Underextrusion and nozzle clogs  

RE: Underextrusion and nozzle clogs

Since the discrepancy between your measurement and the LCD reading seems to increase with increasing temperature you may want to check with the IR temp gauge at elevated (>200°C) temperature as well.

Also, there may well be a difference between surface temperature and temperature inside the heater block where the termistor sits.

A little deviation is expected but 30 to 50K suggest issues with the measurement method.

Where did you place the temp probe, how did you couple it to the heaterblock thermally, how did you insulate it against surrounding air, how did you insulate the wires against heat contuction away from the probe? I assume you used a thermocouple?

Did you try doing a PID cycle?

The resistance of your heater element seems fine. At 24V 40W it is supposed to be about 14,5 Ohm. The 16 Ohm one you refer to is just 36W. But both of those sould be perfectly capable of heating your heater block up to temp.

RE: Underextrusion and nozzle clogs

And since we all know ice water should be 0c ... kind of a hint the two meters you are using are not happy.

The heater block is aluminum. The soaking temp differential should be small if the print fan is off.

You can use this table to verify your thermistor is behaving:

25c should give 100k +/- a percentage point plus DMM error.

RE: Underextrusion and nozzle clogs

ps: the mechanical coupling of a temp probe and the heater block must be carefully thought out to get a fair accuracy. Just touching the probe to the block is prone to all sorts of errors. It also matters if the probe is PT, TC, or a thermistor type: the type dictates contact patch required to maintain accuracy.  Look up "immersion depth" requirements.

RE: Underextrusion and nozzle clogs

5-10C maybe but 30-50C difference no way. The reason I posted this is I was having problems with underextrusion and nozzle/heatbreak clogging. I have tried everything including replacing the entire assembly. I have chatted to Prusa tech yesterday for about 4 hours. Still no luck.

RE: Underextrusion and nozzle clogs

Depending on the setup, 30K would not suprise me at all.

Have you looked at the Bondtech Gears? The shaft of the one which is not mounted to the stepper sometimes slips out of the plastic part which can also lead to underextrusion.

Also, I didn't try to criticize you personally but wanted to find out more about your measurements and if it could have a different source than the heater temp.

So far you answered none of the questions which doesn't help us understand your problem better.

RE: Underextrusion and nozzle clogs

Even 50c errors wouldn't surprise me.  Metrology is an art, with some science poured in.   And your basic reference of ice water being measured at 5c proves your methodology is questionable.  Starting with simple physics: ice water slurries are 0c. they can't be anything else unless you've added copious amounts of something else.  Probably a cold junction error in your gear, but still a problem.  

As for under extrusion.  Let's start there rather than chase temperatures.

Is the extruder making any clicking noises when this is happening?   How about posting an image of the part that is showing these issues? Be sure to use the drag and drop method and set the LINK TO : MEDIA FILE option before clicking INSERT.

RE: Underextrusion and nozzle clogs

I have not taken offense at anything anyone has said he. I have replaced the Bondtech gear shaft with one of proper length, replaced the heater, thermistor, heatbreak, heat block, nozzles (0.4mm, 0.5mm, 0.6mm) , adjusted the idler screws countless times, cold pulls, speeds, temp settings, retraction settings, etc. I just got off chatting with Prusa tech (5 different techs) for over 4 hours the other day. They all asked me to do the same basic stuff and in the end had NO clue how to fix the problem. I just made an adapter from a heater block to attach a thermocouple temp probe inside where the filament gets hot (I remove the filament first) to do my tests. I have found that the temps are varying from 15-25C low. I am in the process of changing the extruder/E3D hotend with a Bondtech-M/mosquito hotend. This has been slow as there are no adapters to use and I have to design my own. I have most of the parts printed but not all.

RE: Underextrusion and nozzle clogs

I forgot to add this file. The nozzle gets clogged just upstream in the heatbreak like in the picture

RE: Underextrusion and nozzle clogs

Well, you probably experimented with different filaments, too?

What filament were those parts printed in and with what kind of settings? Do you get the same issues with different materials such as pla petg or abs?

What are your retraction settings and what is your ambient temperature when printing? Does the hotend fan work properly? Did you use thermal compound when screwing the heatbreak into the heatsink?

RE: Underextrusion and nozzle clogs

The standard E3D-V6 heat break is 2.0 mm all through the bore. Prusa has them modify it by drilling out the upper bore to 2.2 mm. This creates a step that causes problems printing parts that have higher complexity (lots of retractions and z-lifts).

A properly working hot end should not reach melt temperatures above the neck.  And in some cases with the Prusa heat break pumping forces melt up into the 2. mm transition zone where it cools and then jams (2.2 mm plastic doesn't fit in the 2.0 mm melt zone).  Prusa will not admit to this since they depend on the larger bore to make the MMU load/unload cycle a bit more reliable.  But it causes grief for many non-MMU owners.

