Selecting a regenerative blower...need help

[stargategfx]

Contacted our local Gast agent this a.m. to price out a regenerative blower, he reffered me to the Gast website to specify which model I was interested in, as he was unable to suggest one.
The Gast chart had a variety of models & specs, different flow rates, max. pressure, vacuum etc. which was all a bit over my head.
Can anybody with experience with these things suggest the specs for a good all-roung setup?
I cut everything from mdf to plexi and foam, both large and small pieces with very few repeat jobs.
He said I needed to be more specific than just the H.P. rating.
Thanks if you can assist!

[gerald_d]

How big is the power supply to your shop, and how much noice can you (or your neighbors) tolerate?

[Brady Watson]

Boyd,
One thing that a lot of people think is that vacuum is the answer for all projects. It is very difficult to spec out a blower as a one-size fits all...there are vast differences depending on what you are cutting. If you are processing full sheets all day long, then I would say something with 300-500 open CFM and 10-14 inches of Hg (mercury) would be in the right range. However, if you tell me that you are cuttin a lot of smaller parts, then that type of system, with an open bleeder board, will most likely not be suitable. There are a number of ways that you can get great holding power for small parts using a high-quality shop vac. To give you an idea, I cut 5/8" X 1.25" odd-shaped parts using gasketing and a purpose-built vacuum jig.

As with everything else, there isn't a one-size fits all OR free lunch...the free lunch being the idea that we don't have to do any setup, masks or gasketing when using vacuum. For odd types of jobs, carpet tape works well.

-Brady

[simon]

Boyd
I agree with Gerald
Just get the biggest one you can possibly afford
Simon

[Brady Watson]

Not to play devil's advocate, but I don't agree with that reasoning at all. It's expensive, noisy, hot and biggest isn't always best, IMHO.

Just for comparison, 2 Fein Turbo III units will be on par with a 10 HP unit performance-wise, and will be quieter, cheaper and cooler to boot.

Again...it comes down to what you plan on doing with the setup.

-Brady

[beacon14]

Which brings up my question from several months ago, if you have a system with 2 (or 4) Fein vacs, does each one get its own zone or do they both pull from a central manifold into whatever zones are open? Does running 2 vacs in the same plenum increase holding power by a factor of 2?

[gerald_d]

From Boyd's profile:......
Company: MGM Television
ShopBot use: Creating props and set pieces.
.......and the reputation that TV studios have, get the biggest, noisiest, most fuel hungry beast that you can find!


Realistically, for props and sets, I guess that the bulk of your work is stuff bigger than 10 inches square (100 sq inches) and that the materials are relatively lightweight with low cutting forces. Go the ShopVac/Fein route for a start.

David asked: "Does running 2 vacs in the same plenum increase holding power by a factor of 2?" No, it will not increase it by anywhere that much. In fact, if you have few (zero) air leaks, the increase in holding power will be small (zero). Adding bigger/more pumps helps to maintain holding power when the airflow increases (when the system is leaky).

[Brady Watson]

David,
Gerald is on the money...In short, without a check valve, 2 shopvacs connected to the same manifold will only double your CFM, not your vacuum pull. This gets complicated and may be somewhat true if you have a lot of cuts and need the extra CFM to overcome leakage where the kerf is open to the atmosphere.

I have seen a 4-zone setup with 4 Fein Turbo IIIs running each seperate zone. This gives each zone 140 CFM and about 7+" Hg per zone....for a total of 560 CFM at the same 7+" Hg. If you can overcome leakage due to the kerfs created by the bit, then you'll still have enough vacuum to hold your parts down. At a cost of about $1500 for the 4 vacs, he saved a TON of money over a regenerative blower type system...and each zone is turned on by the flick of a switch. Plus you can have a normal conversation without yelling while all 4 are running.

-Brady

[stargategfx]

Thanks for the advice guys, but as Gerald suggested, noise and power supply are not a real big concern, there are ways of dealing with both.
We do however have to justify the cost of our expenditures so this is definitely not a cost is no object situation.
After talking with a lot of people smarter and more experienced than me, I think the re-gen blower is the way to go.
That said, I still need help with choosing specs.
I was hoping that some of you out there might have some practical experience with these devices and could tell me what ratings you are running.
As I said previously, I cut everything on my 'Bot, both large and small pieces and almost every job is a "one off"
Thanks again for your input, this forum was one of the key factors in me choosing to buy a Shopbot.

[elcruisr]

Try getting the specs for the 15 hp FPZ blower from shopbot. I'm sure they'll be glad to quote you a price as well. We've been running one for three years plus on a 6 zone 60 x 120 table. We do just about anything parts wise from large to small and that pump is just barely enough! Remember you'll need to factor in a motor starter circuit as well for anything over 10 hp (at least that's my local code anyways). You can also watch places like ex-factory on the 'net as occasionaly some good used blowers come up there.

Whatever you do for really small parts don't forget tabs!

Eric