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Unread 09-10-2018, 09:20 PM
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Machining aluminum without coolant

Weíre getting the lab cleaned up for this coming season which means itís time to clean our CNC millís coolant system. Itís a Tormach 1100 by the way. This is always a huge mess which brings me to the question.

How bad would it be to mill aluminum without coolant?

We currently just use a constant compressed air stream to keep the chips at bay on our CNC router. Could we do the same with the mill? That way we could just vac them up. Sure the bits wonít last AS long but how big a difference are we talking?

We never machine steel on the mill, itís alway aluminum.

Also, how about the cold saw? Is coolant really important there?
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Unread 09-10-2018, 10:07 PM
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Re: Machining aluminum without coolant

Compressed air is the way to go. You can use mist coolant with a simple tank and an air line, but even compressed air alone is quite powerful. We currently run flood coolant but will be upgrading to mist based on our experiences with the droopy Tormach coolant pump.

I can't speak to cutting metal on a cold saw.

EDIT: 115 runs without coolant, just a vacuum. I like spraying some lubricant on there to prevent galling and chips welding to the sides of the cut. A 4mm endmill at 43ipm in aluminum does well when slotting with a 1/16" stepdown. More aggressive stepdowns in thin material (like 1/16" or 1/8") can actually help reduce galling and chips welding to the work.
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Unread 09-10-2018, 10:18 PM
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Re: Machining aluminum without coolant

We currently run only compressed air, 120PSI standard shop air lines.
Admittedly, we also do shallower DOC and don't usually push the IPM above 80.
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Unread 09-11-2018, 01:05 AM
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Re: Machining aluminum without coolant

Actually - it's pretty cool that you're asking this question. Over the last 5 years my workplace has been moving to a coolant-free machining system for mass production.

It is a little more expensive in terms of tooling and you can't hit the bits quite as hard, but the benefits of being able to recycle the aluminum without them being a waste that needs to be cleaned first is a cost savings on the flip side.

So you're saving yourself the hassle, and being green.
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Unread 09-11-2018, 01:57 AM
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Re: Machining aluminum without coolant

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Originally Posted by Tom Line View Post
Actually - it's pretty cool that you're asking this question. Over the last 5 years my workplace has been moving to a coolant-free machining system for mass production.

It is a little more expensive in terms of tooling and you can't hit the bits quite as hard, but the benefits of being able to recycle the aluminum without them being a waste that needs to be cleaned first is a cost savings on the flip side.

So you're saving yourself the hassle, and being green.
Good point. I was just thinking of the hassle of cleaning out the coolant and then dealing with that toxic waste. Being able to recycle the chips is great.

Anyone have experience with using a cold saw on aluminum without coolant?
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Unread 09-11-2018, 02:09 AM
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Re: Machining aluminum without coolant

Quote:
Originally Posted by Dale View Post
Weíre getting the lab cleaned up for this coming season which means itís time to clean our CNC millís coolant system. Itís a Tormach 1100 by the way. This is always a huge mess which brings me to the question.

How bad would it be to mill aluminum without coolant?

We currently just use a constant compressed air stream to keep the chips at bay on our CNC router. Could we do the same with the mill? That way we could just vac them up. Sure the bits wonít last AS long but how big a difference are we talking?

We never machine steel on the mill, itís alway aluminum.

Also, how about the cold saw? Is coolant really important there?

My experience is that milling/turning Al with constant air is ok as long as you have your feed/speed, DOC dialed in. However, coolant will give you a much larger margin of error. Be sure your air source doesn't move away from the tool. Again, you have less margin and you can't afford to lose the air flow.

When you get the parameters too far off, you'll generate too much heat into the part which will affect your tolerances (thermal expansion). You'll start to gall and clog the flutes. That will exacerbate the problem and then break the cutter and possibly trash the part. Your surface finish will probably not be acceptable.

Remember, the chips will carry away most of the heat from the cutting/shearing/friction of the cutter against the stock. Getting rid of the chips (evacuation) is most important. You can do this, as you state, with compressed air, flood, or mist.

I think most of the problems mentioned above are of less importance to a FIRST bot, but I would hesitate to give those parts to a buyer who is paying $$.

re: Cold saw.
As mentioned, you could do it when your speed/feed is correct. However, in saws I'm familiar with, your speed is already determined and you can't really control your feed rate (other than visually and audibly). Coolant creates a giant mess, so we use stick wax liberally applied.
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Unread 09-11-2018, 05:36 AM
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Re: Machining aluminum without coolant

I’ll add on to the coolant-free club here. We use our CNC mill without any coolant, just compressed air and a bit of cutting fluid on the part. It’s an educational machine so it’s relatively slow (40 ipm, 2mm DoC, 5mm endmill IIRC) but it works well for us. The cuts are all within a decent tolerance, and we haven’t noticed significant wear on the endmills despite getting a good amount of use. This is true for 6061, 7075, and a bit of 6063 (ugh).

