another vac table discussion.

[michael_schwartz]

My original spoil board is finally getting thin so its time to replace it. I also want to start doing more panel processing so of course its obvious what I am getting at.

I currently have a 4x8 sheet of 3/4" birch plywood bolted to the table. My plan is to salvage this but to pull it off and seal it, before bolting it back down.

Then I am planning on using a sheet of MDO for the plenum. I figure that the extra $$ are worth it compared to MDF since it will take much less time and material to seal, and in the end its a better material.

I have asked my usual suppliers if they can get trupan and none of them have ever heard of it. My plan is to use lightweight MDF. I am wondering if there are any specifics (brand/product name or other terminology, I should ask for I don't want to glue this down only to find out it won't work. I do plan on sealing the edges :D

Finally I have a dedicated 110 volt 20 amp circuit available for vacuum motors, and the central vacuums motors (ward lighthouse) seem to be the most appealing to me right now, unless there are any newer suggestions. I don't think I want to jump right into a 4 motor setup, but I am thinking of at least 2 to start. It would be helpful if somebody could suggest a part number that would be right for my needs.

Right now for machining solid wood I prefer screws and or other clamping fixtures but I do envision using the vac table to hold down fixtures, or sacrificial pieces that have a good bit of surface area. I am not as concerned about holding down small parts. I mainly want to get away from using tabs on sheet goods.

Obviously I don't have 3 phase power, and I don't have the budget for a 30 horse regenerative blower so I don't expect to be able to pull down a warped piece of plywood and cut small parts from it with the force of a freight train but I am wondering more or less what would be reasonable to expect from a setup such as what I am leaning towards.

[Brady Watson]

Here's the ideal layup for a dedicated vac table:

1) MDO paper 2-sides Support Board bolted to table au naturel

2) Medex moisture resistant MDF (Sierra Pine) GLUED to support board. Only edges need to be sealed with a 50/50 mix of wood glue & water or straight glue. Machine your grid into this.

3) Trupan Ultralight or Ultralight MDF (Sierra Pine) bleeder. Glue perimeter and around zones. Seal edges with glue with vac on.

--------------------

Ideal layup for a non-dedicated versatile vacuum system:

1) Trupan UL or UL MDF with one big grid machined into it. Flip it over, grid side down.

2) Bore 2" hole(s) into your existing MDO/Medex or MDF spoilboard. Plug vac in.

3) Countersink and screw 'BradyVac' sheet down & get to work.

For jobs that require screws, bolts, nails or adhesive - remove BV sheet and put it aside. Machine on top of regular spoilboard.

-B

[michael_schwartz]

I have a lead on Trupan. Medex might be harder to get but I made an inquiry into that as well. I am still torn between the simplicity of a "BradyVac" sheet and a dedicated top.

Right now my biggest concern is vac loss from un covered areas on each zone because I tend to cut all sorts of odd sizes of material, even when dealing with sheet goods. I would imagine this would be a problem with the smaller vac motors. I am wondering if there is a trick to dealing with this.

[knight_toolworks]

I am replacing all of my table as I was poor when I laid it down and did not use the best materials.
I am going to use 3/4" appleply as the base sheet and as the second sheet as it is what I have. then when I used most of the first sheet of ulralight I will leave some on so I am never cutting down to the plywood.
I have mdf seperate from the grooved layer before and I noticed the mdf breaking free of the cheap plywood it is screwed and glued too. I like the appleply as it has no real voids and should be pretty airtight on it's own. I know the ply won't seperate I can seal it with a oil based paint to keep moisture down.

[Brady Watson]

It boils down to what you really need. If you are doing sheet goods every day and nothing else - then by all means make it as tight as you can. However, if you are always doing something different, with dimensional lumber, hardwoods and other oddly shaped materials, then the versatility of a vac plenum that comes off is clearly superior.

You have to ask yourself what you really need.

-B

[kevin]

Micheal my 2 cent I think that you can't aford to not have an indusrial set up see http://www.talkshopbot.com/forum/showthread.php?t=14322 there a lot of these for sales at a resonble price

Resons
1 You want to expand doing closets want fast turn around
2 A vac moter will burn out sonner than later
3 3 phase can run on a conveter you can add sub panel from your house for more power
4 If you ever sell it will maintain value

They work amazing I bought the small one but I regret I didn't buy the larger one
Kevin

[michael_schwartz]

I am meeting with a salesperson from a plywood distributer next week and they do stock Trupan, along with just about everything else. I think he said he was going to bring a sample of some color core.

