Sunday, March 7, 2010

axies aligned but...

well, worked on mendel last night and got the axies freed up but... now my z axis sprocket has wallowed out and will not stay tight on my stepper. gonna have to either print a new one or glue it to the shaft. oh well.

something that Im also working on right now is a positive displacement pump extruder. Its going to take a bit of machining but i have high hopes about getting this functional. For those that dont know what a pdp is its basicly a gear pump. take two gears and mesh them together inside a confined space with a inlet at one side of the pair and outlet at the other -->8-->. its how a oil pump in your car works, the oil or in this place plastic is moved around the outside with the gears and kept from returning to the inlet side by the meshing of the gears. Ill keep everyone posted on actual progress and when i have pictures ill post them.


  1. This pdp extruder, will that be a hot extruder?

    I'd be very much interested in such a device, particularly because it seems to make it possible to use cheaper feedstock (like pellets or powder).

    See also the screw extruder experiment (not a pdp):

  2. very cool idea, i look forward to seeing how it works out for you

  3. @reinout yes this would be a hot extruder. from the melt chamber all the way to the nozzel. one of the problems with the screw extruder is they are trying to head in the screw which works with continuous extrusion because the heat obsorbtion at the entrance by the new raw infeed keeps its temp below transition point, once a screw extrusion process stops moving the heat begins to equalize through the entire mechanism and will seize the screws every time. In hot melt glue machines they use a bidirectional pump sucking from the bottom of a melt tank so the entire process is kept at temp. Im currently working on getting ahold of one of those to use as a recycling machine (we had a dead one at work that was beeing thrown away but cant seem to find it now). but for a pdp system to work for actual extrusion it has to be realy small and have a melt chamber that holds aproximatly enough material to complete one layer posibly a little more.