Im done figthing the extruder

This is for general discussions. Also FAQ can be found here.

Moderator: speedake95

Post Reply
Lioric
Posts: 116
Joined: Wed Aug 15, 2012 1:13 am

Im done figthing the extruder

Post by Lioric »

I think that was it.

As much as I like the printer and its sleek look, I think today was the last drop. Since yesterday the extruder started to act up (out of the blue), filament jams again, every 5 minutes of printing the extruder stopped, I had to dismantle the extruder from the plastic bracket several times to clean it. Before that the printer was not used in the last couple of months (it was working alright before this)

My initial intention with the printer was to add it as new TOOL to my "toolbox" to finally avoid doing so many mechanical parts that I had to do manually for my other hobby projects (automotive and electronics related), that is why I choose a complete product and didn't went with the "experimental" reprap alike printers

But instead of that, it seems that the printer needs serious amounts of attention and maintenance to complete its prints. So instead of focusing on my other hobbies more easily, my pinter ended up as a very "needy" hobby.

This is my second extruder (the first one was gone a few weeks after assembling the printer, while trying to clean it due to constantly jams), the second thermistor (due to moving the hot end while disassembling) and now it seems that the hot end has scratches inside (constantly jams) and to finish it, it reads a fixed 359 degrees.

Yes, its has a fixed reading of 359 degrees for the hot end, (in Repetier host and while reading manually via serial line). I still have not reviewed what the issue is (will need to test if the thermistor is gone again) but definitely it is driving me crazy.

While cleaning the hot end for the last time, I tested a different method (to avoid scratching the insulator internally, because that will lead to jams when the filament is retracted), instead of forcing a drill bit from the top of the extruder, I heated up this 1.5mm drill bit and inserted on the extruder to melt the plastic that was obstructing, but probably I heated up to the point that the thermistor got damaged somehow

Anyway, just posting out of frustration after a fight of two consecutive days with the printer, and the end result is a non working printer, so I have no idea of how won this round

Trnquill
Posts: 66
Joined: Fri Oct 05, 2012 10:01 am

Post by Trnquill »

First things first: if your thermistor shows number that is not correct, your printer can not work. The head temperature can be anything and jams will occur. Fix that before continuing.

Do you have a filament cleaner? Constantly jamming extruder sounds like dirty filament and/or not sufficient cleaning and/or wrong temperature and/or wrong tension on the filament extrusion follower bearing.

I had quite similar issues before, too. Then I installed a filament wiper and started to clean the extruded as follows:
1) Use the "extrude some filament manually, then pull it back really quick" method for a few times (~5-10).
2) Clean hot nozzle with 0.3mm drill bit. Just push it in and roll it with your fingers, then pull it out. Repeat ~5 times.

My printer has ran without any maintenance for few months now. I use it maybe once a week, using different colors and printing different kind of jobs. I always just heat up the printer and start printing. No regular maintenance or cleaning.

Lioric
Posts: 116
Joined: Wed Aug 15, 2012 1:13 am

Post by Lioric »

The thermistor damage was result of the constant cleaning needed, it was damaged AFTER cleaning it. The jams are not result of a bad thermistor, but the other way, the thermistor was damaged because of the repeated dismantling needed for cleaning the constant jams

Yes, I have a filament cleaning in place, damped with acetone.

I actually replaced the hot end thermistor with the one in the bed, and the bed thermistor replaced with a 100k resistance to at least finish printing the brackets that I need for my project

You miss the point, is not that I (or we, as I see several cases similar here) am doing anything wrong as not cleaning the filament or anything. The point is that the hot end assembly has some inefficiencies in its design, the problem is at the insulator contact point with the metal tip, if even a small scratch is done in this area (even by the same filament, or from factory as was the case of my first hotend that came with the kit) , then when doing a retract (as regularly done when printing to avoid oozing) the plastic will expand here and produce a jam. Have you seen all of those "print stops after x minutes" threads? this is the reason why

