Can I print an object with thin walls? Most specifications for 3D printers show that the minimum wall thickness should be 1 mm.  We printed our object using Selective Laser Sintering with Nylon12 through an online service, and although it looked great, it did not work as expected.
We are hoping to try the print again with a 0.5 mm wall.  What is the best printing method that offers the strongest model for this wall size?
We also found a service that offers even smaller wall thickness - does anyone have any experience with this?
We were also wondering if we could do post-processing to make it stronger - such as metal plating.  Would this work on thin models?
The test print in your question used an SLS printer. The other common alternative is FDM.
For narrow outer walls with FDM printers, you want to think in exact multiples of the nozzle size. Furthermore, unless the printer is well-tuned, you usually want at least two rows for the outer wall. Otherwise any flaw at all in the outer wall leaves gaps or tears in the final print.
Given most printers use a 0.4 mm nozzle, this means the typical minimum wall thickness is 0.8 mm. I use this number fairly often with good success.
If you want 0.5 mm you could step up to a larger 0.5 mm nozzle and give it a shot with only one row. But again, this will end up with flawed prints unless the printer is very well tuned and assembled, and if strength is one of your concerns it will be significantly weaker. Or, you could step down to a 0.3 mm or 0.2 mm nozzle and use multiple rows. Neither of those sizes will give you exactly 0.5 mm, but they can get you a smaller thickness than the 0.4 mm nozzle, at the cost of longer print times.