Eight zones - zero valves

[tkovacs]

After a couple of smaller variations I decided to do a full 4x8 plenum. Here is my variation of an eight zone table with no valves. The plenum is 3/4 MDF which was polyurathane sealed after cutting. Each zone has a separate PVC pipe inlet with an o-ring plug to cover the inlet when not in use. All the zones are simply teed together. Each zone has a separate 23" square 1/4" MDF spoil/bleeder board.

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[billp]

Terry,
Nice, clean design ! Let us know how it works in everyday use...

[myxpykalix]

Terry,
I thought by having shutoff valves at the main Tee that would eliminate having to "vacumn" those lengths of pipe.

I wonder if you aren't losing suction power by having the "shutoffs" at the ends of your pipes?
It looks cool though!

[Gary Campbell]

Terry...
Nice job! I like the larger channels. My next one will have larger channels also.

Jack...
As long as the O-rings seal, there will be no loss. The o-ring held with vacuum may even seal better than a PVC valve.
Gary

[paco]

Very clever! I remember reading about this a few year ago... keep us post.

[khaos]

I wonder if creating vacuum in the longer run all the time creates a vacuum reservoir. It would be just like a tank on the side to maintain a more constant cfm when there are short breaks in the seal? I'm no vacuum dynamisist but it seems to make sense.

[maginter]

Hi Terry -

Just curious as to how you have your spoilboard pieces are retained? Did you drop your top surface to creat a pocket, then cut your grid below that? I am getting ready to cut a new table and was looking at a similar implimentation.

Thanks,

Mark

[tkovacs]

Everyone - thanks for all the comments!

So far I have used four zones to cut up a 4x4 sheet of mdf and replaced a spoil board with a masonite mask to hold down a 6x6 block in a single zone and have been happy with the results. The big orange home supply store carries 2'x4'x1/4" MDF and 1/8" masonite - cheap stuff and easy to handle and store in my small shop. Soon I plan to replace the Rigid shopvac that powers this with one of the nifty open-source versions.

Mark -
There is a 1/16" recess to retain the spoilboard pieces and the grid was cut into that recess.
A few of other notes:
- originally the plan was simple grid of 1/2" wide grooves 1" on center to make 1/2" square islands but the MDF does not have enough strength and the islands were popping off during the machining. Plan B - make some of the grooves only 1/8" deep - hence the castle shape.
- I used 1-1/2" PVC pipe and found that a 1.9" dia hole makes a tight fit.
- rather than seal the whole working side of the cut plenum it would have been much easier (and probably better) to seal the back side and edges.
- I press fit the feed pipes from below and used the bot to cut a nice clean surface for the o-rings to mate to.

If you like, I would be happy send you the partworks file.

Terry

[bleeth]

Terry: I have a few thoughts about possible issues:
1. Although you can draw vacuum through 1/4" mdf you actually do better through thicker ultralight or trupan that has been skinned. (That being said I use straight mdf skinned all the time in a pinch when my local suppliers are MIA on ultralight supply)
2. When cutting multiple parts out of a larger sheet (complete through cutting or cutting with tabs) you will have no vacuum in the areas between your zone plates (probably not a big deal) and they will tend to curl after getting a bit of cutting on them if they are only 1/4" to start (a real pain in the neck).
3. They may only seem cheap until you find yourself buying new ones every week! The big orange store charges more for mdf (and anything else) than any cabinet substrate supplier.

If this becomes an issue thean you can always change your spoilboard system to the usual 3/4" ultralight skinned on both sides and cut holes over your vacuum intakes and make a deeper plug and thus still avoid the valves.
To me the biggest advantage of vacuum is not having to cut tabs or skins left on parts. Re surfacing a chewed up spoilboard surface weekly and replacing it monthly takes a lot less time than cutting parts out after machining.

[tkovacs]

Dave -
Thanks for the thoughts.
Yes the MDF curls a bit but the vacuum pulls it flat quite easily. Only experience will tell me if the space between the zone plates is an issue. I don't have enough vacuum to cut small parts without tabs and with tabs there does not seem to be a problem.

I would like to try some trupan or similar but up here in northern VT it is not so easy to come by. Maybe after I get some experience with this rig I will order a sheet.

[benchmark]

I have been using a similar system on my Alpha 120 x 60 for about 6 months. The setup has 10 zones which can be shut off individually using basket strainer wastes(not sure what their called in the US) from a kitchen sink, they feed into a 4" pipe that has 5 zones each meeting at a 4" branch meeting at the vacuum. I use a 3mm or 4mm MDF sacrificial sheet on top of the grid... the whole setup works really well. The problem I found with the plasic shut off valves is they can become very stiff and seem to require more plumbing fittings that a swimming pool plant room.

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Paul

[tkovacs]

Nice idea to use the sink strainers. All those valves and the plumbing seemed daunting to me too.

Terry

[frank134]

Hi Paul
would you be willing to share that parts work files on your table. I just got a new 60 x 120 and still learning to work partsworks. I realy like the way you did your.
thank you
frank

[geneb]

I really like the vcarved grooves in the table. How deep are they? At a guess I'd say 1/4", but my guesser has been known to be WAY off.


g.

[john_hartman]

I looks like you have 1.5" pcv going into your 4" main. By doing this, is there an increase in suction/vacuum?

[benchmark]

Sorry Guys,

I missed the post.

Frank, I can send the files allthough they are metric, plus the setting out is dependant on the position of the Shopbot cross rails. Just let me know if they would be of use.

Gene, they are 6mm deep so it was a good guess.

John, yes they are 1.5" into 4" main. There is no increase or loss in vacuum with this setup.


Paul

[frank134]

Hi Paul
Yes I like to try. you could send them to me direct at frank134@hotmail.com (mailto:frank134@hotmail.com). I have the same size takle 60 x 120. Could you also tell me did youdo this with shopbot software or another software.
thank you
Frank