Thanks! Yeah, I've got a bit of a thing for trying to figure out how to get the best possible results with a given tool, material, or process. Note, due to the nature of the printing resin it's very forgiving when I photograph it, hiding some of the worst surface issues that are all but inevitable with 3D printing. But, even those 'bad' spots are very subtle and reasonable given the high resolution of the prints.
In this case, the simple answer is that I'm printing at a layer thickness of 20 microns (0.02mm), which is my preferred height to minimize any noticeable layers, and the printer has an XY resolution of 51 microns (0.051mm). However, there is more to it than just that, as large flat surfaces provide a unique challenge. There was a YouTube video (How to Angle your Resin Prints for the Smoothest Surface Possible
) that I watched several months back that does a better job of visually explaining how it works, but it all comes down to some trigonometry.
arctan(Layer Height/XY resolution) in degrees; plug this into Google with the correct number that suits your printing situation, so in my case: arctan(0.020/0.051) in degrees = 21.412969, which I round to 21.41 degrees. Note that if the Layer Height and XY Resolution are exactly the same, then the prefect angle is 45 degrees. However, if the specs list the printer as having a 50 micron XY resolution make sure it's not actually 51 microns (like my Mars 2P) as that seems to be very standard in many printers these days.
So, any flat surface printed at 21.41 degrees to the build plate will print as smooth as it can possibly be if I'm using a layer height of 20 microns. The mixed blessing of this is anything flat facing away from the build plate will print super smooth, but at that low angle, anything facing towards the build plate will be slightly distorted even if you used the required forest of equally spaced supports to hold the parts securely so they print with the desired precision. That's the price you need to pay and since we're only interested in the outside of the model it's an obvious choice to design the parts to sacrifice the inside to get the high-quality outside surface.
This is something I'll be getting into more as the studio moves forward. I don't just want to make models, chop them up, and send them out into the wild for people to do their best with. I'm working to really understand the process and create designs that are intended to avoid printing pitfalls and produce the best possible results. It's something the studio will be showcasing in the demonstration models it produces and I'm glad it's already showing in this early prototype.