Under Everything SLS’s video on the SLS4ALL Inova, a viewer asked, “Would it be possible to print white PA powder?” The creator replied that the Inova’s 10 W diode laser works around 450 nm. Most white PA12, he wrote, needs a CO2 laser at about 10,600 nm to absorb the energy. White SLS powder comes down to one thing: whether the powder can soak up the light your laser emits.
Why can’t most desktop SLS printers use white SLS powder?
Because bare polyamide barely absorbs near-infrared light. A peer-reviewed 2022 paper from the Technical University of Denmark explains that polyamides absorb strongly at the CO2 laser’s 10.6 µm, thanks to vibrations in their carbon-hydrogen bonds. At a fiber laser’s 1080 nm, absorptivity is very low and most of the energy is lost to reflection and transmission.
The usual fix is an absorber. Formnext’s report on Sinterit’s BIANCO2 puts it plainly: the near-infrared diode lasers used in cheaper machines rely on carbon-black-loaded powder, and that’s what limits them to grey and black parts. BIANCO2 switches to a 30 W CO2 source so white, natural and colorable powders can run.
Can you get close to white without a CO2 laser?
Lighter, yes. The DTU team mixed white and black PA11 for a 1080 nm fiber laser. Its best batch was 80/20 white to black. It also reported workable parts with as little as 0.34% optical absorber, though the whitest mix needed a large increase in laser power.
Formlabs sells Nylon 12 White Powder for its Fuse 1+ 30W, a fiber laser machine at 1070 nm. It’s compatible with that printer only and needs bed temperature tuning and powder aging before the first print. Formlabs recommends a nitrogen atmosphere, since parts printed in air may yellow as the powder ages. It doesn’t publish how the powder absorbs the laser.
What should you check before promising white parts?
Look up the laser on the spec sheet first. If it’s a CO2 laser, white PA is normal. If it’s a diode or fiber laser, ask the printer maker which white powder it has qualified for that exact machine, and print a color sample before you quote a white job.
Related on the Solvi blog: SLS Nylon Yellowing: Why White Parts Turn Yellow; White MJF Parts: Can HP Jet Fusion Print White?; SLS Laser Window: How Often Should You Clean It?.
Sources: YouTube: SLS4ALL Inova part orientation (Everything SLS), viewer question and reply; SFF 2022: Process optimisation of PA11 in fiber-laser powder-bed fusion through loading of an optical absorber (PDF); Formnext: Sinterit opens up compact SLS with a CO2 laser; Formlabs: Nylon 12 White Powder; Formlabs: Using Nylon 12 White Powder; Formlabs Fuse series tech specs.