Regarding your temp readings, I can't emphasize enough how difficult it is to make accurate temp measurements. Especially with thermocouples.  For example, are you using cold junction compensation?  If so, are you sure you are using the correct materials at the cold junctions?  It is not as simple as connecting a TC to a meter and reading the voltage.  And back to that ice water problem... 0c is 0c - not 5c. If you can't measure ice water accurately, don't bother with more difficult challenges.  Not a put down, because there are so many places for electronics to fail you.

I am speaking from professional experience... measuring the true temperature of things is not straight forward.  

RE: Underextrusion and nozzle clogs

Posted by: timo.m

Well, you probably experimented with different filaments, too?

 

What filament were those parts printed in and with what kind of settings? Do you get the same issues with different materials such as pla petg or abs?

 

What are your retraction settings and what is your ambient temperature when printing? Does the hotend fan work properly? Did you use thermal compound when screwing the heatbreak into the heatsink?

Don't use ABS. I love PETG. That print was from Carbon PETG. The printing specs 240-265 and 60-75. I was printing that at my normal PETG settings (that also prints perfect at that setting) of 245/85;  1mm retraction at 0.5mm/sec;   25% infill;  30% fan at layer 4; 30mm/sec print speed. It does an OK job now for PLA. Took some more temp reading for the thermistor and they were off from 15 -25C. I said let me check thermistor resistance. I have 3 brand new ones at about 94K ohms each but the one in the printer is showing 160K ohms resistance. I think that might be the villain a bad thermistor. It was brand new too!!

I did use thermal compound.

RE: Underextrusion and nozzle clogs

Posted by: Tim

 

  And back to that ice water problem... 0c is 0c - not 5c. If you can't measure ice water accurately, don't bother with more difficult challenges.  Not a put down, because there are so many places for electronics to fail you.

I am speaking from professional experience... measuring the true temperature of things is not straight forward.  

 

OK I might not have laboratory grade equipment at home but 15-25C can be measured correctly. By the way I re temped my cold water and it was 0.1C and 0.15C. Good enough. By the way and not to brag I have 3 Masters degrees in engineering (one of them is Electrical Engineering) and a PhD in Biochemistry so I do know how to use certain equipment

RE: Underextrusion and nozzle clogs

You still haven't described how you are solving the cold junction problem.  But I guess you have it all handled, so let us know what you find.

RE: Underextrusion and nozzle clogs

You know, after thinking about it more, the funniest part in all this is a guy with "multiple advanced degrees" didn't notice a glass of freezing water measured 5c and didn't ask "why?"  I'm having a good chuckle over it.  Thanks.  You've restored my faith in advanced degrees being nothing but pieces of paper.

RE: Underextrusion and nozzle clogs

Posted by: jim.h9

[...]  1mm retraction at 0.5mm/sec

Sorry, what is at 0.5mm/sec? Is that your retraction speed? I'm using 50mm/s with PETG with good success.

[...] I did use thermal compound.

I don't want to get in the way of you guys slinging quals around, but where did you apply the thermal compound?

Otherwise, your settings sound sane for PETG. Interesting that you can print with PLA and not PETG. Most of the heat-related issues we hear about are with PLA due to its lower melt temps. Summertime is a good time to learn PETG. Have you tried simply dialing speeds back with the front knob to something like 50% to observe whether it still jams? If that helps, slicer settings should help. 

RE: Underextrusion and nozzle clogs

One more note: Carbon fibre-filled materials require very slow speeds. See what your Filament Settings->Advanced->Max volumetric speed is set to. Try it at 1 (the value used for Colorfabb XT CF20).

RE: Underextrusion and nozzle clogs

Posted by: Tim

You know, after thinking about it more, the funniest part in all this is a guy with "multiple advanced degrees" didn't notice a glass of freezing water measured 5c and didn't ask "why?"  I'm having a good chuckle over it.  Thanks.  You've restored my faith in advanced degrees being nothing but pieces of paper.

 

I said 'ice water' not frozen ice!!!

RE: Underextrusion and nozzle clogs

Lol -- "freezing" vs "frozen"... yes, English is a tough language.  Besides, water ice is generally colder than 0c.  No worries, you are in good company: Pons and Fleischman also didn't understand metrology, and a bit of history tells us where that got them.

ps: sorry Bob ...

RE: Underextrusion and nozzle clogs

Found my under extrusion problem. First was the thermistor. I had some Chinese thermistors that the resistance was 160K ohms and not around 100K ohms. The Prusa firmware uses #5 thermistor tables based on 100K ohms. This made the temps read 15-25C hotter than they actually were. Second was the heatbreak had a split at the neck junction. Fixed both of these plus I put some new thermal compound I just bought on the heatbreak (Thermal Grizzly Kryonaut Thermal Grease Paste). https://www.amazon.com/gp/product/B011F7W3LU/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

I just printed out 2 prints with the Atomic Carbon PETG and they were perfect.