Blockage troubleshooting.  

Re: Blockage troubleshooting.

So.....

I have replaced the Heatbreak and the heater block (I bought these from Prusa because I though mistakenly I had broken it), installed the spare PTFE tube which did have a chamfer and the inner chamfer is at the top. I reset the calibration and the proceded to re-run it going through each menu item in turn. Everything calobrated with no issues, I have run the Temperature Calibration and at this point I am confused by the 'Temp. Cal. [OFF]' Option there. What does it do apart from calibrate the temperature when set to [ON]? I haven't as yet run the PID calibration, should I?

I ran the z-height test from the Calibration Menu and I determined mine to be at 790. Then I printed the Prusa Logo from the SD card which is the Single Filament print (and not to be confused by the orginal MK2 Prusa Logo gcode file). It printed ok, the top layer does not overlap with the perimeters correctly but I'll take that for now. The first layer printed just fine with the temperature set in the gcode file, 220 if I remember correctly but as I watch the print the temperature fluctuated as much a 3º either way of the 220 which concerns me somewhat.

I must be getting somewhere or am I tempting fate?

I downloaded the 'PrusaLogo4C_MMPP.GCode' and set about printing it. I used a mixed bag of filaments but all within the same temperature range. The GCode file's temperature settings weren't a good match for my filament and I noticed the loading od each colour had all of the extruder motors grinding away. I manually change the Temp. from the 'Tune' menu which was kinda ok but I also notice that the filament was being pushed a bit too hard I think and this lead to grinding even though I had the Temp. set up to 220. Which to be honest I did expect as some of my Filament was towards the low quality end of my collection.

Its getting late here now so I will try and continue testing and tweaking tomorrow. If one of you kind peeps could explain the 'Temp. Cal. [OFF]' to me and whether I should run the PID Tuning I'd really aperceate that.

Re: Blockage troubleshooting.

Have you replaced the nozzle as well?

Re: Blockage troubleshooting.

Its getting late here now so I will try and continue testing and tweaking tomorrow. If one of you kind peeps could explain the 'Temp. Cal. [OFF]' to me and whether I should run the PID Tuning I'd really aperceate that.

OK, ther temperature calibration is an attempt to calibrate the probe for temperature differences.

There is a different probe response at different temperatures and this heats the probe up to a "known" temperature prior to the 9=point calibration. However it's something I don't use and other users have reported issues with this procedure. I find it better to start with the probe at least 100mm above the bed while pre-heating before a print.

PID tuning is well worth running; it will stabilise the temperature to about a half degree swing (or less).

Regarding your filament. If this is PLA, you should be extruding at 205 degrees (or less), with the first layer at 215 degrees. 220 is really too hot and you will get stringing and blockages during filament changes.

Best thing to do is to print the temperature test cube (in the first post of this thread) for each extruder and filament. Stop the print if the filament start to skip or grind. Measure up from the bottom to the point where you are getting a decent finish all round. The cube starts at 215 degrees and reduces 2 degrees per millimetre.

Peter

Re: Blockage troubleshooting.

OK, I swapped the nozzle for a brand-new one and got exactly the same result as last time (using the same gcode). It even started skipping on the same layer (single mode tree frog, minimal retracts). The filament blob at the end looks like a mirror image of the one I posted earlier on. I'll contact Prusa support tomorrow, see if they send me a new heatbreak&radiator assembly.

Re: Blockage troubleshooting.

Peter: Can that temp cube be used for single extruder? Or is it gcode for MMU only?

Re: Blockage troubleshooting.

Peter: Can that temp cube be used for single extruder? Or is it gcode for MMU only?

Because of the load and unload, it is MMU-fitted single extruder G-code.

It's easy enough to generate; just download KISS and the profile and use the wizards to create. KISS is free for single extruders.

Peter

Re: Blockage troubleshooting.

Follow-up question:
I have a rusty-red coating sticking out of my heatbreak, between the heater block and heatsink. I assume it is normal, but:
- Does everybody have it?
- Is this some sort of thermal contact paste or just a way for Prusa to detect if someone unscrewed their heatbreak?

Re: Blockage troubleshooting.

Follow-up question:
I have a rusty-red coating sticking out of my heatbreak, between the heater block and heatsink. I assume it is normal, but:
- Does everybody have it?
- Is this some sort of thermal contact paste or just a way for Prusa to detect if someone unscrewed their heatbreak?

There's a thermal paste used between heat break and heat sink, but that's usually white or light grey.

