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We are attempting to print some single-use prototypes using an SLS printer. The parts must be somewhat water-resistant for short-term usage, but do not have to been waterproof entirely.

According to this page, Post processing for SLS printed parts - Water tightness, any silicone type or vinyl-acrylate sealant should work well, but I was hoping that the Stack users here might have some specific suggestions.

Does anybody have specific recommendations for sealing SLS prints?

Trish
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JPeroutek
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  • I think it's going to depend on two things: what is the material made out of (for the print) and what are you trying to seal it against? Water is going to be different from alcohol which would be different from oil. If you wanted to seal it against acid, that'd be an ever bigger challenge. – Pᴀᴜʟsᴛᴇʀ2 Oct 17 '19 at 18:15
  • All of these prototypes will be tested in water. Further prototypes will be constructed of cement and used with an oil-based fluid. Material is “Versatile Plastic” from Shapeways. I believe it is a Nylon. – JPeroutek Oct 17 '19 at 18:20
  • clear spray acrylic sticks to most things and is completely waterproof once dry. – dandavis Oct 17 '19 at 18:23
  • Most SLA resins are water resistant, while nylon SLS could be dunked in resin to get it into all the print. – Trish Oct 17 '19 at 18:27
  • @Trish Wouldn’t a resin bath require a UV laser to harden it? We opted to use SLS over SLA due to a 300% price difference. – JPeroutek Oct 17 '19 at 18:30
  • @dandavis Something skin to this? https://www.amazon.com/dp/B001K65K26/ref=cm_sw_r_cp_api_i_KYiQDbZ2BCYNR – JPeroutek Oct 17 '19 at 18:34
  • @JPeroutek no, most Resins are actually not UV curing: Most resins that are mixed with hardeners, which then could be used as coating. Epoxy, polyester and Styrene-acrylonitrile Resins are such options. Another option could be Polyurethane. – Trish Oct 17 '19 at 18:35
  • yes, that would work, but seems vastly overpriced. Rustoleum clear "spray paint" is the same thing, but imho, better than krylon, who seem to be marketing it as something more special than what it is, clear coat, that you can buy for $5/can at walmart or home depot. Clear nail polish works too btw, i use it as conformal coating in outdoor projects. – dandavis Oct 17 '19 at 18:35
  • @Trish some of our geometries are quite small, with around .6 mm gaps that need water-proofing. Picture a small 1” diameter fan with about 15 overlapping tilted blades. Will the resin block those fluid paths? In my experience, epoxies are very viscous thick fluids. – JPeroutek Oct 18 '19 at 17:27
  • @dandavis Perhaps repost your comments as an answer? – JPeroutek Oct 18 '19 at 17:33
  • @JPeroutek it could, but the viscosity is dependant on the ammount of hardener and the exact mixture. Some resins change viscosity based on temperature. 0.6 mm is very tiny though... 1 component Resin-laquer, thinned a little, could be an option. – Trish Oct 18 '19 at 17:57
  • @Trish could you possibly submit that as an answer? – JPeroutek Oct 19 '19 at 01:44

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SLS prints from nylon are somewhat porous. This means, that they will let a stabilizer soak into the outer surface to some degree.

What kind of stabilizer is needed is depending somewhat on the properties you want, but generally I believe these might be useable depending on the viscosity:

  • 2-component resins could be used, but they are usually very viscous. Their viscosity, however, is dependent on the exact type and mixture and could be altered by temperature.
  • 1-component (air-hardening) resins or resin lacquers can be thinned to achieve a solution into which the item is then dunked and dripped off. How much thinner is adviseable depends on the exact material
  • Nitrocellulose lacquer, like it is used in guitar building, is extremely fluid and could be used for treatment via dunking.
  • PU lacquer could be used too.
Trish
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