FDM Post Processing

Everything you could ever need to know about post processing for FDM printed parts is right here. ” FDM 3D printing is best suited for cost effective prototypes produced with short lead time. Layer lines are generally present on FDM prints making post processing an important step if a smooth surface is required. Some post processing methods can also add strength to prints helping to mitigate the anisotropic behavior of FDM parts.”

This article discusses the most common FDM post processing methods so you can optimize your work flow. Topics covered: support removal, sanding, cold welding, gap filling, polishing, priming & painting, vapor smoothing, dippy, epoxy coating and metal plating.

“Support removal is typically the first stage of post-processing for any 3D printing technologies that require support to accurately produce parts. Support can generally be separated into 2 categories; standard and dissolvable. Unlike the other post-processing methods discussed in this article support removal is a mandatory requirement and does not produce an improved surface finish. Glass storage containers, like a mason jar, make excellent vessels for dissolving with Limonene. For dissolving in water, any non-porous container will work. For HIPS/ABS prints, a bath in a 1:1 ratio of (R)-(+)-limonene and isopropyl alcohol works very well for rapid support removal. Many other support materials, such as PVA (used with PLA) and HydroFill (PLA and ABS), simply dissolve in plain water.

Pro-tip: Speed up the dissolving time of soluble support material by using an ultrasonic cleaner, and changing the solvent solution once it becomes saturated with dissolved support material. Using a warm (not hot) solvent will also speed up dissolving time if an ultrasonic cleaner is not available.”

“Sanding should proceed up to 2000 grit, following common sanding graduations (one approach is to go from 220 grit to 400 grit, to 600 grit, to 1000 grit and finally 2000 grit). It is recommended to wet sand the print from start to finish, to prevent friction and heat build-up from damaging the part and keep the sandpaper clean. The print should be cleaned with a toothbrush and soapy water, then a tack cloth, between sanding gradations as well to prevent dust buildup and “caking”. FDM parts can be sanded up to 5000 grit to achieve and smooth, shiny finish.

Pro-tip: Always sand in small circular motions evenly across the surface of the part. It may be tempting to sand perpendicular to print layers, or even parallel to the print layers, but this can cause “trenches” to form the part. If the part discolors, or if there are many small scratches from sanding, a heat gun can be used to gently warm the print and soften the surface enough to “relax” some of the defects.”

This was only a fraction of the information provided in this guide. Read the full article here to access everything from cold welding and gap filling to priming & painting so much more.

Categories: Design & Process