- For detailed plans for building a support extruder tool head, see SupportExtruder 1 0.
One of the biggest limitations on the geometry of parts that can be printed by Darwin and Huxley is the fact that the extruded molten plastic needs some sort of support under it to stay in the place it was printed. This limitation is the reason many parts produced on a RepRap have "teardrop" rather than completely circular holes.
A "support extruder" removes this limitation, allowing practically any possible geometry (within the resolution limits of the machine) to be produced.
A support filler extruder would most likely take the form of a Syringe Based Extruder.
It would extrude a material that is easy to remove once the part is finished yet provide enough support to print properly.
-- Main.ZachSmith - 11 Feb 2007
sodium acetate dissolved by water supporting any plastic
One idea for a support filler extruder would be to use a supersaturated solution of sodium acetate, which crystallizes very fast on shock.
One advantage would be easy removal, since soaking the finished object in hot water would dissolve the acetate very fast. The disadvantage is that it is extruded as a liquid, making it hard to control, and that it must be kept heated from the container to leaving the toolhead.
Polyethylene glycol (PEG) is another a potential water-soluble support mechanism.
PLA dissolved by propan-2-ol supporting ABS
oil dissolved by soapy water supporting any plastic
The Huxley page briefly mentions the possibility of an "oil pen", presumably used as a Release Agent between the desired solid plastic part, and scaffolding made out of the same plastic. (In some cases the scaffolding needs to be cut into several shards to make it possible to remove from the desired part. The same release agent that goes between the desired part and the scaffolding also goes between each shard).
What would happen if you took a very low melting temprature plastic, and a very high melting temprature plastic? I found a plastic that melts at only 60 degress. If you take it up to 90, maybe it will "run out" of the model. Its just an idea. In RepRap style, it is reusable.
Simply print it, stick it in a container with hot water, turn it around a few times and take it out. However, i am not sure how "runny" it is and how quickly it would leave the model, nor how it would support the model. It might be melted by the high temperature plastic on top when it is added. :?