Aixiz acrylic lens?

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o_lampe

Can I use my Alu-heatbed to test CW-power? Aiming the laser close to the thermistor and see how far the temp rises?
-Olaf

I thought about it with a water cooled plate. Water is better (imo) because you can measure the flow and the temperature rise. With alu exposed to air you don't know the heat loss to the surroundings.

I abandoned it because I am pretty sure it needs to be calibrated to give a trustworthy reading. To calibrate you will need a well defined laser already, and there. A simulation with a heating element might work as well but suddenly it becomes a lot of work.

If I really get into this laser diode business I might buy a meter. They cost some 220 USD at cheapest.

... this "6mm lens" could be from the salvaged diode banks - have several salvaged Casio beamers with the empty banks -- every of them has 24 of this glass-colimators, so more than enough

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Viktor
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Quote
VDX
... this "6mm lens" could be from the salvaged diode banks - have several salvaged Casio beamers with the empty banks -- every of them has 24 of this glass-colimators, so more than enough

OK, but will they fit in the M9x05 collimator housing?

Yesterday I lost an auction about a Casio beamer, where the seller already stated, there would be missing some blue LDs. But it would still work with 6 LDs left.
-Olaf

... later this evening I'll test it with fitting one of the 6mm-lenses into a collimator ...

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Viktor
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... could do it faster - short answer: yes, it fits -- the original lens is 6mm in diameter too, but shorter/thinner in length.

Attached an image with one of the (empty) Casio's 24x laser banks, one collimator with the original lens on the left, the lens from the other (left one) compared to one of the casios lenses (right one) and the other collimator reassembled with one of the thicker casios lenses.

The focal length seems similar (so the original lenses are made either from glass with more density or higher curvature, so thinner than the casios) -- will try in the next days to compare the beam specs of the two different collimators ...



Edited 1 time(s). Last edit at 12/20/2015 12:38PM by VDX.

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Viktor
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... tested with a 405nm-diode at around 80mW - attached an image with the focus points in 1m distance -- left the original, right the 'casio'-lens.

It's a bit more 'fuzzy', but it seems like more UV light is passing through ...

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Viktor
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Thanks Viktor for all the work!
Did you find time to compare power losses between the two lenses? If it would end up between the three layer lens and the G2, it would be awesome!

Funny thing, no one who used Casio/OSRAM 1.6W LDs before came up with the idea to use the Casio lens.
Same thing with the G9-lens that come with some Nichia 9mm LDs. ( OK, you have to make a collimator housing were they fit in, but the lenses are for free )
-Olaf

... my first feeling says, the 'casios' lenses let's pass more or the 405nm-UV, so here even better, than the original collimator lens.

Can test this later with my power-meter for the 405nm- and one of the 445nm-diodes to get more precise numbers ...

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Viktor
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... tested - not this big a difference

405nm-diode @100mA (200mW-diode)
without ~120mW
Std-colli ~ 105mW
Casio ~ 99mW

445nm-diode @500mA (6W-diode)
without ~150mW
Std-colli ~ 123mW
Casio ~122mW

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Viktor
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Cool!
Do you see any disadvantage from the thicker Casio lens.
Problems with focusing?
Needs shorter spring?
etc...

I think, I'm already tired of my DVD LDs, even before I got the TO-18 housings to burn some holes in papersheets...
The typical laser disease is: I want more power
-Olaf

... no disadvantages yet, "same procedere" as with the standard lenses -- will try with the 3.5W and 6W-diode, but this can take a while ...

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Viktor
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Yesterday I was finally able to test the red LDs in a housing ( not genuine aixiz ) with acrylic lens. It seems they made the collimator housing to short or the laser housing to long.
I had to turn the collimator all the way in and still got no sharp focus. Nevertheless I was able to leave some burn marks on a piece of cardboard
I raised the current to 0.5ish and the LD turned dull in an instant. The slider of my wire wound resistor on my LM317 current source is a bit jumpy, so fine tuning can kill the LD.
Advice: Use a less critical power consumer ( eg. common power LED ) to tune in the current.

