These parts are to provide the means of mounting two PrintrBot Alu direct drive extruders to a PrintrBot Plus version 2.1 (1311) though it may work on older printers. This does not work for any Plus with the X-Z upgrade; I intend to do that to my printer in the future and then create a derivative of this for a X-Z upgraded Plus.

It also has plenty of 40 mm fan mounting places for cooling: 2 to cool the motor in the back, 2 to cool the alu extruder pieces, 2 to cool the ubis extruder, and 2 to cool the print job. You obviously don't NEED most of these but the holes are there for you to use. It also has slots to hold the M3 nuts for some of the fan mounts to make your job easier. It is easy to convert the design to use a single 80 mm for the alu extruder parts and the motor but I'm trying to keep the weight down by using 40 mm.

All the little 2-4 mm tall raised slots around the edges are for zip-ties to keep wires nice and tidy, something I'm always a huge fan of.

This will cause you to lose roughly 20 mm of X axis movement since it is wider to accommodate the 2nd extruder. You must program your max movement to be around 180 mm on the X axis.

The extruder offset is 37 mm on the X axis. This means its 37 mm from the center of the left extruder (extruder 1) to the center of the right extruder (extruder 2).

It is 17.45 mm to the center of the extruders from the 'support wall' along the Y axis. When I say 'support wall', I'm referring to the vertical wall behind the extruders where you mount the linear bearing sleeves. For reference, the center of the original wood based extruder is 15.76 mm and the center of the PrintrBot designed single Alu extruder is 17.4 mm both from the same wall.

You will likely want to slow down the printer with all this installed as the extra weight of a 2nd extruder + motor + hot end will make it shake more than it does. I've been able to print at 75 mm / s without issue but I don't see a point in going faster.

I always print all my printer parts out of ABS (because I don't have nylon or other more exotic filaments) and have the infill around 50% or higher. PLA may not like the temperatures the motors or hot end can get to when printing using this system.

I used four M3 15mm nylon stand-offs to mount the ExtrudrBoard next to the PrintrBoard within the boxed area in the bottom. There should be already-existing holes for it but I only used two of them as the other two would interfere with the y-axis belt system. The other two stand-offs were just to help maintain strength with plugging cables into the board.

You will likely have to re-flash the firmware on your Printrboard for it to print. My bot came flashed with firmware for 3 extruders and it would give Min Temp errors when I plugged in the ExtrudrBoard until I reflashed firmware set to two extruders.

I'm going to include the .hex file for the PrintrBoard firmware. It is pre-configured with a max X-Axis of 183 and set for dual Extruders. The PID's are set to what I use and they may be different for you. I also use M8 threaded rods for my Z-Axis so the Z-Axis steps may not be correct for you. I'm also including the SketchUp file for anyone who wants to modify it.