A bit of an introduction:

We are using the extrusion machine in the video as a main inspiration. We put a conveyor band at the end of the tube that is supposed to move the material once it’s out of the tube. But, we weren´t allowed to make plastic thread (yarn) for a 3D printer for example, so we thought of making kind of round solid bars, that could work, for instance, as the sticks of brooms, shovels, etc. or also in the school people learn to work on lathes with plastic bars so the final product could also help the school. Then, we also added a cooling box, were we put 8 computer fans (coolers) 80x80mm that are above the conveyor band and will serve to cool the material once it’s out of the extrusor. We are not planning to inject it since we couldn’t find an easy way to make it. The project has to be a model mainly, but if it woks it’s much better. The idea is that it would go out of the extrusor with the round shape and hopefully, if everything goes right, it would end in the final round solid bar.

We were planning to do it from PET plastic but since we have problems shredding the plastic we are having trouble to find it so to use it as our source of material. It’s somewhat expensive to buy it already in pellets so we have kind of a problem there.
We have come across some things:
Our concerns are about many things:
1) Since we can’t shred the plastic, what can you recommend us to do? Change the plastic? Whatever idea is welcome
2) Once the material is no longer in contact with the heat from the heaters, how long does it take to get to a mostly solid state? We need it to be formed with the shape, that would be almost enough. We also have the coolers that will help with that.
3) How can we do to get the round shape? Because, I guess that as the drill will be working continuosly, the plastic will get out fast, without getting the shape we need. Should we “block” the end of the tube in some way? So that some amount of plastic accumulates and then would it get out as we need?
4) Do you have any idea on how we could do to get a specific length on the bar? Should we cut it some way?
We hope you guys will be able to help us sail through these difficulties since we are a bit confused without the answers to the previously posed questions.