Vacuum pump question

[ttwark]

I am reading some specifications on a vacuum pump and the description goes like this. "oil free, Flow rate: 250 m3/h at 50 Hz and 300 m3/h at 60 Hz." Can any body decipher this for me. There is no further info in the literature I'm reading.

[steve_g]

Oil free = diaphragm pump
250 cubic meters per hour at 50 cycles electricity (European standards)
300 cubic meters per hour at 60 cycle electricity (Americas)
1 cubic meter = 35.314 cubic feet
SG

[ttwark]

Steve
Hate to be stupid, but what is the cubic meters referring too?

[steve_g]

How much free air it can move per hour, It says nothing about its ability to pull a vacuum!
The specs are basically worthless…
SG

[ttwark]

Thanks, I kinda figured as much, that the info didn't really have any meaning. I do some further resaerch
Tom.

[ttwark]

I was able to find more info about the pump specs that I started this tread with. Here it is: (SCFM @0in Hg) 173 CFM. Max continuous vacuum (in Hg) 25" Hg. I'm using the "black box" design with 4 lighthouse motors that pulls around 10.
Am I to assume that this pump pulls 2 1/2 times more that the set up I'm using? This is a Becker model VTLF 250.

Any knowledge you could share would be appreciated.

[Brady Watson]

I was able to find more info about the pump specs that I started this tread with. Here it is: (SCFM @0in Hg) 173 CFM. Max continuous vacuum (in Hg) 25" Hg. I'm using the "black box" design with 4 lighthouse motors that pulls around 10.
Am I to assume that this pump pulls 2 1/2 times more that the set up I'm using? This is a Becker model VTLF 250.

Any knowledge you could share would be appreciated.

A VTLF250 will suck your face off. It doesn't move as much air (CFM) as the 4 lighthouse motors, but it pulls about twice as hard. If you are doing cabinet parts all day long, the Becker is OK, but a regen blower might be better since it moves more air. The one SB sells is pretty good. The Becker is a top of the line industrial grade rotary vane pump. It is made for production. The lighthouse motors are for 'garage bands' who either don't have 3phase or can't afford a real pump. Big Iron CNCs often run these pumps in modules of 4 pumps to get the CFM numbers up. There is little those setups can't hold down.

The Becker will pull a real honest 25Hg" (max vac @ sea level is about 29.9Hg") - although while working, when you break through your material all the way, that creates leakage & the draw starts to drop. I might start at 25Hg" and then it drifts down to 12Hg by the time the work is done. For *most* jobs, if you can maintain 6-7 Hg" throughout the job, you're good. This of course depends on many factors.

When I don't feel like running 10hp (Becker) I run a 5hp Regen that does 8Hg" and 200 CFM.

Do lots of research & search this forum. There's LOTs of info. Google some of the terms so you know what they mean....such as [Hg"] and [rotary vane].

-B

[harryball]

Yep, search the forum, lots of good information.

To summarize roughly what you'll find, inches Hg is the "amount of suction" and cfm is the airflow. The amount of suction = holding power and airflow = forgiveness of leaks. Anything less than 5" Hg is considered not enough holding power and anything less than 100cfm is considered no forgiveness of leaks. Those numbers are generalizations of the boundaries and greatly depend on what you are doing. i.e. 4.5" on with 80 cfm on a 2'x2' area might do just fine. For a "good" full table hold that magic boundary to be comfortable seems to be about 6" Hg with 250cfm or more. You'll find that generally people would rather have 6" Hg with 300 cfm than 10" Hg with 100 cfm. Again, what you are doing specifically has an impact on the choices.

I currently run the 4 motor blackbox vac, the actual purchased one, the Hurricane model. I run with 2 motors 80% of the time and only use the 2nd two when I have more air leaks such as really stubbornly warped material I need to hold down because it leaks more air around the edges.

In your case, the Becker will hold better but not tolerate leaks as well as your light house motors. This means while cutting, if you open up too many leaks, even though you have 15 in Hg in place you could suddenly see it drop to 4" or 5" and your parts start sliding around where if you'd been running your black box style vac, it would have held at 7"+ the entire time and your parts stayed put.

Yeah, that doesn't help you decide much but it does explain the balance of what is going on. Brady is right, for average cabinet parts the Becker would probably be fine at 150+cfm. But as for myself, from experience I'd rather have more cfm and less vacuum than that Becker will provide. But that's for my application, your needs will vary.

