Recomendation on replacement Optics for the K40

[Boostinben]

Hello,

I am looking for a recomendation on which mirror and lense to consider in replacing my original optics in my k40. I noticed today that there is a small crack in the mirror on X axis gantry, the rear mirror looks ok but i also want to replace the lense. I am looking to optimise the machine for cutting if i had to choose. Or maybe I could buy one lense for cutting and another for engraving ?

I see a lot of options for both lenses and mirrors on the site.. not sure which one to get?

[Tech_Marco]

The reflection mirror that comes with original K40/D40 usually is 20mm gold plated. You can still use the same type or "Si" but you won't get much difference for small laser machine. The focus lens, however, will get you better cutting power if replaced it by higher quality ZnSe lens. It used to be 18mm in diameter but nowadays there are many different models of "K40" that may comes with 15mm or 14mm focus lens. It is either lower quality ZnSe or GaAs.

For K40, the optimal focus lens is 50.8mm. If you increase the focus point, true that you can get more straight line on cutting edge but you lost a lot of cutting power by increasing the focus point. For example, if you can cut 4mm pine wood with 8mm/s with 50.8mm lens. Once you upgraded to 63.5mm, you may need to drop the cutting speed to 5mm/s. If you upgraded to 68.5mm, you may need to drop speed to 3mm/s and so on. So, you gain something but you will lose something.

Hope this help for you to make the purchase decision


Regards,
Marco

[Boostinben]

Thanks Marco,

Which of the two Lenses do you recomend here GaAs vs ZnSe would i see any notible difference between the two? I think i will stay with the 50.8mm focal and i measured my lense to be 18mm

Also since i got the full DSP upgrade kit from you with the air assist head, would you recomend that i go ahea an use a 20mm instead of 18? is that a better fit for the air assist head you sell?

http://www.lightobject.com/High-quality ... -P802.aspx

http://www.lightobject.com/High-quality ... -P670.aspx

[Tech_Marco]

Good decision. I would do the same, too.

GaAs seems more sturdy compare to ZnSe. But GaAs is very poison so when it cracked, make sure you ware a glove to carry it. Performance wise I heard not much difference but majority companies in China are using lower grade ZnSe. Can't blame on them using lower grade because competition is extremely hot. I hate that some guys (not from our community) on web keep saying cheap Chinese product ba..ba.ba... Well, it depends how much you paid. Even Dell, iPhone, IBM,HP.... all made in China... agreed? By the way, I just import a batch new GaAs lens from China. It is higher grade I could get there and I paid more than the ZnSe.

Anyway, back to the subject. If you can, get the 20mm as it should be perfect fit into the laser head that come with the kit.


Marco

[Boostinben]

Cool, I will put in my order ... although I dont see GaAS 20mm 50.8 only an 18mm one on the site, was the 20mm 50.8 one of the types you recently imported?

[Tech_Marco]

Sorry, our kit fit 18mm. They (manufacturer) changed it and I forgot about it
So, go for 18mm

Marco