Just showing off downdraft system


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Thread: Just showing off downdraft system

  1. #1

    Default Just showing off downdraft system

    Well I originally was going to use a water table, but after reading a bunch of threads, and seeing cutters in action using the water table and still seeing some some come off the table. especially if The water table isnt very deep like mine was going to be. I decided to opt to make what I think (when I get the machine up and going ) a pretty kick ass down draft table. Here are some pics of what I did and all in all only cost a few hundred bucks for all the duct work and parts,

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  2. #2
    Community Moderator Jim Dawson's Avatar
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    Default Re: Just showing off downdraft system

    Nice concept, but that particle board would not be my first choice for a plenum for hot sparks. Looks like a fire waiting to happen.



  3. #3

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    Quote Originally Posted by Jim Dawson View Post
    Nice concept, but that particle board would not be my first choice for a plenum for hot sparks. Looks like a fire waiting to happen.
    That particle board is about 2 feet from the grates and the grates won't easily allow sparks or even hot Slag into them and if it happens to all the plenums have 1/16 inch screen mesh in them to catch debris. (I thought of the fire aspect)



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    Default Re: Just showing off downdraft system

    Very nice. I might copy your idea.... Its been doing my head in how to do downdraft...

    Rod Webster
    www.vmn.com.au


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    Default Re: Just showing off downdraft system

    I think you are heading for trouble with your current design.

    My table has both a water table and a downdraft system. The top of the water is about 5 inches below the top of the slats. The plasma stream hits the water surface and boils off the water. From the pics, it looks like you will have around 4-5 inches to the table top so you'll have that hot stream hitting the table and the fan intakes. They could get damaged from the plasma stream.

    It looks like you are using fans with inline motors. Plasma generates staggering amounts of metal dust and debris. A good percentage (10-20%) is fine metal particles that are also slightly magnetic after plasma cutting (steel cutting). These particles destroy motors. My table uses a belt drive to power the fan and it has lasted 6 years. My first attempt used a inline fan and sealed(??) motor and it lasted 2 weeks.



    Just my $.02.

    Willy



  6. #6

    Default Re: Just showing off downdraft system

    well we will see how it works I rekon, im not worried about the fan intakes getting ruined the ga metal on them is pretty thick and if they get chewed up there only $5 each. I will only be cutting stainless with this machine, and The actual Box where the downspouts come in have baffles in them to trap debris before it reaches the inline fans, there is a clean out now in the box to clean of debris.

    I had a worry the pan was not deep enough, but it is what I had to work with, Do you have a picture of your two way design.

    - - - Updated - - -

    well we will see how it works I rekon, im not worried about the fan intakes getting ruined the ga metal on them is pretty thick and if they get chewed up there only $5 each. I will only be cutting stainless with this machine, and The actual Box where the downspouts come in have baffles in them to trap debris before it reaches the inline fans, there is a clean out now in the box to clean of debris.

    I had a worry the pan was not deep enough, but it is what I had to work with, Do you have a picture of your two way design.

    - - - Updated - - -

    well we will see how it works I rekon, im not worried about the fan intakes getting ruined the ga metal on them is pretty thick and if they get chewed up there only $5 each. I will only be cutting stainless with this machine, and The actual Box where the downspouts come in have baffles in them to trap debris before it reaches the inline fans, there is a clean out now in the box to clean of debris.

    I had a worry the pan was not deep enough, but it is what I had to work with, Do you have a picture of your two way design.



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    Default Re: Just showing off downdraft system

    Look at my build, "A Different Machine - Downdraft/water table", especially the beginning. It shows how I laid out the water table, slag shield, screen filters, and blower. The one thing I wish I had done was to make the screen filters (before the blower) much bigger. Mine clog up after 15 - 20 min of operation and I have to stop and clean them otherwise the downdraft is reduced. What gets through the screens is exhausted through the duct to the outside (mostly smoke and very fine dust).

    I occasionally cut stainless and it is worse than mild steel to cut. You need much higher amperage and slower speeds . The one good thing is that the sheets usually don't have any oil on them so the smoke is reduced.

