how to focus a big spot ?

equal · Oct 8, 2015

hi,

i am from germany, and i am a new user here

i want to build a additional lasermodule for my cnc machine.

the following items are using:

- Nichia NDB7875
- 2.4A X-Drive V6 Laser Driver
- 405-G-2 Glass Lens
- Adjustable brass laser diode housing (ebay 161804830486)
- a 20W peltier cooler

now, it works together, but my problem is, that i cant get a small laser line and a fine point at a distance. i can 'engrave' wood in ~40mm

in a distance longer than 1m the spot is very big (in 1m ~100mm spot size)

what can i do ? which parts are missing ?

Greetings

Apocalypse · Oct 8, 2015

equal said:
hi,

i am from germany, and i am a new user here

i want to build a additional lasermodule for my cnc machine.

the following items are using:

- Nichia NDB7875
- 2.4A X-Drive V6 Laser Driver
- 405-G-2 Glass Lens
- Adjustable brass laser diode housing (ebay 161804830486)
- a 20W peltier cooler

now, it works together, but my problem is, that i cant get a small laser line and a fine point at a distance. i can 'engrave' wood in ~40mm

in a distance longer than 1m the spot is very big (in 1m ~100mm spot size)

what can i do ? which parts are missing ?

Greetings

Can you take a picture of what you see? What happens when you adjust the focus by turning the lens? Also make sure you have the lens in the right way.

Alaskan · Oct 8, 2015

Appears to me your lens is focused to a fine burning point for close in work. If your work is 1 meter or more away I would expect the lens to be out of focus for that far out producing a large spot due to spreading. I don't know if your current lens can be focused to a point 1 meter away to allow it to be small enough to burn, pictures would help.

Infinity focus will produce a tight beam which can travel a long distance with minimal spreading, but focusing to a spot produces the most energy for burning, however past the point of focus the beam will spread out again, that is why you are seeing a big spot 1 meter away.

equal · Oct 8, 2015

uh ... it is very tricky to make good pics with protection glasses and my mobile phone, but i´ve got it (i hope)

look at the pictures in attachement. this is the best and smallest focus.
With the protection glasses, the point is smaller ...

greetings

for making pictures i used a low current (not the full power)

RedCowboy · Oct 8, 2015

The multimode diodes have one axis that diverges a lot more rapidly than the other.
So short of a cylindrical pair to reshape the beam followed by a telescope set the easiest thing to do is move it closer to your work piece.

You could go with a 405 or other single mode diode, that will give you a very tight beam that's easier to focus tight at 1 meter.

Or just use a C02 set up, they are getting cheap.

equal · Oct 8, 2015

with a gray filter i have taken this picture...

it is the "Nexus" beam

Alaskan · Oct 8, 2015

A "16X" single mode 800mw 405nm laser diode will focus to a very fine spot at a greater distance, I just don't know how long such can be used in a CNC laser setup, I suppose if the Peltier cooler keeps the diode cool enough, that isn't a factor?

autonomousperson · Oct 9, 2015

equal said:
uh ... it is very tricky to make good pics with protection glasses and my mobile phone, but i´ve got it (i hope)

look at the pictures in attachement. this is the best and smallest focus.
With the protection glasses, the point is smaller ...

greetings

for making pictures i used a low current (not the full power)

Is the lens securely in place? It may be the lighting but the lens looks weird. Put the lens in without the silver ring and slowly turn it until you get your desired point. Then put silver ring on and lock it in place. Focus it far away and not close to you. The side of the lens where the glass is on faces towards the diode.

equal · Oct 12, 2015

thanks all,

the lens is correct in place, my problem is that the lens is touching the diode. i can not put it closer.

after some tinkering: i can focus to a low distance to engrave wood, thats ok for me,

but a small and tight spot is not possible

greetings

Bionic-Badger · Oct 12, 2015

Have you tried flipping the lens barrel around backwards? The glass-lens side of the lens-barrel should be closest to the laser diode. If both sides have glass for some reason, try flipping it around to see if it helps.

equal · Oct 12, 2015

no,

i do not.

I thought that the new 405-G2 Glass lens is supplied correctly .. i will try

greetings

DTR · Oct 12, 2015

equal said:
with a gray filter i have taken this picture...

it is the "Nexus" beam

Your lens looks like it is in correctly as long as you are screwing the end without the slots in first which is with the glass closest to the diode. See this for spot size you can expect.
http://laserpointerforums.com/f65/there-something-wrong-my-beam-spot-59400.html

Can you take the lens out and get a picture of the raw output of the diode on a wall as that output looks a bit distorted but not sure if it is the camera or how it is.

how to focus a big spot ?

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