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James Jaragosky
07-21-2010, 11:31 PM
Today I connected a 5hp dust collection motor to my Rabbit laser to be used for smoke extraction.
First I had to enlarge the factory exhaust hole in the laser cabinet from 6in to 8in. Four foot of 8inch pipe and 4 elbows later and I am ready to test the new exhaust system out.
I tossed a 12 x 18 inch piece of warped 3mill Baltic birch on the 23 x 33 cutting bed and flip on the blower motor, Wow the birch straightened right out. I have so much suction now that I can hardly open the lid with the blower motor on.
Now I am a little worried that I may have too much suction.
Jim J.

Rodne Gold
07-22-2010, 12:37 AM
You only have too much suction when the laser engraver casing implodes :)

Dan Hintz
07-22-2010, 6:32 AM
FIVE HP?!!! Sheesh, I'm doing fine with the 1HP red unit from HF, and I'll be upgrading to a 2HP unit soon enough, but FIVE?!!! :P

Mike Null
07-22-2010, 7:28 AM
There goes the air conditioning in the summer and heat in the winter.

Randy Digby
07-22-2010, 9:05 AM
Afterburner...ON! :D

Dan Hintz
07-22-2010, 9:07 AM
Not for me... I exhaust back into the room (after scrubbing, of course). No loss of heat/cold.

Scott Challoner
07-22-2010, 9:39 AM
Be careful if you have an aluminum honeycomb table. I made some mods on mine for more suction underneath and now my grid is bowed. I have to put scraps of 1/2" Corian underneath to support it.

Richard Rumancik
07-22-2010, 10:20 AM
Just a small point with this - people should not confuse high suction with high flow. James, you may have high suction, which is demonstrated by the fact that there is enough differential pressure to straighten the warped material. But suction does not mean flow. In fact, a traditional vacuum hold-down uses a lot of horsepower but the actual flow rate is not that large.

As an analogy, I can use a vacuum cleaner to lift of a heavy rubber ball. The vacuum cleaner is generating a lot of suction (differential pressure on the ball) but the actual flow is zero (as the hole is plugged). If there are leaks around the ball, I can generate both flow and suction.

If the 5 hp was used entirely to generate flow, then you might be able generate a flow approaching 1000+ cfm. But if that same flow is throttled (by enclosure impedance) and used to generate vacuum instead, the actual flow could be considerable smaller.

You might be in a situation that you can generate a lot of flow as well as create a pseudo-vacuum table. But it is normally a trade-off.

On some lasers the manufacturers have tried to accomplish what you are doing (creating a vacuum table as well as an exhaust system with the same blower.) But in my opinion it does not work very well for traditional exhaust systems (often less than 1 hp). You seem to have shown that at 5 hp the concept might work - but to be honest, not very many people would go to such a larger blower.

Dan Hintz
07-22-2010, 10:32 AM
If the 5 hp was used entirely to generate flow, then you might be able generate a flow approaching 1000+ cfm. But if that same flow is throttled (by enclosure impedance) and used to generate vacuum instead, the actual flow could be considerable smaller.

As a point of reference... the DC2000B from PSI generates 1,000 CFM at 6" H20. And it's only a 2HP unit... strong little sucker (no pun intended).

Anthony Scira
07-22-2010, 10:37 AM
Can not believe it has not been said yet !


YOU SUCK !


Just kidding, man that is a big fat pipe ! With that kind of airflow I would think you would be almost ok to cut some PVC materials.....but I know its still not recommended.

James Jaragosky
07-22-2010, 11:28 AM
As a point of reference... the DC2000B from PSI generates 1,000 CFM at 6" H20. And it's only a 2HP unit... strong little sucker (no pun intended).
Here are the specs on the motor I used.

Specifications:
Motor: 5 HP, 220V, single-phase
Air suction capacity: 3961 CFM
Static pressure: 14.6"
Intake port with manifold: 4" x 4 Holes( I have 1 8" pipe)
Intake port without manifold: 10"
Impeller size: 15" balanced steel, curved fin
Collection bag capacity: 24 cubic feet( not in use)
Bottom bag material: plastic ( not in use)
Upper bag filtration: 2.5 micron ( not in use)
Machine collection capacity: minimum 4 machines
Detachable base
Overall dimensions: 74" W x 29" D x 134" H
Approximate shipping weight: 326 lbs.


