One of the big reasons why I decided to upgrade to a Lulzbot Taz 5 was to be able to add a dual extruder. I figured it would be a great way to add accents to printed objects and open up some new doors in creative design. This however proved to be just a dream.
Admittedly my first few prints (weeks ago) turned out great. It only took a few days for things to degrade in very mysterious ways. The first print that showed problems was a shift knob for the D2 that had a section in the middle that was printed sporadically. Then things got worse with prints barely being able to start without the extruder becoming jammed, clogged, or just plain failing to extrude filament. Since my printer works just fine with the single extruder tool head I figured it had to be the extruder and had it replaced under warranty.
After waiting a week for a new tool head to arrive I thought my problems would be solved. To my disappointment the new tool head exhibited the same problems. After sending countless emails to the Lulzbot Tech Support (who are great people by the way!) both before and after getting the tool head replaced, I still have yet to get the dual extruder to complete a print reliably and consistently.
The tech support people have had me tweak settings, temperatures, tightness of the idlers that keep tension on the filament. In one experiment where I swapped filament from one tool head to the other the problem seemed to follow the filament leading one to conclude that the filament is to blame. I replaced the filament with another brand of the same color, the problem still occurred. So if it is the filament, it would be silly to only be able to use very specific colors and batches with the dual extruder tool head.
One possible cause of the problem would be what is called "heat creep" which as I understand it, is the effect of heat moving up into the filament and parts of the extruder where having heat is undesirable. This is prevented by having a heat sink on the hot end that helps keep the heat down near the nozzle where it belongs. My prints were less than 19 minutes long however and tended to fail about 10 minutes into the print. So if it is heat creep, there would be little hope that the dual extruder would be able to complete larger prints reliably.
An additional problem with the dual extruder is it is inherently messy and yields lower quality prints due to the increased mass of the tool head. Slowing down the movement of the tool head could help improve quality along with additional tweaking but slowing the tool heads movements can contribute to greater "heat creep".
In the end I have decided that its best to continue to use the single extruder tool head and simply find other ways to add color to prints. Print quality with the single extruder is great and it seems to be very reliable with a multitude of materials. I don’t know if there are people who actually have success with the Taz 5 dual extruder, I’m sure there are. When I suggested it might be a firmware issue they found firmware wasn't actually available on their website for the Taz 5 dual extruder V2 (the current model) which is concerning. Perhaps I'll give it a try again when they have the "dual extruder V3".