As far as the cold saw, I’ve never used coolant with a saw on aluminum. A miter saw with a non-ferrous metal blade will do pretty much everything you need. You can use a bit of cutting fluid or blade wax but it isn’t really needed. With the tolerances we expect a saw to hold for an FRC application, thermal expansion isn’t a big factor.


Edit: To be clear, I’m not recommending running the cold saw without coolant. I just think a cold saw is overkill for FRC and a miter saw makes a lot less mess.
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Last edited by AriMB : 09-11-2018 at 10:36 AM.
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Unread 09-11-2018, 06:15 AM
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Re: Machining aluminum without coolant

It really depends on what kind of cut you are making. If you are just face/side milling stock down to size, it will be more than okay to use no coolant whatsoever or just mist coolant. If you are making deeper cuts (for aluminum Iíd say anything over 0.5Ē) into the material, it would definitely be wise to use flood coolant to avoid chip buildup on the tool or on the part, as this can ruin your endmills very fast. I personally have ruined a brand new carbide endmill by milling a slot in material without using coolant.
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Unread 09-11-2018, 08:08 AM
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Re: Machining aluminum without coolant

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Originally Posted by Dale View Post
Good point. I was just thinking of the hassle of cleaning out the coolant and then dealing with that toxic waste. Being able to recycle the chips is great.
You could use alcohol, it cleans itself Just be careful not to mist it.
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Unread 09-11-2018, 08:29 AM
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Re: Machining aluminum without coolant

When we got our CNC router it came with a Unist mister. It basically sprays a fine mist of light oil. A small cup sized reservoir lasts all year. I was so impressed with how well it worked, I put misters on nearly all of our machines (mill, lathe, chop saw). They aren't cheap, but they are so much cleaner than coolant. We tried a conventional coolant setup on our CNC mill, but in a school where machines sit idle for long periods of time, the coolant was always evaporating and getting fouled. Admittedly for heavier machining the mister doesn't clear chips as well as flood coolant, but the reduced mess makes it so much better.

I would love to cut aluminum dry, but in my experience dry cutting has always been a gamble. Sometimes it works fine, but things go wrong very quickly when chips start to stick to the tool.
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Unread 09-11-2018, 09:28 AM
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Re: Machining aluminum without coolant

Quote:
Originally Posted by Monochron View Post
You could use alcohol, it cleans itself Just be careful not to mist it.
I'd also recommend having some fans set up for alcohol (if you don't have any sort of air-circ already) to help clear fumes.
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Unread 09-11-2018, 10:04 AM
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Re: Machining aluminum without coolant

I would keep the coolant on the cold saw, those blades are not cheap! The cold saw blades are HSS typically, and have a coating to prevent galling as they pass through the metal. Without cooling you would destroy this coating quickly.

We run very high tooth counts blades for aluminum, 250-280 alternating, 3mm width. One of my favorite tools, very accurate, straight, & clean cuts on any aluminum shaft or section.
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Unread 09-11-2018, 10:07 AM
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Re: Machining aluminum without coolant

I run an 1100 in my shop without flood coolant (the stock pump seized up years ago from lack of use). I have a koolmist style mister setup that I'll use for harder materials, like stainless and titanium, but I generally don't bother with it for aluminum or mild steel unless I'm really trying to nail a finish or I'm new to the tool/material/program. Nine out of ten times I pull the pickup tube out of the coolant and use it as an airblast.

The 1100 is a low enough power machine, and modern CAM is so good, that it's hard to overheat even HSS tools or the part when cutting aluminum at proper feed rates. So the problem you're left with is evacuating chips to avoid recutting, something an airblast generally does just fine.

Last edited by Andy A. : 09-11-2018 at 10:17 AM.
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Unread 09-11-2018, 07:34 PM
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Re: Machining aluminum without coolant

I don't see a issue with it, the only problem you might have is if you're using a coated carbide end mill, it'll wear the coating right off it.
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Unread 09-11-2018, 07:44 PM
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Re: Machining aluminum without coolant

Here at IMTS I'm watching Datron machines cutting aluminum without coolant. I believe they may be running a mister though.
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