The result of my team’s senior design project this past semester. Be aware that this is effectively a proof-of-concept machine and while it works, there are plenty of bugs and deficiencies in the design we neither had the budget nor the time to address.
http://grabcad.com/library/ramrod-filament-extruder
I think a lead screw as the “Ramrod” would make it much more powerful and accurate.
The problem with a batch-based process like a piston would seem to be the length if the filament you can generate from a single piston full. How much would that be?
With respect to lead screws, it was an option but we went with a rack for a simpler and cheaper mechanism (three month and $500 limit for the whole project).
As far as the batch size, the machine can handle up to a full kilogram of plastic at once. The fastest processing speed it could hit with some of the improvements is 1 kg every 2-3 hours.
Right, so batch size is not really a problem. Any chance of an in-action video and/or some pics and/or measurements of the resulting filament? Particularly interested in the stability of diameter over the run.
Stability isn’t all that great at the moment. The machine actually extrudes too fast for our fan to cool effectively, which tends to result in necking once the strand gets above about six feet in length. If a second cooled section of the die was added, that may fix some of it.
We were able to do several test prints though, and when the filament was within tolerances it worked just fine. I’ll upload the video to of the test prints as soon as I can.
Awesome.