Air assist, Cone v Tube?

[Dave Johnson29]

Hi All,

I am thinking of adding air assist to my laser. I have shop air on supply and I would like to get opinions on the different methods of air delivery.

From an Engineering standpoint I favor the cone as it seems the better approach being a more direct method of air delivery.

With Epilog's tube, does it just blow a large volume of air in the general direction of the beam spot to blast away stuff?

Obviously the cone will be more machine time, but if it is quite a bit better than the tube, then I do not mind. However if there is not much difference between the cone and tube then the tube is going to win out.

Thoughts, opinions and suggestions gratefully accepted for cogitation and application.

[Jack Harper]

Not only does the cone increase the pressure and focus on the material, it also reduces the opening for debris to bounce back on the lens. If you are going to add air, why not also add air dams to your mirrors while you are at it? Just make sure you have an air dryer and good air filters on your shop air!

[Dave Johnson29]

If you are going to add air, why not also add air dams to your mirrors while you are at it? Just make sure you have an air dryer and good air filters on your shop air!

Thanks jack,

I have a pretty aggressive extraction system and my open mirrors have not clouded or dusted up in the past 2 months or so since the last clean. I have the luxury of very low humidity and clean country air.

I do have a refrigerated dryer for the shop air so that would not be a problem so I think I will just opt for the air assist.

Thanks for the comments I am still leaning very much towards the cone.

[Michael Simpson Virgina]

I think an after market conical system is a major undertaking. And if you still have any kind of warranty forget about it.

[Dave Johnson29]

I think an after market conical system is a major undertaking.

Mike, you are going to kick yourself here.

My Signature. "Shop full of metalworking CNC machines," when I said, "make" I meant "make!"

And if you still have any kind of warranty forget about it.

My Signature, "ULS-1700 open frame laser," (Circe 1992)
Now, ULS may give good warranties but I suspect mine may be a toot outside even their envelope.

OK, back to the serious side of things.
Also on the warranty issue, while the Magnusson-Moss act is still alive and living, a correctly fitted cone kit would not affect any valid warranty.

[James Stokes]

I have 2 laser one has the cone assist and the other one is the Epilog tube. The cone does a much better job in my opinion. The only thing is your alignment has to be good or the beam is going to hit the cone. I als do not have to clean the lens every day using the cone, it definatly keeps the lens cleaner.

[Michael Simpson Virgina]

What I was getting at is that if you are under warranty making a conical system is going to void it. I do know on the ULS conical system it has to run all the time (Even when rastering) or the lens will over heat.

One of the things I liked about the ULS was the conical air assist but I did not like the idea that there was no solenoid so it spit air 24/7 unless you manualy turned the air on and off. You can get a nice 1/4 NPT air solenoid for less than $100 but you will still have to manually turn it on or off unless you could find some sort of control point on the laser.

Also I thought I would add this. I did not notice much of a difference between the cuts I got from the ULS conical system and that on the Epilog (Non conical). If anything the cuts on the ULS were not as good. That said we were cutting Acrylic I am not sure the same could be said for the nastier items like PCBoards or MDF. I would think that if you could dial in the conical you could fine tune it to a much higher degree.

[Scott Shepherd]

I do know on the ULS conical system it has to run all the time (Even when rastering) or the lens will over heat.

It doesn't overheat the lens because of the cone, it creates a vacuum and it sucks debris onto the hot lens like a magnet and if you're not paying attention and catch it quickly, it will crack your lens because of the build up on the lens.

One of the things I liked about the ULS was the conical air assist but I did not like the idea that there was no solenoid so it spit air 24/7 unless you manualy turned the air on and off. You can get a nice 1/4 NPT air solenoid for less than $100 but you will still have to manually turn it on or off unless you could find some sort of control point on the laser.

There is an option that controls this. My air assist is controlled on and off at the control panel, by color.

If anything the cuts on the ULS were not as good.

That wasn't a function of the machine, it was a function of the settings used to cut the acrylic.

[Dave Johnson29]

What I was getting at is that if you are under warranty making a conical system is going to void it.

Mike,

That's why I mentioned the Magnusson-Moss act. It is highly unlikely that a correctly fitted and operated after market conical could void any warranty.

The M-M Act puts the onus of proof on the manufacturer to establish that the after market item caused a failure. They cannot arbitarily cancel the warranty just becaue something non standard is fitted to anything.

