If you have an exposure time that works, you probably don’t need to fiddle with that. If you’re experiencing warping, you should increase your exposure time. More pigments is key though. With sufficient pigmentation, you can have almost infinite exposure times without creating overcure (and more importantly, less exposure doesn’t substantially improve overcure).
For instance if you take a look at this part:
You can see from the little nut nub that I printed this flat against the build plate, with horizontal and 45 degree overhangs near the blue arrow.
This is MJ G+ with extra pigment with 14 second per layer exposure (the default Kudo3D recommended). I’m a pigment fanatic now – it’s not complicated, I often just eyeball the darkness and estimate the volumes.
This brings up a second issue around printing flat against the build plate.
This is possible, and not that hard. However, you do need a big attachment layer (I aim for 4X the surface area of my part, meaning double each of the X and Y dimensions) and you need to cure the first layer pretty hard (like 75 – 120 seconds) and the first mm quite hard as well (around 30 seconds).
You also should lift slowly on high surface area layers. I have a part that’s around 170mm x 80mm, and I lift at 10mm/min for all the the solid floor/ceiling layers. On depicted part, I think I start at 15mm/min and then go up to 25 mm/min until I reach the lower surface area wall portion and take it to 40mm/min.