Howdy guys! This is my first post at Reprap and I am glad to be part of this community. So I went to a Prusa Mendel Build Off here in Louisville in early march and built a Prusa Mendel i2 machine. Originally we used 1.75mm PLA and my prints looked great using the default parameters we derived. About two weeks later my prints went to poo and the J-Head started to ooze out of the side. Many cleans and repairs later... I found out it was a clog in the nozzle tip (a bad one). The extruder jammed much plastic in it too but it seems to work fine still. I have taken it out and watched it turn.
But things did not go back to normal because the J-Head seems to be extruding inconsistently. Sometimes it pushes 80mm instead of 100mm and sometimes it does 90mm instead of 100mm (same speed) but I use the same value as it was before (when it worked fine). I cleaned the gear head on my Plastruder and it is shiney and particle free. I've tried different levels of tension to grip the PLA. When I print things the hot end seems to run against the higher levels of plastic (like it is sliding and not as high as it should be)... I though maybe my J-head was just jacked from all the cleans and re-assembles.
So I bought a MK-IV J-Head from here:
J-Head I bought for ABS
I am only going to use it for ABS as to avoid clogging.
Also got some black 1.75mm ABS (Brand:Octave)
I use 230C on the hot-end and 110C on the bed.
I have inserted the thermister values into the arduino program (seems to work just fine)
I have a Ramb0 board.
Well the ABS prints do the same thing as the PLA did which tell me the J-Heads might not be the issue. Wavy sides and the tip of the nozzle starts to melt into the top layers slowly; almost as if either too much plastic comes out, the abs swells, or the z-axis is missing steps. X, Y, and Z are calibrated though. I tell it to go 10mm and it goes 10mm in the x, y, and z. I tell it to do 30mm, it does 30mm on the money. The bed is level and the adhesion is really good (Kapton with abs slurry).
Also there is no evidence of hot end leakage on this new MK-IV or the old one that I use for PLA (anymore).
black ABS cube and wall model
20mm side wall model on bed
Side view of wall structure
20mm cube
You guys have any ideas what it could be? Important to note that the E-calibration for the black ABS is about perfect. Could I have temperature swings in my hot end? I did the M303 command (then uploaded the code with new PID settings) and usually wait till it stabalizes before printing. The temp does not jump over 2C during the print. I tightened the helical couplers and nothing seems to be slipping on the Z-axis. The hot end is mounted pretty rigidly.
Any suggestions would be appreciated.
