Quality CO2 laser optics

[grossmanator]

Hi,

I recently purchased a chinese laser cutter and I'm looking to make some small improvements to get a little more power and if possible, a cleaner cut. In particular I'm looking to buy a high quality laser lens and maybe some higher quality mirrors. I'm assuming the optics that lightobject sells a step up from the optics that I received with my laser cutter... Also, I was hoping to find a long focal length lens (130mm-150mm) for some thick cutting, but it seems as though lightobject does not have anything longer than 100mm. Is there somewhere where I can buy a 20mm lens with a focal length around 130mm-150mm?

Also, I've looked at other companies like ophir and II-VI that sell very high quality optics for lasers (250$ for a lens) and I was wondering if anyone knew whether these lenses were even a step above the lenses that lightobject sells and whether they are worth the extra cost. I assume they must be somewhat better because they are significantly more expensive.

Appreciate any comments,

thanks,

- Will

[Tech_Marco]

What kind of machine you have? Longer focus lens offer less cutting incline but it will take more power to drive a longer focus lens as well. If you're trying to drive anything over 100mm focus lens, I suggest you to get Reci 130W or higher power tube. Remember, you gained something but you will lose something as well.

If I tell you some of lens/mirror carrying by II-VI are the same grade we carry, will you believe it? That's what my supplier told me about it. If you feel that $250 will do better, give it a try. I didn't have an experience of using II-VI lens so I'm wanting to know from you folks as well

Marco

[grossmanator]

Hi Marco,

Thanks for the answer. I don't really want to spend 250 for the lens, but I was curious to know if anyone has tried them and how good they really are. I imagine (no evidence here) they're probably a bit better than your lenses, but is it really worth it for the cost? For example, If I'm only getting a 1% increase in power and a 2% decrease in beam size, then it's definitely not worth it...

How about this question: Are the high quality lenses that you sell significantly better than the cheap 20$ lenses that came with my machine? Again, I assume the answer is yes, but how much better is what I'm interested in.

Also, I just purchased a high quality 100mm lens from you guys, so I'll let you know how it goes in a few days.

cheers,

- Will

[Raman Narayan]

Hi Marco,

On a different note, do you think lightobject will carry a longer cone with air assist
for the 18-20mm laser headhttp://www.lightobject.com/1820mm-Laser ... -P701.aspx,
for say an 100mm focal length lens?

Thanks/Regards
Raman

[Tech_Marco]

Will:

FYI, most machine imported from China come with "improved grade" (note that I named it that way) ZnSe focus lens. It is a lens that with material made in China and polished in China. There were two of those grade so far I know. The worst one is the one came with ShenHui K40 machine. The clarity of the lens was bad, fuzzy, and blurry. Then there is a better one which I'm calling "Improved".

The High quality lens is made of materials imported to China from either US or other country like Australia. Then, the lens is cut and polished in China. The clarity of this HQ lens is very good. I did post a picture to compare these 3 kinds lens on the forum. The polishing skill in China I believe that it is good enough to make fine lens, even though it may not reach to the level as US, UK, Germany, or Israel. But compare to the two factors; material vs. polishing, the effect of lower quality material lens play significant.

If you replaced the stock lens with a HQ lens, I believe that the output can be boosted by 20% overall.
For example, if you can cut 10mm epoxy , then with the upgrade to HQ lens, you may cut 12mm with the same speed.

I agreed with you, I won't spend $250 to get another 3~5% more power gained. Not worth. Remember that your point is to get better output performance. So, $52 upgrade to HQ lens and can get you about 20% (beware though I can't guarantee this number), what else you can ask for? Agreed?


Marco

[Tech_Marco]

Roman:

Longer focus lens can be used in laser head with shorter focus lens but not the other way around. However, there is an issue: air pressure lost quite a bit if not used proper longer hallow laser head. Air assisted is very important especially for cutting. The K40 laser head comes with a bigger hole for the beam so there is not an issue to use 50.8mm or 100mm focus lens. But, I don't see any reason to use anything over 68mm for the K40. Two reasons: 1)longer focus lens need higher power laser to driver. The K40 comes with a 35W tube which is OK to do simple cutting and engraving with 50.8mm or 63.5mm lens. A 68mm is quite hitting the ceiling; 2)K40 has a fixed table so you will not be able to use 100mm focus lens to focus an object without having the table removed. Unless you use my special made power Z table, otherwise I don't see a better way:
http://www.lightobject.com/Power-table- ... -P722.aspx

Hope my answer may help

Regards,
Marco

[Raman Narayan]

Hi Marco,

Thanks for explaining the issues in using the 100mm lens in the
place of the 50.8mm one. I have one of those funky "4 mirror"
artsign machines that could handle tubes upto 60W(But only
50w tubes could be fully enclosed by the machine, there is
provision to make the tube stick out while using a 60W/1200mm
tube). My machine is similar to the one in the following link:
http://artsign.en.alibaba.com/product/6 ... chine.html
Wish I knew about lightobject when I ordered my machine

Now that I have a replacement lightobject tube(but getting
only 40W instead of the max 50W), I already ordered the high quality
Si mirrors, to improve the available power. The machine already
has powered-Z table. I also posted a request for additional
air assist accessory, since I have a powerful 1HP compressor driving
the air input. The idea is to have a low volume but high pressure
air assist at the precise cutting point on work surface, that would
ensure a high blowing with less cooling, since there will be already
less available power due to a wider beam from the 100mm lens.

Thanks/Regards
Raman

[Tech_Marco]

It's OK. We're learning everyday. I know Jinang, the city of ShangDong in China. This place product a lot of laser machine and CNC machine. Price for laser machine is low there but the quality is in "doubt". The issue is low skill tech used to build the machine. But most folks like you and me were attracted by the price they offered there and couldn't see the 'problem' behind it.

FYI, Jinang was the first city I started with to start doing laser business. Even though I was warned by two friends about the quality issue before going there , but I still decided to go there because the price was so tempted, lower than other placed I found. Of course, I learned a lot after that by fixing broken machine and fine tuned it. So, I won't consider the journey all bad at all but I'll be taking it as 'learning lesson' to help me to grow! No pain no gain -> good game.

Marco

[Raman Narayan]

Hi Marco,

Good to know that Jinan Artsign is not all that bad for a starter machine.
Actually I did not go for it because of the cost alone, but due to a
local distributor(I regret after getting the machine delivered with a
used/bad tube with zero warranty ), to avoid hassle with ocean
shipment clearance and possible local support(too bad to find out, there
was no support after all ).
If I ever buy another one(many ), either to replace/upgrade or to upgrade capacity,
there is no question whom I will go for .
It will be the pre-built ones from lightobject or a high quality DIY(using lightobject kit).

I still strongly believe the glass tube lasers with quality machine parts/construction
are much more economical than the over priced big brand name machines.
Who would want to put 5-10X more money without a cashflow to guarantee
business will be profitable to pay for it.
There is some need for learning curve, but what machine does not
have that(I feel the more smarter the machines are, they are going to have a lot
more downtime needed to fix them - unstable autofocus, dust/smoke in high res encoder
mechanism for servos, damage due to faulty controls in air assist,exhaust, intermittently
faulty RF drive to laser,to name a few).

I also not sure if all the big brand name machine owners will get the same level of support
lightobject provides .

Thanks/Regards
Raman