3D Print Smoothing Made Easy with New 3D-CMF Process from Waseda University

I admit that I actually kind of love print lines. I think it’s really neat to be able to see the grooves that indicate where each layer of filament was laid down to create a fully shaped object out of nothing more than plastic string. My 3D printing has mostly been for fun, though; I haven’t done anything more than print a few little figures and small household tools. If I were to start 3D printing as a commercial artist, however, I’d probably feel quite differently about print lines, along with all of the other annoyances that come with at-home desktop printing in particular.

If you’ve ever tried to smooth a print, you know how much time and effort goes into eliminating those print lines. Sanding until your wrist hurts and there’s dust everywhere, or trying not to breathe in the toxic chemicals that can smooth your prints but might burn a hole in your hand (okay, perhaps that’s being a bit dramatic). You’ve undoubtedly wished that there was an easier way – and thanks to researchers at Waseda University, print smoothing may soon be as easy as coloring with a marker.

3D-CMF conceptual illustration.: A shows printed surface with no smoothing; B is first step using the pen to reduce high spots; C shows the progress as high spots are further reduced and dissolved material fills in low spots; D shows how difference between high and low spots is reduced for much smoother surface.

The tool developed by Waseda University’s Kensuke Takagishi and Shinjiro Umezu reminds me of one of those spot-removal pens that you can apply directly to your clothing to remove a stain – only instead of dissolving spaghetti sauce, it dissolves resin. The researchers named the process 3D Chemical Melting Finishing (3D-CMF), and it’s simpler than it sounds – the pen-like tool is used to selectively apply solvent to a finished print in as small or large an area as you choose. The solvent in the pen melts the raised ridges, and the melted resin then fills the indented grooves to create a smooth surface.

“By controlling the behaviour of this pen-style device, the convex parts of the layer grooves on the surface of the 3D printed structure are dissolved, which, in turn, fills the concave parts,” the researchers explain. “The layer grooves are thus smoothed. Using this pen-style device, a localized removal of the layer grooves in 3D printed structures is possible, and the amount of solvent used can be kept to a safe level. Unlike polishing, as this method does not need to shave the materials, it does not create dust.”

The ability to be selective with the application of the solvent is key as well. Other chemical smoothing treatments can have the unfortunate side effect of blurring or removing details, while the pen application system lets the user carefully work around fine details.

In addition to smoothing, the researchers were also able to successfully use the 3D-CMF method to fill cracks in printed pieces with melted resin, repairing and strengthening the parts; in fact, 3D-CMF treatment led to stronger printed parts in general.

Comparison of printed surface before smoothing (1), with smoothing by conventional methods (2) and by 3D-CMF (3). CMF result (a-3) is more uniform than polishing (a-2), and b-3 shows CMF better preserved surface detail than b-2 (solvent vapor).

“By observing internal changes in the 3D printed structures made by 3D-CMF, we confirmed that the effects of 3D-CMF are not limited to improving the surface roughness precision,” the researchers continue. “Thus, by analysing the materials of the surface layer changed by 3D-CMF, we measured the depth of the 3D-CMF effect on the 3D printed structures. We compositionally verified that the quality of the 3D printed structures was changed. The examination of the mechanical characteristics of the 3D printed structures after 3D-CMF treatment confirmed that this treatment produced 3D printed structures which more resistant to deformation.”

The research was documented in a study entitled “Development of the Improving Process for the 3D Printed Structure,” which you can read here. Discuss in the Waseda University forum at 3DPB.com.