Smoothing 3D Prints

Smoothing out 3D print layer lines is one of the most time-consuming parts of building a 3D-printed droid. Over the years I’ve tried a number of different techniques, but the method I keep coming back to uses Bondo Glazing & Spot Putty thinned with acetone.

I mix the putty with enough acetone to create a brushable consistency, then apply it directly to the printed part. The acetone evaporates very quickly—usually within seconds—leaving the Bondo behind to fill the layer lines and other minor surface imperfections.

Once the part is dry, I sand it smooth to remove the excess filler while leaving the filled layer lines intact. At this point the surface is already dramatically improved, but I take it a step further by applying a high-build filler primer. My personal preference is UPOL Filler Primer, which does an excellent job of filling any remaining imperfections and creating a uniform surface.

After the primer cures, I wet sand with progressively finer grits until the surface is smooth and ready for paint. While the process takes time, the results are well worth the effort and can make a 3D-printed part look much more like a manufactured prop than a printed object.

Like most aspects of droid building, there are many ways to achieve a great finish. This is simply the technique that has consistently given me the best results across multiple full-scale droid builds.