital sanding by hand. :grinning:

What about just using a sanding disc in the router?



awesome simple idea,

Smack!!!" (slapping forehead)

I had considered this, but was worried about swirl marks. I had tried something similar using dremel bits to clean up bowls, but it had its problems. Mostly, there was no give in the bit. I broke one and scratched several test peices. The metal rod would poke through. I am almost finished my prototype. I’ll upload some video tomorrow once I finish it.

Here is part of the jig. I also have four 4" shock absorbers and two small brackets to attach the shocks to the router cradle on the z.

It works!

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Interesting. I am also an amatuer astrronomer and have never ground my own mirror but have considered trying one of the home built automated mirror grimders. If I could use this idea to do the rough spherical grinding on the longmill, and maybe the initial parbola formation, could reduce the time of hand grinding…hmmmmm.

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I used the 2 inch sanding disc, it worked great. Haven’t figured out how to send attachments on reply’s or I’d send the video I took of it.
I ran a 3 surfacing tool path with different angle’s each with only a 0.005" cut depth with 3 passes.
It worked really good until the very last pass and GSender had one of it’s random ‘Hard Stop Error’s’ and stopped moving, left a burn mark before I could shut it down.
I used it on raised panel cabinet doors. I still used my orbital sander for the finish work, which you’d want to do even with a drum sander for the finer grit sanding.