This is my attempt to make a drop in cover for the hole underneath of the heated bed in the Monoprice Mini Delta Printer.
Print this on top of a glass bed. You will probably not have a good ring around the cap if you do not. The gap between the heating area and the frame of the printer is so small that I could not make the ring as thick as I would like.
You might find it easier to open the bottom and pull the heated bed wires into the electronics compartment to help you put the cap in place (with the pointy side facing the bottom of the printer) and get the heated bed secured.
Do not use support material. That would cause problems. I designed the part to not really need it.