Saturday, July 09, 2005
While I remember, I was thinking about a possible enhancement to one of Vik's ideas for using a threaded rod (or bolt) to draw feedstock into the extruder.
The main purpose of this is to eliminate the need for bending the feedstock rod. In fact by slanting the thread by the same angle as its pitch, then the force drawing the feedstock downwards may be more efficiently applied (as in the diagram, the threads end up being completely horizontal). To get more angle, you could slant the threaded rod at twice the thread pitch and still be no worse off than having it completely vertical.
By also facing the low ends of the threads towards each other, it leaves more space for gearing to drive the threads. It will probably require bevel gears to make this work nicely. The downside is that this will also produce a sideways force, but the rod needs to be passed down a tube in any case so this will keep the feedstock moving vertically only. At the same time, with the thread in the right direction, there is also a sideways force in the opposite direction. [Do they come close to cancelling out?]
The points in the diagram marked with a * indicate a point where a bearing or bushing is required.