I used the new extraction system this morning and it not only holds down material it removes all trace smells as well. That's with the lid open.

So far I am pleased with the new set up.
I can see a need to add an outside air intake to the cabinet.
And it is much nosier than my OEM blower.

Chuck Stone
07-22-2010, 11:37 AM
I wonder if this is related to the article I just read..

Dee Gallo
07-22-2010, 11:45 AM
CHUCK, YOU ARE HYSTERICAL!

:D dee

Chuck Stone
07-22-2010, 11:48 AM
I'm early for an appointment ..I have too much free time! :p

James Jaragosky
07-22-2010, 11:51 AM
I'm early for an appointment ..I have too much free time! :p
Thanks for the laugh:D
I may have moved into the Tim The Tool Time Taylor zone on this one.

Joe De Medeiros
07-22-2010, 1:27 PM
Today I connected a 5hp dust collection motor to my Rabbit laser to be used for smoke extraction.
First I had to enlarge the factory exhaust hole in the laser cabinet from 6in to 8in. Four foot of 8inch pipe and 4 elbows later and I am ready to test the new exhaust system out.
I tossed a 12 x 18 inch piece of warped 3mill Baltic birch on the 23 x 33 cutting bed and flip on the blower motor, Wow the birch straightened right out. I have so much suction now that I can hardly open the lid with the blower motor on.
Now I am a little worried that I may have too much suction.
Jim J.

the other advantage is very little flare up when cutting.

paul mott
07-22-2010, 1:29 PM
Just one question Guys and Gals.

For those of you working in residential areas - do you have any problems with noise from your outside venting exhausts ?.

Paul.

Lee DeRaud
07-22-2010, 1:59 PM
Thanks for the laugh:D
I may have moved into the Tim The Tool Time Taylor zone on this one.The whole thing did remind me of a Tim Allen bit where he complains about the anemic suction of his wife's vacuum cleaner: "So I hooked up an old Buick V6 I had out in the garage, now I have the world's only 165hp rear-bagging Eureka...that thing'll suck the eyes out of a parrot!" :eek:

My only concern is that I'm under the impression that the big DCs really don't like running without airflow. You might want to have one 4" inlet with a wastegate you can open when you're running full-sheet jobs.

James Terry
07-22-2010, 6:08 PM
Just one question Guys and Gals.

For those of you working in residential areas - do you have any problems with noise from your outside venting exhausts ?.

Paul.


Paul, to avoid noise and smell complaints I did an upblast vent (http://www.webglider.com/laser/stackhead.html). It is as centered on my property as I could reasonably get it so there are no focused spots. Most of the sound blasts up and away along with the vapors.

The only problem I have had with this new exhaust system might also be related to too much power, I dunno. So far no complaints though.


http://www.webglider.com/laser/2010/DSC07183a.JPG

Chuck Stone
07-22-2010, 6:35 PM
heh heh .. we might have a LOT of Tool Men here.. :p

Chuck Stone
07-22-2010, 6:40 PM
My only concern is that I'm under the impression that the big DCs really don't like running without airflow. You might want to have one 4" inlet with a wastegate you can open when you're running full-sheet jobs.

I wonder if you could rig a gate with a spring on it? So that if there's zero
suction it would pull the gate open enough to get airflow. Might be difficult
to figure out how much tension the spring should have though. But if you
have the right spring, it could be self-regulating. Laser cover open, the
gate would close. Close the laser cover, the suction would pull the gate
open. I think it would have to be a flapper that pivots in the center, rather
than a gate that goes up and down. I forget the work I'm looking for..

