ULS air assist maxing at 10-12 psi, normal?

[John Tolman]

I recently setup a new VLS 3.60 with the air assist option. I purchased a GAST DOA-P707 (http://www.drillspot.com/products/35...or_Vacuum_Pump) from the ULS distributor I purchased the system from that also came with an oil catch and desiccant dryer.

The manual specified that the air source should provide 50-60 psi at 2.5 CFM. Surprisingly I was only getting 10-12 psi with the regulator opened all the way. I spoke with their technician who told me that is not good and proper, but then when they got back to me after speaking with the other tech, they told me that it is normal and that's how their systems run. I am re-reading that portion of the manual on manual air assist, it specifically says 50-60 psi at 2.5 cfm, and yet that spec list I linked to above says that at 50 psi it is only rated for 0.25 cfm. In fact, it doesn't look like it's possible to get 2.5 cfm at any pressure.

So, will I find 10 psi adequate for most jobs (currently I'm using it on corrugated cardboard, thin wood and G10—the only material that I'm really concerned about having enough air from an equipment safety perspective). Can someone confirm for me that this is just an underspec'd compressor? If that's the case I'll have to see if they will take it on return, and purchase an adequate unit from somewhere else. If that ends up being the case I'm sure I can find some posts on recommended units for this system. I'm not too thrilled about the idea of having an underpowered system that while maybe adequate most of the time, may jeopardize my optics or lead to poor cut quality. I noticed I have a slight amount of char on corrugated cardboard that rubs off, as opposed to samples I got from the vendor which were absolutely clean. This could just be coincidence or non-optimal cutting settings.

One last thing, the desiccant filter takes a small amount of desiccant (a cup or two) but it would be nice to have a second set so I have no downtime when I need to reactivate it in the oven. Grainger sells a replacement set for this Wilkerson filter but it's $60. Seems steep for a little desiccant but maybe I have a poor concept of the cost of silica gel. If someone has another source of equivalent silica gel that'd be great.

BTW, this is my first post but I've been reading these forums over the years in envy. I'm pretty excited to finally have a laser cutter to play around with myself!

[Scott Shepherd]

We have a shop compressor that can give us much more than we need for the ULS spec's, but I can tell you that I keep the pressure around 10-15psi on our PLS 4.60 on almost all work we do that requires air. I've not found any use for cutting anything yet that requires or does better with 40-60 psi of air running through it. Maybe it's out there and I haven't run it yet, but I've run a ton of various materials and 10-15 seems to work just fine.

[Dan Hintz]

I keep mine set to around 10-15, like Steve, and mine comes from a chop compressor, as well. 10-12 is usable, but it's not what is advertised and should be remedied.

For desiccant, you can buy quart containers for around $10-15.

[John Tolman]

Thanks for the replies. I'm not sure what to do at this point, I'll have to think about it. I spoke with ULS tech support and they are telling me that although at this underpowered state the machine is safe, I won't get optimal improvement on cut quality with some materials. That somewhat contradicts what I've read around here as far as what pressures ULS users typically use.

I contemplated just getting the ULS compressed air unit until they told me the price—no thanks. Hence I wonder if I am better off just sticking with this unit that may be perfectly fine for everything I'll be cutting and it wasn't *that* expensive.

[Scott Shepherd]

This probably won't come across quite like I mean it, but with all due respect, most people in tech support in all laser manufacturers have never run lasers for a living. Many of us probably have more hours in front of a laser than most tech support departments as a whole.

40-60PSI into a cut isn't going to do much other than make the cut cool faster. If you're cutting thicker material, you don't want to cool the cut before it's finished cutting. You'd actually reduce the depth you could cut with a laser if you cranked the air way up. You'd be cooling the cut and it wouldn't work. You need enough pressure to blow the debris out of the kerf while cutting, not to cool the material rapidly to stop the flow of the cut.

That's just my opinion.

At one point we were cutting a lot of 1/2" thick acrylic. We tried just about every pressure available and it ended up less than 20 psi on all test and production we did.

You don't use it with raster engraving too often, so high pressure there would only blow debris back into the cut, which would be bad. I honestly can't think of when I'd want really really high pressure. Again, the application may be out there, but I've never seen it. I think you're perfectly fine.

