DIY Vacuum Box

[kenkelsey]

I'm back. A few days ago I reported that I had finished by 2 vac system and it worked. I was pretty happy until I hooked up a vac gauge tonight. Most of you have reported 8 to 10 hg with 2 LH motors and the Gary Campbell black box design. I'm only getting 3 with all valves closed. 3 Hg does hold down pretty well, but I want to get up there with the rest of you.

I know that I built the vac box wrong. I thought the vac motors actually extended into the box's plenum area. I see from others pictures that the motors are mounted on a board above the plenum with a gasket. I also used construction grade plywood. It may let air pass through the walls of the box.

Its back to the design board for me. I keep using what I have (it does work) and start building a new box with furniture grade plywood. I'll be back. Any comments/suggestions encouraged.

[kenkelsey]

Joe: You were right. My design (mistake) where I had the motors extending into the plenum area was not correct and was not good. You suggested that the vacuum might escape around the holes where the motors protruded into the plenum area. I think you were right. I got my system running, but only pulling 3 HG with both motors running while most others are reporting 8 to 10 hg. I'm going to keep using what I have (it does work), but I'm going to rebuild using your photo. I wish I had gotten some photos from the forum before making my box, I thought I knew what I was doing, but I did not.

[kenkelsey]

I did order this same remote temp gauge and found that it only displays up to 122 F. I returned it and ordered a different gauge with a range up to 300 degrees F. About 20 bucks.

[Brady Watson]

Just a few comments...

It is nice to see people trying to learn. Keep at it, don't give up and do lots of homework.

All the questions, trials and tribulations you are going through have been answered many times over the years by yours truly and others. There are a number of assumptions and outright 'violations' going on in both this thread and the Black Box thread regarding proper vacuum setup for a 4x8+ machine. There are too many to spell out, but I'll just add some info to point in the right direction.

BT Vac system - great on a BT with an aluminum deck. Not the same animal as a larger machine. It's smaller machinable area eliminates a number of issues.

The proper layup for a 4x4/4x8+ machine is:

1) 3/4 or 1" MDO or other high quality (no sheathing or potato chips) plywood that gets bolted to the machine chassis.
2) 3/4" Medex moisture resistant MDF, Extira MDF or regular MDF for plenum, glued, weighted and edge clamped overnight using Titebond.
3) Ultralight MDF (Trupan Ultralight preferred) or LDF bleeder board,edges sealed, left to float on top of plenum or glued down with Titebond. (No silicone - too thick, it WILL fail and it will also dish the panel unless you put it in the center too - which will block flow in some channels)

*No gasketing is used on this system. Seal the edges well with 50/50 glue & water. Not sealing edges on a 4x8' machine equals 3 square feet of leakage area.

This layup has been used successfully on these machines for many years. Using this setup (or a BradyVac) I have successfully held down materials with a single Fein Turbo 3 (7.3 Hg" max) vacuum over a 4x8' area. It's HOW you use the vacuum. 2 LH motors are OK; 4 being preferred on a 4x8 machine for the CFM.

No gauge = floundering in the dark.

Test each vacuum motor for about 10 seconds (when cool), using a 2" pipe flange, a little bit of rubber sheet gasketing on the bottom, a 2" pipe and cap with nipple threaded in for your gauge. Like this (put the 2" cap in place of the check valve, on the end of the short 2" pipe) - and screw in your vacuum gauge. See what it shows on the gauge. Test all motors this way. Then you KNOW 100% for sure what it is, is & what ain't, ain't. If you don't get that on top of the table you have leakage somewhere. Start by draping plastic sheeting (or a bunch of trash bags) over the bleeder board. What does the gauge say? If it read 10 on the motor & it shows only 3 on the table bagged off, then you've got leaks...

...and YER GONNA have leaks if this is your first rodeo. Track them down. You can't do things like a hogan...You must glue your PVC properly and teflon tape all your threaded connections. Pretend you are hooking up a gas line in your kitchen...seal that puppy good - then go back and inspect with your ears for the tell-tale whistles.

Carry on...

-B

[kenkelsey]

The proper layup for a 4x4/4x8+ machine is:

1) 3/4 or 1" MDO or other high quality (no sheathing or potato chips) plywood that gets bolted to the machine chassis.
2) 3/4" Medex moisture resistant MDF, Extira MDF or regular MDF for plenum, glued, weighted and edge clamped overnight using Titebond.
3) Ultralight MDF (Trupan Ultralight preferred) or LDF bleeder board,edges sealed, left to float on top of plenum or glued down with Titebond. (No silicone - too thick, it WILL fail and it will also dish the panel unless you put it in the center too - which will block flow in some channels)

*No gasketing is used on this system. Seal the edges well with 50/50 glue & water. Not sealing edges on a 4x8' machine equals 3 square feet of leakage area.

