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  1. #1
    Join Date
    Apr 2006
    Posts
    76

    How I built a fog-less coolant mister

    Hi everyone. I have been building a fogless coolant mister and I thought I would share how I did it. Most materials are available at a home improvement store. I have rigged up a solenoid valve which I can actuate from EMC2. I am pretty pleased with the result, and the total cost was about $120 dollars.

    Let's get started:

    Step one: Go shopping (any home improvement store will get you started).

    I started with the following:

    Inline water filer canister (you can bin the filter as all you need is the filter)
    Some 1/4 inch compression fittings
    Some barb fittings
    Some 1/4 inch rubber tubing (length will depend on your machine)
    Various pipe fitting (plan on making a few trips)
    An air pressure regulator
    Attached Thumbnails Attached Thumbnails Mist Build 010.jpg  

  2. #2
    Join Date
    Apr 2006
    Posts
    76
    Step 2: start plumbing

    This system works by putting air pressure on the top of the coolant to force it out to the nozzle where it is mixed with air. We need to be able to get the coolant out of the bottom of the canister. We will need a special fitting to do that. I did this by turning down a barb fitting and soldering it to a compression fitting. This way I can feed a hose to the bottom of the canister and seal it at the outlet at the top.
    Attached Thumbnails Attached Thumbnails Mist Build 013.jpg   Mist Build 014.jpg   Mist Build 015.jpg   Mist Build 016.jpg  

    Mist Build 017.jpg   Mist Build 018.jpg  

  3. #3
    Join Date
    Mar 2004
    Posts
    1543
    http://www.machinistblog.com/

    Or the originals:

    I just had about my 100th request to make a copy of my zero fog mister. its
    a device to spray coolant without that annoying fog the cheap misters put
    out. Anyway I looked up the links and thought I'd repost here also.

    Karl


    http://www.metalworking.com/dropbox/...Fog_Mister.txt
    http://www.metalworking.com/dropbox/...Fog_Mister.DWG
    http://www.metalworking.com/dropbox/...Fog_Mister.JPG
    http://www.metalworking.com/dropbox/...Fog_mister.pdf



    http://groups.google.com/groups/sear...nsend&safe=off

  4. #4
    Join Date
    Apr 2006
    Posts
    76
    Step 3: build a nozzle

    You need to build a nozzle to mix the coolant and air and get that to where you want it. You do not have to follow my dimensions exactly. The key concepts are that you need a very small outlet nozzle to choke down the air flow and maximize the velocity. You also need a small passage for the coolant since the coolant flow rate will be much less than the air flow rate.

    I made mine from brass so I could solder it. The pressures in the system are low enough at this point that you could easily use aluminum or something and just epoxy things together. The nozzle is brass rod which I bored from both ends with a 3/32 drill bit (hence the short length). Then I added an extension which is bored most of the way with 3/32, then through with 1/16 drill bits.

    See my drawing.

    I also whipped up a little mounting arm. You can copy my design if you like. It clamps to the spindle collar and articulates in 3 points. CNC helped for this!
    Attached Thumbnails Attached Thumbnails Mist Build 023.jpg   Mist Build 024.jpg   Mist Build 036.jpg   Mist Build 034.jpg  

    Mist Build 029.jpg  
    Attached Files Attached Files

  5. #5
    Join Date
    Apr 2006
    Posts
    76
    Step 4: Wrap up the plumbing

    I added a solenoid valve and an air nozzle to clear off chips. I also made a mounting bracket. I added the tubing from the nozzle to the canister.
    Attached Thumbnails Attached Thumbnails Mist Build 039.jpg   Mist Build 031.jpg  

  6. #6
    Join Date
    Apr 2006
    Posts
    76
    Step 5: Pause for reflection

    The mister works very well. I run about 15psi and the coolant and air use is pretty minimal. I wrapped the tubing in vinyl tape for protection. It looks a bit low rent, but it was the best idea I could come up with.

    Mistakes I made that you should avoid:

    I initially had plastic lines from the canister to the nozzle. They were too stiff and would pull the nozzle all around as the machine moved. I switched to 1/4 OD vinyl tubing and am much happier.

    I initially had copper tubing for the nozzle. This was very flimsy and in my opinion the wrong inside diameter to work properly. The brass is much better. I have seen some examples where a MIG welding tip was used a nozzle. It might work.

    The mounting bracket needs to be strong. Mine is too weak.

    I added a barb fitting to the end of the tube inside the canister to give it some weight and keep it on the bottom.

    Thanks everyone.

    -Wes
    Attached Thumbnails Attached Thumbnails Mist Build 025.jpg   Mist Build 028.jpg  

  7. #7
    Join Date
    Jul 2008
    Posts
    922
    great write up!

  8. #8
    Join Date
    Jan 2009
    Posts
    237
    How does this set up eliminate the fog?