None of the methods posted works for cleaning jams, the extrude some then retract some is not working, because at the point where the plastic expands and produces the jam, is just in the insulator area and as you know in the insulator is a bad heat conductor so the plastic cools down, so putting some filament and retracting does nothing (as the filament is not melted to glue to the existing plastic in the hotend)

Only the drill bit works, but I have to push it really (and I mean really) hard to unjam it, but as I suspect this can scratch the inner surface (leading to more pronounced jams)

I'm very grateful of your reply, but I'm not asking for solutions or methods to clean it, what I'm proposing is for a redesigned hotend, or a suggestion of a different hotend that some user might have tested with better results

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

Hi Lioric,

I'm sorry to hear about your continued troubles with your two hot ends. As you might have seen by my previous posts in various threads, I have been in the same situation. I hope you are able to "brush off" your frustrations and find a solution that works for you.

A couple of things that might help:
- decrease the retract length from 3mm to e.g. 1mm for decreased back pressure
- add more cooling around the peek part
- assemble the hotend parts while the hotend is heated for tighter fit
- add a connector to the thermistor for easier unplugging with less wear on the wire

From what you describe I believe you say that the peek part has become scratched. Is that correct? If so you might ask Guillaume for a new peek part?

I wonder if the hotend would be easier to handle if it used a 0.5mm hole instead of a 0.35mm hole? I'm uncertain how much testing Guillaume did on 0.5mm versus 0.35mm.

If you consider switching to another hot end I would try an original J-Head if you can get hold of one (and not a China clone). It seems to be one of the most (if not the most) reliable designs. I have thought about buying a 3mm version of the J-Head before due to having 7 KG of 3mm PLA available but never gotten around to order and design an extruder setup working with Felix.

Please keep us updated on what you decide to do.

satoer
Posts: 436
Joined: Mon Oct 01, 2012 8:00 pm
Location: Netherlands

Post by satoer »

Kjetilei wrote: - assemble the hotend parts while the hotend is heated for tighter fit
Materials expand while hot, makes more sense to assemble while the hotend is cold for a tighter fit.
My Felix 1.5 printed designs on Thingiverse
E3D V6 Hot end upgrade for your Felix
Tweezer bracket for your Felix
Led bar upgrade for your Felix

Kjetilei
Posts: 334
Joined: Fri Mar 16, 2012 8:26 pm
Location: Stavanger, Norway

Post by Kjetilei »

satoer: you're completely right regarding materials expanding when heated, but somehow I had much better success with it not leaking when tightening it up while hot ;) Don't ask me why :)

Trnquill
Posts: 66
Joined: Fri Oct 05, 2012 10:01 am

Post by Trnquill »

Using extensive force when cleaning the hot end sounds bad and will most likely cause deformations which in turn lead to various problems. But if your hot end jams right above the peek insulator I can see why some force and disassembly is needed. I would first try what Kjetilei suggested and add cooling above the insulator. Plastic should never melt there.

I would also strongly advise against replacing the thermistors with fixed resistors. By bypassing the feedback circuitry you are effectively telling the heater logic to "give more current, we're cold! Don't stop heating, ever!" Or if the resistor value translates to even a hair too low a temperature the heater will stop heating altogether. If same "fix" is applied to hot end thermistor the results will be catastrophic: too much or too little heat and hot end will jam. Too high temperature will make PLA plastic first very thin and after cooling extremely hard and will cause a hard-to-remove jam in your extruder. I read somewhere you will most likely destroy your hot end if you extrude PLA too hot. It will jam and the residue is almost impossible to remove. Do you think you might had too high a temperature at some point? Jams above the insulator might also be cause by too high a temperature.

hvdd
Posts: 71
Joined: Tue Jul 24, 2012 11:43 pm

Post by hvdd »

everything mentioned here i have seen in the past...
i had to open the extruder also after each print with the same problems.
my solution is quite simple.
A: in each profile i changed in dimensions 'retract when not printing' standard 1.5 mm change to 0.4 mm.
problem with filament for 99% solved while printing.
B: after each print the filament is also retracted.
so after slicing each object i check the gcodefile and almost at the end of the file i see G ?? E-10
i changed this value to -2.
now at the end of a print session the filament is not retracted for 10mm - more than the distance of isolator ! into 2mm
the hot filament will stay below the isolator and will not stuck into thealu part above after cooled down.
C: with 1 small steel wire from a steel brush i clean the nozzle each time.

