Thread: Tumbling Aluminum

We got new tumbler media and when the parts come out of the tumbler they have a dull finish. In my experience, after they get anodized they will ahave a matte finish. We are looking for a brighter finish. I think the person running the tumbler isnt using any detergent or other additives. If anyone has some advice on how to remedy this problem I would greatly appreciate it.
The tumbler media is plastic triangles 3/8 x 5/8. And the parts are about 3 x 3 x 1/2.

You must change your media. Years ago, we tumbled some aluminum pulley castings. I think that we tumbled them four times with progressively smoother & harder media. They came out looking chrome plated. Talk to your media supplier.

Depending on the parts finish before tumbling and what kind of finish your trying to achieve will determine what kind of media and how many media changes will be necessary. Remember it's just like using sand paper...you start with coarse grits and move to progressively to finer grits.
Good luck,
Carl

We use a vibratory deburring machine with plastic media for all our aluminum parts. We use a solution of water and Simple Green as a cleaner and it works great and once rinsed off the parts have no residue what so ever. The finish never comes out shiny as in "chrome like" appearance, but they do look great and it does a great job on the burrs. If there is some other media that you can use to have them come out looking polished, I sure as heck would like to know about it too.

Later,
Russ

to get a polished finish on aluminum, use walnut shells covered in a polishing compound. thats what i've been using for years and it works well. i do a two stage process, first is plastic triangles to debur and smooth to a uniform matte finish, the the walnut shell tumbler with polishing compound. after that if they need to be annodized you can get them brite dipped and then annodized for a nice shiny part.

We use ground Walnut shells with a Red Rouge bonded on. Run dry and then run them through a dish washer with Palmolive gel soap. Looks like this:

You can get a Hobart Commercial Dishwasher with a 3 min. cycle for not much money used.

mitty - what do you mean by "bonded on" - do you cook the walnut shells with red rouge, bathe them in it? or do you buy them from a media supplier in that state?

also, was that a one stage process (did it deburr/break edges too?) or was it just final polishing?

Originally Posted by bryan_machine

mitty - what do you mean by "bonded on" - do you cook the walnut shells with red rouge, bathe them in it? or do you buy them from a media supplier in that state?

also, was that a one stage process (did it deburr/break edges too?) or was it just final polishing?

Who's your source mitty........fess up!

You guys are killing me, now you want trade secrets. Okay, just this once and since you asked so nice.

1. Never ever glass bead blast Aluminum anything and Anodize it later, if you Anodize black and touch it - it will turn gray, colors will turn murky.

2. Tumble Aluminum in Green plastic Media triangles from C and M topline at: http://www.candmtopline.com Call them they know what works as well. Take care of your media (wet and dry, and it will last a long time)
Use warm water and Simple Green as the lubricant and cleaner. Usually 30 min. to 90 min. will do. It will give you a dull but deburred part. Wash the parts in a dishwasher using palmolive gel soap (don't use no name or cheap brand as it will etch your part).

3. After you clean out the tumbler and dry it, disable the pump and tape over the drain with gaffers tape or duct tape - use something durable.
Fill Tumbler with Tumble dry with rouge (red or green) available from the Graves Company (http://www.gravescompany.com/grit.htm) Load your parts and run, could take 24 - 96 hours depending on how highly polished you want your parts. You can run shorter and Electro-Brite the parts which is a chemical process to brighten the work piece. Electro-Brite is usually used before Anodizing. After you polish with Red Rouge and Walnut Hulls you want to run them through the Dishwasher again.

You can get a Commercial Dishwasher like a Hobart (there are other brands) used from a restaurant supply for <1K in good shape. You can also spend a small fortune for a fancy parts cleaning system. The reason I like a Commercial Dishwasher is because they are usually Stainless Steel on the inside. have water heaters built in to jack up the water temp, and have a short cycle (typically 3 min. or less).

If you anodize anything, your Anodizer may charge you less if they know that you have precleaned your parts and they don't have to. Besides sometimes they use caustic chemicals that may take your parts below critical tolerances.

When parts come back from Anodize - never ever hot wash the parts as you might damage the sealer which is usually Nickel Acetate and is sesitive to hot water washes (ask me how I know).

So there you have it learning through Trials and Tribulations how to make your Aluminum parts look like a million bucks. But hey you all are big Boys and Girls so do as you see fit, if you want to save money and time follow the steps. I have tried every short cut and process known, I know what works. But if you want to try stuff like "Nice and Easy" or some acid process - its your hands and face and clothes.

I stick to non-harsh chemicals so I can breath and retire without dragging oxygen around on a cart.

Frank S. in Tennessee

One more thing - Taking parts to Anodizers or sending them to Dragon Anodizing? Wrap them in News Print paper (unused). You can get drops or end rolls from the local News Paper or from Uline buy a roll and wrap your parts. It cuts down on damage, oxidation etc. Don't use News paper from Sundays paper. The ink will leech into your parts and you will not be happy.

