This is a remix of the support pylon for FDM_Guru's excellent X Gantry Support System for the Monoprice Select Mini 3D printer.
It appears that there are now variations in different releases of this printer, as the dimensions for the original part differed substantially from my own printer ordered from MP on 2016-09-15. Issuing an M115 gcode on my printer returns the following information:
NAME: Malyan VER: 2.7 MODEL: M200 HW: HA02
The model is now exactly 120mm across which just fits the MP Select Mini 3D's build plate. This version has been extensively tested and aligns perfectly with the hole patterns on my printer.
This part is a reinforced bolt-over support pylon for a 6mm linear shaft. The panel thickness has been increased to reduce/remove flex, additional support has been provided by extending the part forward to one of the front screw mounts, screw holes have been recessed to fit the factory screw heads, and the pylon has been moved in order to fit my printer. The bearing holder has been extended to hold both bearings securely with two zip-ties each, and has an added lip around the front side of the gantry to constrain the part's placement and to provide additional rigidity.
I've created modified mounting pieces compatible with 3dkarma's Raspberry Pi Camera Mount. Both pieces provide zip-tie mounting to the bearing holder bracket, allowing you to attach accessories (such as the rPi camera) to the gantry which will move with the Z-axis. This is helpful for webcam monitoring of print progress as the camera will move vertically with the print as it builds up from the plate. The zip-tie mounting allows the placement of up to 8 arms on the gantry.
This build will require a pair of 6mm LM6LUU linear bearings and one 6mm x 300mm linear rail along with a pair of 8mm M3 screws + nuts to lock the linear rail into place on the support pylon (optional).
All credit goes to FDM_Guru for the original idea and for working through the dimension problems with me, janbbeck's idea to provide additional support, and 3dkarma for the camera mount.
Printed on the MP select mini 3D using eSun PETG. All parts have been designed and oriented to print without support, just position them on your bed and hit print!