for weeks now it is almost a deskjet :)

rgds

Lioric
Posts: 116
Joined: Wed Aug 15, 2012 1:13 am

Post by Lioric »

Trnquill wrote:I would first try what Kjetilei suggested and add cooling above the insulator. Plastic should never melt there.
Of course plastic will be melted there, you know that the expansion coefficient of PLA along with extruder retraction will make melted plastic go into the Peek part. As a matter of fact I'm not really sure that increasing ariflow in this area might help, as it will harden plastic faster (you know, the thermal coefficient of expansion do its job + airflow to harden it == jams faster)
I would also strongly advise against replacing the thermistors with fixed resistors.
No worries, I am well aware of how it works. The resistor that I replaced the bed thermistor with is a 100k, so it should make it think it is at 14 degrees, then I connected a digital contactless Infrared Thermopile Sensor (TMP006 chip) to the main control module to read the real bed temps, this along with my modified firmware to control it in a closed loop mode completes the circuit. When the contactless infrared sensor detects 66 degrees the bed heat is turned off. My printer is a "bit" different, lets say that it has more processing power than the equivalent of 1000 of normal ones ;)
Do you think you might had too high a temperature at some point? Jams above the insulator might also be cause by too high a temperature.
I regularly print at 220 to 230 for the first couple of layers, to solve the curling issues. This should be a "in range" temp for PLA, this is mostly backed up by the fact that jams are way later on the printing process (with temps of 190) and none of them on those layers
hvdd wrote: A: in each profile i changed in dimensions 'retract when not printing' standard 1.5 mm change to 0.4 mm.
problem with filament for 99% solved while printing.
B: after each print the filament is also retracted.
so after slicing each object i check the gcodefile and almost at the end of the file i see G ?? E-10
i changed this value to -2.
now at the end of a print session the filament is not retracted for 10mm - more than the distance of isolator ! into 2mm
the hot filament will stay below the isolator and will not stuck into thealu part above after cooled down.
C: with 1 small steel wire from a steel brush i clean the nozzle each time.

for weeks now it is almost a deskjet :)

rgds
Yes, similar to what I was doing (only that all this is automated in my a "bit" different printer)
Differences are:

M120 is added to g-code after the HOME command
M106 is removed if the file was imported from SFACT
Fan is turned on only after the first layers and when the temps are at 190
The final retraction is completely removed

And yes, doing that my printer was more like a laserjet :) for the last months until it started to jam again.

Odd thing is that yesterday there were no jams at all.

daveinhull
Posts: 66
Joined: Fri Jan 11, 2013 2:31 am

Post by daveinhull »

Hi Lioric

I was getting a little the same way but recently (touch wood as we say) things are working well.

What I did was:
a. new z-axis bold and coupler with plenty of crinkled washers to stop the wobble
b. Painter blue tape on the bed to stop the curve edges
c. use the standard production profile
d. heat hotend to only 185 degree
c. heat the bet to 70 degree, higher than I think is normal becuase of the painter blue tape.
I regularly print at 220 to 230 for the first couple of layers, to solve the curling issues. This should be a "in range" temp for PLA, this is mostly backed up by the fact that jams are way later on the printing process (with temps of 190) and none of them on those layers
This sound way too hot, when I tried at that temperature I just got a mess.

I think the production profile is the best as it starts by extruding some filement and then goes to print, when it finishes Im not sure what it does with the filement but when I come to use it again it sems to work ok. I've crashed the hotend a few times, scraped the bed a few times, mess around with the hotend but never had a jam (oh please do not let that be an omen :(

Hope you do find a way to get it to work right.

Regards
Dave

Post Reply

Return to “General”