Beam Expander Recommendation

powerfade
Posts: 45
Joined: Thu Jan 13, 2011 12:59 pm

Beam Expander Recommendation

Postby powerfade » Sat Oct 28, 2017 10:55 am

So I was told putting a beam expander on my table would be a benefit. I was hoping someone could give me some insight as to which size would be appropriate. My table is ~4’x5’ with the 100 watt RECI laser at the back end of the table. The spot size coming out of the laser I believe is 8mm for the 100watt RECI. The 2 mirrors that bounce the laser to the cutting head are 25mm and the mirror inside the laser cutting head attachment is 30mm. (It's the SPECIAL PRO HEAD LASER MOUNT) The focal lenth of the lens is 50.8mm and the beam hole where the laser enters the cutting head says it’s 20.25mm, but it’s closer to 23mm. Curious if anyone has a recommendation as to what size beam expander would work for my machine?? I have attached a picture of the machine as well if that helps.

Thanks everyone
Chris
Attachments
20171028_102125.jpg

Tech_Marco
Posts: 4369
Joined: Mon Jun 15, 2009 3:00 pm

Re: Beam Expander Recommendation

Postby Tech_Marco » Sat Oct 28, 2017 4:18 pm

Hey Chris:

A little busy here so didn't answer your PM message in time. Sorry about it smile
(We're making some products for a winery and it kept me busy like an ant. Plus, we just got a new ocean shipment, there are some new 'toy' for me to play like the Hybrid metal/non-metal machine)

You may go for 1.5x or 2.0x beam expander in your case because you purchased our 30mm mirror and the special laser head. The beam spot diameter of a Reci is about 8mm in a feet distance but it is getter wider to 10mm or even 12mm at the far end. To select the beam expander size, you need to consider the beam diameter after the beam expander. Let's say the beam is 8mm in diameter and after a 2.0x expander, it would be 16mm. A 30mm reflection mirror will provide 30mmx0.707 workable diameter which is about 21.0mm. If you used 2.5x expander instead of a 2.0x, you will get 8x2.5 = 20mm which is very closed the limited that the 30mm reflection mirror can support. Don't forget the mirror mount may take up to 2mm per end so instead of 30mm, you only 26mm. After times (x) 0.707, you only have 18.38mm (diameter). So, definitely a 2.0x is the max size you can go for.

Hope this help

Marco

powerfade
Posts: 45
Joined: Thu Jan 13, 2011 12:59 pm

Re: Beam Expander Recommendation

Postby powerfade » Sat Oct 28, 2017 10:15 pm

Hi Marco.. Thank you. New toys are fun. Sorry I didn't mean to make it seem like I was impatient. I figured I would throw it out to the forum as well as it might help someone else one day. My mirrors before the cutting head are 25mm (the SPECIAL LASER HEAD has the 30mm mirror), so I may have to get the 30mm mirrors if I want to go with the 2x beam expander I imagine. I think the 25mm mirrors would be okay for the 1.5x?? Do you think I would notice much difference from the 1.5 to the 2.0 in terms of power gain?

Thanks again,
Chris

Tech_Marco
Posts: 4369
Joined: Mon Jun 15, 2009 3:00 pm

Re: Beam Expander Recommendation

Postby Tech_Marco » Tue Oct 31, 2017 5:15 pm

I'll go for 2.0x if possible. You may get better collimation result. However, there is a 'drawback'. Now the beam angle will be sharper so you will have more 'slope' on the cutting edge. But engraving should be improved much better because of wider beam and more fine beam spot. If you want to offset the deeper slop effect, you may need to get a longer focus lens. But again, you lost something while gaining something: engrave quality will be less than without using longer focus lens but won't be bad, at least better than without using the beam expander (need you to proof it and post what you found please)

Marco


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