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  1. #37
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    Default Re: 4'x8' vacuum table build questions

    You need to get into troubleshooting mode and simplify as best you can. The one difference between your setup and mine based on what I know of yours is the check valves, which I don’t have. Even if you had a leak, it would have to be a huge leak to not get any vacuum from 4 motors. Since you have a rubber connector for vibration purposes, as do I, you can pull your vacuum motor assembly away from the table plumbing and check that everything works.

    1. First, do you have the gaskets made for the vacuums? A few of the first DIY Black Box vacuum setups ended up burning motors up because they didn’t use the gaskets and likely tightened things down too tight. I wouldn’t run the vacuum motors without those gaskets. They’re fairly thick too, which allows them to seal without much mounting pressure, too much pressure of which could distort the base and may stop the motor from turning well.
    https://www.centralvacuummotor.com/Gaskets/gaskets.htm

    2. If you want to filter now or later, you can pull the rubber connector and install a “filter”. The “filter” could be as simple as a piece of aluminum window screen stretched over the pipe as you slide it into the rubber connector. But really you’d only need this filter during initial setup as long term the spoilboard acts as a filter since it is a closed system. And when you’re doing final removal of the spoilboard, you’re not trying to hold the glued spoilboard down so why would the vacuum be running? Make sure not to leave the screen in place or make sure you check it periodically as you’d hate to starve your motors of vacuum as if they get clogged, they’ll work too hard and burn up. I once put some plastic down to cover unused parts of the table and you could hear the significant difference in the motors so I quickly pulled the plastic and put pick foam down to cover unused areas.

    3. Now you can get to troubleshooting. I initially had #4 before this but in keeping things simple and moving from furthest upstream to downstream, the first thing you should do is check your wiring. Make sure each wire connecting your motors is 120 volt when your multimeter is connected to the ground, Your multimeter should show 220/240V when both leads are connected to the black and white load wires of the vacuum.

    4. Pull the motor assembly and turn on each motor with your hand loosely over the end where the rubber connector would normally go and see if you have suction. If not, your check valves may be a problem or installed incorrectly.

    5. If you’re still not getting suction, before pulling apart your glued plumbing, you need to simplify and separate each motor. I’d build a single, simple box with a single outlet port. One at a time, mount each motor to the simple box WITH THE GASKET and make sure you’re getting suction. If each motor works then you know you have an issue with the plumbing in box as opposed to the table plumbing.

    Hope that helps. And sorry for not responding yesterday but I was with the wife all day out and about. The kids are at the grandparents for the weekend, which rarely ever happens.

    David

    David Gage
    Deep Sea Sound


  2. #38
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    Default Re: 4'x8' vacuum table build questions

    Quote Originally Posted by wmgeorge View Post
    Agree, no filter If your pulling a vacuum directly through the MDF but you say LDF so I do not know. Low density meaning more porous or less?
    LDF is lightweight MDF though I use Trupsn ULDF, which is lighter, less dense, and allows more vacuum through.

    David Gage
    Deep Sea Sound


  3. #39
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    Default Re: 4'x8' vacuum table build questions

    Quote Originally Posted by dgage View Post
    LDF is lightweight MDF though I use Trupsn ULDF, which is lighter, less dense, and allows more vacuum through.
    So its not possible to plug the porous LDF with dust? He was surfacing that spoil board as I read above, so where did that dust go? So I went back and looked at your photos. You have a plenum grid routed in the lower panels fed each by its own piping. On top of each you have a LDF panel held on by what? I am assuming the edges of the LDF is sealed but we are looking for it worked and now it does not thing. I still think dust in the pores or fan blades.

    As an electrician who has been involved with troubleshooting industrial wiring circuits for many years the way to check 230 volts is line to line not line to neutral. or ground. Its possible to have only one side of the 240 volt feeding and the motors would still run at some speed but lacking power.

    I posted the information I found on LDF in my post above.

    Last edited by wmgeorge; 01-20-2019 at 02:55 PM.
    Retired Master Electrician, HVAC/R Commercial union shop and Lots of hobbies. FLA Saturn 2 4x4 CNC Router


  4. #40
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    Default Re: 4'x8' vacuum table build questions

    I have 4 layers; 2 base layers of MDF attached to table cross braces, 1 layer of epoxy-sealed MDF with plenum cutout (Gary-Wiant used a phenolic/plastic layer for his plenum), and 1 layer spoilboard of ULDF, milled both sides (to remove surface glue) and epoxied to plenum. Edges sealed with many coats of poly. I’ve never had problems with the LDF being sealed. Dust is handled by a dust collector but the dust left on the table is easily brushed off before the next run. No problem with dust clogging the table.

    My thought is the issue is with the check valves, which I don’t yet have. If the check valve was able to run open when initially turned on, that would explain it working initially but not sure. Either way, the troubleshooting steps I gave should identify which set of plumbing is the cause, plumbing near motors or plumbing connecting plenum.

    Of course, a simple step I left out is to make sure the shut offs are set correctly with open having the handle wings inline with the plumbing. If the wings are turned 90 degrees to the plumbing connections, this is closed.

    Regarding 240V wiring, I don’t have any experience with industrial machines and only single phase so you would know more than I. Since it is such a simple check, I check across the hots (240V) as well as each leg to neutral (120V). Any deviation would have me check the entire set of wiring.

    Last edited by dgage; 01-20-2019 at 04:17 PM.


