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Thread: Building the ShopBot Vacuum Table

  1. #11
    Join Date
    Jan 2012
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    Tallahassee
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    17

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    Quote Originally Posted by bradywatson View Post
    Noah,
    Thanks for posting pics. It looks like you put some real effort into your vac system. Bravo!

    You mention that your max Hg" value is 21, but you have 13 Hg" with nothing on the table and all zones open. This tells me that your bleeder is most likely not true ultralight MDF or LDF, and/or it has a significant amount of resin content which prevents it from bleeding/breathing very well.

    So...While your vacuum shows the potential of 21 Hg", in all reality you are achieving a max of 8 Hg" (delta) of usable vacuum. This is a little bit better than a good shopvac, such as a Fein. Good strong vacuums, such as yours can get away with regular MDF or LDF that has more resin than is ideal - However, you are missing out on a substantial amount of hold down power with your current bleeder board - a factor of 2.5x what you are getting now. You are getting 4hp of performance out of your 10hp setup. The rest is being wasted.

    The only way to really rectify the situation is to machine off the bleeder you glued down to the grid. Extra points for thinking about them moving together. Going forward, the only way to tell how good your bleeder will be is to open up all zones with the new sheet on the grid & check the gauge. Ideally, you want 0 Hg", but since you have such a high powered system, up to 5 Hg" is acceptable.

    There is a possibility that the small inlet pipe is hurting your performance as well, especially if it is on a long run with a few bends in it. This can cause the pump to cavitate and be under suction with no 'load'/valves closed because it is choking.

    Also, this business about machining off the 'paper layer' on one or both sides of the bleeder is an old wives tale. Save yourself the agg and just put it on there as-is, then flatten the top to true up the surface & you're ready to work.

    Hope that helps!

    -B
    Thanks for the info!

    That 13" reading was at the tank on the pump, not at the table. I'm thinking that will make a big difference. Keep in mind the pump is rather far away and up stairs. I am not sure on the # of bends but it is more than a few.

    I just checked and with both pumps running and all zones open the zone gauges read 2-3inHg.

  2. #12
    Join Date
    Jan 2004
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    iBILD Solutions - Southern NJ
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    7,986

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    No problem guys. Sometimes the obvious isn't so obvious!

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  3. #13
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    Jan 2012
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    Tallahassee
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    Man it's been a while! I recently started working at the Facility for Arts Research again and they tasked me with putting a new spoilboard on the ShopBot. I discovered a comm error in the process that I eventually narrowed down to the dust collection system causing interference on the usb. The machine would completely lose comm with the computer. I went ahead and added grounds on the outside of the hose all the way to the spindle. I now have continuity between the spindle and the dust collection motor ground.

    On to the pics!
    IMG_5059.JPGIMG_5060.JPGIMG_5062.JPGIMG_5063.JPG

  4. #14
    Join Date
    Mar 2004
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    Delray Beach, FL
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    Unless you didn't have your dust collector on it looks like it's getting choked up from the mdf dust and not sucking.
    Typically this is due to too many gates open or dust jamming up in the hose somewhere. If your hose has sags in it this could be the trouble spot.
    Or, need stronger vac.

  5. #15
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    Jan 2012
    Location
    Tallahassee
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    Quote Originally Posted by bleeth View Post
    Unless you didn't have your dust collector on it looks like it's getting choked up from the mdf dust and not sucking.
    Typically this is due to too many gates open or dust jamming up in the hose somewhere. If your hose has sags in it this could be the trouble spot.
    Or, need stronger vac.
    Haha yes I turned it off for those pictures, sorry I forgot to mention that. That's how I figured out what the problem was.

  6. #16
    Join Date
    Feb 2013
    Location
    River Fall WI
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    796

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    What are you doing in the last 2 pictures? Seems like a lot of dust, even with the DC off.
    Kyle Stapleton
    River Falls Renaissance Academy
    Math/Technology Education Teacher


    PRS Alpha 96x60 2.2 hp spindle, Double Air drills, 6" indexer, Fein 5 zone vac table
    Desktop w/spindle
    Potter Pen
    Aspire 8.5, Creo 3.0

  7. #17
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    Jan 2012
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    Tallahassee
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    Quote Originally Posted by Kyle Stapleton View Post
    What are you doing in the last 2 pictures? Seems like a lot of dust, even with the DC off.
    Planing the bottom of the new spoilboard to remove the skin. Just .01" over 4x8ft adds up. The board is then taken off, glue rolled onto the plenum tops, then placed back with the vacuum on to clamp it. Then once it is set, the top of the spoilboard is machined flat.

  8. #18
    Join Date
    Oct 2009
    Location
    Elgin Illinois
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    706

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    In re-reading this thread, I noticed that Brady said: "Also, this business about machining off the 'paper layer' on one or both sides of the bleeder is an old wives tale. Save yourself the agg and just put it on there as-is, then flatten the top to true up the surface & you're ready to work. Hope that helps! -B" Chuck
    Chuck Keysor (circa 1956)
    PRT Alpha 60" x 144" (circa 2004)
    Columbo 5HP spindle
    Aspire 9.0, Rhino 5

  9. #19
    Join Date
    Apr 2015
    Location
    Myrtle Beach, SC
    Posts
    6

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    I saw in one of the pictures, a black bag over the table to help with the vacuum. We took this a step further and cut pieces of 1/8 pvc board (I don't remember the name of the stuff) that matched our vacuum chambers and another set that matched some of our mis-mosh shaped pieces. It works beautifully and helps with the vacuum as well. Just figured I'd add a little

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