    Willy



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    Default Re: Just showing off downdraft system

    I was shown a down draft table where the air intakes were a row (across) a series of V shaped tubes with holes drilled on each side of the V. The tubes ran into a manifold that was tired to two 12" dia ducts that existed out of the table and then outside the building. It was explained to me that the system was designed so there was a down flow of air but the point was not to suck the dust and debris into the air holes but to simply cool the super heated air below the cuts and the particles dropped into a pan underneath. I went out and looked at the outside and after 2 years of cutting there was NO build up of anything. I was also told it was designed by a HVAC engineer ad the hole openings , fan ratings and duct sizes were all carefully engineered. The design was not for sale but I saw it work! When it was running there was not a hint of smoke or dust inot the room.



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    Default Re: Just showing off downdraft system

    Interesting Tom. I sometimes wonder if we've been conditioned into thinking that we to evacuate the whole table bed. This might be the case if your table is 90 metres long with multiple heads like one of my suppliers, but maybe its overkill for a small 4x4 or 4x8 table? After all, the source of the fumes comes from a single point. I think I'm going to try building a trough arrangement under the slats that spans the gantry ends and therefore will track the torch. This would be connected via a flexible duct to a small multistage welding fume extractor. If it was mounted on drawer slides, it would be easy to pull out from under the slats to clean.The downside is the flexible duct but there are many machines with moving duct work in industry. If that does not work (and it would only be because of insufficient fan capacity). then maybe a small bowl shaped fixture on a belt driven stepper could track the actual torch as it travels across the table and feed the dust into the extractor fan.

    Rod Webster
    www.vmn.com.au


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    Default Re: Just showing off downdraft system

    What I found most interesting in the builders explanation was that the objective was not to remove the debris and dust but to remove the heated air that kept it in suspension So it was an air removal system (heat exchanger) rather than a dust extractor. I saw the tray underneath and it was full of particles large and small. It resembled a large gas grill (Barby) with the flame tubes tied to two ducts. One duct ran the length of each side tot he back and the V - Vents were tied in perpendicualar and went acrsoss the table. He said it would not work unless the airflow as evenly balanced and that meant precisely placed and correctly sized holes along each if the V-tubes. took some time on a slide rule for that design !



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    Default Re: Just showing off downdraft system

    Quote Originally Posted by Torchhead View Post
    took some time on a slide rule for that design !
    Ouch! don't remind me that I'm old enough to have actually used one!

    Rod Webster
    www.vmn.com.au


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    Default Re: Just showing off downdraft system

    Haw! I have an old Pickett that is hanging on my wall just like the one I used in EE classes!



  13. #13

    Default Re: Just showing off downdraft system

    cool, ya i will be cutting 12ga stainless pretty much 90% of the time. I have seen some tables with downdraft vents like mine that were fairly close to the cutting top 4" or so like mine is, so im hoping mine will work, as I dont really want to remake the bed at this point, I have yet to cut anything. I am trying to find someone that can guide me through one cut on my sheetcam software I just got and am not familiar with. If there is any takers into helping me set this up I would be more than greatful and compensate.

    I wont be using my machine much more than 20 mins at a time I rekon, and I have just put in a removable trey where any glad that falls into the vents I can remove from the "wind chamber box" I made, and a washable filter before the fans to catch any metal dust that would happen to clog them. so after how every many minutes of cutting if it does get clogged I can simply wash and reuse in minutes.



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    Default Re: Just showing off downdraft system

    Suggest you skitter on over to CNC Systems Made in the USA | Arclight Dynamics and their training videos and watch the one on SheetCAM. Its better than the included tutorials since it focuses on using SheetCAM for Plasma.



  15. #15

    Default Re: Just showing off downdraft system

    Thank you very much sir.



  16. #16

    Default Re: Just showing off downdraft system

    Well after a few cuts the downdraft system works great. There is quite a bit of metal dust that goes through there like someone mentioned. But I figured out in my opinion one hell of an ingenious way to prevent that from going through the fans... A big ass magnet right in front of the fan grabs any metal debris before it enters. No need for a filter that will clog or anything. I just did a 5 minute straight long cut project and there was about zero smoke in the shop. Very happy



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    Default Re: Just showing off downdraft system

    Magnet isn't going to pull aluminum out of the flow. Use the machine to cut parts for a thien or cyclone separator.






  18. #18

    Default Re: Just showing off downdraft system

    Quote Originally Posted by rocketflier View Post
    Magnet isn't going to pull aluminum out of the flow. Use the machine to cut parts for a thien or cyclone separator.



    that certainly is nifty. I dont cut aluminum though. and have no room for that big ass thing.. lol



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