Aluminum Polishing with CNC mill?

[kevperro]

It seems reasonable, that it would be possible to design a polishing tool for use with a CNC process. I would envision a large diameter flat end-mill, with the appropriate material and a planned tool path that would include occasionally moving over to a polishing compound to re-apply.

Is there a commercial solution like this? If not, has someone built their own?

[Caprirs]

Put simply, it is not advised. You would be deliberately introducing some abrasive media into your mill. That material will eventually find it's way to the ballscrews and ways and ruin them. The wipers and seals on most mills are designed to keep chips out, not polishing compounds.

[Kipper]

Originally Posted by kevperro It seems reasonable, that it would be possible to design a polishing tool for use with a CNC process. I would envision a large diameter flat end-mill, with the appropriate material and a planned tool path that would include occasionally moving over to a polishing compound to re-apply. Is there a commercial solution like this? If not, has someone built their own?

Nope...but the seed is sown! I envisage a rollerskate bearing propelled cnc polisher will be arriving......someday. Who gives a rats if the skate bearings or some old pipe get pounded.... Good idea Kev

(I guessed you didn't mean using an existing expensive machine...)

[Geof]

I am going to be contrary and say that it could be a workable idea, but I had better back that comment up otherwise Caprirs and Kipper are going to be all over me.

On many commercial machines the way covers do a very good job of keeping stuff away from the guides and ballscrews.

The abrasive material is going to be in a suspension or slurry not an airborne powder and the speed of the polishing head is going to be slow so it is not going to carried in an aerosol. Indeed I think most of the compound is going to remain on the work piece and it would be possible to have a tray with tall sides to catch any splash.

The polishing pocess itself would not require coolant but I would arrange coolant nozzles to copiously wash down the way covers so that any polishing compound that did escape the tray would be collected and carried in the coolant.

It would be necessary to have far better than normal filtration for the coolant circulation but this is feasible.

Really when you consider things most CNC machines actually circulate a very dilute polishing compound in the coolant in the form of aluminum oxide particles. Just about every coolant tank on a machine running aluminum has a sediment at the bottom of the tank that grades down from discrete chips to a grey sludge; this sludge is mostly aluminum/aluminum oxide particles.

Would I use one of my machines for this application? Yes, a few years ago I bought a Haas GR510 and one of the intended applications was to try and develop procedures for doing decorative sanding and polishing on sheets of stainless or aluminum. Often hand finished sheets are used as panelling inside such things as elevators; I figured it could be possible to do the same thing in a controlled manner to actually sand pictures. My idea was to greyscale the picture and assign different grit sizes to the grey levels. The whole project did not go anywhere for a variety of reasons but being worried about polishing on a CNC machine was not one of them.

[Kipper]

Originally Posted by Geof I am going to be contrary and say that it could be a workable idea, but I had better back that comment up otherwise Caprirs and Kipper are going to be all over me.

Nah not likely.

[BlueFin]

My 2 cents is that it would be very workable and would probably be a whole lot faster than doing any of it by hand. As far as increased wear and tear or damage to the machine? As long as you know what to expect then that decision is entirely up to you. I used to ride motocross bikes on the sand dunes because of the pure enjoyment of it, and a lot of friends did as well. But there is always those few guys who refused to even think about it. They insisted that the sand was "hard on the bearings and stuff". I did not care, I specificly bought the bike for the dunes from the beginning and rode it there because I valued the experience higher than any other enviroment. The resulting increased wear and tear was not an issue, it was just the cost of living the one and only life I have been given to the fullest.

If you truly hold value to polishing metal in an automated fashion then by all means go for it, it won't matter how much you trashed a machine 35 years from now (at least thats what I think I have left in me) when your laying on your death bed with proud memories of shiny metal in your past. But if you don't do it you may regret it.

[justgary]

...and I have to chime in here after BlueFin. If you polish with a paste and put up plastic barriers, you will catch almost all of the polishing compound. Then, instead of rinsing everything with your coolant, clean it with warm, soapy water and catch the runoff from the table drains in a bucket for disposal. After a rinse you can hose it down with your coolant if you want to. I don't think that you will get very much grit in the ways or on the ballscrews.

A pencil eraser (just chuck up a short pencil with a new eraser) dipped in lapping compound will make a great jeweling pattern on metal. I have also used polishing cups from the dentist for jeweling, since they hold the grit a little longer. I used to jewel things by hand on a drill press, and I would dream of the day that I could rig up a machine to step over a precise amount... Now that I can easily do it, I can't think of anything to jewel.

You can mitigate almost any possibly damaging use of your machine. Some will tell you to mitigate by not doing it at all, some will tell you to just go for it and replace the parts when they wear out. Your answer will lie somewhere in between those two. As for me, I'd put up some plastic sheet and polish until I was sick of it, then clean the machine and go on with my life.

Show us pictures!

Regards,

- Just Gary

[BlueFin]

Originally Posted by justgary I have also used polishing cups from the dentist for jeweling, since they hold the grit a little longer. - Just Gary

What is with you and the Dentist? I go every 6 months for a cleaning, but never thought about walking out with everything they own to chuck into my spindle to see what it does.

I am scheduled for June 8th for a cleaning and I am going to see about getting some of those end mills for making brass brands.

[justgary]

Originally Posted by BlueFin but never thought about walking out with everything they own to chuck into my spindle to see what it does.

...not even that one hygienist?

Seriously, I was probably 18 or so when I asked about used burrs for my Dremel. When she handed me an envelope of them instead of just one, I figured out that they really go through them, and usually they keep them for the person that asks. I have a lot of scrapers, explorers, picks, etc. that they gave me also.

I had my hygienist trained for a few years; I would come for my appointment, and she would put burrs and picks in the goodie bag with the floss and toothpaste, all because I asked one time.

Good luck!

- Just Gary

[cheetahcnc]

proud memories of shiny metal in your past

LOL! Sounds like a few of my previous cars.

Jim

[LeeWay]

This is really what vibratory finishers are for.
Why polish with a mill. If it's running, it needs to be cutting parts.

[kevperro]

All good answers. I'm of the mind that I'll use the machine until it dies. I doubt if I'll outlast it.

In terms of the vibrator tumbler. I've found the round ones, and some much more expensive square tub ones but nothing in my price range. I'd want to keep the cost down around $1000 and I need to put 16"-17" long parts in it. I've not found a solution in my price range. If someone knows of one, I'm all ears.