[Zvi Grinberg]

I also recommend to keep the pressure at the lower range.
I saw customers who used too high pressure and their air assist piping suffered severly.

However one additional point should be considered. I
In general higher pressure compressors (off the shelf at relatively low cost) have larger tanks for buffering compressed air.
Using compressors for air assist is usually for long time periods. There are jobs that take a full hour or more.
You might want to give your compressor some rest during the job, and avoid overheat. Stronger units with larger tanks would be more comfortable in such conditions.
There are of course several types of compressors, some can work continously. But they also vary in price.

[John Tolman]

Hey Scott, I get what you are saying about the limited experience of tech support, and from my limited experience would agree with the exception of maybe one person at the distributor. That's reassuring that you never go over 15 on your system and have no issues. I'm content with keeping this unit and if I move it into a larger shop with a compressor with a large tank I'll consider switching for convenience.

Zvi, this pump does get pretty hot if I'm cutting for more than 15 or 20 minutes but I usually don't run it constantly longer than that, mostly so I don't load up the desiccant faster than necessary. I can't find a rated duty cycle for the pump anywhere, but maybe I will look some more.

[Dee Gallo]

John,

I always use a mere 10 psi - which is what Epilog recommends in the manual. It has proven to be enough, since it only has to blow away smoke, small flames and tiny particulates. I suspect that having too much pressure will cause a few possible problems, like maybe moving your substrate in addition to slowly eroding the small tube directing the air. If it's anything like an airbrush's white metal, air flowing over it can wear the metal away. 10 psi will not bother it.

I've had tiny pieces of paper, cardboard and even veneer fly around from the air flow, which can get in the way of things. More pressure would increase that likelihood.

I would do some tests to find out where the optimum settings are for avoiding as much char as possible, such as ppi, rather than rely on air assist to do that. And learn to accept that sometimes you just can't eliminate all char.

cheers, dee

[Robert Silvers]

My compressor's regulator seems unreliable at lower pressures (much below 40 psi). My plan is to set the compressor to 50 psi and then adjust the volume with the needle valve near the lens.

[Dan Hintz]

My compressor's regulator seems unreliable at lower pressures (much below 40 psi). My plan is to set the compressor to 50 psi and then adjust the volume with the needle valve near the lens.

Make sure it's designed for that pressure. I think on many ULS machines the tube starts popping off around 60psi. Sounds like you need a better external regulator rather than beating up the on-board one.

[Scott Shepherd]

Make sure it's designed for that pressure. I think on many ULS machines the tube starts popping off around 60psi. Sounds like you need a better external regulator rather than beating up the on-board one.

I don't know what people are cutting with that much air. I run 3-15 psi on both our lasers and don't see any benefits from higher pressure. In fact, Synrad recommended like 1-2 psi for cutting thick acrylic. Honestly, there is little need for that much air. I'm not saying there isn't a need for it for some application, but with all the things I've run over the years, I've never had super high air pressure on anything.

[john banks]

We do a lot of oak cutting and use 30 PSI and elongated cones to bring the coaxial air assist close to the wood so we don't have to mask or sand, or in fact just trash the piece to a charred mess if we use say 15 PSI. 3HP compressor just about keeps up on about 50% duty cycle.

[Scott Shepherd]

We do a lot of oak cutting and use 30 PSI and elongated cones to bring the coaxial air assist close to the wood so we don't have to mask or sand, or in fact just trash the piece to a charred mess if we use say 15 PSI. 3HP compressor just about keeps up on about 50% duty cycle.

How thick of oak are you cutting? I've cut stacks and stacks and stacks of various plywoods, etc, and I'm not getting charred edges on anything. Maybe you are the exception I mentioned. Charring typically comes from too high a ppi.

[Robert Silvers]

PSI does not tell you how much air. If you run it through a tiny needle valve it is not much air.

[Dave Sheldrake]

If someone has another source of equivalent silica gel that'd be great.

Bob Martin cat litter (kitty litter) is good silica, very pure and turns green when wet

Pressure / volume is less important than efficiency for air assists, as John said (Hi John) close to the job and a small exit hole is far more important than huge compressors.

. Charring typically comes from too high a ppi.

Chinese lasers my friend, no adjustment available for ppi

cheers

Dave