[eeboy]

I am looking to convert the air assist on my laser cutter (Gweike 150W) to shop air. I find I am mostly cutting acrylic and plywood/mdf. What should I be looking for in a compressor? Should I invest in a dryer as well so that moisture/oil is removed prior to the laser head?

[Melody-gweike]

Hi, Eeboy,

Why are you going to modify your air assist? Is the air compressor we sent to you with the machine not good? Have you met any problem? Please kindly let us know.

Melody
[email protected]

[eeboy]

As I understand (from reading other users posts), the more air assist the better when cutting plywood/mdf. The small 'compressor' provided is pretty limited in comparison to what I could get from shop air.

Moreover, the compressor provided has quite an annoying hum. Going the shop air route might be much louder, but only for the brief period of time it's on.

[pontiacg5]

Hi, Eeboy,

Why are you going to modify your air assist? Is the air compressor we sent to you with the machine not good? Have you met any problem? Please kindly let us know.

Melody
[email protected]

Sorry, but the compressor that comes with a Gweike machine is a complete and total piece of crap. Mine made the most annoying popping sounds, plus it didn't put out hardly any pressure. The air it pumps is not even either, it comes in very noticeable pulses, sort of "fanning the fire" when cutting wood.

I moved over to shop air, it's really rather easy. My shop has a humongous screw compressor, but you should be able to get by with a little round "pankake" compressor.

My setup uses three filters, first a 20 micron, then a 5, then a coalescing filter. I used three because my shop has dirty steel pipe and a nice coalescing filter will get taken out extremely quick with dirty air. But, coalescing filters work great for filtering out water and oil so it's really the only kind you want to use. If you are using a little compressor and rubber line by itself to run the machine I'd just use a coalescing filter and be done with it. If you clog a lot of the finer mesh coalescing ones add a few particulate filters in front like I did. Don't skimp on clean air. If you get oil or water on the lens the laser will cook them to the lens, possibly even cracking it. Either way the lens will be toast, gotta keep it clean!

You'll want a regulator too, one that has a lot of fine adjustment. When you buy one make sure it can reliably regulate down to 1psi.

You'll also want a 120V air solenoid and a 24V relay to control the compressed air with the laser.

Before I upgraded my 80W machine I could barely cut 1/2" MDF. Now, at 50PSI I have no problem at all. I've left all the stock air lines in the machine, figured I'd replace them when they started blowing out but that never happened.

Let me know if you need any more help upgrading.

[pontiacg5]

Figured I'd post some pictures...



The setup. Guess I only used one particulate filter, could have sworn I used two..



Little relay at the bottom



Laser cut 3/4" plywood. Remember this is only an 80W machine. This is a crazy long focal length lens though (4") and I did make a new nozzle that moved the end of the nozzle further towards the focal point to keep air pressure on the cut. You can see it in the far right there.



Nice edges! Burned a bit, but hardly any taper from excessive burning.



And what it was used for

[eeboy]

@pontiacg5 That was a very helpful post! Thank you for the pictures to supplement!

As for the actual compressor. I am thinking of purchasing something like this. It suits my needs for other uses... see any problems with using it for air assist as well?

[pontiacg5]

@pontiacg5 That was a very helpful post! Thank you for the pictures to supplement!

As for the actual compressor. I am thinking of purchasing something like this. It suits my needs for other uses... see any problems with using it for air assist as well?

That would be more than adequate, you'll be able to run much less of a duty cycle on that compressor than one with a small tank and low SCFM. That's always a good thing! Less noise, and less wear on the compressor.

Just be sure to drain the water out of the bottom of the tank every day and you should be fine.

[eeboy]

@pontiacg5 Ok, I've got a compressor on the way.

I am looking at using the following [ame="http://www.amazon.com/Ingersoll-F35121-400-VS-4-Inch-Filter-Black/dp/B0057D8LII/ref=sr_1_5"]filter(s)[/ame]. They have a 5 micron and 40 micron cartridge for it.

I can't seem to find a regulator suitable for my needs (fine adjustment down to 1 psi). Can you recommend a model?

Also, I noticed you placed the solenoid prior to the regulator. Any reason this could not or should not go after the regulator?

