direct extrusion of PLA granulate

Hi guys.
I do not have very much experience in reprapping. I finished my first Prusa i3 though and I made a small clone of Jordan Millers Baricuda sugar extruder.

I just wondered I anybody ever tried to put granulate directly in a heated syringe an extrude it with air pressure. The air could take up more granulate from a stock bottle or something, like it is done in sandblasting. You do not have the issue of making a filament of old prints or plastic waste as Recylcebot etc. does.

So can you tell me if anybody ever tried that or if it would be worth a try?

Greetings, Hendrik

Don't try that, it's extremely dangerous.
WHEN it breaks, the air will send shrapnel and hot molten plastic flying in all directions.
You will experience debilitating pain!
You will be deformed, plastic surgery will be required.

Search images for "burn surgery" to get an idea for what can happen to your skin.

In a laboratory environment, I have pressure tested devices with high air pressure.
NOTE: it is preferred that water be used than air, water is much safer because it does not compress as much as air.
The device was inside a safety chamber.
Every engineer and technician left the lab on their own fruition.
No one wanted to be near it, even when it was inside a safety chamber.

I trusted that my math was spot on, and I wore my PPE

Hmm. I guess that might be an issue. But I don't imagine it very difficult to design it rigid enough that it won't break. I am printing sugar with 2bar overpressure in a glass syinge and it does not really make any problem. Maybe I should ask Jordan Miller if he ever tried it.
Since printing of PLA or ABS emits ultra fine particles, the printer should be in a fumehood anyway. Mine is, so I don't mind if my extruder breaks in first attempts.

The question is rather if you could reliably control extrusion with air pressure. So if you don't know of anybody who tried it, I will.

I'm guessing that you are probably going to need about 150 to 200 psi to push ABS through an 1.75 mm orifice.

I see. Then I totally agree with what you said and won't die in the near future (at least from that). Thanks.

See Makibox Ramen

[www.youtube.com]

greenman100
"I measured 150-200psi melt pressure when I was designing the Filastruder"
[forums.reprap.org]

I tried to do it and a pressure of 2-3 bar seems to be enough. The problem is rather that if the air finds a way out through the nozzle, you have a stream that constantly cooles the plastic and thus prevents it from closing the hole. So it is kind of intrisically unstable. Maybe one could fix that by heating the air somewhere before...