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How to get best "mirror" machined flat finish on 6061 aluminum

Ryan Destree

Plastic
Joined
Sep 5, 2009
Location
Manitowoc WI
I have recently been machinig alluminum cylinder heads and i found a tool that gave me a great finish. It is a miltech i think it is a freedom cutter. it is a dedicated finishing tool so we cannot take heavy cuts. We take about .002 off. I run it at 800 rpm and 180 ipm. the tool only has 2 insert and my part has one area that the wall is only .187 thick which gave us alot of vibration issues, now I run it with only one insert and it works great. One other good thing was they let us try it out for a few months before we had to buy it. Good luck.
 

ions82

Stainless
Joined
Nov 1, 2006
Location
ABQ, NM
The top of this block needs to be highly polished, after some pockets have been machined in it.


I'm just curious. Why does this part need to be polished? Does a certain function depend on the polished finish? If a customer just wanted some bling, I'd just polish them out and charge accordingly.
 

kg2v

Aluminum
Joined
Apr 12, 2009
Location
Bayside, NY
what I don't get - you say the part is 1"x6", and you have a 3" diameter cutter so it won't cover the work - how about feeding the OTHER axis, aka feed along the 6", the cutter then covers the work
 

PaulT

Stainless
Joined
Mar 4, 2002
Location
Brisbane, CA, USA
Why does this part need to be polished?

This is a product we're manufacturing and marketing ourselves, and the polished appearance definitely pays off in terms of customers being willing to put their money down.

The polishing is going pretty well already, I'm just trying to optimize the process to cut down the production time and costs as much as possible.

Regarding cutting across with the 3" cutter, that of course works but anytime you make multiple passes you will have some slight lines at the overlap points (at least on my not so rigid machine). These lines add substantially to the amounting of sanding that has to be done, and if you don't get the lines totally out they really show up on the surface.

If you can make the entire finishing cut in one pass (ie no lines at all) its a big time saver on the polishing effort.

Paul T.
 

K&Y

Plastic
Joined
Jan 30, 2008
Location
Montreal, Canada.
I've read that diamond inserts make a lovely finish on aluminum and other soft metals.

There's never been enough money here for me to try it though.

You are absolutely correct. You will attain a substantially better finish on aluminum, brass, gold, platinum, etc. (non-ferrous materials in general) if you use a diamond insert (whether it is a natural or synthetic diamond) as opposed to PCD or carbide. PCD tools can be used to rough out the piece and the single-crystal diamond tool can be used for the light finishing pass, giving you the finish you require. And as far as price is concerned, they aren't as expensive as one thinks, given the fact that these tools can be relapped numerous times and will pay off in the end.

A few variables are very important in achieving an optical finish on parts. Machine rigidity being the most important factor. Single-crystal diamond tools are used in machining high-end aluminum wheels, racing pistons, ophthalmic lenses, and drums for laser copying machines (pictures attached).
 

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pirko

Aluminum
Joined
Jan 1, 2010
Location
Czech Republic
You must checking machine by Ball Barr test from Renishaw. After Checking Hardware condition, you must using right tool and cutting condition. Best Regards Libor Pírko
 

K&Y

Plastic
Joined
Jan 30, 2008
Location
Montreal, Canada.
Carbide tools can be very effective for "hogging" out aluminum. However, the poster is trying to attain a "mirror" finish. That cannot be done with carbide tools.
 

kustomizer

Titanium
Joined
Aug 17, 2007
Location
North Fork Idaho
The "brand" of the aluminum is a big consideration also, perhaps as much as the tool you cut it with. We get much better finishes with say Kaiser over Sapa or Alcoa. They all make 6061 T6 but they are not the same, something to do with the process I imagine.
 

mordantly

Plastic
Joined
Dec 31, 2009
Location
CA
the best overlap i have ever seen is about a half tenth... and that was fine for the anal engineers that didn't have a concept of GDT where i worked. you will never eliminate this unless you clear the surface in one pass.
 

spork2367

Aluminum
Joined
Jul 30, 2008
Location
USA
Carbide tools can be very effective for "hogging" out aluminum. However, the poster is trying to attain a "mirror" finish. That cannot be done with carbide tools.

