More extruder randomness

Recently I’ve been having a great deal of success with the printer, aside from the occasional Z calibration it seems to have been working well.

Over the weekend I was able to print the remainder of the parts for the lower section of a MendelMax with little drama, there was consistency in the print quality and I was able to bang one out after another stopping only to remove the completed parts from the bed.

Yesterday I started on the top MendelMax frame sections, expecting to continue my run of complication free printing. I fear that this (if it already hasn’t) may soon come to an end. As I had taken the printer out for the weekend I knew that the Z axis would need to be tweaked to get the first layer to adhere properly, this however took a lot longer than normal as the resulting distance between the end of the extruder and the bed varied in ways which would not be expected based upon the adjustments made. Furthermore after printing for about 1/2 an hour the offset between the two needed to be increased by .15 of a mm in slic3r in order to obtain the initial, correct gap. I would expect some expansion of the hot end as it heats but I would have thought that this wouldn’t have resulted in such a delayed increase. (note this also happened again when I fired the printer up tonight).

Once I finally got the first layer printing properly I started having a problem that I never had before, the outer perimeter wouldn’t sit properly on the previously printed layer but would droop and hang down the side of the printed part (as on the black printed part below). I stuffed around with the settings in slic3r which dealt with the speed, retraction, z-lift and extrusion multiplier all to no avail.

I then noticed tonight that occasionally the color of the extruded material would change from a light blue to a darker blue as would the consistency, from what I have always experienced, to something what was more akin to 50% PLA mixed with 50% water (like the stuff you get if waterbased paint in a tube separates or is not mixed properly). You can see the areas where this has happened on the print below to the left of the right had bolt hole, below the left had bolt hole and on the left center side of the lower face.


Initially I thought that I was something in this section of the PLA, some contaminant or change in plastic brew so I swapped out the blue for some purple and tried to print a model of a tornado.


Greatly improved but the outer face still had some imperfections in it that I hadn’t got on my earlier prints. I also had another test piece behave slightly strangely with the purpler and not adhere to the bed on the outside edge of the extruded path when in-filling the first layer. It almost looked like the printer wasn’t extruding enough plastic for the distance it was covering.


I then swapped out the purple for some black where once again I had the droopy issue. The final 10 mm of the model (at the bottom in this pic) I dropped the extruder temperature 5 and then 10 degrees to 175 which weirdly seemed to stop the problem.

If it is a case of the temperature being wrong I’m not sure why it would happen all of a sudden and especially why it would be out by 10 degrees. I understand that different colors will extrude at slightly different temperatures but if the poor quality with the blue filament is solved in the same way as with the black (i.e a temperature drop) then what has gone wrong to require this. Nowhere have I heard of the temperature having to be adjusted by such a large factor across approx 50m of filament.

I noticed that the base of the extruder body seems to be deforming slightly in the same way as the first one. There also seems to be some burnt material seeping from between the joint of the PEEK and the brass sections of the hot end. If the base is deforming slightly as it heats up then this would explain the expansion issue that only presents after a period of printing but at the moment I’ve got no idea what the burnt stuff could be.

I guess tomorrow I’ll have to rip apart the extruder and hot end and have a look inside to see how things are, perhaps there are answers in there as to why all this strangness is happening.

3D printers are cool, really cool, but man they can be a pain in the ass. Badly behaved, they don’t tell you how they are feeling and then just when you think everything is fine they go and crap themselves. Bugger it all

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