The idea behind this cold end is that it too is well placed behind the sheet metal. Here is the inital concept. Because this printer will eventually have two extruders, it was important to build them in such a way that fillement could be fed from either side. This is because the extruders will be mounted on each side of the printer. This can be best shown in the Solidworks rendering below.
Note the location of the light gray stepper motors to each side of the main geared stepper motors. These are the locations for the extruders.
The hobbed gear is purple in the rendering above. The bearing carrier is green and the main block is the brown part. Notice the small hole in the main block. This is where the filemant will passes through. There is an identical hole on the other side resulting in the feed direction being reversable. This cuts down on the number of different parts that must be designed and machined.
Machining the bearing carrier.
The stud and the bearing carrier are all one part. This decreases complexity and also the number of parts made.
The main block with the bearing carrier installed.
Resting on the stepper motor. Note that the bearing carrier is upside down in this picture to better illustrate the assembly.
This is the proper orientation for the cold end. The carrier is pushed from right to left against spring compression in order to load filament. There is a spring pushing against the central post which returns the bearing carrier and maintains compression on the filament. It is adjusted through the use of a set screw. The NEMA 17 stepper motor is mounted using an L bracket purchased from Phidgets.
And finally, here is the cold end mounted to the sheet metal. Four 4-40 bolts are used to hold it in place. The compression adjustment set screw is more clearly seen in the picture above. The other cold end will be mounted in the mirror position on the frame. Though the holes for the filement to pass through have not been drilled yet, they will allow the PTFE tubing to pass behind the geared stepper motors and come around from the opposit side, maximizing lenght so that the filament does not experience too sharp of a bend on its way to the hot end.