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UV Laser for Selective Laser Sintering of Polymers?

Posted by DrDFlo 
UV Laser for Selective Laser Sintering of Polymers?
December 28, 2017 08:28PM
Why are predominately IR lasers used for sintering polymer powders? Most polymers like PCL and PMMA have high UV absorbance peaks. Would a UV laser like a frequency tripled Nd:YAG be efficient at sintering powder?

This is for a high resolution commercial application. CO2 laser's large wavelength make them a poor choice for small spot size.

Thanks!
VDX
Re: UV Laser for Selective Laser Sintering of Polymers?
December 29, 2017 06:06AM
... it's mostly for speed (better = energy density per scanning speed) and white powder materials.

The needed speed is only achievable with XY-galvo-scanner, where you'll need good laser beam parameters, what's much better with CO2-lasers, than with diode lasers ... and too - the energy, needed for melting while fast scanning ... here some hundred Watts with a CO2-laser are much cheaper, than 5 or 10 Watts with UV-diodes ...


Viktor
--------
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Re: UV Laser for Selective Laser Sintering of Polymers?
December 29, 2017 10:26AM
Thank you for your response. There are a couple discrepancies in my post and your response. I would not be using diode laser, but instead a a frequency tripled Nd:YAG (Q-pulsed not continuous like CO2), which has great beam quality (almost comparable to a Yb fiber laser). Also, most white powder materials have a IR and UV absorbance band.

While CO2 lasers may be more efficient/cheaper, their spot size cannot be reliably focused down to below 100um because of wavelength and beam quality. However, a sub 100um spot size can be achieved with the proposed Nd:YAG laser.

I am going to rephrase my initial question. I have a polymer powder, which I want to sinter, that has absorbance peaks at 280nm (UV-vis) and 10um (FTIR). I want to create the smallest spot size possible, so I want to go with a UV laser over an IR. At the same fluences will the polymer absorb similar photothermal energy from a laser emitting a 280nm vs 10um wavelength?
VDX
Re: UV Laser for Selective Laser Sintering of Polymers?
December 29, 2017 11:20AM
... OK, let's rethink - with same or better beam parameters, UV should work better ...

What's with the needed power vs. scannig speed? - You doesn't need high pulsing energies, but more the time to distribute the heat in the material to achieve some melting/welding.

Then -- what's with the absorbance depth? - can UV heat/melt deep enough, to fuse the loose particles to the previously solidified body?


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
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