  9. #9
    Join Date
    Apr 2006
    Posts
    76
    Quote Originally Posted by CalG View Post
    How does this set up eliminate the fog?
    CalG,

    Most misters use a venturi effect to pull coolant up from a reservoir to a mixing block to mix it with air. The side effect of this venturi is that the coolant is atomized, or turned into tiny, tiny droplets dispersed in the air. This atomized coolant is not dense enough to to follow the stream of air and can float up as "fog".

    A fogless system uses air pressure to force the coolant from the reservoir to the mixing block. The coolant droplets are much larger (and there are fewer of them). These larger droplets tend to stay inside the air stream and avoid forming "fog".

    See this diagram which I lifted form Bob Warfield's site www.cnccookbook.com.


  10. #10
    Join Date
    Oct 2006
    Posts
    669
    Good tech, thank you.

  11. #11
    Join Date
    Jan 2009
    Posts
    237
    Ahh

    Air stream entrained coolant drops. Makes sense Thanks

  12. #12
    Join Date
    Jul 2005
    Posts
    12177
    I have a cautionary note:

    You are using a clear plastic domestic water filter housing.

    My shop has used these for coolant filters for years without problems and I have suggested their use many times here on cnczone. Recently, however, someone did install one and the plastic housing fractured making a bit of a mess with coolant all over the place.

    With your setup the housing is under air pressure, not liquid pressure, and when it is almost empty of coolant it is almost full of air at 15 psi; if this housing fractured it could fling plastic shards around.

    A metal shroud around it may be a good idea.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  13. #13
    Join Date
    Jan 2009
    Posts
    237
    My house water pressure ranges from 40-70 psi!

    What a watery mess if one of the two filters would just Crack!

  14. #14
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by CalG View Post
    My house water pressure ranges from 40-70 psi!

    What a watery mess if one of the two filters would just Crack!
    Yes but then you could sue them.

    My thought was that they cracked in use on a machine because they were subjected to pressure cycles every time the coolant pump turned on, leading to a fatigue effect; in a house application the pressure stays constant nearly all the time.

    It was on a Haas machine with the high flow pump that generates around 20-25psi.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  15. #15
    Join Date
    Jul 2008
    Posts
    922
    Quote Originally Posted by Geof View Post
    I have a cautionary note:

    You are using a clear plastic domestic water filter housing.

    My shop has used these for coolant filters for years without problems and I have suggested their use many times here on cnczone. Recently, however, someone did install one and the plastic housing fractured making a bit of a mess with coolant all over the place.

    With your setup the housing is under air pressure, not liquid pressure, and when it is almost empty of coolant it is almost full of air at 15 psi; if this housing fractured it could fling plastic shards around.

    A metal shroud around it may be a good idea.
    I think a cheaper solution would be to get one of those big ball buckets they use for baseball (if you buy a tub of sunflower seeds those buckets)
    http://ak.buy.com/db_assets/large_im.../206226886.jpg
    and just place it in there.

  16. #16
    Join Date
    Jul 2005
    Posts
    12177
    Just make sure the top half of the filter unit cannot fly out like an air propelled mortar.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  17. #17
    Join Date
    Dec 2003
    Posts
    24223
    I used an ex propane tank on Karl T's design.
    http://www.cnczone.com/forums/showthread.php?t=87439
    Post #11
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  18. #18
    Join Date
    Apr 2006
    Posts
    76
    The water filter canister is rated for over 100psi, and pressure is pressure, whether it is water or air. The commercial unit from Hench uses the same sort of clear canister. Of course, if you drop the canister or something, it will be weakened. Still, I am only at 15psi.

    I will try to post a video of the unit in action.

    -Wes

  19. #19
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by UWP_Wes View Post
    The water filter canister is rated for over 100psi, and pressure is pressure, whether it is water or air...
    No, pressure in the form of a gas can be much more hazardous than pressure in a liquid. Liquids do not compress, at least not measurably at low pressures, gases do compress. When a pressure vessel containing a liquid ruptures the pressure is lost almost instantly and the escaping liquid does not propel the fragments of the container anywhere. When a pressure vessal containing a gas ruptures the gas expands rapidly, potentially propelling fragments of the container in all directions at high speeds.

    You can choose to disbelieve but you can demonstrate the difference quite easily. Fill a balloon with air, stick it with a pin and you get a bang and the balloon tears widely. Fill a balloon with water to the same volume, stick it with a pin and you just get a sploosh.. The pressure inside the balloon is the same in both cases.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  20. #20
    Join Date
    Mar 2004
    Posts
    1806
    Geof is absolutely correct! I have seen the results of both. When I was young and stoopid, I used some pvc on an air line. Fortunately, when it let go, I was not in the building! As a fire protection engineer, I have seen water pipes burst and the result is a lot less dramatic:})
    Art
    AKA Country Bubba (Older Than Dirt)

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