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View Full Version : Where to get a good deal on a focus lens and mirrors for my laser cutter



Adrian Page
11-18-2014, 9:09 PM
My laser is working fine but I scratched the focus lens cleaning it. It seems to work fine but I would like to have a spare in case I totally trash it next time I clean it. I see lenses for sale on ebay for 16 bucks shipping included. How do I choose a lens comparable to what I have now? I assume it's a domestic product from China. Same with the mirrors... I suspect I will be no less ham fisted when I clean those.

Adrian

abby ZHANG
11-18-2014, 10:59 PM
sent you an message Adrian

Dave Sheldrake
11-19-2014, 7:41 AM
Hi Adi,

Chinese made lens's and mirrors are very good in general, there are a few lower optical qualities but to be honest very few you will ever notice. They can vary a tiny bit on focal length or index of reflectivity but only really anything that would notice on a lab bench. The next stage up is Chinese made but made by II-VI Infrared over in China (A US company), better quality and a little more consistent so a good choice, at the top of the tree you have US made stuff from either II-VI or RMI, VERY good quality but you pay a premium for them (think $250 for a lens)

Mirror wise go for Molybdenum (MO) , very scratch resistant and survive well being dropped, they will also handle the highest power levels so no need to invest in better mirrors if you increase tube power at a later date.Very slightly lower reflective index but again nothing that will notice.

Really it's a case of what fits, after all is there really any point putting a Ferrari Engine in a Ford Focus? (an RMI lens in a cheap Chinese laser) when it's unlikely you will see much in the way of benefits.

If you get up to the medium cabinet lasers (1200 series) or the flatbeds than a good lens can make a difference but under that, well, you are just chucking money away to be honest.

cheers

Dave

Gene Howard
11-19-2014, 7:54 AM
If you know the exact size and focal length of your lens try Design Research Optics in RI. You will certainly pay more than the average eBay Chinese lens but you will receive very good support and warranty service if needed. We had one mirror of a batch of 4 burn out prematurely, more likely due to poor cleaning than a defect, and they replaced the entire batch "just in case" it was their error. The owner Bruce is very quick to respond to inquiries and get product out the door.

Adrian Page
11-19-2014, 8:08 AM
Thank you for the info.

I'm not sure what is involved with the focal length. Mine is 63.5mm or 2.5". I have to set my lens tube 6mm from my work surface. Do different focal lengths allow more clearance? I'm asking because I crashed the tube into a block of wood I was using to weight down some warped plywood and snapped off the tube. If I had a little more room between the work and the lens it wouldn't break my heart.

Adrian

Bill George
11-19-2014, 8:46 AM
I get all my laser machine needs from LightObject dot com. He is a fair and honest vender and has went out of his way to accommodate customers, me included. Yes its Chinese sourced but good quality.

Dave Sheldrake
11-19-2014, 9:34 AM
Thank you for the info.

I'm not sure what is involved with the focal length. Mine is 63.5mm or 2.5". I have to set my lens tube 6mm from my work surface. Do different focal lengths allow more clearance? I'm asking because I crashed the tube into a block of wood I was using to weight down some warped plywood and snapped off the tube. If I had a little more room between the work and the lens it wouldn't break my heart.

Adrian

You can increase focal length to get more clearance but it comes at a price, longer focal length = bigger spot = lower power density. The longer the focal length of the lens the deeper the cut you can make and still have straight sides to it though. It's all a trade off somewhere along the line.

cheers

Dave

Adrian Page
11-20-2014, 10:49 AM
Thanks Dave. I suppose the air jet works best close to the work as well. I'll just have to be more careful.

Adrian