I love that title stuff, like a Bullwinkle episode.

After I sent the above response, I wanted to add another process for large pieces.

We do a lot of large flat plate work and our fit and finish has become well known in the circles in which we travel. To that end here goes.

If you have a large part and your client wants a satin or dull finish with Anodize here is what we do.
Use a DA sander either electric or air (like a body sander) and use either hook and loop or glue backed pads (6"), wear gloves, eye protection, wash hands before eating. Do this work outside on a nice day not in sun light as the sun will heat the parts and may cause abrasive failure. wash part in Dishwasher as in the above process.

If you want a polished part (large) then get a right angle grinder 7" or 9" with some horsepower and attach a hook and loop backer pad. Use the Blue Green polishing pads like you can get from ENCO, Fastenal, etc.
ENCO Model #505-6196 7" BLUE 3M HOOK & LOOP DISCS Master Catalog Page 263
Disk Pad Holders are on page 264

Polish using a firm hold (hold it tight or it will smack the crap out of you and may break your arm) on the grinder and use the flat face with a slight tilt I use a couple of strips of wood screwed down to a wood table to block the work piece). Keep a spray bottle close by and give the part a squirt every now and then. The pads last a while but not all day. If the sun is out then wear sunglasses or you will sunburn your eyes and eyeballs (ask me how I know - couldn't see crap for two days except pink spots).

Wash parts as outlined in above diatribe.

Good luck and you guys owe me big time, drop and give me twenty - what you thought I meant pushups?

Frank S. in Tennessee

I agree with all of Frank's procedures. The problem most company's have is they are looking for the one shot cure..... It ain't out there. The walnut is the last / final step. Before that it depends on what your parts look like to start with. If you are new to providing a polished part, you will find your self machining much differently. Might as well let the machine do most of the work.
The rouge is worked in to the walnut by just adding, and letting the vibratory unit run, for what will seem like forever. Also a trick I have learned, with the walnut it is so much lighter than any of the plastics you will want to run the tumbler as full as possible. It will produce a better action.
And don't bother with the smaller mesh walnut. Nothing smaller than 12/20 or it is a wast of time (for alum).
I have used this company for a long time and they have been the cheapest. Get a pallet for best price. Don't worry you will use it, and you can mix and match sizes. 4/20 and 8/12 are my favorites.
Drop and give me $20...I like that..
Gary
http://www.ecoshell.com/Media.htm

Whilst hunting for goodies on the net, I ran across this unit and wow! it looks exceptional
http://www.massfinish.com.au/

Nice video showing separation and it comes with a VFD which converts single to three phase and 220V, nice variable speed feature and they have a dealer in MI.

Just to let ya know, cause its always a crap shoot on anything used.

Frank S. in Tennessee

It has been our experiance that you can tumble deburr or you can tumble polish so the condition of the part has a lot to do with the process as described above you may have to chanfe media to get a better finish each time. The only thing I would add is that you may have to look at your machine too as a deeper machine is better for deburring and a wider shalower one seems to polish better, we run 7 machines with a varity of media to avoid changing it so many times and speed up the process.

Frank, I just glass bead -blasted a couple of 6061 parts that I was going to send to Dragon for some samples, then of course I come home and read your do's and don'ts list, where you specifically say not to.

If I wanted the texture of the glass bead in conjunction with anodization, is there a better media to use?

Thanks,

Burt

Burt

I would probably use a SC or Silicon Carbide type material to blast. Use something fine like 80 or 120 grit. A place called Salem Distributing sells grits like that. We used them for grinding mirrors for telescopes. They sell stuff so fine that you would have to polish for days. Stuff like zirconia slurry. They will send you a catalog on request. Their grits are very high quality but reasonably priced.

I once used the zirconium slurry with optical pads to polish a piece for Laser Optical guidance that a friend was doing in his shop. He had to remove the gold plate from a piece of steel or some type of substrate.

Anyhow I would use SC for what you want. Remember to clean well before sending. Remind Dragan Stankovich that you heard about his place here, from Frank at Mitty. Doesn't get me anything but lets him know that word of mouth is bringing business his way.

That glass bead blast is nasty. Embeds broken glass in the material.

Let me know how it works for you.

Frank S. in Tennessee

Remember no glass bead - keeps you from doing this

Thanks Frank,

You just saved me unknown amounts of grief. I guess I can come down off the ledge now.

Burt

Glass beads have a lot of thing going against them...but health is the biggest one.
If you need to blast you might want to look at the walnut shell in -100 mesh.
Shell will never cut as fast, but it is relatively easy to filter and much safer, to you and the rest of the equipment in the shop.
Gary