I want to eventually get a laser cutter for cutting paper or balsa wood or anything else thin.

what I would like to know, is what type, and how much power I would need

red
green
ir
near Ir
blue
violet
and what power I would need..
it wouldnt be thick wood

... for paper and balsa (until 3mm) ==> 445nm (blue) with 1 to 2 Watts (first 3.5Watt-diodes costs around USD700) ... don't count on the stated power values, better read the datasheets ...

... for thick wood (some mm to maybe 2cm) ==> CO2 with>60Watts

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I have a 445nm blue diode laser, which I got for USD $140 including housing and lens. The datasheet (Nichia NDB7875-E) claims a maximum forward current of 1.7A and and optical power output of typical 1.6W at 1.2A.

I seem to be able to comfortably run it for extended periods at 2.0A which (if the forward current to optical power output is linear) implies optical power output around 2.66W. This is a fairly popular unit and it is widely claimed to be a 3W unit. It is possible to push the current higher but as I understand (based on the physics of the edge-emitting diode) this can significantly shorten its useful life. The datasheet unfortunately doesn't provide a graph of forward current to optical power output, and I don't have a thermopile to measure it. All in all it still seems like a good value...

This cuts rather cleanly through single-wall corrugated cardboard and much more quickly through paper and cardstock. I haven't tried it on balsa wood and cloth yet. Of course it works quite well for removing black paint from copper for etching...

... if you drive a diode with currents above the max. value, then regardless how good you cool the housing, the chip will heat above his 'safe' values with sometimes drastic reducing of his lifetime!

I've found somewhere in the PL-forum a good summary of the temperature distribution for a good cooled brass diode-mount:




... so even if you hold the temperature of the housing/mount below the needed 30 degC, the overpowered crystall can easy go above 40degC with severe degrading above 50degC

So for longer lasting you shouldn't overdrive the max. currents with more than 5 to 10 percents ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

OK, so basically if I used the maximum forward current of 1.7A plus 5% as an absolute maximum, that's a maximum current of 1.785A and optical power of around 2.33W

Not 3W but still decent, and I'd rather have it last longer. Most of my testing has been at 1.7A and I think I'll stick with 1.7-1.8.

Interesting diagram of the heat distribution - that's quite a large range from 42C to 28C on the can. I suppose cooling the block actively using Peltier units might help drain some of the heat from the emitting edge.

... yes, active cooling can help a lot.

But I'm more a friend of passive cooling and 'underpowering' of the diodes -- 10% below max. will rise the expected lifetime to 'infinite'

For higher powers than 2 Watts with the 9mm-diodes (costs actually around 150€ in single counts) I'm adding 6 of the much cheaper 1.2Watt-diodes:

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]