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Thread: Least expensive way to drive 8W 915nm laser diode

  1. #1
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    Question Least expensive way to drive 8W 915nm laser diode

    Hi all,

    I'm new to this forum, and new to lasers in general. But I'm familiar with electronics in general.

    I have a small CNC (Shapeoko) that I want to convert into a small laser cutter/engraver. Searching through ebay for high power laser diodes, I found this 8W 915nm laser (http://www.ebay.com/itm/110959792691). According to the datasheet, it should be driven at 10A@1.8V. I contacted the seller to explain my inteded use and to see if he could source a low-cost driver that was capable of driving this laser and he told me that the cheapest driver he was aware of cost some $500, which I think is way too high. Though, he did say that he got asked about that frequently for the same use I have in mind.

    Given that the laser comes coupled with a 1 meter long 100-micrometer fiber, I think it would be suitable for the kind of application I am interested in (mainly, cutting plastics and engraving wood or soft-metals). The package can also easily be coupled to an off the shelf heatsink to dissipate heat.

    How feasible would it be to build a driver capable of driving this diode while also able to be triggered from a TTL line (so it can be turned on and off by a microcontroller) for under $150?

    I can design the PCB and build the driver myself if provided with the circuit diagram. Heck, I'd be willing to take the plunge and make a small run of kits for such a driver and sell them almost at cost to get things started. I'm pretty sure there are many other home "makers" like myself who would be interested in such a driver as it can convert their home CNCs and 3D printers into laser cutters relatively easily.

  2. #2
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    what about a couple of these?

    http://www.photonlexicon.com/forums/...788#post232788

    Quote Originally Posted by IraqiGeek View Post
    Hi all,

    I'm new to this forum, and new to lasers in general. But I'm familiar with electronics in general.

    I have a small CNC (Shapeoko) that I want to convert into a small laser cutter/engraver. Searching through ebay for high power laser diodes, I found this 8W 915nm laser (http://www.ebay.com/itm/110959792691). According to the datasheet, it should be driven at 10A@1.8V. I contacted the seller to explain my inteded use and to see if he could source a low-cost driver that was capable of driving this laser and he told me that the cheapest driver he was aware of cost some $500, which I think is way too high. Though, he did say that he got asked about that frequently for the same use I have in mind.

    Given that the laser comes coupled with a 1 meter long 100-micrometer fiber, I think it would be suitable for the kind of application I am interested in (mainly, cutting plastics and engraving wood or soft-metals). The package can also easily be coupled to an off the shelf heatsink to dissipate heat.

    How feasible would it be to build a driver capable of driving this diode while also able to be triggered from a TTL line (so it can be turned on and off by a microcontroller) for under $150?

    I can design the PCB and build the driver myself if provided with the circuit diagram. Heck, I'd be willing to take the plunge and make a small run of kits for such a driver and sell them almost at cost to get things started. I'm pretty sure there are many other home "makers" like myself who would be interested in such a driver as it can convert their home CNCs and 3D printers into laser cutters relatively easily.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  3. #3
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    Quote Originally Posted by swamidog View Post

    Thanks for the quick reply.

    Correct me if I misread that, but aren't those 2A drivers? The diode is rated at 10Amps at 1.8V!

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    that's a quad channel driver. each channel can do 2-2.5A.

    Quote Originally Posted by IraqiGeek View Post
    Thanks for the quick reply.

    Correct me if I misread that, but aren't those 2A drivers? The diode is rated at 10Amps at 1.8V!
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Quote Originally Posted by swamidog View Post
    that's a quad channel driver. each channel can do 2-2.5A.
    Oh, saw the 4 FETs but didnt read the title so I thought it was a single channel.

    Would it be safe to tie in all the channels to drive a single diode?

    I'll get in touch with Badpip and ask about driving the laser at 1.8V.

    Thanks

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    i would not expect any issues tying all the channels together, but do please check with badip. i would hate for you to smoke your diode on my behalf.

    please let us know how it works out.

    Quote Originally Posted by IraqiGeek View Post
    Oh, saw the 4 FETs but didnt read the title so I thought it was a single channel.

    Would it be safe to tie in all the channels to drive a single diode?

    I'll get in touch with Badpip and ask about driving the laser at 1.8V.

    Thanks
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

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    Quote Originally Posted by swamidog View Post
    i would not expect any issues tying all the channels together, but do please check with badip. i would hate for you to smoke your diode on my behalf.

    please let us know how it works out.
    I just sent him a PM explaining what I want to do and asking for his help. Haven't bought the diode yet. Want to sort the electronics before doing that. If he thinks his driver can do the job, I'll take the plunge and order a diode in a couple of weeks (going on vacation for xmas). Will sure keep you guys posted

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    Let us know what badip says.

    Thanks

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    still waiting to hear back from him.

