New extruder method proposal

Hi,

This is a crazy idea from someone who has no experience in the field (me), who has not yet seen the plastic extruder in operation, and has no intuitive sense of the properties of molten PLA. But I've seen that the extruder puts strict limits on build speed and precision, and also requires a filament instead of more readily available granules.

I thought of this last night and I thought I'd post it here, before I forgot it.

Basically, you have a loop of some kind of braided wire/thread/rope, which is porous enough of a structure that hot PLA will adhere to it. This loops through a heated chamber of PLA, so that the rope becomes saturated with PLA. It then passes out of the chamber and over a heated disk/pulley (with a very small radius - it doesn't even have to be a pulley; it could be more like a blade). The PLA re-melts, is stuck to the substrate, and the rope loops back.

The advantage is that the PLA doesn't need to be under pressure, as it isn't being forcibly driven at a high speed through a narrow nozzle. It's just carried by a rope. So there's no need for high-torque steppers, or even for filament.

The disadvantage is that there's probably a hundred reasons why it won't work, which I invite you all to go ahead and point out!

[disclaimer: I haven't seen an extruder working yet either]

I think getting a consistent layer height would be very difficult, also the rope would stay full of plastic after depositing some, so you would have to heat the rope's whole path, or somehow design pulleys that still work when choked with solidified plastic.

Perhaps use a belt instead, and only putting plastic on one side? Even then you would have the complication of having to rotate the extruder so it rolls in the same direction as the head is moving.

Remember that the plastics are very viscous (like cold honey) at the temperature where they can be extruded without melting the previous layer or burning.

You would also need to take into consideration the thermal properties of your rope or belt. A plastic or nylon one may also melt at the temperatures of the heated PLA. Plastic or metal would both stretch at the higher temperature so
tensioning of the rope/belt could be an issue.