Introduction: 3D Print Finishing Technique for Improved Surface Quality

Picture of 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

Picture of 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

Picture of 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

Picture of 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.

Comments

fbujold (author)2017-04-07

have you considered a less abrasive media? ie sodium bicarbonate, corn

efoster6 (author)2016-08-28

could you make a thick solution with abs and acetone and paint it on pla like varnish to give a smooth finish

spudziuvelis (author)2016-03-25

Damn, my neighbor just bought a sand blaster (it may be too powerful). Going to test it.

HumbertoB3 (author)2016-01-05

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,

StellanH (author)2015-11-17

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

Aeroab-911 (author)2015-05-11

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.

I wasn't able to measure a significant change in dimensions on any of the parts that I sand blasted.

jmpm4619 (author)2015-06-02

Awesome job! Do you offer printing services? I would like to have something printed.

blockh34d (author)2014-06-09

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.

gtoal (author)2014-05-29

For someone who doesn't have a sand blaster, I suppose a rock tumbler would be too violent?

andreasbastian (author)gtoal2014-05-31

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.

Tumblers with natural materials seem like they'd work pretty well. I've seen people use walnut shells, cornmeal, etc.

1Vega (author)gtoal2014-05-29

not the same IMO

Claydiz (author)2014-05-31

What about a case tumbler?

simonrafferty (author)2014-05-30

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.

hazzalandy (author)2014-05-27

What are you blasting them with ( what abrasive)?

120 grit garnet powder. I'd be curious to see the impact of other abrasives though.

efahrenholz (author)2014-05-27

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.

Porda (author)2014-05-27

Great idea, I'll have to try this out on my next FDM print.

Jan_Henrik (author)2014-05-27

Very cool idea, i have never seen this before!

sheetmetalalchemist (author)2014-05-27

Might be awesome to try the ultrasonic cleaner too to get something more consistent without a lot of effort...super interested to see how that works. I haven't tried to pass this by the Pier EHS yet, but you may want to consider a mixture of THF in water to try and partially dissolve PLA (its been a long interest of mine actually), and smooth out the rough edges. If THF is too aggressive, also take a peek at its methylated counterpart - Me-THF...which also has way better water miscibility.

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Bio: Engineer, designer, and artist who develops and applies novel 3D printing technologies.
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