Possible problem with heating resistor?
I normally print PLA @ 190 degrees. But for the last week I've been unable to complete a print due to poor (or no) extrusion. So after trying various options (like disassembling printhead, different filament, different Z-heights, higher temperatures, etc.) what seems to be happening is the printhead will extrude ok for about a minute or so, but then all extrusion stops. At this point I can neither manually feed filament through the hot end nor can I retract the filament out of the hot end. The only way I can get extrusion back is to disassemble the entire printhead and remove some melted filament stuck in the bottom of the nozzle.
Sometimes heating to 240 degrees helps resolve the problem, but not always. So I'm thinking there might be something wrong with the heating resistor - even though the LCD temperature readout seems to be OK.
I have seen the video about how to completely disassemble the printhead, so perhaps I should try replacing the heating resistor. Are the specs for the Atom2 heating resistor published anywhere? Perhaps there is a place here in the US where I can get a replacement.
翻譯年糕
Charlie Ting
2015-12-25 08:05:10
Seems not. Details will be later in hours. Today is a tough day to me.
Birk Binnard
2015-12-25 08:11:17
Clarence Lee
2015-12-25 09:00:13
If it's problematic after a few mins, the first I would check is the back cooling fan effective.
It sound like coldend too hot.
Try to measure the temperature around coldend area.
Birk Binnard
2015-12-25 13:50:25
The back fan is OK - I can tell by the sound it makes. I did stall the blades once when I reassembled the printhead, but that was immediately obvious and has not happened again.
Only one of my side-blowing fans works (I should have replacement fans in a couple more days) so this could result in uneven temperatures, but would this be enough to cause hot-end clogs?
Clarence Lee
2015-12-25 14:06:10
hmm I don't think so, but did your inner 3*2 ptfe tube already got the replacement?
Maybe a photo focus on the hotend & effector.
wondering there might be something related.
To tell the heat resistor and thermistor ok or not.
Check the temperature by other thermometer.
Birk Binnard
2015-12-25 16:48:43
Yes, I did replace the inner PTFE tube and have checked it several times. It is OK; not burned or melted at all and filament passes through it OK. All the parts in the hot end look good actually - I'll take a pic next time I have it disassembled.
Charlie Ting
2015-12-25 17:35:11
Birk Binnard
For your situation, I guess you should try to use the smallest allen wrench to push or pull out the materials stuck in the triangle field of hot-end.
In general, the printhead have three regions, PTFE, triangle area, extrusion hold. And we
always aware to replace PTFE, but never pay attention to the triangle area.
As my personal experience, this area is the most important about the printhead. So, after you clean it up, you may solve the problem you have encountered.
Sébastien Pierre
2015-12-25 23:39:35
Could this be that the PTFE tube can be easily moved within the hotend? The extruder sometimes pull back the filament, which I imagine could also pull the inner tube, leading to some filament getting stuck in between the hotend and the end of the tube. I have similar issues from time to time, but manually pushing the filament usually solves the problem.
Clarence Lee
2015-12-25 23:59:38
that means inner ptfe tube too short
Or you are talking about longer one?
Birk Binnard
2015-12-26 01:00:08
Here is a pic of my disassembled hot end. The internal PTFE tube is 19mm long and filament passes through it OK. The Quick Connector is just below/behind the 2 yellow wires; it has white filament in it. The heatsink comes off easily and is not clogged
or dirty. The pieces of electrical tape are mine - they cover up solder joints where I had re-soldered wires I broke during previous disassembly/reassembly attempts.
I am a bit reluctant to take the entire hot end apart for fear of breaking either the heating resistor or the thermistor. I have used the end of a paperclip to poke down the top of the hot end and clean out whatever filament is in there, but the same problem keeps recurring.
Clarence Lee
2015-12-26 01:15:10
19m is too short, it would moving inside up & down when retract
Birk Binnard
2015-12-26 01:30:08
Originally the PTFE tube was 23mm long, but I found that the bottom end (the end inside the hot end) was ending up in a slight conical shape that seemed to restrict the filament moving through it. Plus, the PTFE tube is a tight fit inside the metal piece that holds it so I don't think it moves very much (if at all.)
I guess I can try a piece 23mm long again just to see what happens.
Birk Binnard
2015-12-26 02:27:54
OK - I tried a longer tube - 25mm to be exact. Pic #1 shows the longer tube next to the shorter one (19 mm) I had been using.
The longer one failed pretty badly. At 200 degrees I was able to push a tiny bit (maybe 4 mm) of filament through the hot en
d, but that's all. After that I could neither feed nor extract any filament. So I raised the temperature to 240 degrees - hotter than I have ever used with PLA before - and the filament was still stuck. So I disassembled the hot end and found that the PTFE tube was stuck in the hot end. I managed to get it out with considerable effort (again heating to 240) and Pic #2 show how it looked when it came out.
Birk Binnard
2015-12-26 02:28:24
Here is Pic #2
Sébastien Pierre
2015-12-26 03:56:43
Yes, the inner one. Mine lost its triangular head when I pulled after it was stuck, so it does have more wriggle room that what it should.
Sébastien Pierre
2015-12-26 04:00:56
Just out if curiosity, what is the yellow bit in the lower left below the fan?
Birk Binnard
2015-12-26 05:09:46
It is one of 2 identical horseshoe shaped printed parts called a quick_connector_spacer. It fits in the space at each end of the Bowden tube and significantly reduces the movement of the tube when the printer does retracts. The bottom line is it helps a lot with reducing stringing.
I couldn't find it online so here's a link to the STL file:
https://drive.google.com/....../0B3EpEEIPcV....../view......
Birk Binnard
2015-12-26 06:05:08
I put a new piece of PTFE into the hot end and reassembled it. Before I did this I made sure the inside of the hot end was clear of any old filament or PTFE residue. With the new PTFE and temperature at 200 I can manually push filament through the hot
end, but it takes a lot of pressure to do this - basically I have to grab a piece of filament with some pliers and push hard on it to get any extrusion.
I doubt any extruder gear would be able to push filament with that much force so my only conclusion is there is something wrong with either the hot end itself, or perhaps the heating resistor.
Could the resistor be heating unevenly?
Clarence Lee
2015-12-26 07:42:28
Could you check if resistor not loosen?It should be stable touch the hotend.
But since you said the temperature is stable, it`s not like its moving.
Or maybe the thermistor problem?
Anyway， use multimeter to measure the heat resistor resistance.
Clarence Lee
2015-12-26 07:46:48
Birk Binnard
try to use smallest allen key or others to cleanup hotend inside deepest area when heatup the hotend to 200.
Sébastien Pierre
2015-12-26 09:21:35
What is the expected ohm value? I had a broken thermistor when I first assembled the printer and remember that the manual was quite elusive, something like "it works if it is not zero".
Clarence Lee
2015-12-26 09:38:23
it's a range usually not all the same by batch
So it's better recalibrate by M303
it shouldn't be 0 or open
As I measured before on different batch I got , usually around 2~4 ohm.
Birk Binnard
2015-12-26 13:15:29
It doesn't look like there are any places on either the resistor or the thermocouple to put the multimeter probes. I might be able to see better tomorrow during the day.
Birk Binnard
2015-12-26 13:18:07
Actually I found that a 1/16" twist drill works very well for this purpose. Of course I turned it by hand and not in a drill chuck.
Clarence Lee
2015-12-26 13:19:16
multimeter probe on wires where you connect it.
Birk Binnard
2015-12-26 13:20:55
OK - I'll try that tomorrow. Thanks.
