Air compressor stats needed - FAD, CFM, etc...

[Mike vonBuelow]

I tried the search, but no luck finding what I needed - is anybody "in the know" about what is both the minimum needed and would-be-nice-to-have ranges re: air compressor/air assist.
Mine is on it's way out, so I'd like to get the gouge on what I should be looking for. A heavy day for me is 4-5 hours of use, but I'm usually in the 1-2 hour range.

CFM
PSI
FAD
and ???

Thanks in advance - and if you know of a thread, please link :)

[Gary Hair]

None of the specs you list really mean much for the typical laser usage. Most lasers seem to need between 10 and 40 psi and most compressors will put that out at more than enough cfm to accomplish the task. What you really need to decide is where you want the compressor, what type, and how much you want to spend. I have a 5hp, 60 gal tank compressor in my garage that supplies air to my small blasting cabinet and the laser. If I am running air for an hour the compressor may turn on once to refill the tank. It's loud, and that's why it's in the garage. If you want it close by then you need something like an industrial-strength airbrush compressor. Don't expect to spend less than $400-$500 for something that you can run 4-5 hours a day. Even if it's only once in a while, 4-5 hour runs will kill most compressors. I killed a cheap Harbor Fright compressor in about 45 minutes... then I ran lines from the big compressor and haven't regretted that decision. Some laser manufacturers will specify psi/cfm requirements, but they know less about compressors than they should - my bet is that they bought something and it worked then they simply took the specs from that compressor and called it "standard" or "minimum".
Go to Home Depot and get a compressor and it will last you for years.

[Rich Harman]

[QUOTE=Mike vonBuelow;2421677]I tried the search, but no luck finding what I needed - is anybody "in the know" about what is both the minimum needed and would-be-nice-to-have ranges.../QUOTE]

I use a Gast 71r as a dedicated air assist compressor. No storage tank. You won't need anything bigger than that. Many people use a much smaller compressor with success. If you are going to do a lot of cutting then go bigger rather than smaller.

If you use shop air then you will have to take precautions to keep moisture and oil out of the air assist. You don't want that on your lenses.

[Keith Colson]

Hi Mike

Where you need the most air is for cutting things like mdf, plywood and acrylic with the "paper on". The air puts out the fire. I find that I need no more than 50psi. My compressor is always charged to a 100 psi and I have a dedicated regulator by the laser machine. I run from 10 to 50psi depending on the job.

I like dental compressors because they are super quiet. I got one for about 500 dollars. It is rated at 2.5CFM @ 100 PSI and that is just enough to meet the 66% duty cycle on the compressors spec. An under rated compressor can overheat if it does not get some cool down time. I really love the low noise, I can still use the phone and talk to customers. My old compressor was so noisy I missed all my phone calls.

As Rich said, putting dry air into the laser is most important. My air dryer cost $2,500. There are some diy versions you can do using car transmission coolers. If you get your mirrors wet and laser them, they may burn and fail.

Cheers
Keith

[Matt McCoy]

Here's a good compressor that is quiet, oil-free, and inexpensive:

http://www.homedepot.com/p/California-Air-Tools-6-3-gal-1-HP-Ultra-Quiet-and-Oil-Free-Steel-Tank-Air-Compressor-6310/202977399?N=5yc1vZc27pZ8te

[Keith Colson]

Hi Matt that has pretty much the same spec as mine except it is half the price. Looks perfect!

Cheers
Keith

[Tim Bateson]

No need to spend a lot of money. I've been using this $70 compressor for 8 years. I believe I got it on sale for $49 at the time: http://www.harborfreight.com/16-hp-58-psi-oilless-airbrush-compressor-69433.html

[Matt McCoy]

Hi Matt that has pretty much the same spec as mine except it is half the price. Looks perfect!

Cheers
Keith

It's pretty sweet. I didn't hesitate to try one after it was suggested by someone on this forum. I've had several dozen compressors (not for laser air-assist) of various types and sizes. One that was capable up to 70-90 PSI, reasonably-priced, and quiet has always been an elusive combination.

[Glen Monaghan]

I have one of those little HF compressors as well. Works, but gets scorching hot after a while if I don't put a fan on it. Rather noisier than I like, too. Mine's about 6 years old and starting to sound like it may be coming apart...

[Mike vonBuelow]

^ ^ Increasing noise, that's why I'm asking

[Bill George]

I have one of those little HF compressors as well. Works, but gets scorching hot after a while if I don't put a fan on it. Rather noisier than I like, too. Mine's about 6 years old and starting to sound like it may be coming apart...

When I was doing pneumatic system controls work and we needed a compressor and tank, here is what we looked at for spec's. The unit was sized to run only 1/3 of the time or less. The longer a compressor runs the hotter it gets. Hot compressors tend to use oil and send the vaporized oil into the system, bad. We installed oil separating filters to help. Hot compressors failed, usually because of the loss of oil.

Compressor air storage tanks need to be drained at least daily, we put automatic drains on the tanks most of the time. All the systems had a refrigerated air dryer with automatic drain.

My personal observation, the belt drive units last longer and have much less noise. My shop compressor was sized to run my plasma cutter on the CNC table. It might run 10% of the time with my ULS laser. Its rated a little over 10.5 scfm

[Joe Pelonio]

I have several compressors of various sizes in the shop, but for the air assist I use a $49 airbrush pump that puts out 25 PSI, is very quiet and has lasted 8 years so far. With a quick connect, I can easily remove the tubing if I need to do some airbrushing.

[Dave Sheldrake]

CFM is pretty much a useless figure, it's usually the air displaced by the piston or valve at rest (swept volume of the cylinders much like a car engine)

FAD is the important figure, (Free Air Delivery) this is the measure of air displaced AT pressure

A compressor with a CFM of say 8 will have a FAD of 60psi between 4 and 5 CFM.

Have to be honest, go with the Gast 71R that Rich mentioned, quiet and has enough FAD to do what you need without overheating the system (direct drive are usually 50% duty cycle and belt drive are up to 100%)

More is better, hot air when it expands causes condensation although it's pretty easy to deal with given a metal can filled with silica gel cat litter.