I wanted a better knob for the control panel on my Prusa i3 MK2, but none that I found on Thingiverse were quite what I wanted. I designed this version with two main advantages over others. First, it has a four-point star shape that comfortably accommodates your right thumb for navigation without looking away from the screen (with a recessed center area for clicking the current selection). And second, the back side has a flexible socket patterned after the original Prusa knob, which makes installation much easier than a simple hole on the back. In the sample shown, I changed filament near the end so that I'd have a contrasting ring in the center button area.
Because this part is relatively small, I opted for much more infill than I normally use on larger items. The 35% infill provided plenty of support for the concentric rings at the top. A smaller infill percentage might work just fine, but I haven't tried it.
Due to the fine detail on the first layer, I found it helpful to print layer 1 at half the speed of the normal, already slower first layer. Also, a layer of glue stick on the build platform helped the details stick well. Once the second layer started, I cranked the speed back up to 100%, and the printing was easy after that.