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Bit cooling when cutting aluminum

Discussion in 'CNC Routing & Laser Cutting' started by Rocco G, Sep 14, 2020.

  1. Rocco G

    Rocco G Member

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    Hi all,

    I'm about to order a new CNC router (finally, the pandemic made me hold tight for six months) - 6' x 10' table, vacuum hold down system, ATC, etc.. When cutting aluminum it looks like I have two options for cooling the bit. First is a misting/coolant system (i.e. Unist or similar) or a stream of cold air (vortex cool tool is one example). I really like the idea of the cold air stream since there is no cleaning of the part after, no fluids to refill, etc. Does anyone have experience with the cold air stream method instead of a coolant system? I have a friend who swears by the Unist system while another swears that the cold air is best. If I can avoid the whole coolant/cleanup issue I think I'd be ahead of the game.

    Thoughts?

    Thanks!
     
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  2. Jester

    Jester Slow is Fast

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    We recent bought an Exair cold gun kit (vortex tube spot cooler). We haven't installed it yet so can't give you any feedback on its efficacy.

    [Links didn't work for everyone, so see post #4 below for text of referenced case studies]
    We don't run a vacuum table, but this case study is directly applicable to your use: Machining Aluminum Sheet on Vacuum Table (This is the medium-size cooler they specified https://www.exair.com/index.php/5215.html. We have the two-outlet kit #5315.)

    Cooling Router Bit in Sign Making (In this instance they are using the large two-outlet cooler)

    Cooling Carbide Cutters (Cutting carbide steel. Feed rates went up AND the tool life increased from one shift to one month!)

    Be aware that vortex tubes use a large volume of compressed air so you may need to upgrade your compressed air system. We have the medium size, rated 15 CFM @ 100 psi. There is a small model which uses 8 CFM, and the large one requires 30 CFM!
     
    Last edited: Sep 14, 2020
  3. Rocco G

    Rocco G Member

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    Jester,

    I already knew that I need a good amount of air for a cold air system. I have an old 60 gal upright compressor (240 V) that we used to use for spray painting back-lit sign faces. Hmm, probably giving away my age there. Anyway, it was quite sufficient for a spray gun. I was just out looking at it but don't see a CFM capacity plate anywhere. TBH, now that I've looked at it, I'm considering a replacement, since it's from 1986. Also, the case study link requires a log in but I was able to see the unit you bought. The vacuum table for the machine I'm going to buy has a dedicated 10 HP compressor but I doubt I could combine the two. Have you installed your air gun on your machine yet? I'm interested in how you "piped" it in. I'm guessing hard pipe from the compressor to the unit, then some sort of flex to the gun itself?

    Thanks!
     
  4. Jester

    Jester Slow is Fast

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    Here is the text of the case study: "This customer machines screen printed aluminum sheet stock. A vacuum vise holds the piece, so conventional coolant could not be used since liquid would foul the vacuum generator. They used ethanol because it evaporated, and, as a gas, did not foul the vacuum generator. Ethanol, however, is very expensive ($200/gallon) and discolored the aluminum. To protect the against this, a clear coat had to be applied prior to machining. As an alternative to the liquid coolant, they installed a Model 5215 Cold Gun Aircoolant System. This provided ample cooling, eliminating the need for the ethanol and clear coat operation. This resulted in an annual savings of $20,000."

    Here's another one: "Customer routinely cuts letters and various other shapes out of 1/8" aluminum sheet, expanded PVC board and various other non-metal materials as needed per design of the signage they are manufacturing. They currently either machine the material dry or they use a mist lubrication system to help extend the service life of the cutters. The problem is that this adds a large amount of time to clean-up for the operators who use the machine. The material must be very clean prior to going to next step which is usually painting. By eliminating the mist coolant, the customer can eliminate the huge step of cleaning. The cold air has also proven to allow the customer to run less passes with bigger cuts which increases overall machine productivity. The customer has been using Model 5230 High Power Cold Gun System to achieve these results."

    And the third: "Company manufactures carbide cutting tools. Their carbide cutters are only lasting one shift and they cannot get the production rates required. The cooling provided by the Model 5215 Cold Gun allowed them to increase feed rates and the tools now are lasting a month."

    We are fortunate that our building was formerly a cabinet shop. We inherited a 10hp rotary compressor rated 22-35 CFM @130 PSI, with 1-1/4" hard line plumbed around the shop's perimeter. I plan on running 3/8 inch hose from the nearest outlet to the vortex gun as recommended in the ExAir installation instructions.
     
