Saturday, February 20, 2010

Extruder design problems

Been a while since my past blog.  Its been quite a mission to get a working extruder built, but i'm nearly there.  The last stepper motor just did not have enough grunt and the MakerBot stepper I have  is reserved for Mendel, so i've bought one from MindKits, 2.3Nm or there abouts vs MakerBot rated 2.6Nm, good enough I reckon as RepRap suggests a minimum of 1.4Nm.

With the new motor attached I paced the bits I planned on using against the plate and motor.

This caused a few problems and I also realized that I also need a way of forcing the filament onto the pinch wheel, this resulted in.


Unfortunately I forgot to take with me to work the copper bracket which will hold the extruder, as such I forgot and drilled a hole where the bottom M8 bolt is.  How idiotic of me.  
The next day took the bracket with me and moved the parts around, and found a few parts lying around that were scrapped, plus a washer, so with more drilling I came up with.


This design enabled me to put in a spring loaded filament pusher, for lack of a better term, and I have polymorph around, and so moulded  some into a bracket for an M4 screw, washer and spring.
The location of the bracket was important as I want it far enough away from the copper bracket which serves a double purpose as a heatsink, and polymorph is malleable at 60 degrees.
The design also allows the filament to be guided into the pinch wheel for when it moves laterally on the wheel.

Though this is by no means a stretch from being completed, for one the bolt for the M4 filament pusher is too long, the spring too long, the M8 remaining bolt is too long, holes need to be drilled underneath and a bracket to lift up the copper bracket, how ironic, a bracket for the bracket.  the pinch wheel assembly also needs to glued together and onto the shaft, the plan for doing the pinch wheel to the shaft of the motor is to use 680 LocTite retaining compound, which from experience from work is extremely difficult to break, often requiring a butane torch directly at the joint for over a minute to be enough for over torque to break.

I am still trying to build this thing to the best of my ability, with hurdles around every corner, very limited funds to work on it, IE none since mid November 2009, and i've still got to get around to migrating the wine I have into a clean demijohn for its 6 month brew cycle.
Ah well, its all fun!

Hopefully, by March it will be up and ready for calibration, Z axis is waiting on the extruder to be mounted so that can be finished.