“How does the black dye wear over time?” A viewer asked that under Avid Product Development’s video on finishing MJF parts. The bureau answered that the black dye is the same kind of product used for dyeing clothing, “so you can expect similar durability as a dyed piece of clothing.” It’s a fair comparison, but MJF dye durability has a more specific answer once you look at how deep the color goes.
How good is MJF dye durability?
It’s durable against light scuffs because it isn’t a coating. DyeMansion, which makes the DM60 dyeing system many bureaus use, says its process lets dye penetrate into the part surface under heat and pressure, so the color can’t chip or peel, and “minor scratches do not expose the uncolored base material.”
How deep does the dye go?
Not very. In its 2020 launch release for colors on grey HP MJF parts, DyeMansion said its dyes “penetrate up to 200 μm into the open pores of the parts.” Its DM60 product page puts penetration at roughly 0.2 mm on EOS PA 2200 and says it’s material dependent. Anything that removes more than that, like sanding, machining or a deep gouge, goes past the colored layer.
On MJF that matters less than on white nylon. The PA12 core is already dark grey from the fusing agent, so a worn spot shows grey rather than bright white. It’s still visible on a glossy black part, though.
Does surface prep change the result?
Yes. DyeMansion’s release names the base material color and the surface treatment as important factors in the final color, and says its MJF colors were developed on parts blasted with its PolyShot process. A part dyed straight after depowdering won’t necessarily match one that was surfaced first.
What should you plan for?
For handheld or wear-heavy parts, design so the edges that rub aren’t sharp, since edges lose that 0.2 mm first. Do any machining, reaming or tapping before dyeing, never after, or the cut faces will come out grey.
Related on the Solvi blog: Should You Dye MJF Parts Black or Vapor Smooth Them?; White MJF Parts: Can HP Jet Fusion Print White?; SLS Bead Blasting: What Causes Residue on Parts?.
Sources: YouTube: Multi Jet Fusion (MJF) Explained (Avid Product Development), viewer question and reply; DyeMansion: Vibrant color line for grey HP MJF parts (press release, April 2020); DyeMansion: DM60 coloring system.