Wednesday, December 24, 2008
This setup is made with a 2" flat washer sandwiched between two 3/8-16 square bolts on the heater barrel. In the flat washer are two M3 holes which will be used to hold the heater a specified distance away from the extruder body. Basically, the air has become our thermal break thus changing the slow thermal gradient to a very fast thermal gradient.
I then threaded the ABS filament down through the pump body and into the heater barrel assembly. I was sorta doubtful about this setup, it seemed too easy, and I was right.
Upon initially heating up the barrel, the filament had a tendency to pull to the side once the plastic got warm enough to deform if there was any lateral forces cause by misalignment or by a curvature in the filament itself. This isn't a show stopper, however, because a guide can be constructed to hang down from the extruder to align the filament a few millimeters form the heater opening.
Once the heater got up to temp--which took longer and required more power due to the huge increase in surface area presented by the nuts and washer--I turned on the extruder and this is what happened:
Perhaps just a nozzle and with a heater around it. Then a short section of PTFE or PEEK and then an aluminium heatsink. Stainless steel bolts through the lot to hold it together. I will try that over Christmas.
I would really like to eliminate the PTFE or PEEK altogether as it is not a common item.
Looking forward to seeing your progress.
It seams we had some similar ideas at the same time.
On the plus side, one foot of tubing would be enough for a few extruders. On the downside, since it is just a tube you'd have to somehow put the teflon tube fully supported inside something else and mate it carefully to the heater barrel.
I'll take a look at your post.
the idea is to have a very short temperature transition zone-- on commercial machines, on the order of 1/2". this keeps friction to a minimum while keeping the incoming filament stiff.
I have seen several people use heaters to keep the build platform temp elevated to minimize shrinkage. Perhaps a stream of air over the extruder inlet, then directed at the build area, would accomplish both purposes?
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