    Donno if my message was sent or not. It doesn't appear in the sent items, but then again, I've seen forums where it doesnt appear in the sent items until the recipient reads it. Can anybody confirm?

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    it should appear. give it another try. i've bought from badip in the past and he's been very responsive.


    Quote Originally Posted by IraqiGeek View Post
    still waiting to hear back from him.

    Donno if my message was sent or not. It doesn't appear in the sent items, but then again, I've seen forums where it doesnt appear in the sent items until the recipient reads it. Can anybody confirm?
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  11. #11
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    ... I'm driving 975nm-diodelasers with 9Watts or 25Watts @9Amps and TTL-switching through a MOSFET with a group of LM317 / LM350 / LM338 configured as current regulators and running parallel to sum the curent.

    It's a simple circuit - you can find some infos in my lasercutter-WiKi: http://www.reprap.org/wiki/Laser_Cutter_Notes

    I've made this Wiki some years ago then with 5Watt-diodes running with 5Amps max, but you can replace the LM317 (until 1.5Amps, continuous current 1A) by LM350 (until 3Amps) or LM338 (until 5Amps) to receive more current per chip.

    My actual driver has two LM317 and three LM338 configured to 1A+1A+2A+2A+2.5A, which i can switch together in any combination for predefined max current from 1A to 8.5A for different diodes or running the 'big' diodes with lower current than the max. spec of the diode says (what will enhance the lifetime until 'forever').

    The 'finetunig' is made with TTL-level (0-5V) through an opto-coupler and PWM-switching the MOSFET, that drives the current through the LM's and the laserdiode.

    Recently I've found an analog circuit with a LT1215 OP, that can drive the same LM-configuration with analog voltage level until 1MHz clocking rates! and will solder and test this in the next weeks ...

    Viktor

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    Quote Originally Posted by swamidog View Post
    it should appear. give it another try. i've bought from badip in the past and he's been very responsive.
    I second the above. I know for sure that he is very very busy these days, as i also contacted him for drivers and it took him 3-4 days to come back to me.
    But things worked out well

    I do seem to recall the idea to tie all 4 channels together as a good one, but let's wait for Thomas to come back to this.
    "its called character briggs..."

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    I've sent the message again last night (had the text saved on my computer), and still can't see anything in my sent items

    Not in a hurry, so I don't mind waiting. I'm using the time to read about SLS, specifically researching about aluminum powder SLM (Selective Laser Melting)

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    ... aluminium powder is a bit tricky, even with inert gas shielding - better use brass powder or common sintering powder what's composed from - Fe89% Cu8% Pb3%

    I have some kg dark brown lignin powder, what's a natural thermoplast extracted from wood dust ... and made some tests with black mineral microspheres and dark plastic dust without inert gas.

    With the IR-diodes you need dark powders or you have to mix shiny materials with dark thermoplastic pigments or carbon to get enough energy absorbed ...

    Viktor

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    I'd definitely prefer to work with plastics, but haven't been able to find a "cheap" source of powdered plastic (sub 100 micron particles).

    Bronze wouldn't be much easier to work with as its melting point is about 300C more than aluminum and without some gas shielding it would too oxidize (granted it wouldn't combust like aluminum).

    The only reason why I'm looking into aluminum sintering is because the powder is widely available. Otherwise, plastic would be my first choice.

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    ... you can try with grinding down some black thermoplastics like POM or ABS (maybe you have to cool it while grinding) and sieve the dust for selection.

    But best methode would be jetting a stream of molten plastic on a fast rotating disk, so it will be spreaded into micro-droplets and while falling down they'll solidify to perfect uniform micro-spheres ...

    Viktor

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    Quote Originally Posted by VDX View Post
    ... you can try with grinding down some black thermoplastics like POM or ABS (maybe you have to cool it while grinding) and sieve the dust for selection.

    But best methode would be jetting a stream of molten plastic on a fast rotating disk, so it will be spreaded into micro-droplets and while falling down they'll solidify to perfect uniform micro-spheres ...

    Viktor
    Trying to make my own powder is too complicated and probably too expensive to justify the effort.

    Just did a search on alibaba.com (for some reason I hadn't thought about searching there until your comment!), and found a supplier in china for powder plastic that is advertised specifically for SLS uses (http://www.alibaba.com/product-free/...ter_rapid.html), but their minimum order quantity is 30kg, which is A LOT. I'll try to contact them tonight to see if I can get them to sell me a couple of kilograms and get more info about pricing.

    An 8W laser will be much faster working on plastic than on metal powder, not to mention a much simpler workflow as it won't need gas shielding (just good ventilation).

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    ... the linked powder is white, so not really usable with the IR-diode - try to get some dark coloured powder or thermoplastic pigment colour to try with it pure or to mix with the white powder.

