Grinder Auger Design

Hello, new to the forum and I have a similar issue to another that I seen on the forum from the late erase42, but the previous thread never specified if he solved his problem...

I am trying to build a system that will grind large pieces of EPS foam and then melt the corresponding pieces. Attached is a rough sketch of the system we have built. Essentially, large chunks of EPS foam are put into the hopper and the grinder successfully breaks them into small pieces. An auger then picks them from the bottom of the hopper and moves them through the auger casing. If I do not close off the end of the auger casing the auger successfully moves the particles through the auger and out the end of the casing. The problem is that I would like to place heating coils onto the casing, melt/compact the foam to some degree and move them out of a smaller opening at the end of the casing. It seems that anytime I close the end of the casing off, there is not enough pressure to force the foam out of a smaller opening on the closed off end. This is the problem whether you heat the casing or not, essentially anytime you close off the end it just packs the 6" gap at the end of the casing and will never force any material through the opening. I have tried to even just taper down to a smaller diameter as well rather than just closing off the end of the casing but even then it just backs up behind the tapered down section.

I have never designed a system quite like this so I may be missing something basic, but my original thought was that as long as the auger continued to move it would create enough backpressure to force the material down to a smaller outfall.

I would appreciate any advice as to what I am missing or how to improve upon this!

Thanks,
Jake

Evidently, the auger is not creating enough back-pressure to force the material through your nozzle. That's probably due to a combination of factors. First off, the foam material itself is light and compressible. Once the auger threads are loaded with the stuff, it just sits there - there's no reason for more of it to enter the threads, the pile of it just floats on top. Second, your auger stops short of the nozzle; instead of the material being forced through it, it enters a chamber where it can just sit there like a traffic jam. It might be that an auger feed just won't work with this sort of material. Have you considered a piston instead? If you need a continuous flow of melted foam, perhaps a dual-piston assembly would work, with two barrels terminating in a single heated chamber with a nozzle. When one barrel is filled, the piston starts compressing the load and the hopper fills a second barrel. When the first piston is at the end of its stroke, it withdraws and the second piston starts compressing the load in the second barrel, etc.