I am running a Stratasys Dimension 768 SST, with a "rebuilt" extruder (dual setup includes support + model). This extruder, basically, follows the OEM design with exception to the tubing diameter (few mils smaller for rebuilt, although there is a generous inlet taper and/or bushing, larger than the filament diameter feed stock) and the way the tubing has thermal contact with extruder body and cartridge heaters. The OEM design, apparently, had some thermal epoxy to "bed" the 2 nozzle tubes, which are brazed into the nozzle tip block. The approach, I am using, is Al foil packing around the SS tubes, tight to the Al extruder body (still brazed connection to the nozzle tip block). I had no choice but to recondition the extruder, because of a breached nozzle tube. In any case, with a cleared out nozzle inlet to start each time, I do get transient extrusion at standard temperatures of 250 (support) and 280 (model ABS), and in an adjusted temperature range, with some preliminary experiments. I clear out the nozzle inlet with a metal pin, down to the tube bend (I don't get why the design had this problematic 90 deg bend radius close to the cold end, feed wheel!) For the support, the extrusion goes for about 5 secs, then slows down, and the support filament feed stock stalls and strips out the filament, turning it into white debris. For the model, the extrusion goes longer for about 20 secs, and also slows down, and, in this case, the model feed stock splits and gets fed outside the nozzle tube inlet, but no white debris in this case. This cycle may be repeated by cleaning out the inlet clogging with the stiff metal pin.
I realize this is not a perfect description of the system, but I am hoping that someone who knows this extruder configuration or a similar one (system is quite old, unfortunately), may chime in here with suggestions. I will add, that I am running the system in a so-called maintenance mode and have some minimal adjustment of the firmware (like the hot end temperatures - defaults mentioned before) for the build mode (which is only during actual part run).
Thanks in advance for your help or suggestions!
Here are some diagrams/link to descriptions for the extruder as well:
My exact extruder (i.e., head) system: http://www.amtekcompany.com/pdf/dimension_bst_sst_elite_768_head_clog_guide.pdf
A similar extruder (showing heaters, extruder body to isolate model & support paths, tips, and thermocouples) https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwifyLnJsu7OAhVIOCYKHaSIDLQQjRwIBw&url=http%3A%2F%2Fwww.3dprintforums.com%2Fshowthread.php%3Ft%3D2237&psig=AFQjCNGM1BTAiWzUn4fNJ8-z5HDWxa6OEQ&ust=1472824417165187
This site shows another user take apart/redesign the extruder in question (pay attention to the 90 deg bend in the nozzle tubes) (see attached picture)
I also have a few documents: user manual, service manual, etc. that I may share, if I knew how to upload to this website.