    Last edited: Sep 14, 2020
  5. netsol

    netsol Active Member

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    rocco, no experience with that type of bit cooling, but, if the cold air can meet your needs, sounds like the way to go. we have a coule weka drills for concrete coring, etc

    you can cool with air or water, just by changing the hose. water is a better cooling agent, but if you are the one who has to clean up, the air seems superior

    we are just starting to dabble in cnc, i am thinking a sabre 408 will be our starting point
     
  6. JBurton

    JBurton Signtologist

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    Cold air can't stand up to long term cutting. What you are doing with a cool air gun, is separating the cold air from the hot air in the compressor line. The gun has a rear chamber and exhaust that takes the heat from the separated air and exhausts it into the room. Eventually the room will hit critical mass, and if the air intake for the compressor is in the same room, it will eventually stop cooling.
    You can go with alcohol, and nearly never clean your parts, fine mist lubricant, that will help your bit's last for a long time but tremendous cleanup and care with dialing in the amount of mist vs air, or go with a cooling fluid that is water based. I've used trico MD20(I think that's the number...), a cold air gun, alcohol fed through the reservoir for the trico oil, and finally settled on Kool Mist 77 and cheap chinese siphon type mister. Alcohol was the best, but most expensive, and I'm a smoker and the CNC is in a big bay, so I had this constant fear of blowing myself up with the alcohol. Kool Mist was the cheapest and simplest to clean up, and since more of my bits break due to accidents vs actual wear out, I haven't noticed a drop in tool life.
     
  7. JBurton

    JBurton Signtologist

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    Don't you dare replace that compressor. Call a compressor company, ask for a quote to tune it up, and while you have the tech there, ask him what he thinks about it. The old stuff is made from metal, can take a pounding, and tends to last longer.
     
    • Agree Agree x 1
  8. netsol

    netsol Active Member

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    exactly what i was thinking. he will be scrapping the brand new compressor, and the tech will change a belt on the old one, prepping it for another 10 years.
     
  9. ikarasu

    ikarasu Very Active Member

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    Depending on what you're doing... Most aluminum has some sort of oil on it before it even gets to your cutter. Traffic Signs especially need to be acid etched before application to be 3m certified.

    I know you can buy some pre etched stuff... But it was quite a bit more pricey so we didn't even bother with it when the sales rep came around.


    I'd look into what your aluminum supplier has, see if going air would even save you.from washing the material.
     
  10. Souldar

    Souldar New Member

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    Mist system. Period
     
  11. John Miller

    John Miller Member

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    We cut lots of .25" aluminum letters and occasionally some .375" aluminum. I have an air jet system that we never use. We buy single flute bits from tools today that are specifically designed to cut aluminum (others sell them too) If you set the speed and feed properly, the cut will be very clean with no cooling necessary.
     
    • Like Like x 1
  12. Signed Out

    Signed Out Very Active Member

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    Does the aluminum to be routered have printed vinyl already applied to it? Have been looking into a router to pump out large orders of small 040 and 063 aluminum signs. We currently use a shear and pneumatic hole punch and corner rounder. Always curious how a router table would handle say, (2000) 8"x4"x.040" aluminum signs with printed/laminated vinyl mounted to 8'x4' sheets. Does the vinyl and adhesive gum up the bits, make a mess? And then adding a misting system seems like a mess, would you have to clean each of the (2000) signs individually after routering? How many 8"x4" signs could you router from an 8'x4' sheet? I can yield 144 using a shear butting all the signs together, but with a router do you need to leave some material between each sign?
     
  13. spectrum maine

    spectrum maine Member

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    It depends on how much aluminum you want to cut. We cut a fair amount of o63 and 125. What we do is fill up a spray bottle with cold water and a few drops of dish detergent. We then spray small puddles in front of the bit and the bit passes through the puddle. if you are not pushing too hard the bit will cut dry but we find an occasional puddle works better.it is not enough to wreck our spoilboard and the bits last 2-3 times longer. On 125 or thicker we run 1 pass cutting a groove in the material then squirt the fluid into the groove for a fully lubricated 2nd pass. works great. In aluminum you have a very small window of feedrate and spindle speed. The chips should come out as little 1/2 moon chunks. The heat is mostly removed in the chunk/chip.
     