What colour filaments have you been printing with? Could be your nozzle/heat break seal is not good - the filament usually goes upwards and exits the top of the heat block.

Peter

Re: Blockage troubleshooting.

That's not it, the red stuff was already there when I unpacked it and the hotend had absolutely no visible filament residue in it. I don't think they test print them, do they?
Also it's not plastic, more like paint with a copper sheen. That's why I just assumed it's thermal paste.
The top end taper looked spotless and there was nothing inside the heatbreak when I had it apart. The block was clean.
Just speculating that some of that stuff spilled into the lower opening of the heatbreak and causes friction there.

I'll not unscrew the heatbreak from the heatsink for now (unless they tell me), just in case the stuff is meant as a seal. I hope the red doesn't mean "mock-up sample, do not use in real printer" 😀

Re: Blockage troubleshooting.

That's not it, the red stuff was already there when I unpacked it and the hotend had absolutely no visible filament residue in it. I don't think they test print them, do they?
Also it's not plastic, more like paint with a copper sheen. That's why I just assumed it's thermal paste.
The top end taper looked spotless and there was nothing inside the heatbreak when I had it apart. The block was clean.
Just speculating that some of that stuff spilled into the lower opening of the heatbreak and causes friction there.

I'll not unscrew the heatbreak from the heatsink for now (unless they tell me), just in case the stuff is meant as a seal. I hope the red doesn't mean "mock-up sample, do not use in real printer" 😀

Ah, it may be a "non-stick" thermal paste. The type they were using went cement-hard and it was impossible to remove the heat break.

You do need to unscrew the heat break half a turn to properly install the PTFE tubing though...

Peter

P.S. Nothing so far...

Re: Blockage troubleshooting.

Well, it doesn't come off only using the nozzle to counter. I'll have to stick it in the oven and use a couple of M6 hexnuts, but not before contacting support. In case it breaks I'd rather not pay for it.

Re: Blockage troubleshooting.

Follow-up question:
I have a rusty-red coating sticking out of my heatbreak, between the heater block and heatsink. I assume it is normal, but:
- Does everybody have it?

yes I have that too. The first time I saw it I thought it was PLA which oozed upwards somehow lol but then I figured too that it must be a thermal paste or insulation or something like that.

I'm sorry to read that swapping the noozle didn't work, I hope support will not let you down 😉

Re: Blockage troubleshooting.

[/quote]
Best thing to do is to print the temperature test cube (in the first post of this thread) for each extruder and filament. Stop the print if the filament start to skip or grind. Measure up from the bottom to the point where you are getting a decent finish all round. The cube starts at 215 degrees and reduces 2 degrees per millimetre.
[/quote]

I have run the PID Tune and I'm now runing another filament trhough the Temperature Test Cube of yours. So far I have had no clogs, jams or grinding from extruder 1. Maybe the PID tune has taken care of the temperature fluctuation.

looking at the first Temperature Test Cube I can see the the filament really doesn't like the lower temperatures, once it drops past 185 there are issues with under extrustion which is what I would expect. I normally print at 210 - 220 but I think lower is better as you have said. Even my lower (and much older) filament is printing which proves that if the crap will goe through the better should be more than fine?

The cheap old rubish filament.... Yes I know but if the crap will work just fine the the theroy is the good will work very well?

Re: Blockage troubleshooting.

OK, the fun continues....

I have replaced the filaments now as it's time to get serious. The four filaments I have loaded now are all the same brand and all printing withn the same temperature ranges.

I'm trying to print the Prusa 4 Colour logo. It's not going very well. First off my z-height at 790 was off (again) so I have now adjusted it to 690 and it looks kinda ok for the first layer. But the the yellow jammed on loading it so it missed the first few layers. Next the organge jammed and I can hear it grinding away as the temperature start to get down in to the 200ºc area, the other three so far are ok, the other three are still printing just fine.

Next up I have a box of rigid ink samples and I'm going to repeat the print with a random selection, let see how brand name filament performs and if the problem does continue then I will be disassemlening and going back to a single extruder, when everything I through at the printer just printed.

Now as I continue to write here the orange filament is no longer jamming... how random is that?

Re: Blockage troubleshooting.

OK, the fun continues....
First off my z-height at 790 was off (again) so I have now adjusted it to 690 and it looks kinda ok for the first layer.

My z-height is becoming an issue, it's now down (or up) to 530 now and still looks too low. I have used the long cable tie as detailed in the build manual to set the probe height from the bed. I have let the printer cool right down to room temperature between prints before starting another print.

