What do we know about Laser Exhaust System?

[Andrey Anfimov]

I suggest to collect in one place everything, that we know about Laser Exhaust System.
After perusal of many User Manuals I have found very good recommendations for those
who wishes to make itself Laser Exhaust System.
You can find the original article at the address -
http://www.gravograph.com/usa/Support/pdf/Engraving-305/Laser%20Exhaust%20Requirements.pdf

Laser Exhaust Requirements

1. To properly exhaust fumes and smoke from the laser engraving system during operation,
it is necessary to provide an exhaust unit moving a minimum of 200 CFM (cubic feet per minute)
at 6 inches of static pressure (inches of water). Please refer to the sample diagramme.

2. The blower MUST be mounted on the OUTSIDE of the building either on the roof or on a cement
pad next to the building possibly mounted on vibration dampeners. Rigid tubing should be used for
90 % of the distance travelled. The tubing should be smooth walled and have as few 90 degree bends
as possible. Two 45 degree bends have better airflow than one 90 degree bend. Use tubing with a
diameter that matches the blower unit (usually 6 inches/1524 mm) and use a reducer to couple the
tubing down to fit the exhaust tubing on the laser within a few feet from the laser system. Also consider
installing a gate to control airflow and to close off the exhaust from the outside environment when the
laser is not in use. This is especially useful in colder climates where it can be damaging to the laser
system to have cold air coming into it from the outside. Do not connect the rigid tubing directly to the
laser system. Use a short piece of industrial grade, wire reinforced rubber tubing to connect the end
of the gate, or rigid tubing, to the laser system. This will provide mobility and will dampen blower
vibrations. Use only a few feet because it’s spiral construction reduces airflow. Install a hose clamp
(if possible) on both ends of the hose to prevent leaks and to prevent the hose from slipping off.
Have the blower wired to a wall switch in the same room. The chart below is based on the measured
distance from the outlet of the laser system to the inlet of the exhaust blower. It assumes that you will.
It is important to purchase a high pressure blower that meets or exceeds these requirements.

Measured Distance Blower Required
(Look at the Image_0002)

Best regards,
Andrey

[Dan Hintz]

Well, you've posted probably 90% of the useful info right there. Though I can't say I agree with their "MUST" and "OUTSIDE" word choice when it comes to blower placement... it may be less noisy, but I would hardly call that a must.

[Joe Pelonio]

I'd also warn that the requirement varies by laser manufacturer, mine for example requires double the flow, 400CFM. I'd also add that debris will accumulate inside the vent tubing and it should be taken apart and cleaned out annually.

[Dave Johnson29]

I'd also add that debris will accumulate inside the vent tubing and it should be taken apart and cleaned out annually.


Good point Joe,

I have a house-heater air filter in front of the extractor outlet. I have one for air coming into the laser cabinet and one before the house outlet.

Because my laser was a bare-frame ex production unit it had no cabinet, therefore I had the luxury of designing and making the cabinet the way I wanted it. That included incoming and outgoing air filters. It may not be pretty but it works well. :D:D

[Tim Bateson]

Thank you Andrey. Very useful as I am getting ready to move my setup to a new office in the basement. I will likely add the damper to control back flow when not in use. I'm also going to add a speed control as I don't need the 600CFM when doing low odor/low smoke items such as anodized aluminum. My blower is in another room connected directly to the outside vent with a trap to empty debris as Joe has suggested. I'm also going to be switching to PVC pipe as the metal pipes leak too many fumes.

[Tim Bateson]

Excellent point Dave. I put a cheep filter over my laser intake fans a few months ago & was surprised how much dust it trapped that could have been passed through my system.

[Mike Null]

The are some important elements in the OP's comments.

1. Use hardwalled pipe.
2. Keep 90 degree angles to a minimum. They severely restrict air flow and lower the efficiency of the system. Consider length of run and the number of L's in the line as more of either requires more cfm capacity.

There is no need to mount the blower outside. If you want a quieter unit consider an inline blower.

Do not think that more is better when it comes to cfm. Buy what it takes to evacuate the smoke and debris. Buying bigger units only robs your shop of heat and air conditioning as well as making it difficult to hold down some materials on the table.

[Joe Pelonio]

I will likely add the damper to control back flow when not in use. I'm also going to add a speed control as I don't need the 600CFM when doing low odor/low smoke items such as anodized aluminum.
Again, be careful, on some brands the laser tube is cooled by the flow of air drawn in by the exhaust fan, reducing the speed could cause it to overheat
and fail.