I killed another diode just from trying to solder wires to it and put it in the housing. The third one now works nicely with 0.36A. ( beside the focusing issue )
So, again waiting for the "Casio" lens and find a way to open the collimator. It's back has a pressed in cover, not a screw, like I've seen on other lens barrels...

Resume: I'm glad I started with some cheap DVD LDs before I got to the serious stuff. Saved some $$$
-Happy new Year
Olaf

Hi Olaf,

the focus will come nearer to the lens, if you turn the collimator OUT, not in

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Viktor
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Quote
VDX
Hi Olaf,

the focus will come nearer to the lens, if you turn the collimator OUT, not in

I turned the collimator all the way out and aimed the spot to a 1m distant wall.
Then I began to turn in the colli and the spot got smaller and smaller. I expected the spot would becomer bigger at a certain point, but that didn't happen.

How do I find the sweet spot for my LD/lens combo?
It seems, I can focus it to almost any distance I like, but the energy will be best at which focal length?
I placed the Laser 20mm above surface, focused it to the best of my ability and was able to engrave really slow ( 60mm/min ! )
Then I placed it 30mm above, refocused it and was able to engrave faster ( 100mm/min ).
Do I have to repeat this over and over again, until I found the best height?
-Olaf
PS: I love the smell of burnt cardboard in my living room

Hi Olaf,

... 30-40mm is a good focal distance for engraving and cutting -- 40 to 60mm is better for cutting, not so good for fine engraving, 20-30mm best for engraving.

Adjust the focus with lowest power setting (slightly above threshold current) to the smallest possible spot on a black surface in e.g. 35mm distance.

Then rise the current/power to lets say 30%, so it will only engrave in the right focal distance.

Then create a testing file - for example 20 small quadrats of 2mm size and 1mm distance with rising Z-height of 0.5mm for every quadrat -- so you'll get a 60mm wide line of quadrats with varying distance with an overall Z-variation of 10mm.

When you position your diode at 25mm (or proper start for another focal setting) distance above the surface of a cardboard and run the file, then the perfect distance will be shown by the thinnest quadrat with equal wide engraved lines in X and Y

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Viktor
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Thanks Viktor,
right now I'm testing with the dvd carriers, so I only have 38x38mm test area and no z-stepper. ( similar to the pocket laser engraver )
I'm working on a 800x800mm XY-plotter but parts delivery are slow these days.
Following your tipps, I have to add a small z-adjustment too.

After some more tweaking I'm able to engrave with 150mm/min, but I see a few spots were the beam has cut through the material and other spots, where the laser didn't burn the surface at all.
The square test you mentioned would work best with equal quality material. ( eg. not cardboard from recycled paper )

... get some (dark) coloured cardboard ("Tonkarton" in German) -- with the right settings even white paper will be possible, but then you'll need perfect adjustment and >700mW of power.

DVD carriers or other thermoplastic sheets will show much thicker engraving lines for bigger melting zones around the spot ... better search some duroplastic materials and/or coated sheets, which will show good colour changing.

With good settings this will be even working with coloured anodized aluminium.

I'm engraving mostly with 30-50mm/s (1800 to 3000 mm/min) and cutting with 5-10mm/s (300 to 600 mm/min) ... or faster with thinner sheets or good absorbing/evaporating materials ...

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Viktor
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With DVD carriers I meant the stepper driven slides that move the head (carrier) in a DVD drive. I don't want to burn plastic in my living room and my workshop is unheated *brrrr*
Will go shopping for some better cardboard.
-Olaf

... ah - OK, misinterpreted for the different meanings ...

But even with cardboard - vent/exhaust the fume out through the next window or build/search a carbon-filter!

