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J-Head: Delay of Extrustion after Cleaning - Hot End broken?

Posted by sguzzel 
J-Head: Delay of Extrustion after Cleaning - Hot End broken?
January 21, 2015 03:24PM
Hallo everybody,

I currently have a Problem with my Mendel90 from nophead after having really problems after printing Laywood. Let me tell the story:
Due to the fact that my girlfriend wants to have name signs made of Laywood D3 for our upcoming wedding, I gave Laywood a try. Before that I only printed with Faberdashery and only had the common problems one coud have in a cold cellar. (Warping on the side facing the door, etc).
I printed the signs at 180-240 degrees and made the terrible mistake to wait for the extruder to reach the temperature. After several failed prints I gave up and tried to flush the whole hotend with the original supplied green PLA. I don't know what went wrong, if I was too slow, if I used a too high temperature,... nevertheless the PLA got stuck in the COLD end! That's why I had to pull the J-Head apart and remove the stuck PLA with the help of a hot copper wire i stuck in the PLA and a cup of hot water. After the removal I put the whole thing together, cleaned the hobbed bold and inserted PLA filament again.
Now here is the problem: When I heat up the PLA to lets say 185C and extrude it, it comes out with no problems. But if I try to print, the first view layers with 3mm height looks more like a 0.05mm height and an infill more like a field of tiny little dots. About the second or third layer all gets to the normal state , maybe even more filament is coming out then normal. I tried to flush the whole system again, but couldn't improve it. Suprisingly the retracted filament does not have the normal shape of a dot, it is more like a long long string, sometimes with dots.
That's why I am thinking I ruined my hotend. Is there any way to fix it?
(I ordered some drills with 0.3mm diameter but they didn't arrive yet and that's why I cant say that poking may be an option)

I really woud appriciate your help

Regards

Christoph
Re: J-Head: Delay of Extrustion after Cleaning - Hot End broken?
January 21, 2015 03:47PM
If the first layer is too thin it looks like your Z calibration is out after replacing the hot end. Maybe it isn't pushed as far into the Wade's block, so it is a bit lower. Seems like it is actually pressed hard against the glass and is effectively blocking the nozzle.

Note this can cause overpressure that causes the hot end to leak.


[www.hydraraptor.blogspot.com]
Re: J-Head: Delay of Extrustion after Cleaning - Hot End broken?
January 21, 2015 05:12PM
thx for the very fast reply - this really would mean I just have to play around with the z height in the config file. Thank you for your help
Really good news winking smiley

I keep you all informed
Re: J-Head: Delay of Extrustion after Cleaning - Hot End broken?
January 22, 2015 03:52PM
Update: the Z Height was really the problem. Thanks for your help nophead!
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