Nozzle Gap and Focal point??? 4

[LaserSpyder]

i was taught that the rule of thumb for Laser cutting Nozzle gap and focal point should be 1/2 to 2/3 into material for Aluminum and right on top of material for Steel, does everybody use this formula? i run An Amada F0 3015 Laser......we dont follow this Formula exactly and are always having to change the focal point to have decent cutts

 

[LASERNINJA]

Sorry but I think your going to have to ditch your rule. It is true that that is a good point to cut metal but with your machine its different.

When Amada came out with that machine they added and adaptive optic. This is a special mirror that flexes based on an input from the control / cutting condition. Stainless and Aluminum need a tighter beam so the mirror becomes more concave making the spot size smaller when it hits the focus lens and thus smaller on / in the material.

In the upper left of the cutting condition page there is a section that says "STD, Alumi, Clean, Thick" or something like that. This is the input for the A/O. If you don't know what to set it on refer to the "nozzle matrix" if you don't have one let me know.

Anyway, lets say you set up the 7.5" focus lens, focus test, THICK on the cutting conditions, and it comes out to 13mm. That may work great for CRS0.250, but when you change to CLEAN, the beam is smaller when it hits the focus lens so, I think, its actually going to raise the focus position a little, but its quarter inch stainless you want to cut, so you need to drive the focal point into the material.

So, are you starting to understand? Its confusing. If you did a focus test on all the A/O settings you could see the effect the mirror has on the base focal point. Then you could add or subtract the difference to half or 2/3 of your material thickness.

 

[LaserSpyder]

Damn LaserNinja you should go to work for Amada and come to my shop!
I dont think we have a Nozzle Matrix Ill ask but if you can tell me or show me id appreciate it, we do all our focus tests on .060 CRS and set it to Stnd we do this for both our 7.5" and 5.0" lenses and we mostly cut .190 and .125 Alum sometimes smaller and with Steel we mostly cut .188 and .120 sometimes .250 but we always have to change our settings ill post an example of how we were cutting our .190 Alum a couple of months ago when Amada came out and how we are cutting .190 now Big difference between the two...............Thanks again LASERNINJA!!

 

[LaserSpyder]

these are the conditions that Amada help us set ill post the conditions we use now in a bit

 

[LaserSpyder]

this is how we are cutting now and if we try to cut with the other conditions we start loosing cuts especially on the second half of sheet and we do not know what gives, a pinched line is going to be my next suggestion for Amada to search for what do you think LASERNINJA??

 

[LASERNINJA]

Couple of things going on with the second picture. Good pics by the way, that helps. I like the second set of cutting conditions because of the Duty less than 100%. 100% duty means that there is feed back between the laser and the control. This is less than desirable on aluminum and stainless because when a small amount of power is reflected back to the laser, the control see it as making extra power and backs off what is commanded.

Things I don't care for on the second set is "WACS" on. Not good. I imagine you water tank is empty but if there is just a little in there it can put water where you don't want it and really mess up the tracking sensor.

Next, you switched a/o settings from std to Alumi. Not a big deal. But you should pick one and stick with it. I think STD is actually a little hotter and may work better.

Last thing, Freq. The maximum frequency on a Fanuc laser is 2000. Doesn't matter if you go over, but it just looks strange.

 

[LASERNINJA]

A couple more ideas for ya.

I would clean both sides of the focus lens. Wipe down the threads of the lens, lens adapter, and adapter threads. Make sure you have the gaskets between the lens and adapter, and adapter and machine. Calibrate the sensor head, then cut some holes and squares.

I move in 1mm / 0.040" increments with the 7.5" lens. What I do is move down, down, down, until it can't cut anymore and then make note of that focal position. Next I go back to my original starting point then go up, up, up, until it doesn't cut. Make note of that position. The ideal focal setting for that material is right in the middle of those two end points.

Example: Starting at -0.060, next,-0.100,-0.140... and at -0.240" sparks and sputters.
Then -0.060, -0.020, 0.020,0.060... and sparks and sputters at +0.100"

​

I am not sure if I did the math right but I think the center between -0.240" and 0.100" is -0.07".

That position would the work great for 0.190, and 0.125 AL.

P.S. I tried that, working for Amada, Great Machines, pretty good company. Private practice is way better.

 

[LaserSpyder]

Thanks LaserNinja!! i turned off WACS, but I have one more ?? is it not weird that our focal inch is so different than the first pic why were those settings working so good then and not working at all anymore?? Thanks again!!

 

[LASERNINJA]

Its hard to say. When one A/O setting is Alumi and the other is STD, its like comparing apples and oranges. You would need to find a good focal point for each setting. I believe both will work, just one will make a prettier edge or one will be faster.

Something else to consider is the focus point changes on the focus lens. If its brand new, there is one focal point, if it has a dozen spots on it, it has another. The more spots on it, the more heat it absorbs, the more heat is absorbs the more it flexes when it gets hot. Any time you have an optic change shape the beam is affected, the trick is being able to roll with it.