[Tim Bateson]

True, that's why I use a cheap porous filter. It doesn't catch everything, but some is better then none. I would assume dust build-up on the tube housing or tube fans could also lead to over heating and failure.

Updated - One shows how thin the filter is, the other shows how much dust it stopped in just a couple months of low-moderate use. I changed the filter just as Christmas orders were ramping up.

[Richard Rumancik]

The advantage of the blower outside (or at least outside the working area) is that if there are any leaks in the output tubing, it doesn't come back into the room. If there are small leaks in the vacuum side, no harm done.

I don't think that in-line blowers can meet the specs that most laser manufacturers are providing. I know some people are satisfied with them but they will not have the pressure/flow performance of a centrifugal blower.

[Andrey Anfimov]

From ULS manual for Versalaser:

The exhaust system

- MUST be capable of supplying a minimum of 150 CFM (cubic feet per minute) of airflow while under a load of 6 inches of static pressure (254 m3/hr at 1.5kPa).
- DO NOT install forward incline, backward incline, in-line, or ventilator fans because these types of air handlers are inadequate and inappropriate for this type of installation.
- A high-pressure blower MUST be used to meet minimum airflow requirements.
- For personal safety and noise control reasons, we recommend that the blower be mounted OUTSIDE the building.

- Rigid tubing should be used for 90% of the distance traveled between the blower and the laser system. The tubing should be smooth walled and have as few 90 degree bends as possible.
- Install a gate to control airflow and to close off the exhaust from the outside environment when the laser is not in use. Place this gate within 5 – 10 feet from the laser system.
- Use a short piece of industrial grade, wire reinforced rubber tubing to connect the end of the gate to the laser system. This will provide mobility and will dampen blower vibrations.
- Have the blower electrically wired to a wall switch in the same room for easy ON/OFF control.

[Mike Null]

Inline blower are available in many varieties and are superior to centrifugal blowers. They do cost more.

I won't argue with an outside installation but it is not required. Mine is running right now (it's 10 years old) and I can carry on a conversation in normal voice. It's about 6 feet away from me.

[Tim Bateson]

Mine is mounted just inside the basement. I had built a ventilated box around it to lower the noise level. However I removed the sides when I noticed it was getting very warm when used for a period of time. The current box is double the size of the blower. I'm going to try enlarging it and closing it back in to once again lower the sound while keeping it cool.
My question is if located outside - especially in a weather proof box even if ventilated - wouldn't it have the possibility to overheat in the summer?

[Andrey Anfimov]

I too have put exhaust system in a room near to Versalaser.
I use very short (60 cm) wire reinforced rubber tubing attached to inlet and outlet of blower.
High-pressure blower - 1.6 kPa and 600 m3/h made by Soler and Palau Ltd. Power of motor 0.75 kW.
In the future if I instal exhaust system far from the engraver it is necessary to replace blower with more powerful.

[Keith Outten]

Tim,

There are lots of motors that are used outdoors year round that last for decades, well pumps are the first that come to mind and there are literally thousands of other applications in the commercial field like HVAC motors mounted on rooftops.

Winter would be the worst case with very cold temperatures affecting the bearings when the motor starts up.
.

[Richard Rumancik]

If you put an electric motor in a box outdoors with no cooling or just passive "vents" it is quite possible to overheat in the summer. If you can put it out of the sun, it will help. Of course it depends on where you are geographically.

If you look in motor catalogs you will find that a large proportion of standard electric motors are rated for a 40C environment (about 100F). This ensures that the insulation temp stays below the maximum permitted. There are some specialty motors that are rated higher but most people buy their blower and motor together. Most likely it will be a standard 40C motor.

On a 30C summer day you can easily get over 40C in a closed box.

I dealt with this issue because I wanted to put my blower in a garage "attic". In on a summer day it can get very hot (more than 40C). The blower motor is semi-enclosed (not tightly sealed). I added a small 6" centrifugal blower bringing in fresh outside air to the motor enclosure through a dryer duct. I also have a high temp. cutoff switch, in case the small blower fails.

If I was building a box outside I would probably install a small blower inside the box to force air through it. It could be on a temperature switch, so it only runs when needed.

Many HVAC motors (air conditioners, heat pumps) are set up so that the moving air cools the motor. It may even be just a large propeller type fan blade mounted to the motor shaft. Most centrifugal blowers do not have any cooling air flowing over the motor itself.

