Optics Size Compatibility

[evokanevo]

Please verify my understanding:

1) A beam expander not only widens the beam, but it also straightens the beam and eliminates measurable divergence.
2) The focus lens for the laser heads being sold here are held in place by the air nozzle - i.e. they sit between the z-axis tube and the nozzle.
3) There is a design flaw: The laser head being sold makes it pointless to use 30mm reflectors and severely limits the choice of beam expanders that can be used. The beam must travel through a small beam hole of 15.5mm on the laser head. Any mirror at least 21.92mm (equal to 15.5mm * sqrt(2) because of 45 degree angle) or larger can reflect the entire beam that gets through the laser head beam hole. Here is a different technical drawing, showing an even smaller beam hole.

To further clarify the beam expander choices due to 15.5mm limitation:
100W Reci: 6-7mm output = 12-14mm with 2x expander: OK, but larger expanders not OK
130W Reci: 8-9mm output = 12-13.5mm with 1.5x expander: OK, but larger expanders not OK
150W Reci: 9-10mm output = 13.5-15mm with 1.5x expander: Bad, requires perfect alignment and there's no point buying this tube with the available optics/mounts

[Tech_Marco]

Yes, I agreed with your point. After I received the laser head I found the issue right away. I then started a conversion with the manufacturer and asked him why was that. Well, his answer didn't suprise me at all "I didn't receive any complain from others. You're the 1st one who complain about it". Even though I tried very hard to explain the issue but I found that I was wasting time to discuss with him. Most manufacturers in China don't know what is a beam expander and you hardly see a machine using it except for the YAG machine, a metal engraving machine always have a 2.0x beam expander installed. For other CO2 machine, I saw "zero" from last 6~7 years traveling in China.

Well, all I can say is that the big laser head is good for 1.5x beam expander for Reci W6 (8~9mm) and good for W8 if you have good patience for fine tuning the mirror (9mm~9.5mm beam diameter). I was told by the Reci, the diameter of W8 was 9mm on most tube. So, giving it a little margin, say 9.5mm and use 1.5X beam expander will end up 14.25mm in diameter. The hole diameter of the laser head is 15.5mm so there is about 1.25mm margin for the beam to fit in. So one must be very patience to fine tune the 2nd stage reflection miror in order to perfect fit in to the laser head. The good thing is that once you have that done, the light beam will hit the center of 3rd mirror and you will get the best focus point and power.

Bigger mirror and bigger lens are not soley desigend for beam expander, it is also good of releasing stress (heat) caused by the laser beam. Bigger size = better heat dissipation.


Marco

[liaoh75]

Hey Guys, I discovered this problem and I wasn't using a beam expander with a RECI 150 Watt tube. I ended up using one of these below. It has a 38mm mirror and 25mm focus lens. You can only use either one of two lenses. One is a 2.5" focus and the other is 5" focus for cutting thick stock up to 25mm acrylic. Is there anyway to mate this with the stages? I'm sure it will slow you down because it isn't very light. The down side is, it isn't cheap. I remember paying in the neighborhood of $600+ for it and that doesn't include the mirror or lens. Here is the link to the site.

http://www.aliexpress.com/item/CO2-Lase ... 03296.html

Double Focus.jpg (18.79 KiB) Viewed 1817 times

I would really like to see a separate mirror and head arrangement like this:

Laser Head.jpg (97.38 KiB) Viewed 1817 times

It makes adjusting much faster and easier. It is often difficult to do final adjustments on the Chinese laser head because putting a target below the nozel will smoke your down reflecting mirror in the housing.

David