  14. ikarasu

    ikarasu Very Active Member

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    You can't us mist if there's graphics on it. So you have to turn the mist off.... Otherwise it contaminates the glue. Not a problem when cutting a sheet or two, but if you're cutting tons of sheets it is.

    Depending on the vinyl it'll gum up the bit. Using regular cast or vinyl doesn't seem to be an issue... But using road reflective we've never been able to get good cuts.

    8"x4" is small... You might have issues with the bit pushing the pieces around. When we cut that small we have to double sided tape the back to the table. You could do tabs or a really thin finish layer, but we found double sided tape to be the easiest.


    We do a lot of license plates in roughly that size. Thousands at a time... It's a lot of work. It'll never cut it perfectly with no mess because you generally use an up it bit on aluminum.... So it tears up the overlam leaving a rough edge. We always have to do a quick sanding pass to make them look nice.


    That's just our experience with thin, sheeted aluminum.


    And yes. You lose either 1/8" or 1/4" between each sign/side with a router vs a sheer
     
  15. JBurton

    JBurton Signtologist

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    I've only had experience with ij35c laminated then cut, but the media tends to sliver up and restick to the face, so masking was necessary. Oddly enough, translucent 3m vinyl doesn't do the same thing...

    I'm rather impressed by this. What diameter bit, how many passes, and what speed/rpm are you running this at?
     
  16. GaSouthpaw

    GaSouthpaw Active Member

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    In your specific instance, I'd stick with the way you're doing it. You wouldn't see any benefit by switching.
    To your specific questions:
    - Yes, the vinyl could possibly gum up the bit. Usually, though, no.
    - Yes, you'd have to clean the misting fluid off- and make sure you're not screwing up the print/media/laminate. Since most fluids are water or vegetable based, you can use dishwashing liquid, but then you're either drying them or have to wait for them to dry.
    - Using a 1/8" bit, you're only going to yield 132 pieces, give or take. Much like cutting with a saw, you're losing the width of the cut in material with every cut. Nesting would help gain a few pieces, but it's never going to yield as well as shearing.
     
  17. Josh Martinez

    Josh Martinez X-Edge Products Excellent Speed, Excellent Quality

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    Yes I have done both. Cold air works okay, But not good as using some coolants. I work for X-Edge Products we offer a coolant call Liquid X. This is an alcohol base coolant designed to be uses in a misting system. With it being alcohol base mist, you use less off it making it easier to clean up. Also the alcohol cools the tool when air is moving. Many of our customers use the Unist mist system and aluminum chip collectors. https://www.xedgetools.com/x-edge-store/LIQUID-X-MISTING-FLUID-c19010037 Hope this helps, Let me know if you have anymore questions. Feel free to call me. Josh (866)591-9991
     
  18. MikePro

    MikePro Major Contributor

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    vortex air is the bare-minimum, but you'll still have to feather your feeds & speeds as metal/metal friction quickly overcomes the cooling effect of expanding air.
    never hurts to start "cheap" and learn your lesson/workarounds BUT if you go with a coolant/mist system then you'll never regret it. Plus, when you're using GOOD bits at $40 a pop, the coolant system pays for itself over time thru bits&substrate savings alone.
     
  19. JBurton

    JBurton Signtologist

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    I used to pay that for a Belin/LMT/Onsrud bit, but when my sign distributor started carrying them, it dropped to $20/per.
     
    • OMG / Wow! OMG / Wow! x 1
  20. Rocco G

    Rocco G Member

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    Wow, thanks for all the replies. And as usual, there are many ways to accomplish the same thing in the sign game. It's always been that way which is part of the interest of this game.

    For those who recommended keeping the compressor, I will rewire it and then see how well it works. it's been sitting for at least fifteen years but has been stored inside all this time.

    I got a response from Shopbot about using a mist system and also vacuum hold down.
    "In order to use vacuum hold down AND a mister you would need to use gasketed hold down (not “through the spoil board” hold down)."

    That just doesn't seem right to me. I've installed thousands of FCO letters made from aluminum and it would be madness to think of making gaskets for cutting out letters. I might as well put a new blade in my bandsaw and do them all by hand. Do you folks that have a misting system use an air filter between the spoil board and your pump to clean the returning air? Or would an alcohol based coolant evaporate quickly enough to not cause problems?

    Again, thanks for all the help and info.
     
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