[Rodney Gold]

If you don't pressurise the lens and/or mirrors with your air assist (we actually found the nozzle pressurisation was making our lenses even more dirty than no air running thru it) then you don't need fancy filters etc - we just bent a tube and aimed it at the cutting point , much better than the coaxial air feed out the nozzle which tends to splatter stuff around.

[pontiacg5]

If you don't pressurise the lens and/or mirrors with your air assist (we actually found the nozzle pressurisation was making our lenses even more dirty than no air running thru it) then you don't need fancy filters etc - we just bent a tube and aimed it at the cutting point , much better than the coaxial air feed out the nozzle which tends to splatter stuff around.

I don't follow, you are saying that you don't pressurize the lens/nozzle and just run pressurized air right next to the nozzle outlet? It seems like the air wouldn't actually be on the cut if the laser was traveling in certain directions, do you ever see that causing a problem?

Were you running any filters with your pressurized coaxial air assist? So long as the air is always ran with the laser and a proper micron filter is in place (and properly purged) I don't see how you could ever dirty a lens that way. Mine sure don't...

Getting a regulator that goes down to a very low PSI is important though, that way you can regulate it way down to almost stock pressures while cutting thin light stuff like paper and foam. Trying to cut those things at 50 PSI would not turn out so well. Most normal regulators flake out around 10PSI, and even that would be enough to make cutting light things exceptionally difficult.




I got mine from MSC. MSCDirect.com. Run a search for air regulators and eventually you'll get to a list that will let you filter all they offer by "minimum PSI".

Try following this link, not sure it will work properly though.
Regulators - Filters, Regulators & Lubricators (Frl) | MSCDirect.com

I'll check tomorrow and see if I still have a part number for the one I used for ya.

Edit: I don't think it matters where exactly the solenoid goes, but I picked after the regulator. It seems the thing might last longer if it only has to switch high pressure on and off on occasion, if I put it on the other side it would constantly be switching 130+ PSI on and off. After the regulator the most it ever sees is 50PSI.

[keebler303]

Mcmaster carr has a full complement of regulator pressure ranges.

on the valve, just make sure the valve will work with low pressures. I don't see it mattering too much which side of the regulator it is on, just make sure it is after the filters so it stays clean too. Some valve types may not function properly on 1 psi.

Matt

[Rodney Gold]

Pressurising the cone gave rise to some sort of back swirl , making our lens get dirty with smoke etc. Melt splatter was bad with coaxial.
All my GCC's have an aimable tube air assist and that's what we did with my chinese machines. The air is obliquely aimed at the cut , works a charm
Considering you don't have optics or mirrors in the path of air assist this way ,you can use non filtered and non moisture trapped shop air.

[wolfau]

Interesting thread.

I removed my air assist and attached it on the outside like Rodneys using the compressor supplied by Gwieke.

I used an oxy brass tip which I cut and converted.

I could not believe it. Before the modification I could cut 4.5mm acrylic at full power. After the modification I could not cut 4.5mm acrylic at full power.

I own the LC 1290 powered by an 80 Watt Reci.

In my case the oxy tip though its about 8mm wide only had a hole in the middle of about 3 or so mm so I am presuming the lack of air going through it is the reason why it could not be cut.

This was confirmation to me that air is important for a laser cutter.

I put everything back and tomm will rig up an airline that I will connect into my 12 cfm compressor with a filter and regulator at the compressors end and another filter on the lasers end.

With this experiment I I have the feeling that the air would assist more if going through the lense rather attached from the outside.

Just my thoughts.

Should be all good.

Joe

[pontiacg5]

Your problem was using that cheap chinese diaphram air pump. It is completely and totally useless, the volume of air it puts out is nowhere near enough for laser cutting.

Remember, a laser cuts by vaporizing everything in it's path. That stuff needs to get out of the way of the cut, and the best way is air pressure. Do you want your air blowing against the direction of the laser, or with it?

I think you've already discovered which works best! Take a look at the real CO2 cutting lasers too, the big ol' metal cutting ones. They feed the cut gas through the lens, and in most cases the cutting head is designed to give those cut gasses a swirling "vortex" effect.