It sounded as if he wanted to get as close as possible. If that meant a mirror finish off of the mill great, but if it just meant less tooling marks to polish out that would be good too. Yes, the shearhog will leave some lines, but they can be buffed out with a small buffer quickly. I assume that the investment in diamond inserts and a holder is going to be much higher. He also said his machine wasn't the most rigid. It would make him pretty unhappy to buy expensive cutter and find out his machine wasn't as capable as the cutter. At least if he buys a shearhog he can rough out some serious material, leave the best finish his machine is likely capable of, and not spend a fortune. Just my .02.
 

CalG

Diamond
Joined
Dec 30, 2008
Location
Vt USA
For my .02,when it comes to polishing flat alu, the as milled finish means nothing. It's a waste of time to try to achieve near mirror results at that stage.

Several stations of progressively finer abrasive paper stuck down to a sheet of glass will accomplish all that is required to prepare for buffing in a few strokes.

Rework is as easy
 

K&Y

Plastic
Joined
Jan 30, 2008
Location
Montreal, Canada.
It sounded as if he wanted to get as close as possible. If that meant a mirror finish off of the mill great, but if it just meant less tooling marks to polish out that would be good too. Yes, the shearhog will leave some lines, but they can be buffed out with a small buffer quickly. I assume that the investment in diamond inserts and a holder is going to be much higher. He also said his machine wasn't the most rigid. It would make him pretty unhappy to buy expensive cutter and find out his machine wasn't as capable as the cutter. At least if he buys a shearhog he can rough out some serious material, leave the best finish his machine is likely capable of, and not spend a fortune. Just my .02.


You have a valid argument with regards to what he'd like to attain, given the equipment he possesses. Although, no special tool holder needs to be purchased in order to utilize an indexable diamond insert. I will post some pictures later on this afternoon, so that I can show you. Whether you use Kennametal, ISCAR, Sandvik, etc., it is possible to have any of those manufacturer's inserts available in a single crystal diamond format so that the client's expensive investment of toolholders isn't wasted. Whether the operation is milling or turning, this can be accomplished.

In reading his goals, he did say that he'd like to "optimize the process to cut down the production time and costs as much as possible". This can be accomplished by reducing the amount of steps that it takes to complete the part, attain a better surface finish, and please the client.

We presently have a client in the Microwave industry that is manufacturing duplexers, couplers and a host of other aluminum based parts. Their original operation consisted of face-milling the parts with either 3", 4" or 6" flycutters with APKT carbide inserts installed. Then, they'd sand the parts by hand with fine-grit sandpaper to achieve the best results. The problem with this procedure was that the surfaces were mating surfaces, and they had a difficult time in maintaining consistency throughout the lot process. Now, bear in mind their machines are not the most rigid either, but we were able to cut down on the time-consuming sanding process by replacing it with the the following procedure. They'd first rough out the piece with PCD-tipped inserts, giving them a better finish to begin with as compared to the carbide inserts. That would be followed with the use of a single diamond insert set up in the 4" face mill with blank inserts to balance it out). They would take about 0.002"-0.005" off on the final pass in order to get the finish they desired. The diamond has a 100mm Radius, with a 10° cylindrical clearance, and 0° rake. I will be able to post pictures of this later as well.

They have cut their process time by more than half at this current stage, sped up production, decreased their cost per piece due to longer tool life and less down time (fewer tool changes) and now can attain the finish they desire.
 
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spork2367

Aluminum
Joined
Jul 30, 2008
Location
USA
I'd like to see some pictures of your standard single diamond inserts. I checked out your website earlier before I posted.
 

Tonytn36

Diamond
Joined
Dec 23, 2007
Location
Southeastern US
You know, it still irks me as to why PCD/Diamond tool insert manufacturers don't put anywhere near enough PCD/Diamond on the inserts. Why is that?....In the case of PCD, the PCD segment is the cheapest part of the tool!...All the cost is in the seating, wire work and grinding.
(I know, we make PCD tools in house for our own use).
 








 
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