Continued Bowden extruder issues

[fredini]

Hi all-
I've just returned from travelling for a month and am psyched to finish getting my Max up to speed, but have hit some more roadblocks...

Question: Do those compression tittings go bad? Upon first firing up of my machine the compression fitting over the extruder rollers let go of the teflon tube. Nothing I can do will make it grab it again. I've ordered a replacement fitting but am frustrated by the continued issues I am having getting this extruder to work properly.

I also wonder about replacing the teflon tubes in the hot end. Mine seem to have compressed in the hot end. Below you see show the inner tube has compressed and is constricting on the filament. It now has a segment of filament jammed inside. I've ordered some replacement teflon and a second extruder tip- I saw some posts here saying something about the extruder tip's design has been modified. But the outer teflon sleeve in the hot end(which is slit down the length on mine) also had some compression on it when I last saw it, but is now stuck up inside the hot end and I can't get it out. I'm afraid that if I go digging in there to remove it I'm going to really destroy it. Seems like I should replace that as well. Can anyone tell me what size tubing this is and where to get it?

Any advice? I may have experimented with hotter temperatures when I was first calibrating but have consistently been printing 240 degrees for the first layer, then 235 degrees for the rest of the print. Lower temperatures have not worked at all for me. This does not seem excessively hot to me.
[img]http://farm9.staticflickr.com/8381/8503643267_490ea06c3f.jpg[/img]

[daftscience]

There are two teflon tubes in the hot end. The first has an OD of 6mm and an ID of 4mm. If you're using 3mm filament this is all you need.
If you're using 1.75mm filament that tube will have a slit in it to allow the smaller tube to fit inside. The smaller tube has an OD of 4mm and an ID of 2mm. I believe the liner tubing and bowden tubing are the same, only difference is length.


To me it looks like there might have been too much compression. When I got my new style nozzle I cleaned out the hotend with ABS cleaner (its a perfectly clear, water like liquid. NOT ABS cement.) It took a while but I got it so the PEEK and two aluminum fitings went together without resistance and the nozzle (without the teflon liner) screw in without resistance until it bottomed out (Like the picture below.)
[img]https://lh5.googleusercontent.com/-ljvT ... 105813.jpg[/img]

Then I put the liner in and slowely cut it down to size to make sure that it made a seal, but there was as little compression as possible.




Now, to the extruder grip. Clean out all the dust from those rollers. Then with the tension bolts very loose set repetier host to extrude 100mm. Slowely and evenly tighten both bolts (alternate half a turn on one side, half a turn on the other) until it starts to grip, then keep going a bit more for good measure. While you're doing this watch the filament and see how the tension changes the grip. What this did for me was give me a really good idea of what is the right amount of tension.

Hope all that is helpful.

P.S. I bought a bunch of these # 91251A159. I am using them for the extruder bolts and for the endstop screws. They are much easier to adjust than using a philips head.

[mhackney]

Here is what my tubes look like after probably about 30hrs of printing ABS.

[img]http://mhackney.zenfolio.com/img/s2/v1/ ... 0630-4.jpg[/img]

Yours really look like they were overheated. I've been printing ABS at 220 C and one of my filaments (black) at 230. I've seen a lot of posts here about folks printing at 240ish and if that is the true temperature, that is quite high.