Introduction: 3D Print Finishing Technique for Improved Surface Quality
Fused Deposition Modeling (FDM)/ Fused Filament Fabrication (FFF) technology is often described as "low-quality" largely because of the visibility of individual layers. Optically, this high degree of visibility is a result of the smooth, reflective surfaces of the extrusions. Light reflected off of resonant features, seams, and other irregular/noisy regions on the surface of the object that catches the eye and makes the surface of the object harder to visually parse. This is less of a problem with laser sintering (SLS) technology because the resulting surface is by nature matte or with SLA, in which the surface has an even finer matter finish.
One effective method to mitigate this noisy reflection problem is to apply a matte surface to the printed object. Sand-blasting is an excellent way to evenly abrade the surface of a printed object to remove the smooth, reflective surfaces of individual extrusions and create an homogenous, matte surface that scatters light evenly rather than with sharp reflections. This results in less optical noise and makes the visual task of parsing the printed object's geometry mush easier.
Step 1: Before Sand-Blasting
Before sand-blasting, all the printed objects had reflective component extrusions. This made them both difficult to visually parse as well as difficult to photograph (especially the black PLA) given the high dynamic range of the surface.
Three types of PLA were tested, all from Ultimachine, and each part was printed on a Makerbot Replicator 2. Parts, in order of appearance:
-Black PLA, 0.3mm layer height
-Black PLA, 0.3mm layer height
-Black PLA, 0.3mm layer height
-Black PLA, 0.2mm layer height
-White PLA, 0.3mm layer height
-Natural PLA, 0.3mm layer height
Step 2: After Sand-Blasting
After sand-blasting the parts with 120 grit garnet media, they were washed with soap and water and dried with compressed air after a pat-down with a paper towel. Ambient air drying resulted in spotting on the surface.
Step 3: Side-by-Side Comparison
These side-by-side photos of the same part show the difference in appearance under the same lighting conditions.
Conclusions:
- Even blasting helps the final surface quality.
- Additional shells (3 or 4) help keep the print sealed during washing.
- After blasting, the matte surface is prone to absorbing skin oils and other particles, much the way an SLS print does.
- The blasting grit will alter the color of lighter PLAs-- the white took on more of a bone hue and the natural clear developed a somewhat murky color. The black PLA blasted to a very nice matte grey.
21 Comments
5 years ago
have you considered a less abrasive media? ie sodium bicarbonate, corn
6 years ago
could you make a thick solution with abs and acetone and paint it on pla like varnish to give a smooth finish
6 years ago
Damn, my neighbor just bought a sand blaster (it may be too powerful). Going to test it.
7 years ago
Hi. Nice job!
One question: have you tried to follow the 120 grit abrasive with a finer abrasive? This in hand finishing produces excelente results but is very tiresome and uneven on corners and irregular shapes. In the blasting process I´m guessing you could "jump" a few grit grades with good results.
Cheers,
7 years ago
Do you think one of these would work for blasting parts?
http://www.ebay.com/itm/AIRBRUSH-SANDBLASTER-Etching-Glass-Etcher-Air-Abrasive-Sprayer-Eraser-AB78-/390595827839?hash=item5af153587f:g:bjAAAMXQDfdRrFJ2
7 years ago on Introduction
Could you comment on the effect on dimensions? I am sure there will be a difference in precision and will be needed to take into account while printing. Also if the sand blasting is not a automated/uniform process, it will affect the final dimensional precision consistency.
Reply 7 years ago on Introduction
I wasn't able to measure a significant change in dimensions on any of the parts that I sand blasted.
7 years ago
Awesome job! Do you offer printing services? I would like to have something printed.
8 years ago on Introduction
the item with natural finish that has a honeycomb structure, what is it? It looks like it could be part of an armor system, maybe the forearm. Any more info on that? Thanks. Excellent tutorial btw it makes me want to go buy a sandblaster.
8 years ago on Introduction
For someone who doesn't have a sand blaster, I suppose a rock tumbler would be too violent?
Reply 8 years ago on Introduction
It's definitely worth a try! Tumbling will probably take a little longer, but tumble/vibration processes are used all the time in industry to polish/de-burr/resurface parts. Give it a shot-- would love to hear how it goes.
Reply 8 years ago on Introduction
Tumblers with natural materials seem like they'd work pretty well. I've seen people use walnut shells, cornmeal, etc.
Reply 8 years ago on Introduction
not the same IMO
8 years ago on Introduction
What about a case tumbler?
8 years ago on Step 3
If you spray it with 'back to black', Silicone spray for car body & interiors after blasting, it returns it to being much darker in colour plus no longer picks up finger prints etc.
On the down side, the silicone also repels paint so you cannot spray it after.
Filler primer then satin black paint works well too. The filler primer fills in the gaps between layers and can give a very professional finish.
8 years ago on Introduction
What are you blasting them with ( what abrasive)?
Reply 8 years ago on Introduction
120 grit garnet powder. I'd be curious to see the impact of other abrasives though.
8 years ago
I've noticed that PLA tends to bleach when sanded (or in your case blasted.) I've not noticed as much bone color when sanding white. This could be a result of dirt or particles being trapped in the surface of the plastic. As with any sanding, it will produce a matte surface until higher grits are used to completely smooth the part, unifying all defects (pits and valleys). The bleaching is effectively the micro variations on the surface, scattering light.
8 years ago on Introduction
Great idea, I'll have to try this out on my next FDM print.
8 years ago on Introduction
Very cool idea, i have never seen this before!