    Another material interesting for first tests could be dark red or brown clay powder, used in cosmetics ...

    Viktor

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    Quote Originally Posted by VDX View Post
    ... the linked powder is white, so not really usable with the IR-diode - try to get some dark coloured powder or thermoplastic pigment colour to try with it pure or to mix with the white powder.

    Another material interesting for first tests could be dark red or brown clay powder, used in cosmetics ...

    Viktor
    You wouldn't happen to be the same VDX on the reprap forums, would you?

    I read the discussions about SLS on the reprap forums. There were a couple of SLS printer technicians in the thread linked above who said the most important thing for SLS is preheating the material. This prevents the printed object from curling and minimizes the power needed to melt the plastic while increasing the printing speed.

    Preheating is also getting me to think if 8W is really needed. Wonder how fast/slow would the 700mw 405nm bluray diodes be with a preheated pwoder to say 160-180C? Still waiting to hear back from the chinese supplier of the powder about pricing and characteristics. Also sent an email to these guys but haven't heard anything back yet. Also need to think about how to pre-heat the powder and what to make the powder box and Z-axis platform from.

    Still, the powder color isn't really an issue as coloring pigments are widely available (my availability scale is ebay. If its widely available there, its easy to get).

  20. #20
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    Quote Originally Posted by IraqiGeek View Post
    You wouldn't happen to be the same VDX on the reprap forums, would you?
    ... the world isn't really big, is she? --- yes, that's me too ;-)

    Heating will reduce the needed amount of laser energy or enhance the max. possible speeds ... but it's a big chunk more of work, so not really essential for testing different powders for their SLS-usability.

    Another option is to use two lasers - one with a spot of maybe 2mm diameter will preheat the surface without melting it ... the other with 0.1mm pointing in the center of this hot-spot will melt the dust ...

    Mixing white/translucent powder with dark pigments will give some funny results with laser-melting - depending on the energy density, the fused material will change the colour because the absorbing pigment particles will start to vaporize, while transferring heat to the surrounding white particles. So you can start with dark powder and receive slightly coloured translucent objects ... maybe usefull for art or some special effects, like clear windows in opaque parts?

    405nm @700mW and preheating could be enough for melting the uncoloured powder - but could be hard to achieve a melting spot in the size of the laser focus, the transmission/duiffusion between the particles is depending on the optical characteristics of the plastic in respect to the wavelength.

    And there is something more special with lasers melting powders ...

    Viktor
    Last edited by VDX; 12-12-2012 at 05:42.

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    Quote Originally Posted by VDX View Post
    Heating will reduce the needed amount of laser energy or enhance the max. possible speeds ... but it's a big chunk more of work, so not really essential for testing different powders for their SLS-usability.

    Another option is to use two lasers - one with a spot of maybe 2mm diameter will preheat the surface without melting it ... the other with 0.1mm pointing in the center of this hot-spot will melt the dust ...
    Agreed, preheating will not be easy to implement, but based on the reprap community experience, as well as the powder printing threads on the reprap forums and this report it seems to be a necessary evil to prevent the plastic from curling as it cools.

    Quote Originally Posted by VDX View Post
    Mixing white/translucent powder with dark segments will give some funny results with laser-melting - depending on the energy density, the fused material will change the colour because the absorbing pigment particles will start to vaporize, while transferring heat to the surrounding white particles. So you can start with dark powder and receive slightly coloured translucent objects ... maybe usefull for art or some special effects, like clear windows in opaque parts?
    Not really worried about the aesthetics. Just want a reliable, usable, low cost material that can be sourced relatively easily.

    Quote Originally Posted by VDX View Post
    405nm @700mW and preheatimg could be enough for melting the uncolored powder - but could be hard to achieve a melting spot in the size of the laser focus, the transmission/duiffusion between the particles is depending on the optical characteristics of the plastic in respect to the wavelength.
    Haven't tried them myself yet, but from what I've seen on the net, and what is readily available for sale on various sites (including ebay) 100um doesn't seem hard to achieve.

    Quote Originally Posted by VDX View Post
    And there is something more special with lasers melting powders ...
    What do you mean?

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    ... with RepRap's (or common FDM/FFF-printing) we have to deal with warping/curling too - it could help a lot when not printing 'floating' parts in the dust, but print the first layer direct fusing to a stable surface (so you'll get strong support at the edges), and add some support structures too for overhangs.

    The spot size of the laser is not autoamtically the printing resolution! - you have to experiment with particle size and avoiding fusing not melted dust outside of the spot to the molten zone ... or your parts will receive a 'sandy' surface finish with some 'over-size' depending on the diffusion of the beam in the powder, material, ambient temperature and powder size.

    ... and this "something more special with lasers melting powders..." is the really big/complex theme of behaviour of dust while partially melted, what's not really transferrable with forum postings ;-)

    Viktor

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