Summary

A printable replacement extruder for the printrbot plus V2. This is based on hammerFET's extruder and mixed with my Solidoodle mk5 extruder. Has all features required to attach belts, end stop screw, fan and hot end.

Instructions

The original laser cut extruder on the Printrbot plus is very problematic. It is big, heavy, hard to load up, easily to misalign filament and the passage below the hobbed bolt is too wide, causing frequent filament buckles and jams for me.

Instruction correspond to images.

Print the three parts at high infill for strength. Recommended settings are 0.2mm layer height, 50% infill and 3 perimeters.
Insert original linear bearings. It is recommended to wrap them in tape to ensure a tight fit and keep them aligned. Once in place, use a M3 bolt and nut to pull the carriage closed and trap them tightly.
The holes on the rear of the extruder are matched with the standard x belt tensioner. The other boss houses the standard x axis end stop bolt.
Secure the hot end with the original screws. The electronics plugs should face the left hand side.
Use a M3 bolt to secure the tension arm. Ensure it is tight but not so tight the arm can't pivot. Short M3 bolts secure the original fan.
Slide the extruder onto the 8mm x axis rods. Zig zag the x axis belt through the two holes at the rear and then use the wooden tensioner to tighten the belt properly.
The extruder stepper can now be bolted to the extruder, once again with the wires to the left. Plug everything in and tidy the wiring loom by wrapping it to the stepper. The upper filament guide bolts straight to the stepper with M3 bolts.
Use a M5 bolt to secure a 5x16x5mm bearing to the tension arm. Two washers can be placed either side of the bearing to center it. Slide on the filament drive onto the stepper shaft and align it with the filament bore in the extruder before tightening. A long M3 bolt with a matching nut and two washers tensions the arm. I used a spare spring but one of the original Wade's springs could be used it cut shorter.
Use Kapton tape on the extruder body behind the hot end to insulate it from melting. The z axis end stop screw may no longer be long enough, but one of the long screws left over from the Wade's extruder is an ideal longer length. Don't forget to wind it in to an appropriate length.
Two changes are needed in the firmware:
- The extruder stepper logic must be inverted now that it is direct drive.
- The extruder steps per mm will be far too large. My new setting ended up being 93 steps. Start with this, then request 100mm of filament through and measure how much actually goes through to adjust from there.

Printrbot Plus (v2) Replacement Extruder