Maximum Focal Length lens for XLE Air Assit nozzle?

[punitor1]

Hello,

I am going to buy a longer focal length lens for my XLE stage and would like to confirm what the maximum focal length lens the air assist nozzle can accommodate before the beam hits the sides of the nozzle?

Thanks,
Travis

[Chuleo]

I modeled the XLE laser head... 50.8mm is the optimum

63.5mm is possible but very hard to adjust, since the beam has to be perfectly in the middle of the lens.

Alternatively you can make the nozzle outlet wider (3mm)

[Tech_Marco]

Chuleo, this is the best explination graphic that I ever want to make but without the talent like you, I can't handle it. Thank you for your support!

I got similiar answer from my laser machine provider that most laser head is optimaized to 50.8mm focus lens as it is the most popular size to use for both engraving and cutting (4mm or thinner). The max you may go for is 63.5mm but as per Chuelo said, it is challenging to fine tuned the beam alignment if using 63.5mm or longer focus lens. The laser head sooner will get pretty hot as part of the beam is hitting to the laser tip. To fix it, either change the laser tip (not easy as laser head structure vary) or drill a bigger hole (faster solution)


Marco

[Tech_Marco]

Just made a measurement of the tip and found that the laser tip hole diameter is running about 2.2mm

For a Reci 80W tube, the beam diameter is 7~8mm. So, you draw two lines in "X" shape with 8mm separation and the cross point is where the focus point located. As long as the line can pass the hole "2mm in diameter", it should be fine. To do this you must know the distance from the lens surface (facing down) to the laser head tip. The focus point (X point) must be below of the laser tip of course


Marco

[punitor1]

Chuleo,

Thanks for the explanation and great model - looks really good.


Marco,

Thanks for looking into it. I am going to order a 63.5mm lens and drill out the nozzle if/as needed.
Do you have an extra XLE nozzle/focal tube assembly I can buy to make lens changes easier?

Thank you both,
Travis

[Chuleo]

I made another picture which is a little nicer.



I didnt show the measurement from the nozzle tip to the focus point because some manufacturers
provide the Effective Focal Length while others manufacturers provide the Back Focal Length.

[swamidog]

this is quite excellent. my only suggestion is you also illustrate theoretical spot sizes and beam waists from each of the individual focal lengths.

there's an excellent calculator here: http://buildlog.net/cnc_laser/laser_calcs.htm

I made another picture which is a little nicer.



I didnt show the measurement from the nozzle tip to the focus point because some manufacturers
provide the Effective Focal Length while others manufacturers provide the Back Focal Length.

[Chuleo]

The spot size depends heavily on your input beam diameter, the precision of your focusing lens ans the type of your focus lens, so it is not really possible to illustrate it. (except for the in the drawing given beam diameter = 6mm)
Since there is already i well known tool out there I dont think it is even necessary to illustrate it.

But because I'm bored anyway I added a Table... xD