New Dual Pump Vacuum System

[Brady Watson]

I figured I'd post a few pics of my latest vacuum project. This one is on my 5x16 PRT, but only 12' are being used with this gantry & this vacuum project. One pump is an FPz 5hp model that maxes out at 9 Hg" and 200 CFM, the other is a Becker VTLF250 10hp that specs out @ 25.5 Hg" (25.0 Hg" observed on this system) and 173 CFM. Since I have 'other things' going on at either end of the 16' table, I was forced to put the manifold in the center of the table. I guess I could have run it inline with the X axis, but that would have been cumbersome, not to mention ugly.

ShopBot vacuum kits use 2" ball valves, which are fine for most - but there is no way I am crawling under the table to turn knuckle-busting ball valves when I need to close off a zone. I bought some stainless steel paddle knife/gate valves (Valterra brand) online. At first, I got a set of plastic ones, which would be just fine under 11 Hg", but only after getting them did I realize there was a paddle implosion risk with the Becker, so I had to order up the SS ones. The gate valves are push-pull with a handle, and they are really easy to work...but I still didn't want to crawl underneath the table or come up with some goofy set of control rods; visions of John Lithgow in Buckaroo Bonzai come to mind...

I wound up ordering some pneumatic cylinders that could be remotely actuated to open and close the valves. (Thanks to Gary Campbell for sharing some part numbers) It took me a little while to get the mounts figured out, which clamp onto the valve bodies - .005" made a big difference in the clamp, which are made out of hard maple & screwed together. To keep track of all the spaghetti tubing for the actuators, I labeled them to make hook up to the switch valves easier.

All remote actuated valves are 2" & take an appropriately sized cylinder. This includes a block-off valve to seal off the FPz to prevent leakage through the pump while the Becker is running (and to keep the Becker from running the FPz backwards etc). I still need to put an actuator on the 3" valve that seals off the Becker when the FPz runs, (manual setup now). The actuators are really slick - they sound like Star Trek doors when you flip the switch!

I made a quick control panel for all the switches and used the Widget Works plotter pen to mark out where the zones were on the table, with a switch & on/off designation for each. (Thanks Russ Todd!) I made it out of a product similar to DiBond, but it is corrugated - I think it is called DLite. It was laying around & the right size, so there it is!

I had a big job that I needed it for & it proved to work very well. One thing that surprised me is the FPz shutting down in the middle of a cut, making me scramble for the e-stop. I've seen this happen before on the road and knew just what to do. Many new pumps will run fine for about a half hour or so and then suddenly shut down - this is because they start to heat up and require more amperage. I pulled the starter panel off & turned up the amperage a little, and it was rock steady after that. (Whew!)

Why 2 pumps? Well, even though the Becker is quiet as far as most high performance pumps go, it still isn't exactly quiet. Plus, depending on the job, why run 10hp if you can get the job done with 5hp? The FPz is quieter and doesn't produce as much heat as the Becker, but the performance is night & day between them. I was amazed by what the Becker will hold down even with a lot of leakage (no block offs on zone perimeter etc). Plus, I got a great deal on these pumps a few years back and I am just getting around to setting them up the way I wanted. I'm still not done tweaking & need a few things in addition to the 3" actuator for the Becker, like a filter for the FPz pressure relief valve etc. I'd also like to tidy up the spaghetti air manifold a bit to make it look cleaner.

Anyway, here are a few pics during & after:

http://i772.photobucket.com/albums/yy8/braidmeister/VacSys1.jpg (http://s772.photobucket.com/user/braidmeister/media/VacSys1.jpg.html)

http://i772.photobucket.com/albums/yy8/braidmeister/VacSys2.jpg (http://s772.photobucket.com/user/braidmeister/media/VacSys2.jpg.html)

http://i772.photobucket.com/albums/yy8/braidmeister/VacSys3.jpg (http://s772.photobucket.com/user/braidmeister/media/VacSys3.jpg.html)

http://i772.photobucket.com/albums/yy8/braidmeister/VacSysWidgetWorksPen.jpg (http://s772.photobucket.com/user/braidmeister/media/VacSysWidgetWorksPen.jpg.html)



-B

[khaos]

Nice. Thanks for sharing.

[Bob Eustace]

Brady did you realise that you can get Valterra valves actuated by 12 volt DC? Used a lot in high end motorhomes. Nice work! Loved the panel solution!

[dana_swift]

Brady- I use a 5hp Becker, so I am envious of your 10hp! I find my expectations for vacuum are so different than most botters. When the bleeding gets down below 15"Hg I am scrambling to plug the leaks! Most blower/fan systems don't get anywhere near that much pull.

I ran my Becker to a 100lb propane bottle as an accumulator, so it can switch off if there is low leakage. 5hp is both loud and runs up the electric bill, so I put in an electronic pressure switch from digikey. The pressure switch allows setting the "on" and "off" points. Often the becker will be off for a minute or so before it kicks back in.

Vane life is shorter as the vacuum pressure gets greater. I presume you are familiar with all that.

Looks cool!

D

[Brady Watson]

Thanks guys.