[Michael Simpson Virgina]

On the heating issue that's what I was told me by the ULS dealer. But Because he was wrong on other things I suspect he could have been in error on this point as well.

Also there are two types of air assist systems on the ULS machines. Manual and computer controlled. The manual is just like I described. The computer controlled is a better system (The one you have)

The problem is that the computer controlled system is over $2000 extra and is not offered on the VLS models. Only the PLS and above models.

With the computer controlled system you can tweak your air settings and they can be assigned for each color. If ULS would have offered this option on the VLS models I may have considered them.

One more thing. ULS does offer the option to install a tube just like the Epilog has. This was done for the users who do a lot of real wired shapes and the conical attachement can get in the way. This option also lets you turn off the air assist (manualy) when you raster as it does not create the suction you described.

[Dave Johnson29]

It doesn't overheat the lens because of the cone, it creates a vacuum and it sucks debris onto the hot lens like a magnet

Scott,

I really cannot see how that can happen. If there is no air coming through then how can anything be sucked up into the cone and on to the lens?

I can see how the lens could overheat with a cone and no air flowing through it. That's probably why ULS run air all the time to cool the lens because it is mostly enclosed. With the Epilog and other non cone types, the lens is open to the cabinet temperature and circulation.

[Rodne Gold]

Air coincident with the beam is not always the most desireable. The most common reason for using a cone is to pressurise the final optics and thus keep em clean. We use both systems on our lasers , 3 of em using cones , 3 using nozzles. Both work quite well...HOWEVER there are upsides and downsides.
The directable nozzle is capable of directing dross away from the engraving area and capable of ejecting melt etc obliquley thru the cut , sometimes to good effect . But it is very easy to knock the nozzle out of alignment making air assist less than optimal. Sometimes one has to move the cone or nozzle out the way when engraving stuff with lips etc , its easier to do with a nozzle than a cone..remove the cone and you dont have air assist,
It is also IMHO a lot easier to add an aftermarket nozzle system then seal and pressurise a lens box and it is more configureable as to nozzle exit size and thus better control of air pressure at the cut.

One of the reasons we dont like a pressurised lens/mirror cavity is that we have lost lenses due to water trap failure and moisture/oil on the lens itself so we are totally anal about clean dry air to the cone type systems , and far less concerned about this to the nozzle system.

[Robert Ray]

On the 4000 watt machines we use at the day job, I measured the beam profile with a Primus measurement tool and found that with the purge air off, the beam gets wide, and the hot part spreads out randomly from the center, reducing beam density by up to 50%.

As I turn the assist air up, the center of the beam gets hotter in the center of the profile, and the diameter of the spot gets smaller. This is measured without a focusing lens, when the beam is 10mm wide.

At home I have nozzles on my Laser Pro systems, and keep the purge air turned up for the finest cuts. I have turned down the air to cut paper without blowing parts away, then forgot to turn it back up to discover incomplete cuts and extra charring.

-Robert

[Rodne Gold]

I cant quite see how air assist would affect beam width or quality unless its cooling an optic or mirror or the pressure of the air is somehow moving an optic or seating it better?

In terms of incomplete cuts , often air assist does a few things , it can act as an oxygen source to promote better vaporisation (kinda like a bellows)
and it can blow away smoke , dust and byproducts of vaporisation thus leaving the beam a "clean" area to work on with no interference.

[Scott Shepherd]

Scott,

I really cannot see how that can happen. If there is no air coming through then how can anything be sucked up into the cone and on to the lens?

I can see how the lens could overheat with a cone and no air flowing through it. That's probably why ULS run air all the time to cool the lens because it is mostly enclosed. With the Epilog and other non cone types, the lens is open to the cabinet temperature and circulation.

Dave, I'm only going by what's in the manual and what the factory has told me. Perhaps you are thinking of it in a vector situation. Imagine if it's rastering, the big hole in the side of the mirror assembly moving back and forth at high speeds, then the small hole in the nose cone, I'd imagine the large hole flying one direction creates negative air pressure and sucks it up the small hole. Moving the other way probably pushes air out.

I know it happens because I've done it. I've left the cone on without air and rastered and it just about ruined my lens. The lens is hot, the debris gets sucked right up into it and it fuses onto the lens. I had a real time trying to get the melted plastic off the lens. It was also completely black, so I imagine it was only minutes away from cracking.