Am I wrong?
This photo shows why I think large multi-filament prints done with multi-extruder/single nozzle outputs always end up with a clogged hotend. The reason is that when the current extruder retracts filament to make way for next extruder to feed the next filament, there will always be a string of filament left behind in the hotend.
This photo shows what I found after disassembling my hotend so I could install a new one. I had recently finished a print, and when it finished I manually pulled the filament back from the hotend about 20 cm. I did this so I could take the hotend completely apart. After I got it apart I manually pushed the filament forward so I could see what the end looked like. The photo shows what I found.
Note that there is a long string of filament extending pretty far from the end of the filament. So it seems logical that there would be some bits of filament left behind inside the hotend after any retraction, and this is what I feel results in a buildup sufficient to clog the nozzle during a long print job.
I am most interested in hearing other opinions on this. Thanks in advance.
翻譯年糕
邢鳳言
2017-05-22 12:08:27
I used to have long string too, after I made some adjustments to push the PTFE in hotend fimed, the string length became dramatically shortened,
Birk Binnard
2017-05-22 12:12:22
Something happened to the translation - hotels fimed?
黃大丙
2017-05-22 12:19:30
Charlie Ting
2017-05-22 12:26:53
You can have some procedures to avoid this issue.
邢鳳言
2017-05-22 12:28:09
"hotend", spell check problem...
Charlie Ting
2017-05-22 12:30:19
For example, each time when you finish printing with any filament, move hotend aside and extrude some filament out from hotend then retract quickly. (So this string will be as short as possible)
Then pull this filament back after the Y tube to have a clear path to put another filament in.
It's not difficult to do this, but a little bothering.
Birk Binnard
2017-05-22 14:48:34
Hi Charlie - that's exactly what Simplify3D does when it makes a tool change. I found that it works pretty well for small parts, but most of mine are large and for a large one (print time more than say 3 - 5 hours) I consistently got a clogged hotend.
This, in turn, required complete disassembly of the hot end and torching the nozzle with a propane torch to clean out carbonized filament. Since doing this requires cutting & re-soldering wires there are only so many times this can be done before spare parts are needed.
Charlie Ting
2017-05-22 15:36:14
it means your nozzle has something wrong. I think these may happen in your system:
1. Cooling fan is not perform well to cold the nozzle down. (the throat)
2. The thermal resistance of your nozzle is too high.
3. The O-ring is mal-function to resist the thermal passing through.
4. The PTFE tube transfer too much heat from the head to the filament.
You should try to make sure all these works fine, not clean them every time. XDD
Birk Binnard
2017-05-22 20:30:45
Thanks Charlie - I see what you mean now. What you say is certainly possible since my hotend is comprised of parts from 2.0 & 2.5 EX and is totally non-standard. I'll try some different configurations and see what I can figure out.
Birk Binnard
2017-05-24 02:50:15
I think I may have solved this problem. Here is my blog page explaining what happened and what I did to fix things:
http://wp.me/P8JtoQ-96
Harry Cayne
2017-05-28 15:45:06
I also have this issue
Harry Cayne
2017-05-28 15:46:29
I tried to push the ptfe tube as deep as I could but still
Dennis Chen
2017-05-28 16:18:50
Did you try to push the ptfe by rotating it at the same time with the heated nozzle? This would make it even closer to the bottom.
Harry Cayne
2017-05-28 19:06:23
