I Give UP!

Discussion in 'Calibration, Help, and Troubleshooting' started by Papatinker, Aug 1, 2017.

  1. Papatinker

    Papatinker Member

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    I've been fighting this hot end for over a week and I continue to get major under-extrusion.
    1. Installed official E3D hot end
    2. Printed 1/3 of a marvin perfectly, then underextrusion began. (Had nice marvins with old hot end)
    3. Next print was 100% underextruded.
    4. Updated firmware and told the printer which type of thermistor I have and did a PID autotune.
    5. Underextrusion continues about 1/2 way up the marvin.
    6. Swapped out the bowden tube and top bowden tube connector on my printer for more secure fit.
    7. Tried 3 different types of filament. Underextrusion continues.
    8. Found the heat break was not fully seated in the cooling tower. Took apart, checked over, reassembled with the heat break more secured into the cooling tower. Heated and rechecked for tightness. Got an EXCELLENT print. Next print (without changing anything) was back to underextrusion about 1/2 way up.
    9. Found that the filament can be difficult to push through and manually extrude.
    10. Dissasembled hot end, changed out nozzle with brand new. Double checked for blockage or burrs. Checked for nozzle to have a gap between the heat block and the nut area of the nozzle. Tightened and heated and checked. Problem remains.
    11. Put the old bowden tube back in (one that has the curves needed, as in it's been in that shape long enough that it's not being forced or pinched in curves). Printed and got higher before underextrusion happened. Canceled print and tried to push filament through by hand, was VERY difficult. Pulled bowden tube and installed short bowden (the one that comes with the hot end) and pushed the filament through, it was difficult at first, like it was not lined up, or it was jammed, but then all of a sudden it went swoosh, and the filament went through like butter.

    Is it possible that as the hot end advances up, and the bowden tube bends more, that the tube inside the cooling tower is being forced slightly off canter and causing drag? Anyone have any more ideas? I'm about to swap back to my old head and forget this headache. I've spent soooo much time and filament with this problem.
     
  2. Greg Holloway

    Greg Holloway Administrator
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    Hi,

    Are the temperatures stable? Could there be a lose wire or connection to the heater cartridge?
     
  3. Papatinker

    Papatinker Member

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    The temps were stable while I watched, however I did not keep constant watch. I will go back and check the connectors. I tried printing a low lying print to see if the height was part of the issue. It almost printed the whole item, but at the last of the top layers, it started doing it again. I also noted that the bowden tube was popping up and down during retraction. I will go back tomorrow and try to hold that clip up and push the tube down so it's flush to the heat break. I get a lot more resistance pushing the filament through this hot end than I ever had on the other hot end, except when I first start off. I prime the extruder manually, it usually flows smooth. When the fail happens, I pause the print and manual extrusion is extremely difficult. I take out the bowden tube, install the short one that came with the hot end, push through and it's smooth, then go back to the printer's bowden tube and now everything seems better.
     
  4. Old_Tafr

    Old_Tafr Well-Known Member

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    A daft question maybe, but are you getting a build up of filament inside the heat sink/heat break/nozzle e.g. is filament getting scraped off as it passes through?

    As an aside I have a couple of spare heat sinks, they have a countersink in the top of the Al, no brass insert to put a collet into, I may have ordered them in error, so I thought maybe they are for 3mm not 1.75 so I found a old reel of 3mm and thought I would try it for size. The filament has curved due to storage on the reel and was very difficult to pass through the heat sink, straightened it passed through quite easily. I can imagine the resistance if this filament were pass through a foot of ptfe tubing would make the stepper motor work hard and retraction would definitely not work as expected, it would be a bit like hysteresis.

    The reason for my first comment is that I think the whole heat sink, ptfe tube, and general assembly is quite critical and there are a number of things (slightly out of alignment) that can cause the filament to snag as it passes from the top of the heat sink through to the hot end. See a couple of my posts on this........... this includes a slight countersink in the internal ptfe tube.

    It seems like your problem is related to the extruder end of things, but I also had the filament getting crossed on the reel and an ever greater resistance due to this so much so that during a print I had to manually feed it off the reel by hand leaving a big loop at the back of the printer to ensure there was no resistance. Without doing this the hobbed end just ground a hole in the filament.
     
  5. Greg Holloway

    Greg Holloway Administrator
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    Do you have a multimeter that can measure amps? It might be an idea to monitor the current draw on the heater cartridge. It will be a good indicator that there is a lose connection.
     
  6. Old_Tafr

    Old_Tafr Well-Known Member

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    In case there is a large inrush of current, place a shunt across the meter when you switch on, then remove it so the current is flowing through the meter. Saves blowing your meter to bits if it can't cope with the initial current.
     
  7. Papatinker

    Papatinker Member

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    I have a meter that can withstand a 20amp surge at 4k volts, but I have good news, I have had 3 successful prints in a row as of late. I redid the PID auto tuning at 200C (where i usually print PLA) whereas I had done it at 135C previously (where I had printed PETG and which is my ultimate plan to change mostly to PETG). After doing this, my system stays within 1C almost constantly and I've only seen it swing as much as 2C. The other thing I did, was pull up on the black ring of the bowden tube connection and push down on the tube once again to try and eliminate the play I noted in it. The tube still jumps slightly, but less than before. So, I hope that between these two more fixes, I have solved my troubles. I did not make it to open the case and check the connectors, but if the problem returns, that will likely be the first thing I do, or using my meter.
    To Old_Tafr, I have only heard of this word, hysteresis, when troubleshooting a Cummins Diesel engine using a variable geometry turbo. There is a hysterisis test. I didn't know what it meant until you used this word in a sentence! LOL It makes sense though.

    Thanks to both of you for taking time to read my problem and offer solutions. (p.s. I just remembered, I have a current tester that clamps over the wire, so I will not have to worry about the shunt if I have to measure current.

    To Greg, I think you set me back on the right path with the temperatures.
     
    Greg Holloway likes this.
  8. dc42

    dc42 Well-Known Member

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    How hot is the extruder drive motor getting? I read of a case recently where the extruder motor was gradually heating up until it was hot enough to soften the filament. The soft filament was finding the crevice between the PTFE tube and the heat break, causing a jam part way through the print.
     
  9. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    I've had some maybe similar issues before but not 100% sure what the issues were.

    My theories were, forgot to renew new goop between heat break and heatsink. Both these would cause softening of material up the heat break and that would make it hard to extrude when it starts to cool. I would recommend to clean out the old (isopropanol or other alcohol) and add a bit more than needed every time you pick it apart.

    And in addition to this I used a composite filament that requires a lot more torque with 0.4mm nozzle. Overheating a motor past 120 deg internally might degrade the magnets making it weaker. I was using a pancake motor at the time. Now I got a slightly larger one.
     
  10. Papatinker

    Papatinker Member

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    Goop? You're not referring to thermal paste are you? If so, that is to ensure heat conductivity. If not, then I'm unaware of a paste or substance made to insulate the heat break from the head unless one was going to use some pipe tape like Teflon tape, but I would be to afraid of causing problems by doing this and worried it would reduce my hot end's maximum usable temperature (meaning the tape would burn/melt). I had not thought of an overheating extruder motor causing heat creep into the filament at the other end of the bowden tube, but an interesting theory. I shall check the heat I currently get for future reference.
     
  11. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Yes, goop = thermal paste

    I do not think overheating motor can creep into filament but it can deform the mounting and shift its position... With thermal paste I was just trying to ensure you have enough of it so the heat does not creep up the heat break from the block.
     

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