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    Default Re: 4'x8' vacuum table build questions

    Quote Originally Posted by wmgeorge View Post
    So its not possible to plug the porous LDF with dust? He was surfacing that spoil board as I read above, so where did that dust go? So I went back and looked at your photos. You have a plenum grid routed in the lower panels fed each by its own piping. On top of each you have a LDF panel held on by what? I am assuming the edges of the LDF is sealed but we are looking for it worked and now it does not thing. I still think dust in the pores or fan blades.
    Sorry I didn’t read your previous post clearly on my phone and I should also post about the filter I recommended above. With such small surface area (2-3” pipe covered), I wouldn’t recommend the filter material I suggested stay on for normal usage. It should only be used when making changes to the spoilboard just in case material got into the piping, which is what wmgeorge is concerned about. After ensuring the spoilboard is attached well and the system works, you no longer need the filter material. The spoilboard now acts as one large filter that no trash or dust can get through.

    And any machining on top of the table will result in dust that would be handled by the dust collection system and/or swept off after each machining session.

    David Gage
    Deep Sea Sound


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    Default Re: 4'x8' vacuum table build questions

    David are you saying its impossible for the LDF pores to plug with the really fine dust from the surfacing process?

    Its possible also low or no voltage to the vacuum motors would cause them to not power up 100%. You would need a clamp on amp meter to verify each motor is pulling its load. To bad he is not closer, I have at least two of them I can find right now

    Retired Master Electrician, HVAC/R Commercial union shop and Lots of hobbies. FLA Saturn 2 4x4 CNC Router


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    Default Re: 4'x8' vacuum table build questions

    Quote Originally Posted by wmgeorge View Post
    David are you saying its impossible for the LDF pores to plug with the really fine dust from the surfacing process?
    When surfaced, the LDF is incredibly smooth so there aren’t any pores to plug, just a smooth surface. Microscopically we know there are pores but in practice it is smooth as butter and machined dust stays on the surface and easily visible.

    Edited to add: actually, it is hard to seal the MDF. It took many coats of poly to fully seal the edges, and I could tell as there was a noise difference between my “sealed” edges and when I put tape all the way around on the edges. So I had to put more coats of poly on to fully seal the edges. So dust definitely isn’t going to interfere with suction though you wouldn’t want any dust on the surface before putting the plywood down or it wouldn’t seal completely to the table as the dust would hold up the wood leaving a gap for air to enter.

    David Gage
    Deep Sea Sound


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    Default Re: 4'x8' vacuum table build questions

    Ok so I just got the snow at my house snowblown and the driveway at the shop all plowed out.

    I'll start by trying to clear up / answer some of the remarks & questions.

    The edges of my LDF spoil board has 4 coats of triple thick polyethylene on the edges.

    I would like to find a filter that I could leave in place but wouldn't restrict airflow.

    I do not have any check valves on my system. I am waiting on a relief valve to get here so I can install it next week. ( are check valves & relief valves the same thing )

    Yes I'm running the filters from Warren. I mounted them once with bolts then when talking to Warren he recommended me using all thread with a nut at the bottom to hold the all thread to the box, then a nut and washer on both sides of the motor flange. My issue is I know the measurement was 2 3/16" but I forgot to write down if the measurement was to the bottom of the flange or to the top of the flange.

    The dust just lays on top of the LDF and doesn't embed or get into the LDF.


    I went in & did some checking on the vacuum system, here's what I found out.

    The first thing I wanted to check was the easiest. See if the LDF is just too porous & just wouldn't hold itself down.

    So I turned on 1 motor and the spoil board (surfaced side up) wouldn't draw down so for some reason I decided to flip the spoil board over (surfaced side down) and it sucked it down & I couldn't push it at all. So I flipped the spoil board back over to the original location & nothing. Flipped it back so the surfaced side is down again & it worked again.

    My wife said will that hold wood or something on top of it from moving? I had a 4x8 sheet of coroplast laying there so I threw it on top & turned the vacuum on & I couldn't push the coroplast either so I think I'll be good.

    I'm thinking of screwing the spoil board down with brass screws my question is does anyone see any issues doing this? I was thinking about counter sinking the screws about a half inch then when I get to those I'll replace the spoil boards. How many screws do I need to use? Should I put a small bead of silicone around the edge & let it set up to make it act like a runner gasket or isn't that needed?

    Thank you
    Gary



  9. #45
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    Default Re: 4'x8' vacuum table build questions

    So if I understood correctly, you’ve only surfaced one side of the LDF. The reason for surfacing is to clear any surface glue from the manufacturing process. So I’d put the surfaced side down, turn on the vacuums, and then screw it down if that’s what you’d like to do. Then surface the other side and you should be good to go. And no reason to run the vacuum table while surfacing since you’ve already screwed it down but you definitely want to make sure the table is screwed down and doesn’t move (suck down) when turning on.

    And I don’t think you’d need anything around the edge but you’ll need to seal the edge of your top spoilboard too. You’d could put some tape/plastic and glue to the edge if you’d rather not put multiple coats of poly n again,

    David Gage
    Deep Sea Sound


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    Default Re: 4'x8' vacuum table build questions

    Yes I've only surfaced the one side so far but I will surface the other side once mounted. How many screws do you think I should use on each zone?

    Thanks



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    Default Re: 4'x8' vacuum table build questions

    You don't need many screws.Every fifteen inches or so around the edges ought to be enough.They only need to be deep enough to avoid the amount of tool you expect to have extending below the surface.The purpose of the screws is to prevent the spoilboard moving when the vacuum is turned off and as such they shouldn't see huge forces.It must be a huge relief to have a successful vacuum system.



  12. #48
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    Default Re: 4'x8' vacuum table build questions

    I think your on track. Brass screws can take a little milling and not hurt anything. Silicone sealer I always us just a little so it can be pried apart without issues. Your set up looks very well done and I am sure its going to make it nice to work with your machine. Glad you got it handled!!

    Retired Master Electrician, HVAC/R Commercial union shop and Lots of hobbies. FLA Saturn 2 4x4 CNC Router


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