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

  1. #21
    Join Date
    Dec 2012
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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?

  2. #22
    Join Date
    Oct 2012
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    Germany
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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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