An industrial motor is going to have to wait a couple of years until I move up to a larger shop space but I understand how this may very well be a better choice, long term. Right now my priority is to get started working with something sooner than later so I can learn, and start utilizing my shop bot more as a tool for panel processing. I hate cutting sheet goods on a regular tablesaw.

I didn't do a very good job setting up my first spoil board but it has worked fine as long as I surface it as needed. I think I can improve it to get a bit more stability.

After some thought I am going to go with a brady vac setup for now at least. I could meet my needs with 4-5 different sized sheets, ranging from big to small.
In particular I want to work with 5x5 baltic birch pre cut to around 31-32"x60" which would be kind of odd with a traditional 4 zone plenum, so this would solve that issue.

It will be interesting to start experimenting. The good thing is I have material on hand to get started if I do go with this setup.

[curtiss]

For a typical 4 x 8 table with multiple zones: What zone setup is likely the most popular for 2 zones ? 8x3 & 8x1 .......3 zones ? 4x3 4x3 8x1 ............... 4 zones ?

[Brady Watson]

For a typical 4 x 8 table with multiple zones: What zone setup is likely the most popular for 2 zones ? 8x3 & 8x1 .......3 zones ? 4x3 4x3 8x1 ............... 4 zones ?

Only YOU can answer this question...what's popular is not necessarily what will work best in Curtis' shop. What kind of materials do you cut on a daily basis? What size? When you cut smaller materials, what are the sizes? Keep in mind that 4/4 hardwood lumber is almost never completely flat unless it was planed right before it goes on the table.

Also...don't pigeon hole yourself into thinking that one size is going to work for everything you do. I have about 5 different sizes of 'BradyVacs' to maximize the use of a single Fein depending on the material size. I will probably keep the BradyVac idea, although I will be doing some modifications to it after I get the Becker up & running in the new shop. A single Fein or LH vac can take you pretty far if you know how to use the vacuum that you have.

-B

[knight_toolworks]

I just stripped down my table to bare bones. It needed done as I did not do a good job years ago. first layer was mdf that I had cut the air channels in. then a I guess it did not work well and I had put some cheap 1/2 Plywood on top of that and another sheet of mdf. No idea where most of the screws were so I loaded a crappy bit and cut it up. then spent effort tearing it all off. I had jsut glued the pipe in place so I had to clean the ends up. I made simple flange fittings from a connector and a ring of pvc foam. I used 3/4" ero beech ply and the second the same. I flattened it all as it was not super flat. I just used rounded squares for the channels and I drilled the holes for the screws with the machine so I could find them later.
http://i154.photobucket.com/albums/s266/knighttoolworks/posting/IMG_0246.jpg
http://i154.photobucket.com/albums/s266/knighttoolworks/posting/IMG_0245.jpg
http://i154.photobucket.com/albums/s266/knighttoolworks/posting/IMG_0244.jpg
http://i154.photobucket.com/albums/s266/knighttoolworks/posting/IMG_0243.jpg

[curtiss]

Is there any optimum ratio for the channel space in relation to the high spots on the grid ??? How deep should the channels be cut ? The one above looks to be about 33 percent channel.

[Brady Watson]

I shoot for leaving 1" squares on the grid to maximize air flow and vacuum distribution. Typical depth is 3/16 to 3/8" and kerf width 3/8 or 1/2". There isn't a noticeable difference on grid depth using the above combinations. Airflow will be restricted and slowed down by the bleeder no matter what. There also seems to be no difference between a 1/2, 3/4 or 1" thick bleeder - provided that you are using ultralight material.

-B

[knight_toolworks]

I now cut my spoilboard into quarters to make it easier to glue down and handle. I also put yellow glue on the inside edges to it seals the zones better. I find it is much easier to get glue down for 2x4 then 4x8.
http://i154.photobucket.com/albums/s266/knighttoolworks/posting/113769A8.jpg

[michael_schwartz]

I have read elsewhere that your supposed to mill off the skin on both faces of the MDF/LDF bleeder board. Is this really necessary?

[knight_toolworks]

I have read elsewhere that your supposed to mill off the skin on both faces of the MDF/LDF bleeder board. Is this really necessary?
yes the face is harder and stops airflow a bit. got to watch it the sheet likes to warp on you. done one side glue down ther sheet then do the top side.

