Saturday, 25 June 2011

Triple extruder gets a work out

Ok so i have been sort of using the triple extruder, when i made the hobbed bolt i mis-placed one of the hobbings and it doesn't align with the idle roller :(

but i have been able to use the other two feed paths of the extruder, i had some fun with nozzles and such but thats another post..

so basically the extruder works as far as i have been able to test, i have to make a little mod to actually have the material change to happen, so far i have had no cam shaft installed. i am starting to think my measurements are wrong..

i am learning how to use solid works so i will draw up what i have and animate the movements to double check things..

 i have two fans one to cool the heat that the entire extruder soaks up and the motors.
 then the smaller one with all the broken blades cools the print for the first layer and maybe bridging when it all works better.
 top down where the filaments run, only one in the middle path in place at the moment
you can also see the dove tail join that hold the extruder in place, and leaves it removable for when i need to work on it, its a bit tight and i have been hitting it to free it up... bad me :(
 here you can see where the cam shaft with a 40tooth gear on it would go in the bearing and across the tension arms/blades the cam shaft has 180' sections taken out @ 90' to each other, this leaves one position where they are all free or one is gripped by the hobbed bolt.

 this is the 20:1 reduction worm drivve that turns the hobbed bolt that is hobbed in three places 10mm apart

here you can see the micro switch that will run on the head of the bolt that has been filed to only have a lump where the cam shaft has all three springs compressed, thus all three filaments are free to be hand loaded or withdrawn if you need to change it is very easy.

when i built this extruder i used all the conservative numbers where i could so this unit is probably a little on the large side, i picked the positions of the fulcrum points by eye and what i thought the motors could handle not what they can handle.. stepper motors are very easy to under estimate... i could probably have gotten away with a smaller motor for the cam shaft, i think once i complete the rebuild i will have a better idea, maybe i will be able to make it printable. then others can enjoy this as well.

i lost a little print area when i installed the triple extruder but it was only 40mm in the X..
i need to replace the hobbed bolt some day soon.. i also need to install stronger springs to get better grip on the filament
you cant see it well but there is a hobbed bolt in there, its driven by the stepper on the right via a 20:1 reduction worm drive. the stepper on the right drives the camshaft the is not installed in this pic, you can see the bearing on the left above the 40 tooth gear on the left, i used two of these gears to move the camshaft up and the motor and its weight down.

one problem i had was that because my hobbed bolt is so far away from my heater barrels my filament bowed out and refused to go down the nozzle. this was easily fixed with a little brass tube from the hobby store, this was pressed into the peek block that i have holding my three nozzles, this extruder could easily be extended to accommodate more  materials with only a 10mm increase in over size in the X axis with my current install but that could also be taken from the Y axis.

my nozzles are made from 5/8th brass threaded rod that i machine down the thread off and wrap with kapton and nichrome wire. i use 100k thermistors. started out with 0.5mm and now want 0.25mm holes.. but thats another story.
 here you can see two nozzles installed but only one wired up with nichrome wire and thermistor.

So far this has been giving me good filament up to about 1000mm/min but i need to install harder springs and better hobbing to get better speeds, once i ditch the lead screws i will have lots more  speed in my movements and needs a extruder that can keep up..

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