Topic Tag: PET

We are a group of students from Argentina who are working on a recycling project based on one of your videos (the extrusion machine). I'm one of the members of the group, out of 6. A bit of an introduction: We are finishing a technical school and so as it is the final year we have to make a project with some automation (we use Siemens PLCs the school lends us for that). At the beginning of the year, more or less in March, we decided we wanted to collaborate with plastic waste and looking on the internet we came across Dave video on the extrusion machine. So, we made our best to adapt it to the requirements we are asked for. It's because of that we couldn't add the shredder into the hopper since it was really complicated for us to get the razors. As you may know, Argentina has some expensive prices in things like that so we had to give up on that idea. We were requested to add more things so 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 we 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 luckily 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 of course much better. Of course we are doing our best to make it work. 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) We have an electric motor that is around 200 RPM for the drill that will move the plastic, Do you think that is right? Or we should look for one that is slower? We were planning to connect it directly to the drill so that we don't have to do any kind of transmission with chains, etc. 3) We couldn't find a 34mm diameter tube as the one used so the best one we were able to find is a 25.4mm (1 inch) tube with the thickness being 1.2mm leaving us with 23mm as the interior diameter. It's like 50 cm long, are we good with two 150W band heaters? The drill we are using is 45cm (18") long and it's diameter is 22mm. 4) We are looking at the band heaters, and they are quite expensive, we can afford them if there's no other way but we would prefer if we didn't have to, do you think there's an alternative? For the ones we found, this is the data: 35mm internal diameter, 30 mm wide, material: galvanized iron, Power 150W, Voltage: 220V Are they right for melting the plastics? 5) Also how long should we have the band heaters switched ON, heating the tube to start the extrusion process? 6) What temperatures do we need for working the plastic? 7) 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 if everything works right. 8) For what we are going to do, should we make a nozzle or something like that? Do we need one? 9) 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? 10) Do you have any idea on how we could do to get a specific length on the bar? Should we cut it some way? 11) In case we find them, should we use the same electronics that they used in the video? I mean the thermocouple, the controller, etc. 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. I will keep you informed of our progress, hopefully it turns out great! Greetings from Argentina!