Is an Anodized Chip A Clean Chip

Does a black anodized chip equal a “dirty” chip?

Our chip hoppers hold about 300lbs of aluminum chips. We keep them Very clean to get the most from them; I need to slide a small project on this machine early next week that requires facing about 0.020” deep. The part is anodized with a Type 2 black, I assume the chips/shavings will have a black tint to them; will this reduce the value of the container of chips?

The part is 6”x4” long plate, and we are only talking about 15 parts. I just don’t want to clean out the machine for a small run, and start right back to our normal aluminum production.

if your scrap guy complains about the chip not being clean, find a new scrap guy..... anodize is in simplest terms a stain on the aluminum, and if it changes the weight at all, it's such a tiny amount as to be nearly unmeasurable....it's not like it's a layer of chrome or nickel plating changing the purity
on edit.....if you think it might be a big deal, run the anodize parts when your scrap hopper is half full, and run more parts after and the anodize chips are buried in the middle

If your scrap guy is THAT anal and you're worried about it, just fuzz .002" off the plate first to get rid of the black and throw it away, then put the other .018" in the scrap bin. I would imagine it wouldn't be an issue though. Maybe you should call your guy and ask.

"Maybe you should call your guy and ask"
Don't call YOUR guy, call some other scrap recycler. Thay way if you get the dirty word, your guy wont feel the need to be sifting through every drum from now on.

eKretz said:

If your scrap guy is THAT anal and you're worried about it, just fuzz .002" off the plate first to get rid of the black and throw it away, then put the other .018" in the scrap bin. I would imagine it wouldn't be an issue though. Maybe you should call your guy and ask.

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Agree 100%. .002" will clean up the anodized layer and then some.

Clint

From a scrap processing point of view it is a clean chip. Anyone who says different is trying to play a game. Paint is a different story, but not anodized.

Find a good guy who will take care of you and not nit-pick you to death, or look for any reason to downgrade your material.

And remember, that little voice in the back of your mind that says, "Why am I being paid 30% less for this material with holes in contrast to the solid blocks, it melts the same in the pot..." Is absolutely dead on.

Most of your scrap is being recovered as secondary ingot, not prime material.

the dye burns off in the furnace, dont matter what shade of black, blue or pink it is
comes out the colour of ali.
the oxide ends up in the dross bin
[ex ali foundry manager]
regards
mark

take the .020 in one cut. if you try to just skim the anodize off you may be amazed at how fast your inserts go away...

moonlight machine said:

take the .020 in one cut. if you try to just skim the anodize off you may be amazed at how fast your inserts go away...

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Indeed. Ano is hard, I have tools that will attest to this.

I'd not worry too much about it. The heat from the cut will kill the dye to a dark (or light if it's real hot) brown, and the act of rolling up the chip will crack and destroy the ano layer to the point it won't stand out much at all (if it's still even attached to the chip at that point).

Unless you have a hundred pounds of them in the same hopper and all in one spot, I doubt you'd even notice them.

If you take a skim cut, take at least five thou, to get under the ano layer. Much less than that, and you're just abrasive dressing your inserts.

Also, if you don't normally run coolant, you might want to for that skim cut. Otherwise a big face mill will raise quite a cloud of alumina dust (that I don't recon you'd want to breath very much), which will then automatically find every place in the shop that you don't want abrasive dust, and settle there (preferably onto a well oiled surface to form a nice lapping compound ). Don't ask me how I learned that.

EDIT: Just re-read and saw you only had to go 0.020" deep. When I first read that, I thought it said 0.200". I agree with the dude I quoted, take it all in one pass and be done with it, but don't be surprised to find a notch developing in your insert 0.020" up from the end cutting edge. Though, cutting just a few parts with regular inserts, the wear probably won't get that bad. Ano is hard, but it's not diamond. If you use high shear polish/ground type inserts, you'll definitely see a notch start in the sharp cutting edge. I get that kind of wear a lot when making many facing cuts at the same depth through anodize. I know for manual stuff, I save my "not sharp enough to call good, but not broken either" solid carbide mills for taking off ano. Saves the edges on the new stuff.

I agree that it should not be a big deal.The layer of ano is so thin that I dont see it making more of a difference that any coolant that gets in the chips. I have measured an anodized part right before anodizing and after and it didnt even show on the calipers.

Its obvious that the scrap guy is just trying to shave a buck or two off the price. SOme of the recycling people sometimes remid me of tow truck/ impound yard people. I say hide it in the middle or just find someone else.

I have melted anodized scrap into ingots and did not see a niticeable difference in ammount of slag it produced. In fact, I have gotten more slag from regular aluminum chips with dried collant from the cutting operation and dirt from the floor when I swept it up.

I forgot how hard the ano can get, glad that point came up. Shouldn't be a problem to take a 0.020" pass, but I will keep that in mind about the inserts as this is probably going to turn into a production run in the next couple of weeks.

Just to clarify, I didn't call the recycler, so I wasn't really sure if you would even see a difference in the chip and if there was did they have a leg to stand on saying it was considered a mixed chip.

The anodize itself is a very thin film of aluminum oxide. Hard anodize is the same thing but thicker. The color is a dye. I don;t know what kind of dye they use in commercial shops but I understand you can use regular "Rit" fabric dye in a home brew anodize process. Anyway the anodize residues from machining operations will float off as dross when they go to recycle the chips back into ingot.

I think your recycler is looking for ways to downgrade your scrap so he can wring more profit from it - pay you for "contaminated" and sell it for "clean". Gotta watch them scrap dealers.

I remember walking across the floor scale of a scrap dealer and noted I only weighed 160 lb on the readout. News to me because I weighed 288 that morning. When I looked closely at the tare setting the office door burst open and Ben the chisler hustled me over to look at a couple of motors - an obvious distraction from a doctored scale.

I called the state weights and measures people. The scale was used in trade and had a state sticker on it. Note to self: follow up on this see if chiseling Ben got in trouble. Hope so. The bastard.

Another chiseling antic of scrapyards is to pay people that bring their scrap to them in long tons. Being 2240 lbs, instead of 2000, they are getting 240 lbs of "free" material. I wonder if that's still a popular routine?

Richard