A couple of my friends asked about quick tips for finishing up FDM parts so they are smooth and polished looking. I was more than happy to help, but thought that perhaps our industrial users may want an overview of some hints.
First, Stratasys sells finishing systems for FDM parts that include vapor polishing (where acetone vapor smooths the surfaces) and has a referral network to vibratory tumblers and media blasters for other types of smoothing besides sanding. Power tool sanding equipment ranges from Dremel tools to palm hand sanders, but many users complain power tools take off material far too quickly for careful finishing, so most tend to tick to hand sanding.
The parts that adapt to hand finishing best are parts that have a long area of “plain” features. For example, a part that is shaped like a cup would be ideal for hand finishing since there are not small cracks and crevices to try and dig into with a small tool to smooth out. The sides can be smoothed out and if desired, the part can be finished by painting.
First off, remove any support material that remains from the build. If the part will be painted later, you want to print in a color that is as close to your final color as possible. For example, if you intend to have a blue part, print the part using blue filament and after finishing paint in blue. You will find that your part may need little paint in those cases. Starting with your clean part use coarse grit sandpaper to knock off any obvious edges and defects and gradually move down to the fine grit sandpaper. (Start with coarse then move to fine line so – 100, 240, 400, 600, 1500, and 2000 and so on using what you have on hand.) If you have a perfectly flat surface that you are wanting to sand, a sanding block out of balsa wood keeps uneven pressure from your fingers from causing a divot on the surface. Between changes of sand paper washing or blowing off the surface with shop air will allow you to check your progress.
Once you have finished sanding and are looking for the final touches, you can polish the part with a plastic buffing compound. Note that if you are using a wheel or Dremel pressing too hard may cause heat build-up on the part surface. If you intend to paint the part, the part should be washed to remove all traces of grit, dirt or oil.
When painting the parts, make sure that the paint selected is compatible with the type of plastic you are coating. And, thin coats are much easier to control for gloss and drips than attempting to do a thick coating and short cutting the process.
On PolyJet parts, because of the superior surface finishes, you usually do not sand for finishing. On occasion, sanding is used to prep the surfaces for paint, but usually you don’t need to smooth and polish the surfaces. Ensuring the part is free of oil and dirt by washing is a good insurance policy to help assure paint adherence. Some customers prefer to paint matte surfaces and build with this finish and some gloss, but most are not painting. If you have the new J750 machine for PolyJet parts – decoration and painting is not needed – you can get the CMYK colors in and throughout the build by using our latest machine. Logos and colors can be transferred from VRML files and 3Dpdf files into the build data and the 3D printed parts look and feel like the product pieces.
Want more information on the J750 click here.