James Jaragosky
07-22-2010, 7:17 PM
I wonder if you could rig a gate with a spring on it? So that if there's zero
suction it would pull the gate open enough to get airflow. Might be difficult
to figure out how much tension the spring should have though. But if you
have the right spring, it could be self-regulating. Laser cover open, the
gate would close. Close the laser cover, the suction would pull the gate
open. I think it would have to be a flapper that pivots in the center, rather
than a gate that goes up and down. I forget the work I'm looking for..
The problem is not only getting enough air flow through the cabinet but the room as well. I have to open the overhead door 5 inches to get enough air to flow through the cabinet.:eek:

Lee DeRaud
07-22-2010, 7:20 PM
I wonder if you could rig a gate with a spring on it? So that if there's zero
suction it would pull the gate open enough to get airflow. Might be difficult
to figure out how much tension the spring should have though. But if you
have the right spring, it could be self-regulating. Laser cover open, the
gate would close. Close the laser cover, the suction would pull the gate
open. I think it would have to be a flapper that pivots in the center, rather
than a gate that goes up and down. I forget the work I'm looking for..I've got a flapper outlet on my vent system: the air pressure just pushes it open, gravity pulls it shut...I think it's intended to keep birds/rodents out of a dryer vent. Costs maybe $8 at the hardware store. All you'd have to do is McGuyver a spring and stuff it onto the front of an extra inlet port (facing in, obviously).

Chuck Stone
07-22-2010, 8:24 PM
I've got a flapper outlet on my vent system: the air pressure just pushes it open, gravity pulls it shut...I think it's intended to keep birds/rodents out of a dryer vent. Costs maybe $8 at the hardware store. All you'd have to do is McGuyver a spring and stuff it onto the front of an extra inlet port (facing in, obviously).

yeah.. that's what I was thinking of! Thanks.
Now .. how do we open his garage door 5" ? :p

I have a similar problem with only a 1hp unit. my only air inlet is a door downstairs, and
the dust collector pulls the door shut after a few minutes. But it doesn't make me
fight to open the lid of the laser..

Joe De Medeiros
07-23-2010, 1:12 PM
The problem is not only getting enough air flow through the cabinet but the room as well. I have to open the overhead door 5 inches to get enough air to flow through the cabinet.:eek:

This sounds like you need to add another duct for makeup air, if you are restricting the exhaust fan too much, it increase the load on the motor and could burn out the motor quicker. You can also add an auto damper that opens when the exhaust is on.

Larry Robinson
07-23-2010, 9:30 PM
James,

I would be interested in knowing more about your extraction system. With that much air going through it has to be something special.

Larry

Tom Bull
07-25-2010, 10:11 PM
If you are going to get outside air to run through the laser you have to consider temperature and humidity issues. Dan's odor extraction is a great idea, but you'd need a monster. Perhaps a heat exchanger would be better for you, don't know, just a thought.

Dan Hintz
07-26-2010, 7:10 AM
If you are going to get outside air to run through the laser you have to consider temperature and humidity issues. Dan's odor extraction is a great idea, but you'd need a monster.
I would use the same filter I built, but I'd also put in a gate and clamp it down a bit to reduce the flow through that portion of the air circuit. Just because you have 5HP to work with doesn't mean it all has to go through the same pipe.

Mark Winlund
07-26-2010, 12:56 PM
Mine is a 3 phase, 3hp high pressure blower. When running full on, The lid of the laser distorts about 1/2 inch.

The most usefull feature I added was a VFD to be able to control the "suck". I also added a 6" computer fan to the back of the motor to keep the motor cool when running at low rpm's.

Mark

PS... I forgot... I also use custom made thin vacuum tables to flatten out veneers when cutting. They are supplied by their own vacuum pump... which are equipped with hepa filters and pre-filters. This unit is 5 hp.

Large routers are frequently supplied with substantial vacuum pumps. I have a 25hp vacuum pump that requires 440 VAC. This was used on a 5' x 10' cnc router. It is currently waitng for a suitable cnc router to be married to!

Mark Winlund
07-26-2010, 1:21 PM
I wonder if this is related to the article I just read..

Really funny.... I printed it out!

Mark

Mark Winlund
07-26-2010, 1:28 PM
The problem is not only getting enough air flow through the cabinet but the room as well. I have to open the overhead door 5 inches to get enough air to flow through the cabinet.:eek:


One could conceivably have a serious problem.... If your shop is tightly sealed, the negative pressure could damage the walls and ceiling. After all, they are not designed for any serious pressures.

Mark