Hello Everyone

I've got a reprap Huxley and I'm Interested in modifying it to print very small objects, preferably with a feature size of less than 500 microns.

The main interest is to have the stage move in very small incriments, then to focus on a suitable extruder/patterning component to use with the stage

This post is to see what's out there atm.

Hmmm, I have read (that is all I have done yet) that the horizontal can go as low as .1mm (100 microns) and nothing smaller due to how the plastic is extruded so I suspect 100 microns x 100 microns is doable unless I missed something but have a lot of time on your hands as most print at .3mm (300 microns) slices for speed purposes (and I think .3 looks really ugly myself).

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

jump on the irc channel, last night we were printing the naked lady at really low layer heights eg 0.05mm, 0.01mm ,

OMG, really? 0.05 and 0.01?? What was the nozzle size and how did you pull that off as everything I have read and seen says .1 due to dripping and the way extruders work. I am excited as .2 is the highest I would ever go and it even looks really bad to my eyes.

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I await Skynet and my last vision will be of a RepRap self replicating the robots that is destroying the human race.

I have been contemplating this (the obvious imperfections of the repraps capabilities) for a few weeks now. I also REALLY want to print within the hundredth, so knowing if this will work, would be nice before forking out the cash and investing the effort of getting a bare extruder nut lasered to 0.05.

I personally think its possible to extrude plastics with a precision of .05 or more. The only issue would be with the extruder construction on a whole...the current extruder mechanisms are very "spacey" and dont allow for substantial compression. This may lead to the heated plastic flowing in the wrong direction.

I have a concept of an inverted screw (a hollow copper tube (or similar) with a winding on the inside (powered by a stepper, which could turn at a much lower rate due to the expulsion speed)) that could seal the flow in one direction, thereby increasing the compression in the heating chamber, resulting in expulsion out of the hotend. This idea is not even on paper.

At any rate, this extruder method wouldn't be usable with interchangeable filament sizes. Also it wouldn't be on par with the reprap moto (self replication) as, the extruder would have to have a continuous sealed chamber between hot and cold end which presents the issue of cooling (with the only solution I can conceive may be to use printed ceramic parts (currently not sourcable within the reprap community)).

Again in concept its unclear as how much of the extruder assembly will be affected by the heating chamber and the above mentioned "screw type feeder"

As you can see the conundrum continues.

Screw feeders themselves are not nearly as consistent as filament extruders, in my experience. There is a huge amount of resistance from the plastic, which can bog a motor down if its not torque-y enough. Variances in the screw feed will, obviously, affect how much plastic is extruded. You also have to have a nigh-perfect seal, else you get air bubbles that, again, affect how much plastic is extruded.

That being said, I have only worked with plastic flakes/pellets. You seem to be suggesting to use a screw to pull the filament down instead of the hobbed bolt, if I'm reading it right. Wouldn't that give issues with the filament twisting and tangling while on the spool?

Indeed