Page 2 of 2 FirstFirst 12
Results 11 to 20 of 20

Thread: vacuum table question

  1. #11
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
    Posts
    7,986

    Default

    Try not to reinvent the wheel...Size your zones to the size panels you mostly cut. I would do 7 Zones:

    1) 24x24"
    2) 24x24"
    3) 24x48
    4) 48x48
    5) 12x96
    6) 24x60
    7) 24x60

    This combination will give you the ability to hold down a 2x2', 2x4, 4x4, 4x8, 5x8, 5x10, 5x12 by just turning zones on or off.

    6.6 Hg" isn't a lot to work with. You would need a min of 4 Fein vacs to do anything for real and probably more like 6. Lighthouse motors are another option & cheaper.

    Small parts with the Fein? I wouldn't count on it unless you are an expert on vac hold down...However there are ways around this. Look for my 'Vacuum Film Technique' on this board.

    Remember - there is no replacement for displacement. The aspiration here is limp along using the Feins and other 110v solutions until you can afford a real vacuum pump made for production. This was the idea behind the Lighthouse vacuums - just a bandaid...so keep that in mind. There are no 110v (or 220v single phase) solutions out there made for production duty...so expect whatever you are running to die. Not to be all doom and gloom...but I call a rose a rose.


    Knuckle Dragger's Guide to Vacuum Math:

    In an ideal world, you would get 100% of what your vacuum was capable of delivering and have zero leakage from your setup. In the real world, this never happens...so trim your numbers off a bit.

    The entire weight of the atmosphere is holding down your parts when you apply a perfect vacuum to it - In this case, 29.92 inches of mercury (Hg") OR 14.7 pounds per square inch (psi). These two are equal. If you live up on a mountain, you'll have less pressing down. In Death Valley, you'll have more.

    You need to ask yourself if the surface area of your part at a given vacuum value results in enough pounds per square inch of hold down to resist the cutting forces of the router. If it isn't you can cheat by selecting a different tooling profile (downcut, straight) or by cutting with a lighter chipload, with more RPM and/or slower speeds.

    If a 12" square is to be cut out with a total available vacuum of 6 Hg" (we'll take off 10%, very optimistically) The calculation is as follows:

    12x12 = 144 square inches

    6 / 29.92 Hg" = .200 X 1 (14.7/29.92 [these are equal so they represent 1 as a conversion factor to psi]) = 2.94 psi

    Total hold down on part = psi value x square inches

    144 x 2.94 = 423 total pounds of down force

    As the part approaches 0x0" in size, the law of diminishing return comes to play. You aren't going to hold a 1" square down with 2.94 psi - so there comes a point where vacuum just isn't the right tool for the job, or you need to combine methods to make hold down reliable. Furthermore, you need to account for when your cutter breaks through the sealed off material and exposes the cutting kerf where it meets the bleeder board. The surface area of all kerfs can add up quickly and your part hold down will fail in the middle of the job. Gotta small vac? Program for turning on/off zones as you machine, when it is practical. It sucks...but take a portion of your profits and save for a pump. It's a nice luxury when you've been doing this stuff for a while.

    Good luck - search this forum. I've dispensed countless tips and tricks involving vacuum over the years and so have others.

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

  2. #12
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,388

    Default

    J...
    Use the 6.6 (inHg) number
    Gary Campbell
    GCnC Control
    GCnC411(at)gmail(dot)com
    Servo Controller Upgrades
    http://www.youtube.com/user/Islaww1


    "We can not solve our problems with the same level of thinking that created them"
    Albert Einstein


  3. #13
    Join Date
    Jan 2018
    Location
    Los Angeles
    Posts
    15

    Default

    Hi Brady,

    Wow! very comprehensive! Many thanks!

    Everything you mentioned looks to be about what I have discovered so far, and I agree about the zones..

    I actually bought this ShopBot PRT 5x12 from a guy who also gave me a 15hp FPZ, but the problem is what you mentioned.. it's 3phase and I only got me some 220v.

    Right now I'm looking at my options... The specs for this FPZ blower show that it will actually work with anything between 7.5hp and 20hp so I might look into just swapping out the electric motor and getting my machinist guy to make some kind of adapter plate ( if necessary )

    The lighthouse motors is an option that I've considered also.

    The Fein that I tested with here is just because it was sitting here this morning and I wanted to try it out. About how long do you think they last?


    Thanks for the math tutorial, that was really helpful.

    I'll update as things progress.
    -JAMES

    Screen Shot 2018-01-25 at 3.19.18 PM.jpg

  4. #14
    Join Date
    Sep 2014
    Location
    Poughkeepsie, NY
    Posts
    28

    Default

    You have a 15hp FPZ, best option for single phase is to just get a VFD to run it. I think I paid around $900 for mine.

  5. #15
    Join Date
    Dec 2008
    Location
    Diamond Lake, WA
    Posts
    1,746

    Default

    For small parts I use a 1" thick piece of MDO with t-tracks. The MDO is cut to 48"x48". Fits over two of the zones in my table. The vacuum holds the MDO, clamps hold the material. Works really well and I kept my 5x8 PRS to 7 zones. 5 of the zones are used to hold a full sheet of plywood. The other two zones are for 5x5 BB and large slabs and blanks that I surface from time to time.
    Don
    Diamond Lake Custom Woodworks, LLC
    www.dlwoodworks.com
    ***********************************
    Life is not a journey to the grave with the intention of arriving safely in one pretty and well preserved piece; But to skid in broadside, thoroughly used up, worn out, bank accounts empty, credit cards maxed out, defiantly shouting "Geronimo"!

    If you make something idiot proof, all they do is create a better idiot.

  6. #16
    Join Date
    Jan 2018
    Location
    Los Angeles
    Posts
    15

    Default

    Quote Originally Posted by JMCS View Post
    You have a 15hp FPZ, best option for single phase is to just get a VFD to run it. I think I paid around $900 for mine.
    Hi Jeff,

    Can you fwd me the specs on the VFD you have? It would be awesome if I could run this FPZ relatively un-adulterated.

    all my best,
    JAMES

  7. #17
    Join Date
    Oct 2009
    Location
    Larrabee IA
    Posts
    171

    Default

    James I just sent you a PM for a convertor Mark Stief

  8. #18
    Join Date
    Sep 2014
    Location
    Poughkeepsie, NY
    Posts
    28

    Default

    Yaskawa V1000 VU2A0069FAA be sure to double check. All VFD's can run on single phase, they just have to be de-rated for there amp usage.

  9. #19
    Join Date
    Jan 2018
    Location
    Los Angeles
    Posts
    15

    Default

    Quote Originally Posted by JMCS View Post
    Yaskawa V1000 VU2A0069FAA be sure to double check. All VFD's can run on single phase, they just have to be de-rated for there amp usage.
    hi Jeff,

    This looks like a suitable option. How many amps is the circuit breaker you're using on this? ( I don't want to blow anything up! )

    -james

  10. #20
    Join Date
    Sep 2014
    Location
    Poughkeepsie, NY
    Posts
    28

    Default

    I think 65amps

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •