3D Printer Material Feed Problems

    Clear (neutral) PLA plastic fiber had been used to build rafts and supports for many of the preceding runs.  Lately, however, the plastic material exhibited brittleness and broke several times in the extruder head.  Further, it also broke a couple of times in the feed tube.  In the most recent instance it broke several places in the feed tube with small segments separating longer lengths and in a couple of cases with several short segments.  It broke about 6 to 7 times in the overall feed tube while sitting dormant overnight!

    The principle location for the breaks was the curved region above (shown loaded now with black and green ABS).  Several small pieces and a couple of longer segments were located in this area.

  

    The round support feeding the tubes to the extruder heads also had a couple of breaks with both long and short pieces.  In order to remove the broken PLA it was necessary to remove the feed tube from the machine, then break up the remaining longer pieces into short segments and work them out of the tube.

    The tubes progress down to the material spools at the bottom alongside several electrical cable bundles.

    The clear PLA had been located at the rear spool location where the green ABS now resides.
    Perhaps the cooler, drier winter climate here in North Carolina had something to do with this problem, or perhaps it was the fact that the spool was about half empty and therefore the material was curled more tightly.  The PLA is very springy and resists attempts to straighten it by simply snapping in two.  Generally the curled material would feed OK up the tube, but would tend to bend the tube considerably.  As the tube approaches the round cable support feeding the extruder head it is more confined and forces  the material to follow a lessor curve thereby putting stress towards straightening the material.
    As an immediate measure the machine was reloaded with the Green ABS material which is not as satisfactory for raft and supports as it tends to warp and loosen from the platform as will be seen in the next blog.