Vac plenum which to select

[KenC]

Hi,
I am totally new to the vacuum hold down & I knew my budget just would not allow the luxury, until I came across Brady's 9-15 open source vacuum project. Bradly you are a star!
And Gary Cambel's Black Box Vac Source, & his K.I.S.S. are great too.

I took the plunge & ordered a pair of 7123 intending to run them in parallel. Will eventually end up with 4 units in parallel taking the lead of the Black Box Vac Source, that is when money is available.

The next decision is to decide on which type of plenum to choose from.

The plumbing will be as Gary's K.I.S.S. with a set of home made knife edge valve made out of MDF.

I'm torn between the Universal plenum with a fix 1/2" spoil MDF spoil board & Brady's VacI & VacII combo. From my understanding (point me out if I'm wrong), a pair of 7123 in parallel will be limited by small parts & too much cut through jobs on a universal plenum. This is where Brady's VacII can step in & save the day.

As for my work, they varies vastly the board, I can never predict what will come through the door next. Some days I will have cabinets, another week will be flooded with texture board & another month with small profile cutting. Even carving & engraving of various sizes are common...
Material is a big mix too, MDF, hard wood, plywood, soft wood...

I would be most appreciate in getting some advice from the gurus.
Thanks in advance

Ken

[dana_swift]

Ken, that decision is not quite as critical as you think. Whatever you chose there will be times when some other design will have been better. What is most important is to get started. Make something with the intention of replacing it in a year or two. Then you will know how to make it suit your needs better.

My suggestion is go with what you can afford that "should" meet your needs, then get that experience. How well it works depends on your specific materials etc.

I will give you an example, I have cut a lot of pine and soft woods and "trusted" a specific vacuum fixture. Then I started cutting white oak, and the parts were sometimes shifting. I had to reduce my depth of cut to lower the cutting forces about 30% to keep things from moving.

We are all still learning. The only way to learn is get experience, so get started. If the system you build works at all, you will be getting that initial experience.

A lot of what you read in the forum is fine tweaks that have worked for one of us. I find it interesting that what I need is not the same as someone else, yet they get great results also.

Paralysis from analysis.. When choosing from two acceptable methods where you don't have any clear reason to go one way or the other-

Flip a coin, and get started!

Good luck!

[KenC]

Ken,
....that decision is not quite as critical as you think....
....Make something with the intention of replacing it in a year or two...

Flip a coin, and get started!

Good luck!

dana_swift,
Thanks for the head up, I appreciate your kindness.
I am definately getting on with it, any inventory lying around idle is a financial burden...
I am hoping for something more scientific... but Flipping a coin is scientific enough in statistical term.
Will resort to that if I can't get any opinion until the pair of vac motors arrive....:D

Until then, consider this my last chance to firm up my next course of action.:D

[Brady Watson]

Ken,
The absolute simplest vacuum configuration is the BradyVac I. You just put a hole in the center of your table to supply the vacuum & machine a grid about 1/4" deep with a 1/2" bit into a piece of 3/4" Trupan or Ultralight MDF. Flip it over & it's ready to go.

You want to countersink some screws around the perimeter (I like Kreg 1" pocket hole screws) to keep it in place & run a strip of foil or good masking tape around the perimeter to seal. You have all the versatility to remove the plenum at any time & screw things down to your machine if necessary.

You can make smaller BV1 or BV2 plenums the same way. You can also use a combination of vacuum & adhesive aka Vacuum Film ( http://talkshopbot.com/forum/showthread.php?t=11481&highlight=vacuum+film ) to extend the versatility of the system.

Of course there are pros & cons to every setup, and only through your own observation & experience will you be able to find a setup that is just right for you. What I like about the BV1 is that it is 'non-committal' meaning that you really don't have to invest much to try out vacuum and hold down most sheet goods. But if you process sheets on a daily basis, a dedicated plenum and a zoned grid might be a better option.

Don't be scared...Just try something out. When I 1st heard about holding things down with a ShopVac, I thought it was all just a waste of time :D

-B

[bob_s]

Most of what I do is 3d cuts or architectural pieces that I hold down with Baltic birch springboards and a matrix of 60 threaded inserts on my 48x96 table. I use 5/16 18 nylon bolts to bold down the springboards/clamps whenever possible. This all works well, but leaves me in a mess when I try and use a BradyVac on the surface. My table surface is flat and well sealed, but the 60 holes for the threaded inserts are a problem. I first tried to seal them all from the bottom, but they fill with sawdust and I always manage to burst the tape seal when I use one.
I have now decided to seal the bottom of my BradyVacs with a piece of 1/4 plywood that has been well coated to make it airtight. This will solve 2 problems, my table holes and the constant struggle to seal the BradyVac to the table. I used a gasket in a 1/4 groove around the outside of the whole panel, but handling and storing the board without damaging this gasket is difficult. To try it I made up a small Brady vac box that accesses one of my 4 vacuum ports in the table and has 4 recessed nylon bolts in the corners that will hold the panel down flat to the table. These bolts thread into my system of threaded inserts. I only lose 1/4 inch in height and the time and materials it takes to add the bottom to the portable plenum to make it into a sealed box unit
I haven't used it enough yet to declare it a success, but I think that it solved my problems of trying to run a hybrid system of hold downs. It will also allow me to use indexing marks or corner boards on the top surface of a BradyVac panel to cut multiple parts over time without a worry of the Bradyvac moving when the vacuum source is turned off.

[Brady Watson]

Hey Bob,
That's a great idea with the luan...and a heck of a lot easier than crawling under the table to squirt caulk in the holes you can find.

