Tuesday, July 29, 2008
Making CAPA Filament
I've been having trouble finding a CAPA or PLA filament supply, so today I did some experiments today trying to make CAPA filament from granules.
I created this:
It's basically the high pressure screw driven syringe with changeable nozzles. A nut is soldered into one end of a piece of plumbing pipe, and a pipe connector to the other. The wood contains a captive nut, a washer is soldered to the threaded rod to form a plunger, and the handle at the top is turned to force the plunger down.
The pipe is then dipped in boiling water for a few minuites so the CAPA melts, then the handle can be turned and this happens:
The nozzle I'm using has a 3mm hole in it, which created a filament of 3.4-3.5mm (pretty good consistency). I'm going to try making a nozzle between 2mm and 2.5mm tomorrow and see if I can get a 3mm filament.
See more pics on flickr
I created this:
It's basically the high pressure screw driven syringe with changeable nozzles. A nut is soldered into one end of a piece of plumbing pipe, and a pipe connector to the other. The wood contains a captive nut, a washer is soldered to the threaded rod to form a plunger, and the handle at the top is turned to force the plunger down.
The pipe is then dipped in boiling water for a few minuites so the CAPA melts, then the handle can be turned and this happens:
The nozzle I'm using has a 3mm hole in it, which created a filament of 3.4-3.5mm (pretty good consistency). I'm going to try making a nozzle between 2mm and 2.5mm tomorrow and see if I can get a 3mm filament.
See more pics on flickr
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Neat.
Keep in mind that extruded diameter is probably a function of extrusion speed as well, so keeping that constant may give you more consistent results.
Keep in mind that extruded diameter is probably a function of extrusion speed as well, so keeping that constant may give you more consistent results.
I had thought that could be quite a problem, but the i have to turn the handle quite a bit to get it to extrude so keeping the pressure constant shouldn't be too hard by hand, but i'm thinking about motor possibilities, connecting to a cordless drill is a possibility.
Probably around 8ml, but only about a 1/4 of this much plastic can fit in as granules.
I'm considering:
1. a longer barrel.
May have problem with friction
2. motorised piston going back and forth, with a hold in the side to feed in plastic from the hopper.
Getting a bit complex
Switching to an electric heater could work too, as my hot water method only gets the plastic to < 100^C, at which point the CAPA is still very thick
I'm considering:
1. a longer barrel.
May have problem with friction
2. motorised piston going back and forth, with a hold in the side to feed in plastic from the hopper.
Getting a bit complex
Switching to an electric heater could work too, as my hot water method only gets the plastic to < 100^C, at which point the CAPA is still very thick
Very nice!!! :)
I wonder if we could make a continuous process out of this somehow...
Perhaps some sort of centrifugal pump (http://en.wikipedia.org/wiki/Centrifugal_pump) with a hot impeller? The granules would be slowly droped (manually or automatically) in the center of the impeller, would slowly melt, and then be pumped out through a hole. We'd have to find a way to keep friction down between the molten plastic and any stationary sides of the pump, but maybe it could be done?
I wonder if we could make a continuous process out of this somehow...
Perhaps some sort of centrifugal pump (http://en.wikipedia.org/wiki/Centrifugal_pump) with a hot impeller? The granules would be slowly droped (manually or automatically) in the center of the impeller, would slowly melt, and then be pumped out through a hole. We'd have to find a way to keep friction down between the molten plastic and any stationary sides of the pump, but maybe it could be done?
I'd imagine it already does trap air. We really do need something like this for the extruder, though; going through multiple stages like this is redundant and, at this scale, hugely inefficient. The centrifugal pump idea is neat, but I don't think we could easily keep the friction between the outer walls and half-melted plastic down low enough, and you'd probably get granules mixed in with your output, which would clog the extruder. Instead, I think we could do something with a screw inside a heated barrel leading directly to an extrusion head, somewhat thermally isolated from its hopper to prevent half-melted plastic from clogging the pellet intake. A similar design has been tested without the thermal isolation, and worked until it clogged.
Great to see some 'real' work being done on a filament extruder
One issue that is raised whenever someone has ideas for an extruder is air bubbles becoming trapped, how 'bad' (or good) has this been with your design?
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One issue that is raised whenever someone has ideas for an extruder is air bubbles becoming trapped, how 'bad' (or good) has this been with your design?
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