Shopbot as a sander

[sidofengland]

Hi,
Has anybody used the shopbot as a an overhead sander.
I have some corian island units that I want to polish and wondered if this has been done by anyone else?

Thanks

Sid

[Simops]

Sid, i don't have experience with corian but I use my bot often as a planer-thicknesser for timber pieces to big to put through the jointer and thicknesser. I use my 2.25" spoilboard cutter....works a treat and is spot on. I make sure the Z is zeroed to the spoilboard of course.....gives a more consistent and uniform result.

Cheers

[Bob Eustace]

Mike have you thought about getting the insert unit from Amana. Russel and I have one for the same purpose as you are using yours. Was $169.

Sid - havent tried it on a Bot but have seen it done many times on slab levellers. If you dont want to risk something in the spindle, Festool have a belt sander in a frame that works on its own weight that could be adapted in an hour or so.

[bcondon]

I wouldn't do it with my machine... My dad was a machinist and one thing he taught me is to watch the direction of the load on your bearings.

A spindle is designed to load the bearings laterally (side to side) and not
vertically. This is the same reason that you would not use your shopbot as a drill press.

When you load your bearings incorrectly, at some time you will be rewarded with damaged bearings and on a $2200 spindle, this does not seem like a wise investment (to me)...

Bob Condon

[CNYDWW]

I've visited the options of sanding on cnc machines more then once (at employer's request both times) There are a lot of issues to contend with. The main issues is down pressure as well as the sanding head floating on top of the material. A designated attachment would be the trick. The ideas i've brought to the table resemble Widget Works Unlmited's pressure foot with a RA sander attached. I would sub out springs with spring loaded pneumatic cylinders. Adding an adjustable check valve to each cylinder should create a floating effect. This should and/or could solve the issues that come along with a sanding head on material that isn't truly flat. I do have to say that i've never tried this so it's all theory.

Regards
Randy

[bleeth]

Polish or sand?

If one wanted to try to use their bot as a sander then you would need to rig up a spring loaded shaft, similar to a diamond engraver, and use a soft pad. It is possible, and a pretty neat out of the box idea. Best would be a shaft system that spun the pad asymmetrically like a DA. If you machine up a design for one and it worked, you could probably sell multiple units of it, since sanding up solid surface is such a high cost labor intensive job. Now that I've said that, if you want to do it, you may need to move fast as it sounds like a cool idea for the next tool from Widgetworks.
For polishing, one could chuck up a pad holder, put a little polishing compound on it, set it correctly and let her rip. My concern there would be that an effective polisher uses fairly low RPM's and even with a spindle it may spin too fast. You may have compound splattering all over the place and drying out the pad too quick!

Some say "I don't know how so it can't be done", and others say "It hasn't been done so I'll figure out how"

Looks like Randy and I are on the same wavelength

[Simops]

Mike have you thought about getting the insert unit from Amana. Russel and I have one for the same purpose as you are using yours. Was $169.

Sid - havent tried it on a Bot but have seen it done many times on slab levellers. If you dont want to risk something in the spindle, Festool have a belt sander in a frame that works on its own weight that could be adapted in an hour or so.

Hey Bob,

Thats what I use.......it's no different then surfacing the spoilboard.....so I'm confident that I'm not causing any further stress to the spindle!

Cheers

[gerryv]

I've got an air drill attachment that I never use so looking at giving that a try because the lower rpm's are more suitable. True, the question of axial/trust bearing may well mean I should not do it routinely - I've just not looked into that yet.

I definitely will be planing and jointing with the spindle though as I'll be using the 'bot mostly for hardwood lumber and would like to semi-automate that process. First need to finish building the new studio/workshop though so another couple of months.

[myxpykalix]

I have seen a video by Legacy where they sanded a part using a sanding mop in a spindle (i couldn't find the video to place the link here) but here is another one that might be similar:
http://www.youtube.com/watch?v=Amb9mPX5lm8

[sidofengland]

Ok chaps,

Decided to try and sand some corian today.
after setting the depth and slowing down to the minimum speed I drew a continuous vector and copied it several times.
Now, not allowing the sander to leave the material through out the machining is important here because once it is lower than the surface it would most likely wreck the pad when it tried to come back on the surface so the vector has to go half the width of the pad off the material and then all is fine.
Started with 120 grit which left some marks in the material either side of the pad.
Then 220, then 400 and still the marks. Ok take it off of the bot and use Dani designs perfect finish with a maroon pad and voila ( that's french I think) all marks gone and perfectly even finish over 600 x 600mm.
Obviously concerned about the bearing issue on the spindle and all the other possible problems that you have commented on, but this test worked very well. Would have to make sure any material that needed to be sanded was perfectly flat because I was only sanding to a depth of .1 or 2 of a mm. If the corian was bowed and the difference over a 2500mm worktop was 2mm out problems could well arise because at such slow speeds the spindle might well slow to a halt.
Still concerned after the test run I spoke to shopbot tech and they think the machine should be ok to deal with this procedure - Good enough for me.
I Will try a larger piece shortly and let you know the outcome.

Sid

[bleeth]

Cool.
Were you also using a softpad chucked up on the router? What kind of feed speed did you run?
400 and then softpad w/polish-You must have ended up with close to a gloss finish there.

Getting a spring load shaft to mount the sanding pad in could go a long way towards alleviating fears of varying thickness or spoilboard not perfect flat. Very interested in hearing more as you go further. Not too often we have countertops only 600 x 600! More likely I would have to index many of them.

BTW-My other half is a Northerner too.