[Dee Gallo]

I put my blower outside, as recommended by my tech. It's in a waterproof (and mouseproof?) box, which is inside a blueboard box I sealed with silicone, on top of a paver base. It is on the north side of the house which does not get direct sun and I have not had any problems with it at all.

I would have had straighter connections, but the hole in the wall was already positioned for my old laser which was a straight vent out from an internal blower. But even with the elbows, I get good suction and the run is only a few feet long.

In the winter, I put a sheet of metal over the vent side to create a tent which keeps the snow off and the vent area clear.

Inside, there are 2 lasers hooked up with blast gates to close off when not in use. Outside, there is an access panel if needed.

[Tim Bateson]

Thanks for the information. Richard, I know I've seen solar driven fans at HF. It may me a good investment to keep an attic or outside mounted blower a bit cooler.
If I do move my blower outside, it'll be on the SW side, which is sunny 75% of the day here in the summer.
A lot to think about as I continue to redesign my set-up.

[Loren Snyder]

[quote=Andrey Anfimov;987991]I suggest to collect in one place everything, that we know about Laser Exhaust System.
After perusal of many User Manuals I have found very good recommendations for those
who wishes to make itself Laser Exhaust System.

Laser Exhaust Requirements.....<snip>

Hi,
I'm a fairly new laser owner with a Laser Pro 180 35 watt.
I cut thin ply veneer, acrylic and card stock for making model railroad kits and related items thus far.

I've got the laser mounted in a wall closet like enclosure with venting through the ceiling, and the vent blower, (about 650 CFM) is located directly above the 4" ribbed vent tube passing through the ceiling. I can leave the closet doors open or close them for better sound muffling. I realize there needs to be free air flow for the laser so the doors are usually open. I don't mind the noise.

From the blower to the outside vent is about 8 feet. 4" tubing runs from the exhaust blower to the screened vent on the outside wall.

The exhaust tube diameter from the back of the laser is only 2", but then it connects to the 4" line up to the exhaust blower.

So far so good, but I am not happy with the exhaust system thus far. It seems like there is way too much smoke even with the 650 CFM blower.

I am wondering if I need more CFM or maybe a ceiling fan inside the closet to draw room air into the laser closet like a bathroom fan would draw air up and out.

It's the fumes that are bugging me. Everything else seems to be clicking along as fast as I can learn this new tool.

I've read about the exhaust fan being outside, but in my case that is not possible because of location. It has to be in the attic and it sure seems like I have an ideal setup with the exhaust being a short run to the outside, but I need to make some sort of change to get the cutting fumes gone and away.

Can someone suggest what I might do to get more exhaust? Seems to me that Laser Pro should have made a 4" exhaust port in the laser back instead of only 2"

Any help would be greatly appreciated.

BTW, I am awed by the many uses of the laser as I read through these different threads.

A neophyte laser user,
Loren

[Andrey Anfimov]

Loren,
pay attention for Static Pressure of your blower.
It must be at least 1.5 kPa or more.
Look at the picture.

I made simple test for my Exhaust Systems:
I take sheet of paper A4 size and put it to the front of
laser where air are incoming inside. If paper do not fall down I know the blower work well.

[Mike Null]

I have not previously heard of a 2" exhaust port. I believe that is too small to allow the blower to evacuate the smoke from your cabinet.

With that short run 650 cfm should be more than adequate. See if you can switch to a 4" port.

[Rodne Gold]

Is it smoke or smells that you are referring to when you talk about "fumes" , siting the laser in a closet type enclosure or a small room will require an extractor fan.
PS we run 6 Laserpros off 3 blowers , Y'ing the output of 2 lasers to 1 blower , we also run lengths of 20+ meters of ribbed ducting , have been doing so for many years and have no problems with smoke evacuation , smells are of course another issue.

[Loren Snyder]

Mike,
I have a call into my sales rep asking about a larger exhaust for my laser.

He told me originally to go to the 4" exhaust from the laser, but first I had to adapt from the 2" from the laser to the 4".

Seems like a dumb thing to do placing a 2" on the machine itself and then asking the buyer to convert.

In regards to fumes, the smoke and fumes are one, but there just isn't enough being pulled from the machine.

I'll get back to you when I hear from my rep.
Thank you,
Loren

[Richard Rumancik]

Converting from a 2" port to 4" port will reduce the impedance of the hose (ducting) itself, but the largest impedance to airflow is caused by the 2" port itself. The 4" duct has an area of 4 times the 2" duct. You can't solve that by using larger hose downstream. Also, abrupt changes in diameter add their own losses; a gradual transition when a change in diameter is necessary is best.

