This project seems good!
When looking at the design under the sub category "Fully Built:" I noticed that the Z-axis is just two screw rods (looks like M8) with smoothed rods (looks like M5) that it slides on. There is nothing on the top keeping the rods straight/ preventing them from bending slightly. This could cause misalignment in the Z-axis over time and lead to inaccuracy. The Z-axis moves incredibly slow but over a long period of time this could possibly become a problem.
IS this something you have noticed when testing?
Also the custom controller board, are you planning on using the El-cheapo step down converter for the final product? I’m assuming that you’re using it to power the raspberry pi, the rip’s max current draw is 2A and the step down converter is designed for up to 5A. El-cheapo step down has a terrible efficacy, best case scenario its 80%. The reliability of this step down converters isn’t the best and drawing a high continues current at a low efficiency will result in a less reliable DC-DC.
Have you tested the long time use of it?
Other than these small nitpick I think that you’ve done a real good job designing it!