I am planning to try printing in other materials, using ideas based on the Baricuda.
Put simply, it is a heated syringe full of stuff, and a source of compressed air.
I am wondering what is the best, or the easiest way of driving the airflow.
I’m thinking two solenoids, one to connect the extruder to the pressurised air, the other to release the pressure. If it is found to be necessary, it could open a valve to a reduced pressure atmosphere, which would give us some retraction.
It may want a third, to drive the compressor pump, but that could just use a pressure switch.
My question here is of how best to convert the g-code into suitable signals for the solenoid: they are of a different nature to a stepper motor.
One option would be to insert a simple microcontroller chip, such that as far as Klipper is concerned, it behaves like a normal extruder.
Probably it is easier to add some suitable code to Klipper, but I don’t know where to start with that…
Possibly somebody has already done it, and my extensive search has simply failed to find it…
Personally, I do not think that such a system can be controlled reliably.
Air is compressible and has a spring character, so a extrusion based on this will likely be a pain in the neck. And apart from this “pain”, you would need a software that has the algorithms to deal with such. I do not know if there is any.
If you go into such direction, I’d search for a spindle / lead-screw / stepper driven syringe approach. What you extrude is incompressible as well as the drive part via lead-screw is incompressible so you again have a direct relationship that can be controlled by “traditional” means.
There are multiple methods used for managing the air and material extrusion, none of which are trivial to implement. The most successful method seems to use “micro-pulses” of compressed air (which seems to be analogous to step pulses to a traditional 3D printer’s extruder stepper motor).
Honestly, the method that seems to be more appropriate for medication - loading a syringe full of liquid material seems limiting for 3D printing as I don’t think you’ll be able to store enough in a syringe for printing a model of any kind of size and replacing the syringe or reloading it automatically seems like it’s more trouble than it’s worth. I think the method used in the first image above is for making custom tablets for somebody to swallow.
All typically use the same principle of applying the needed force with a stepper and some kinematics. Something which is rigid and controllable and would work with standard 3D printing hard and software.
I think maybe you should try icing a cake…
Also, I think it almost certainly depends on how precise and accurate we want the results to be. It may not be as precise as a traditional extruder set up, but it might be good enough
Ok, so what breaks if it fails?
In a traditional extruder, all that breaks is the traction between the motor and the filament, whereas in the setup you describe, it would have to strip the threads or break the syringe.
Besides, I think it would be a lot more complicated for minimal benefit.
I’m using a 50ml syringe. That’s roughly equivalent to 20m of 1.75mm filament.
If we’re using compressed air instead of the plunger, there’s room for about half as much again.
That’s more than enough to experiment with.