You would have thought it would have been thoroughly tested. Is there any opportunity to change a sheet metal panel to incorporate a 4" duct, at least for a test? (Maybe you could make something out of plastic sheet or hardboard as a test.) It is disappointing to have to rework a new laser to make it work properly.

[Richard Rumancik]

Loren, I tried to find some pics of the back of your LaserPro C180 but no luck. I did see the spec for the single 2" port on the rear. What puzzles me is this: a 35 watt C180 can generate as much smoke as a machine with a larger bed. I wonder on what basis GCC decided that it would only take a 2" hose (1/4 the cross-sectional area) to evacuate the smoke and fumes from this machine? You might be able to get by with a little less exhaust air with a narrower machine but I think they may have been a bit aggressive on cutting airflow. Or they thought you could pump 500-600 cfm through a 2" port? (The velocity of the air would have to increase 4x for that to happen.)

If you have a photo of the rear of the machine maybe you could post it.

I know it would not be a nice thing to have to do, but is there any opportunity to change the port to a larger one? Is there any "free" area where another opening can be made? Yes, this makes me cringe too.

Is this laser set up so that the exhaust air also cools the laser tube or is the laser tube separated from the exhaust air?

I saw something about "vacuum hold down" in the specs. Are they trying to use the exhaust air to hold the workpiece in place? I have come to the conclusion that this approach has a flaw in the logic, when you want to optimize fume extraction.

[Andrey Anfimov]

Loren,
don't make any change in your laser. I think 2" way is very short an does not drop pressure too much only add some noise.
Try to make as short as you can your 4" ribbed vent tube (max 1metr) and use metal duct for the rest way.

What about your blower? What you know about it except 650CFM?

[Andrey Anfimov]

Here is one more instruction from LASERBITS, INC.


Exhaust Systems for Laser Engraving
A key component to the safe and reliable operation of a laser system is a properly designed exhaust system. A necessary component to a laser engraving system, the exhaust is integral to the performance of the system and can add years of life to your laser and assure peak performance.
Safety and maintenance are two important factors to consider when installing or refitting an exhaust system to your laser. A safely operating exhaust system will remove the smoke residue created from the laser process. Smoke from plastics, acrylics, coated wood and many other commonly found materials can generate an out gassing hazard.


The right exhaust will also help reduce the maintenance to our laser systems - you can reduce costly downtime and increase performance with an exhaust that meets the system manufactures specs.

**Air Flow Ratings: Static Pressure and Air Volume. Air volume is measured in cubic feet per minute or CFM - the amount of air that is being moved stated in volume. Static pressure is a measure in Inches of Water which relates to the amount of push the air has behind it. A 12x24 system typically uses a fan rated at 650 CFM at 4 inch static pressure for a 20 foot run of 4 inch duct. Longer duct runs, more turns in the duct or a larger sized laser table will require more CFM and static pressure.
**Fan and Motor Considerations: Factors to consider when choosing an exhaust fan for your laser include the inlet and outlet size for duct connection, voltage 110 or 220 volt, quality of the motor for durability and the noise of the unit during operation.

**Duct Design: The type of duct used is very important - ribbing or spirals can cause more friction as the air travels through the duct. Also, use metal duct, not plastic. This is very important and has been documented for years that plastic duct is an explosion hazard.

**Fan Placement: Placement of the fan unit is always recommended at the end of duct or the furthest point away from the laser system.

Although not the easiest placement, by placing the fan in way the duct will be at a low pressure. As and added safety measure the low air pressure inside the duct will eliminate the risk of hazards of leaks in the duct or its joints as the air will have a natural tendency to be drawn into the duct.

[Loren Snyder]

Well gentlemen, I'm not a totally happy camper, but at least it isn't raining at the moment....here's the scoop.

Talked with my sales rep. He said the C180 comes with an optional 4" exhaust port. That's nice, but as you pointed out Richard, the specs say only the 2" opening is on the back of the machine. There is no way to increase this to 4" so I am stuck with a 2" exhaust.

I looked and relooked at the back. 2" is the order of the day.

My 2" port has a 2" hose that is used to connect to the 4" hose up to the blower, (approx. 4' above the laser)
Blower sits just above the ceiling joist, then 4" exhaust runs horizontally about 8 feet to the outside.

Yes Andrew, the blower could, (with difficulty) be placed closer to the opening at the edge of the wall, but I doubt that would accomplish that much...but am willing to do it.

And yes, I can change to a smooth exhaust pipe and that may help some........

