About 7kg of filament later and lots delightful prints with the BCN3D Sigma we noticed that ground filament and dust had accumulated on the extruder feeder gear. Perfect opportunity to clean the filament feeder by taking it apart, checking out how it is engineered and learn a bit more about the Sigma!
Here is how we did it step by step.
Step 1. Unscrew the socket cap screw shown below to release the bottom Bowden tube. the printed part holds against a nut which is screwed on the tube. Simple and effective!
Step 2. Unscrew the 2 nuts holding the stepper motor board shield and unplug the stepper motor. Try not to lose the tubular spacers! Take them out and store them safely.
Step 3. Remove the top Bowden tube from the feeder by pushing down on the grey ring and pulling the tube out . Then unscrew the nuts holding the stepper motor bracket on the frame. Remove the feeder from the Sigma.
Step 4. Now start taking the feeder apart. Unscrew the large grub screw and remove the tension adjustment spring. Then unscrew the 3 long hex screws which hold all the parts on the stepper motor.
Step 8. Dissemble the feeder and clean all the parts from filament grindings and dust with a small brush. A toothbrush will also do!
Step 9. Reassembly time! Start by placing the aluminium bracket with the bent part facing towards the cables. Then the plastic spacer and pinch levers as shown below.
Step 10. Insert the tension spring through the hole of the top lever and screw in the large grub screw to compress it. In my experience 1 turn after the top of the screw is flush with the lever surface give a good starting point in terms of spring tension.
Step 11. Take the feeder back to the Sigma and fix the bottom Bowden tube on before mounting on the frame, makes life easier! Then slide the feeder on the studs of the frame and fix it in place with the 2 nuts. Connect the motor back to the driver. IMPORTANT! Don't forge the spacers!!! 2 on each side of the board.
Step 13. Fix the aluminium stepper driver shield back on and insert the top Bowden tube. Done! grabs beer...