This is a simple design for holding a typical 30A 12V power supply under the bed of a Kossel printer. Print two long ones and two short ones. I recommend locating the power supply as far as possible to one side or the other, leaving the maximum amount of room for the micro controller. I locate my power supplies on the right hand side under the bed, and I also trim a little bit of the aluminum at the back right hand corner of the power supply, to get it closer to the side. This design works with 1515 extrusions. I've modified Johann's bottom frame corners/motor holders to be taller, so that these power supply holders can be bolted onto the top side of the bottom horizontal extrusions. Here is a link to my KosselPlus printer design: http://www.kosselplus.com/