This layup has been used successfully on these machines for many years. Using this setup (or a BradyVac) I have successfully held down materials with a single Fein Turbo 3 (7.3 Hg" max) vacuum over a 4x8' area. It's HOW you use the vacuum. 2 LH motors are OK; 4 being preferred on a 4x8 machine for the CFM.

No gauge = floundering in the dark.

Test each vacuum motor for about 10 seconds (when cool), using a 2" pipe flange, a little bit of rubber sheet gasketing on the bottom, a 2" pipe and cap with nipple threaded in for your gauge. Like this (put the 2" cap in place of the check valve, on the end of the short 2" pipe) - and screw in your vacuum gauge. See what it shows on the gauge. Test all motors this way. Then you KNOW 100% for sure what it is, is & what ain't, ain't. If you don't get that on top of the table you have leakage somewhere. Start by draping plastic sheeting (or a bunch of trash bags) over the bleeder board. What does the gauge say? If it read 10 on the motor & it shows only 3 on the table bagged off, then you've got leaks

-B[/QUOTE]
Hi Brady. I did not do all that you outlined, but I did do most. I am checking Vac right at the manifold before any valves or piping to the table. It is reasonably clear to me that my issue is the vac box itself. I know now that I installed the vac motors wrong. I actually cut holes the size of the motors and had the motors protruding into the vacuum's plenum area. I think the problem is no seal where the motors pass through the mount. Maybe you can see what I am describing from the attached photo. I am going to redo the vac box motor mount the way that it was supposed to be (my mistake) and see what Hg I get at the manifold. Good news is that I get almost the same Hg reading (3 Hg) with all of the valves to the table open. I guess that means that I have good CFM?

[kenkelsey]

I rebuilt my Vac Box last night (properly mounting the two LH Vac Motors they way there were supposed to be mounted) and got much better results, similar to what many of you have posted. Now reading 7 hg at the manifold with all valves to the table closed. I was only getting 3 hg before correcting the box. (BTW, 3 hg does hold pretty well, but 7 hg is far better). Also confirmed that in my vac box configuration, running one vac motor does not produce sufficient vac to hold anything. I did observe while I had the lid off of the Vac box that running one motor does cause the other motor to spin. Someone here had the theory that running one motor could draw through the other motor and reduce the vac to the table. For me, that is no longer theory, it is fact. I believe that if you want to run only one Vac motor you would have to patrician the Vac Plenum and have two connections to the Vac box instead of one. Life is a journey and I have learned a lot more about vacuum than I ever expected to learn, but it has been worth it.

[David Iannone]

Congrats Ken, glad to hear you goter tightened up. Mine is up and running great. I am still chasing down some small leaks but I am very happy with the results for the money invested also. I think I am going to go ahead in the near future and add 2 more motors to mine for the full 4 motor setup.

I just checked out your website. You do very nice work. I am sure you stay very busy, but when you get a chance here and there if you don't mind "giving back" a little and maybe do some posting in the Sign Making section of this forum. We need more like yourself on this forum that are professional sign makers putting good use to their Shopbot.

Pics of your techniques and brief descriptions help us all to learn and think out of the box.

Dave

[kenkelsey]

Pics of your techniques and brief descriptions help us all to learn and think out of the box.

Dave[/QUOTE]

Hi Dave. I will start posting some pics in the Sign area. Didn't think anyone would be that interested. My stuff pales by comparison to what you and others on the forum are doing.

My webpage is a bit out of date. I have been posting more current signs on facebook Signs of Excellence.

[joe]

I think your posts on the forum are spot on. All of us are in the learning process and encourage everyone to post more of what they're doing.

About Facebook. I'm not on Facebook and many of my friends aren't either. That leaves some of us out. I may need to do that but am very hesitant. Everyone over there must have a desire to tell their personal life story. As if that's important. It's a younger generation who feels that need. Shopbot new leadership is leading in that direction. So goes the Camp Postings.

[80grit]

I'm getting ready to build a vac box for 4 LH motors. I am only buying 2 for now and will buy 2 more when I get the funding. I've been pouring through vacuum posts here for months, trying to learn everything I can. I really appreciate everyone's experience and their willingness to share it.

For those who have used the LH motors, what is the greatest source of the noise? Cooling air intake, cooling air exhaust, vacuum exhaust?

Has anyone ever used another means to assist in cooling, like an external fan?