-B

[KenC]

Brady, Bob,
Thanks for the heads up.
Presently, I use 7 pieces of 32" F-clamps to go about my hold-down. I use cut-off & 1x2 as springboard or spring clamp using my large F-clamp & if all else failed I just put a nail through the spring board onto the table top. The spring board literally eliminate clamp head from chewing up & loose step cause by dust foot running into clamp heads. Hence I really hope to have this option available on the coming vacuum table. Now here is the question, can BV1 take springboard gracefully or must it be remove before applying clamps & spring board, (surely nailing is out of the equation with BV1 & BV2)

Brady, when you say dedicated zone plenum, do you mean those with grid cut into the table top with a bleeder board screw it?

I've just receive an encouraging reply from a client that he will be needing some texture board, so I recon I'll be having sheet stock mostly for a few month to come... This should force me into some immediate decision on the 1st try on vacuum hold down.

Deep in my heart, I would go for BV1, it is an "Alternative" solution, flexible, its easy to cook up & economical. Most importantly, its a perfect match for the vacuum motor.

BUT universal zoned plenum are popular for a reason & can the twin Vacuum cleaner suckers handle it?

I must weigh in the reality & do the right thing... It is a business after all...

"Plenum? BV1?....":eek:

[Brady Watson]

Ken,
I have used a single Fein Turbo III shopvac and BradyVac I to hold 4X8 sheets for years. As long as the material doesn't look like a twisted potato chip, you should have no problems holding it down.

When you lay up your material, it is opposite of clamping or screwing. Always 'crown' your sheets, putting the bow up, so that the outer edges touch before the belly of the sheet. This will allow the vacuum to flatten it. Otherwise, if the edges are sticking up, vacuum will just leak out of the edges.

The setup works good...and it's really easy to put together. What are you waiting for? :cool:

Dedicated setups have been around as long as there have been vacuum systems. They are good for cabinet shops & guys who cut sheets day in & day out. I am a job shop - one day I cut sheet goods, the next I have rough lumber for an oil refinery and the next I have 4/4 hardwood. I simply need the versatility. A dedicated setup with a huge vacuum is downright awesome, but many don't have the $6k-$10k for a big pump. You can get by pretty well on one or 2 vacuum cleaner motors & build a nice affordable system that works.

-B

[beacon14]

The biggest advantage in my book of a multi-zone table with a manifold is the ability to concentrate all the vac power (all I have, anyway) into one zone. Yes one or two shop-vacs will hold a 4x8 sheet if you are careful with your cutting strategy, but they will also hold a lot of smaller items that you might not expect to be able to hold when the other 7 zones are turned off. I do almost all my solid wood cutting with vac hold down; I've held 6" x 6" x 1/4" aluminum plates for cutting all the way through.

Good advice to just get something done and get started. No matter what you do or how hard you think it through in 6 months you will say to yourself, "if only I had considered......"

[KenC]

I sincerely appreciate your advices & sharing your valuable experience.
Honestly, I like to have multi zone configuration with the flexibility. I did considered for multi zone, started with 8 zones, then 6, the 4 then 5 then 2...

In the name of K.I.S.S. & $$$ I come to conclude that a single hole for the full 49"x 97" table (Just get some shower curtain handy for covering the exposed plenum to reduce leaks...) is the best way to go for my 1st outing. Surely there will be 2nd, 3rd.... in the not so distance future.

All that required is a 2 1/2" ball valve for quick bleeder valve, a 2 1/2" T-join, a U-bot & a few feet of plumbing, won't get any easier then that.

So this is it. 1 zone BV1 plenum configuration with twin parallel vacuum cleaner motors with 2 1/2" plumbing consist of a quick bleeding valve.

This is the work plan for a suitable weekend & any other time which I can pull it off . Please point me out if you don't see fit.
1)Face the existing table top. (30 mins)
cut a 2 1/2" hole with 45deg chamfer to 3/4" deep in approximately middle of the board. (15min)
2)Seal the existing table top with 1 coat wood sealer & 2 coats PU. (painting time ~30min x 3, drying time varies...)
3)Attach a T-join to the centre hole & plumb one end of the T to the suckers & the other to a release ball valve at the front end of the table. (90min)
4)3/4" MDF Bleeder board, milling grid 1 1/2" c/c 3/8" deep with 1/2" bit leaving 2" at the edge. securing screw will be at ~16" c/c.seal the edges with a coat of wood sealer, (CAD/CAM 15 min, cutting 30min. painting 15 min)
5)Screw down the BV1 with the flat side up & surface the top. (45min)

Next... the sucker box design...
A sealed MDF box/plastic container/barrel with 3 holes or 2 boxes or no box at all...

[beacon14]

If you are thinking about that option I would consider two holes, and mount one motor under each hole. Rout holes 5 minutes. Mount motors 15 minutes. Plug in motors 15 seconds. Done.

You'll have a de-facto 2 zone system and still have both motors covering the 4x8 table as you are proposing. Then if you decide you want something fancier you don't have a lot invested. Probably get better suction too with two separated vac ports instead of one in the middle.

[KenC]

Hi David,
That is a good solution & it is beautifully simple. I see a few technical factors, firstly, I have no idea how to mount an intake filter me. Secondly, I'll have to craw under the table just to monitor the motors & I can't imagine how its gonna be when I must attend to the motor if any problem arises...

[Gary Campbell]

Ken...
This may give you a couple of ideas, or maybe even answers: http://www.shopbotblog.com/index.php/2008/10/my-4-motor-vacuum-setup/

There appears to be some photos missing, but the info is there

[KenC]

David, thanks for the link.

[KenC]

It took longer then I would wished for, & this is how my motor mounting turn out to be.
12215
Did made a MDF box but it got collapsed under the twin motors prowess... Hench the 2" plumbing all round.