Wednesday, 12 October 2011

Triple Extruder Cold End Prototype BNZII

I have completed a yet to be tested prototype of the BNZII coldend.

this is what it has turned out like it. i have taken nicely out of focus pictures of it from all sides i will try and explain whats what.
here you can see the two stepper motors the one on the left drives the filament via the hobbed axle.

here is a top down shot, you can see the hobbed axle, and the three idle wheels that run in the hobbed can't really see it here but the springs push down on the levers which then press the idle wheel against the hobbed axle.

 not much more detail here, but you can see the same drive system for the camshaft as the filament. 20:1 reduction via the worm drive and spur gear.
 here you can see the camshaft on the left the top lever is engaged to grip the filament this is done via a groove making a low spot in the camshaft this lets the tension from the spring pivot the lever or arm and presses the filament onto the axle. roughly a 1:1.3 ratio (x1.3)

 the middle lever is engaged to grip the filament, i thought it was much easy to work on a low spot to release the spring tension onto the drive axle was a better way to do it, allows the filament not to be exact 3mm.

 this is the bottom lever engaged. this extruder can be modified to take a 1.75mm filament really easy. change of bolt and idle rollers and your ready to roll..

 here all the levers are in the released state, you can turn the camshaft in this state by hand really easy as i have use 7mm OD bearings for each of the camshaft lobes to run on. costs a little and adds a little thickness to the design but i have doubts if the hotend can keep the three nozzles at three different useable temps, two plastics and a fill material may have wide temp differences! i don't know...yet

another shot from another angle, this thing was a PITA to put together in may lap on the couch so with a vice it will be much easier.. here you can really tell its a prototype you can see the hotglue that holding the bearings in place, its just keeps them from sliding out of the holes they live in when it was being handled... its not really structural when required i will epoxy in new bearings and the next one will have 6mm walls for the bearings to live in. when i next need to pull it apart i will take photo's that are in focus and that include the internals. cant wait to get onto the hotend, i cut the brass last weekend its a little over 10mm thick at the moment but i have 3/6 machined edges to go off, will need to get these CNC'd and or water cut but that should be no problem.

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