[Brady Watson]

I have read elsewhere that your supposed to mill off the skin on both faces of the MDF/LDF bleeder board. Is this really necessary?

No, it's a myth. If you really think that it makes a difference, mill off both sides...who the heck wants to go through all that?

-B

[bleeth]

Hey Brady: Is that reply based on anecdotal evidence or empirical testing?

[Brady Watson]

Hey Brady: Is that reply based on anecdotal evidence or empirical testing?

Empirical testing in the field. :rolleyes:

I've set up more vac systems than I can remember & have done both the 2-sided skinning and no-skinning. There is no difference with the newer Ultralight MDF formulations. This may have been an issue years ago, but the ULMDF formulations seem to have changed for the better. This is particularly true when using Trupan & now that Sierra Pine has changed it's ULMDF formulation to Radiata Pine, it is on par with Trupan in terms of performance.

But...as I said before, don't take my word for it. If you beLIEve that you need to machine both sides - go for it! It's YOUR machine. The ONLY way to gauge whether skinning is worth it or not is by monitoring a good vacuum gauge on your setup during the comparison.

-B

[bleeth]

I've always milled both sides for two reasons.
The first is due to the slightly higher density at the surface due to the natural results of the pressing in manufacturing. It's true that it's not much more and my "anecdotal" test is when I am putting a raw piece of mdf on my table to cut parts from there is still enough vacuum coming through the bleeder and the parts piece to grab the z zero plate. So there is no doubt that the factory surface is porous, as you say.
The other reason is for stress relief. With one side milled the piece will have more of a tendancy to curl up with the unmilled side down over time. My vac board is regular mdf sealed with shellac and when putting down a new spoilboard there is always a good ooze of titebond coming out the edge so I am sure there is plenty of glue. Over time I will still have a bit of separation at the corners that require repair.
It is a pain to mill both sides but for now I think I will continue to do that.
I do wish they had something like "porous pvc" to go to a totally different spoilboard system.

[jerry_stanek]

I have tried it both ways also and find that the sheets I have do make a difference. Using a vac lifter no problem lifting a new sheet or even one that has one side skimmed my lifter will not pick up a sheet that is surfaced on both sides.

[Brady Watson]

What brand sheets are you guys using?

-B

[bleeth]

Over time it's been Trupan sometimes and Sierra UL others. Lately it's been Sierra as my local supply of Trupan has come in 48 x 96 which is a pain for obvious reasons.

[Brady Watson]

Oh...BTW, remember the Chilean earthquake (http://www.marketplace.org/topics/world/chile-earthquake-rattles-wood-industry) that interrupted the Trupan supply a few years back?

It seems tragedy has reared it's ugly head again for Arauco...Linky (http://www.woodworkingnetwork.com/news/woodworking-industry-news/Forest-Fire-Destroys-Arauco-Plywood-Plant-136658383.html)

-B

[knight_toolworks]

I wish you could leave the face on it would glue better for sure.

[michael_schwartz]

I am going to go with 2x LH6765-13 (120v) motors which run $120.00 a piece. If I am not mistaken these are similar to the ones used in Brady's 9-15 setup. If I ever upgrade to a 4 motor setup I will have to go with 240 volt motors at that point. I could see adding a third later on.
After spending hours pouring over different motor specs I did end up with a part number that has already been recommended but it was a good learning experience comparing 10 different motors.


I am going to plumb them to supply two ports on my table for Brady Vac sheets. I am probably going to add an additional port to use as a vacuum take off. I suppose I may experiment with a sheet lifter, or some other things.

I do have a good Venturi pump for high pressure needs such as vacuum bagging or gasketed fixtures for small parts. This has no trouble pulling 23-24 HG, and even sucks down my 4x4 vac bag reasonably fast when it has a good bit of air in it.

I also sketched out a layout for a control panel tonight with two switches and a knock out for a panel mounted vacuum gauge today. My electrician is coming to do some work tomorrow so I am going to ask her to get a small electrical enclosure, then install the switches, prewire it, and install some sort of thermal protection.

I have an auto parts store 50 feet from my shop as well so that will come in handy. I suppose I will have to take a piece of PVC pipe over and just let them find a filter that fits tightly on it. They will be wondering what I am trying to do somebody's car.