The fumes of paper, cardboard or wood aren't so healthy too ... and the colours and additives will add some weird chemistry on their own too

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Viktor
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Yesterday, Santa Clause had mercy with me and brought me a blue 2W "M140" LD. I replaced my red 400mW LD with it and left the current unchanged.
I had a hard time to focus the spot, it seems a lot bigger than the red one. ( Still using the acrylic lens )
So I started a test-engraving not expecting much.
The cardboard got cut through in one pass instead of just engraving some text like the red LD did

I had to 3x the speed and reduce PWM to 50% to get the same result. How is that possible ( with such a big spot? )
Is it the difference in wavelength or better W/A efficiency? I'm almost frightened to crank up the current to 1.6-1.8A, like it's supposed to for the M140 LD.

Q: Is it normal that I can hear the PWM frequency coming from the diode?
-Olaf

... max. 1.7A, better stay below 1.6A.

Which current did it have? The powers of different diodes at the same current can be different, so this is not usefull fo comparing cutting capabilities.

Blue light is much better absorbed by the cardboard, so this is another variable, defining effective cutting speeds.

A: - the sound you hear comes from the spot, where you instantly evaporate the material, what's like a small explosion

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Viktor
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The current was set below 0.4A, but the blue LD cut through cardboard like butter.
I can cut 1mm deep in wood in one pass at slow speed. When I get my glass lenses, I'll raise the current and speed.

I got me new batteries for my digital multimeter, I suspect wrong reading there.
Anyway, now I have plenty of power to do some grayscale engraving.
-Olaf

... did you measure the current with the blue diode?

0.4A will be something like 200-300mW with the blue diode -- 'cutting like butter' sounds more like 1W, so the current should be something like 0.9A

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Viktor
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That's why I bought new batteries for my multimeter, I didn't trust my readings. The red LD would have been killed with a current above 400mA. ( Ask me how I know )
Now I have a hobbyking 130A Wattmeter between driver and diode. Don't know if this is very accurate at such low Amps.

Anyway, I have made a few more cuts and I see a difference between blue cardboard and yellow. The blue one absorbs much more energy and cuts easier.
I tried to raster engrave a BW picture on blue cardboard and it perforated the paper instead of burning the surface. ( see attachment )

I also got a three element glass lens for 445nm. Will test it with a little more current, didn't make it to focus it sharp yesterday ( Hands are trembling from excitement )
-Olaf

... after rethinking -- it could be, your diode is below 0.5Watts and cutting like my setup with 1Watt.

As you're moving with only some ten mm/min the power is 'accumulating' to burn through - I'm driving with some ten mm/s and pulse times between 5 to 50 microseconds, what's a really big difference to slower moving and longer ON times ...

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Viktor
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That makes perfect sense. I'm cutting with 600mm/min.

I now have a "luxury"-problem. I focused the three element lens and raised the current to 1A. Now the dvd steppers are to slow to just do some engraving.
I reduced PWM to 64, but it ended in pierced cardboard at the outlines with areas that aren't burnt enough in the middle of a track.
I'm already running the steppers at full speed ( 1400mm/min ). The only thing I can do to switch from cutting to engraving is to reduce current everytime...
Now I know, why you have jumper selectable current settings on your LD-driver.
-Olaf

... this "jumper selectable power" was with my old LM317/LM338 drivers and current steps from 500mA to 8.5A in 0.5A/1A-steps -- actually I'm using 2W or 3.5W diodes at 'full power' (with 1.6A or 3A fixed) settings and reducing the ON-time per pulse down to 1 microsecond for engraving ... or up to 200 microseconds and slower moving for cutting.

With the fiber-laser I'm pulsing with up to 2MHz, so even shorter pulse ON times of around 200ns ...

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Viktor
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#ifdef FAST_PWM_FAN
    setPwmFrequency(FAN_PIN, 1); // No prescaling. Pwm frequency = F_CPU/256/8
    #endif

I've defined FAST_PWM_FAN, but according to this code, the pwm_clock is 7.8kHz?
Or is it 500kHz? 16MHz / (256/8 )
If it's 500kHz, I wonder if the TTL input is able to follow. Will ask the vendor...

For now, I will reduce current for good engraving and make two or three passes for cutting.
-Olaf