My rep said to check closely for any leaks that would rob the suction from the blower.......there are none.

He also assured me that 650 CFM should be sufficient for my needs, and that he recommends no longer exhaust run than 30'. I'm way below that.

Well......I guess I can get the smooth pipe to help a little, and even get a more powerful blower, (gee, like I really wanted to spend another $100+ at Harbor Freight and crawl around the attic again.

Richard, the exhaust is separate from the cooling for the laser. The "box" that comprises the vacuum chamber below the table is only a bit larger than 2" so that is why the exhaust port is only 2"

Here's my plan of attack.....
I'll convert over to smooth pipe to reduce friction and then if need be move the blower closer to the outside as suggested. Then I can also try a larger volume blower. And if that still doesn't cut the mustard my "final option" is to hook the current financial system of the US to the exhaust side of the pipe and place the political system on the opening of the laser. Between all the hot air being blown into the laser and the "sucking" action of the financial situation, I should be able to generate enough air flow to cut my projects without using the laser beam at all....... :o)

I'll return later with an update.

Not looking forward to any of this

Thanks guys,
Loren

[Rodne Gold]

Just one point , are you using air assist to cut , cos that cuts down smoke a huge amount. The port size would depend on the volume of the enclosure , I don't think your 2" port is the problem , you would have to be generating tons of smoke to overcome a 650cfm airflow , thats 50 cfm short of ther carb that feeds my 500 hp 454 motor.....even a 300 cfm airflow would be adequate...
Be aware that air being sucked out needs fresh air to come into the enclosure , perhaps the enclosure is too air tight , vaccum without airflow is not useful for extraction.

[Richard Rumancik]

Yes Andrew, the blower could, (with difficulty) be placed closer to the opening at the edge of the wall, but I doubt that would accomplish that much...but am willing to do it.

And yes, I can change to a smooth exhaust pipe and that may help some........

Loren, you seem skeptical that these fixes will help much and I am too. They won't likely make a whole lot of difference. I doubt that moving the blower downstream will have any measurable effect at all. It is not intended to be a performance improvement.

He also assured me that 650 CFM should be sufficient for my needs, and that he recommends no longer exhaust run than 30'. I'm way below that.

A blower rated at 650cfm is rated assuming a certain impedance to flow. As soon as you start blocking it with a restricted tube your flow will drop considerably. So just because it is called a 650 cfm blower doesn't mean you are getting anywhere near that. You can't block the pipe to 1/4 of the area with no effect. Sure, one can argue that this is a "short" length of reduced diameter but the pressure drop it creates is very significant.


I'll convert over to smooth pipe to reduce friction and then if need be move the blower closer to the outside as suggested. Unless you have very accurate measuring equipment you will not be able to detect any difference between the smooth pipe and the ribbed flexible ducting. Maybe you can improve the flow a few %. Is that worth it? That is not to say that the tube type is insignificant, and I would normally suggest minimal use of flexible duct, but relative to having a 2" orifice place in the middle of your air system, the tubing is a minor issue. I think you would be going to a lot of work and expense with minimal observable improvement. My opinion.

I wish I could see one of these units in person . . . its hard to know what might be done to make the air system work better. But I really think that the culprit is the 2" port. I realize not everyone agrees. If you brute force the issue with a huge blower, I think the noise will become intolerable.

Can you tell me how the table/intake is set up? Are they using the 2" port to create suction on the table to help hold material in place?

[Tom Gooch]

I'm new here--just bought my laser today:eek: :D(epilog Helix 45 watt) and started work on my exhaust system. This is my first post.
Found this great fan for a good price and thought I'd pass it along to all. Availabe from www.grizzly.com (http://www.grizzly.com) here is the link: http://www.grizzly.com/products/1-HP-Light-Duty-Dust-Collector/G1163 Only thing I'm going to have to adapt is the outlet, which as out-of-the-box is made to hold a collection bag instead of discharging to the outside---so it is just slightly larger than 4" duct.

Grizzly is HQ'd here where I live in Bellingham WA. They sell really good tools at good prices, so you might find other stuff you could use as well.

[Mike Null]

I would not buy a larger blower when you're not using the capacity that you have.

Consider how much water you can pump through a 2 inch hose versus the amount you can pump through a 4" hose.

That is your problem.

[Dan Hintz]

<chuckle> I like this one:
http://www.grizzly.com/outlet/10-HP-Industrial-Dust-Collector/G0508

Originally $1,095, but now on sale for $1,595!!! What a bargain!