Using an M140 diode for sintering plastic

[bumpfirestock]

Hey LPF,

I've been browsing on this site for the last 6 hours straight, and have been doing a lot of research into lasers for quite some time now. I have recently been playing with the idea of building a Selective Laser Sintering machine. This is basically a 3D printer that lays down a layer of powder (.003" thick, or about .01mm), then the laser melts a pattern on that layer, then another layer of powder is spread on top of that, the laser marks again, rinse and repeat. Finally you have a full 3D object that was made by melting plastic in layers by a laser.

The plastic can be any thermoplastic, common ones are Nylon-6, Nylon-12, ABS, and must all be in fine-powder form.

Anyways, I have been trying to find a laser that will have enough power to melt this plastic. I came across the M140 445nm diode, which can be powered past 2 watts. I believe running the laser closer to 1W, or 1.5 ish, and traveling slowly would be enough. If it isn't, I could preheat the powder to almost-melting temperature, and use the laser to give it the last push it needs.

I have compiled a few components I will need to purchase:

M140 Diode - 445nm M140 blue laser diode - $49.99 : Cajunlasers Store

BlitzBuck Adjustable Driver - *Pre-wired* BlitzBuck V3.1 (Rectangular) Adjustable 1.2-3.1A - $24.99 : Cajunlasers Store

Collimating Housing, High Compression Spring, and glass lens:
12x30mm collimating housing for 5.6mm laser diodes - $3.49 : Cajunlasers Store
High Compression Internal Lens Spring - $2.99 : Cajunlasers Store
Multi-element glass lens AR coated for 405/445nm - $6.99 : Cajunlasers Store

Diode Press Tool - Laser diode press fit tool (brass!) - $14.99 : Cajunlasers Store

A few heat sinks - Mini copper heat sink - $1.99 : Cajunlasers Store

And finally, safety first, Blue Blocking Goggles - Blue Blocking Goggles (fits over eyeglasses!) - $11.99 : Cajunlasers Store

Now I have a few questions, as I couldn't find this information no matter how much I searched. First, I can't seem to find the spot size of the M140. I want to focus the laser (if it is possible) to a much smaller spot size, for more accurate sintering. I am not entirely sure on how this is done with the lenses. Can they focus to less than a foot?

Second, I chose the 445nm diode because it seems that plastic absorbs a lot of heat from that wavelength. I don't have a source, I just ran across it somewhere and it stuck in my mind, but I want to verify that is true. Or I would like to know if there are better wavelengths for melting plastic powder.

And finally, and this is sort of off topic, but does anyone know how much having an Argon atmosphere affects the laser/plastic melting? I can't seem to find any simple data sheets on this.

If anybody has any advice, different set-ups, different components, knowledge on SLS, or anything related I would love to hear it. Thank you for your time.

 

[emmong]

SLS is one of the best 3d metal printing. It melts the material and the fuse it. But it does not melt it fully, but heat it to the point that the powder can fuse together on a molecular level fully. On the other hand, there is another process known as SLM (selective laser melting). It is similar to SLS but it fully melts the material. SLM is stronger because it has little or no voids which helps prevent part failure. Check this for more information.