/RB

[Ger21]

from experience I'd rather have more cfm and less vacuum than that Becker will provide.

I've never used anything but Becker pumps (for almost 20 years), but my experience would lead me in the exact opposite direction. The amount of CFM the Becker pulls is substantial. I doubt you'd get more holding power with twice the cfm and less vacuum.

We have a 5x12 Morbidelli with two of those Becker pumps. We cut cabinet parts all day long, every day, using mostly 4x8 sheets. We do NOT cover the unused portion of the 5x12 spoilboard, so about 47% of it is uncovered and leaking vacuum. We still have plenty of suction to cut at 1200ipm in one pass through 3/4" board, and only need to onion skin smaller parts.
Just my experience.

[harryball]

I've never used anything but Becker pumps (for almost 20 years), but my experience would lead me in the exact opposite direction. The amount of CFM the Becker pulls is substantial. I doubt you'd get more holding power with twice the cfm and less vacuum.

We have a 5x12 Morbidelli with two of those Becker pumps. We cut cabinet parts all day long, every day, using mostly 4x8 sheets. We do NOT cover the unused portion of the 5x12 spoilboard, so about 47% of it is uncovered and leaking vacuum. We still have plenty of suction to cut at 1200ipm in one pass through 3/4" board, and only need to onion skin smaller parts.
Just my experience.

I'm not sure where your conclusion is "opposite", sounds the same to me. You need 2 of those pumps to have enough cfm to counteract the leakage and still draw enough vacuum which is exactly what I'm saying. If your conclusion was opposite, you'd be running 1 pump, not 2. That's more than 300cfm between the two which is pretty substantial. I'm sure you are running 2 pumps because 1 was not enough, otherwise why burn the power?

Let me fix it... from experience, I'd rather have more cfm and less vacuum than that ONE Becker will provide but of course if I had TWO Beckers I'd have the best of both.

/RB

[Ger21]

Did you miss the part where I said I have a 5x12 table, and am cutting 4x8 sheets on it? I can put a 18" x 36" part on the 5x12 table, without covering the unused 55sq ft, and it still won't move.
There's one zone, so no matter what i throw on the table, I don't have to do anything to make it stick. If it was a 4x8 table, one Becker would be more than enough, but we have the equivalent of two 4x8 tables, and the 2 Becker's can handle any amount of leakage.

[danhamm]

Gerry, tell us about your bleeder board, it has to be highly resistive...

[Ger21]

Regular 3/4" MDF, with .01" planed off each side to start. Edges are unsealed. The table is an aluminum grid with a rubber cord gasket around the perimeter. We'll use the spoilboard until it gets to about .4" thick. We surface off .01" at a time, about every 50-75 sheets cut on it.

[Ajcoholic]

Regular 3/4" MDF, with .01" planed off each side to start. Edges are unsealed. The table is an aluminum grid with a rubber cord gasket around the perimeter. We'll use the spoilboard until it gets to about .4" thick. We surface off .01" at a time, about every 50-75 sheets cut on it.

The way my 10 HP regen blower holds sheet good (and solid wood) parts on my 48" by 48" table, I could see the same unit being quite useable on even 4x8 tables for average size cab parts, or going to a 15 hp or pair of these 10's would be very functional (and thats using standard MDF for the spoilboard.

I was looking at one time at the Becker VTL250. But they run close to $10K here in Canada new, and even used more than 1/2 that.

There is no way 25"Hg is necessary for the universal vac setup where you are cutting cabinet parts. Heck, I can easily hold parts as small as 3 or 4" diameter without moving (no tabs or onion skin) so average gables, shelves and drawer parts are no issue.

If I ever go to a larger sized machine, I'd certainly invest in a similar vac system for the work I do. Ive easily held solid wood chair seats down to carve as well, without any mechanical air - just the vac.

AJC

[bleeth]

Your ten would work fine on a 4 x 8. I've been running a 7.5HP regen for years. It holds cab parts just fine.

[David Iannone]

I am a Sign Guy running a "garage band" Vac hold down, using 2 lighthouse motors. I made 7 zones in my table. After what I know now, I would have made 4 equal zones.

I cut mostly plastics, .040 Al, HDU. All easy stuff to cut and hold down. It has changed the way I cut on the machine. On a budget, don't be afraid of the lighthouse motors.

Dave