Bob - Yes I am aware that both electric & pneumatic actuated 'ready to go' valves are available. It seems the ones you refer to are only available in 1.5 & 3" sizes in ABS plastic (not PVC), and are about $140 each. That's $1,120 in valves for this system. I think I have about half that amount into this setup for stainless steel pressure rated valves and powerful pneumatic cylinders. The electric would be nice for automating, and I considered electro-pneumatics, but...where does it all end? Few are willing to spend $600-800 for just actuated valves for their vacuum system - that I can tell you. For my setup it was a must & I love being able to turn on/off with a flick of a switch.

Dana,
Yes, I know about the scrambling you speak of! The 10hp does that too, but in most cases if you stay above 7 Hg" (delta) you're still OK. I bought this pump used for $1500 years ago and the vanes spec'd out like new. I was pretty happy about that. A 5pc set is like $900...and the pump was around $9k new. The onion-skinning technique really works well with this pump. Cut 90% through all of your parts first, then go back full depth with minimal cutter to material force to shave off that little bit of paper/onion skin on the bottom of the parts. Vac pressure will still go down, but requirements also go down by reducing applied force to cut out parts. In some instances, lightening up the chipload makes the difference between success & failure.

I use buffer tanks (and a 'vac mac') valve on my little Gast set up. It will cycle on & off @ set points to keep the pump from running constantly. This isn't practical on the larger pumps (for me anyway) because the tank would have to be massive. Plus, many of these pumps are not rated (according to the manufacturer) to be turned on & off more than 3 or 4 times an hour because it is hard on the motor & starter when they get warm. This is why SB recommends keeping the pump running & opening the purge valve to bleed off vac when swapping out sheets/material during production.

Also for those lurking...keep in mind that larger pumps like these make vacuum management easier. That is to say, when it comes to vacuum & holding down your parts, it deals with leakage better than smaller vacuum sources like a Fein or Lighthouse motors - to a point. Intelligent vacuum management along with a Fein or other similar vac can allow you to hold down just about anything. It is more important how you use the vacuum that you have, than the size or configuration of the vacuum you have. I used a single Fein Turbo III for years, holding down just about anything & everything, by carefully leveraging the vacuum I had at hand. Yes, at times hold down was marginal, but I was always able to get the job done when I adjusted chipload to stay within the holding capability of the vacuum.

-B

[bleeth]

From the beginning I put my vacuum pump by the back door of the shop so the hot air blows out (quite helpful in Florida). An added benefit is the extended run of piping creates a larger volume of "stored" air. I don't know mathmatically whether this is the reason my 7.5HP vac has such good holdown or not, but it seems to outperform some other larger HP set-ups I've seen. I can cut a whole sheet of desk framing parts (usually around 3" x 30" with a couple of electrical chase slots in each one) out of plywood and have them all come out fine. I also use a skin method for that kind of work, but not for typical sheets full of larger cabinet parts.

[Brady Watson]

Yep - exhaust system with Winter/Summer diverter in the plans. They do get toasty.

Dave - running a 7.5 roots or regen? Cascade, FPz or Republic?

-B

[bleeth]

Regen-Just a straight blower with no bells or whistles. Not sure who made it. The way it is sitting right now I can't see the label and I don't remember but it is US made and 3PH.

[Phillip Fletcher]

Brady

We are looking to do the same Valterra valves actuated by plant air. What should we look for to get the air actuated setup. All I have found is handle style.

Thank you,
Phillip Fletcher

[Gary Campbell]

This should get you going: http://www.youtube.com/watch?v=iXJhTz-Jc7c

[tracys]

Brady.

I've done a lot of onion skin cutting with maybe 80% satisfaction on results. You mentioned above "ut 90% through all of your parts first, then go back full depth with minimal cutter to material force to shave off that little bit" Can you explain minimal cutter force a bit more.

[Brady Watson]

Tracy,
If you don't break through the onion skin, you won't lose suction. The idea is to let vacuum hold down your parts while cutting aggressively (tool pushing back against material with high force) - without breaking through the skin. Then when all of the parts are cut, say .7" deep in .75" thick material, come back and make the tool go .75" deep, cutting all the way through your parts - now breaking through the skin and inevitably letting the vacuum leak through the kerf. Since the tool is only cutting .05" off of the part on the last pass, there is very little force being exerted, and therefore, the parts shouldn't move even with low vac showing on the guage.

There are other things that come into play depending on what you are cutting, how grabby the material is, how high your chipload is and the geometry of the tool being used to cut the parts. If your parts are still moving with good vacuum numbers and onion-skinning, you may want to look into a compression spiral, or even straight flute tool. In more extreme cases, a downcut can be used, at the expense of blowing out the bottom edge and packing the kerf with chips (straight will pack them also - sometimes to your advantage, such as with plastics.)

Does this make sense?

-B

[willmorgan]

Brady,
Which pen are you using to make the control board?
And where did you get it. I can find thick line but that looks pretty thin.

[Brady Watson]

Wigitworks with Micro Sharpie. Now unobtanium. Not WW's fault. Sharpie stopped making them.

I have another setup under development to fill the void for when these dry out. Something completely rebuildable and adjustable.

-B

[willmorgan]

Got it thanks.