Done a couple of other random prits of nothing in particular. I have noticed the temperature >=205ºc works much better than the defaults of 215ºc set in Slic3r, its also much more stable after doing the PID Tuning.

I have notice the the filament can't be being loaded correctly but I could just be doing it wrong. When I unload then reload and start a print the filament is not extruded so I have to abort the print. I did read that someone was having a problem with the slow load, I'm not sure if I am expereincing the same issue. When I load filament I can feel the extruder grab the filament but it doesn't move anywhere, when I press the controller knob the filament loads quickly. As I can't find the exact detailed loading procedure I guess that is is correct. I am considering doing a firmware reset but should I need to?

I have taken the start gcode from the Prusa four colour logo and used it as my start gcode in Slic3r and that has made a big difference as the filament is extruded during the purge lines now which it wasn't before.

Re: Blockage troubleshooting.

For what it's worth. My z offset with PINDA has been a lot worse too since switching to MMU. With single extruder I had to finetune live Z to be somewhere around 0.05mm. Since my upgrade (did the same procedure to measure PINDA to bed distance) my live Z is more than double that.

Re: Blockage troubleshooting.

Mine has been stable but changed after the upgrade, which I would expect (basically every time you remove the hotend the value must be different). Malcinator, either your probe is too close to the bed during warmup, the probe bracket or the hotend itself is wobbling or your PINDA is whacked.
The only other thing I can come up with is the environment, is the printer exposed to quickly shifting ambient temperature (i.e. near a window, radiator, etc.)?

I have done some more testing as well, repeating my misprints using different filament types I have around. Important to note, I swapped to T3 to rule out the MUX, motor, filament path and Bondtech once and for all. It clearly works a bit better (fails later than my T0), but I'd put that down to higher spring tension as I didn't really dial in T3 yet.

I had one of five "successful" single mode tree frogs, but couldn't repeat that one even with the same filament (i.e. it was a lucky shot). I tried 2 different Sakata Ingeo PLA, silver Prusa PLA and yellow eSun PLA. It's not the filament - full stop. The one "successful" print showed terrible banding on the outside and severe underextrusion on the infill, which hints at uneven extrusion that is more pronounced after the layer shift retract. Also, in one case I found a blob of the previous filament polluting the print at about layer 10, so something gets definitely stuck in there.
So far I have had blockage in the heatbreak in about every second attempt, and the extruder cannot unload. In these cases I heat up to 250, remove the MUX and push a bit of PLA through to clear it. But this time I marked a piece of PLA to determine the position of the blockage. It's about 1/3 into the heatbreak from the nozzle side. Again, my fan is fine and reducing retraction speed and/or length doesn't change a thing.
I'l not be around for a couple of days, but I guess I'll remove my heatbreak/heatsink and ask Prusa for a replacement as originally planned.

Re: Blockage troubleshooting.

OK, I have been out today and just seen the recent posts; will try to cover them here...

Live Z During the last year, the Live Z on my printers has changed. With the early Mk2 firmware I started off with Live Z of precisely Zero. With the various firmware upgrades, I have slowly moved to a value of around -0.425. I am guessing here but I think this has been a firmware adjustment attempting to prevent pot holes in the PEI sheet.

Setting probe height How I do this: I set the probe as high as possible such that it will just pass calibration without the nozzle touching the bed. This involves raising the probe and calibrating until I get a fail and then lowering the probe slightly.

Setting Live ZI use the hyperfine bed levelling which allows calibration of the 8 outside points. In the hyperfine bed levelling thread I posted some G-code which allows Live Z to be set without printing and by using feeler gauges (or a folded sheet of copy paper). Once Live Z has been set at the centre point, the 8 outside points can be estimated and corrected individually.

Filament LoadingOne user had bad settings for the bowden tube length. This was amended by doing a factory reset and selecting Bowden Lengths from the menu - NOTE that you do not have to do a factory reset to achieve this, just get to the factory reset menu.

Peter

Re: Blockage troubleshooting.

Follow-up question:
I have a rusty-red coating sticking out of my heatbreak, between the heater block and heatsink. I assume it is normal, but:
- Does everybody have it?

yes I have that too. The first time I saw it I thought it was PLA which oozed upwards somehow lol but then I figured too that it must be a thermal paste or insulation or something like that.

I'm sorry to read that swapping the noozle didn't work, I hope support will not let you down 😉

Having recently worked through a blockage issue with Prusa support, I can tell you that this red band signifies that the hot end is the E3D rework for the Prusa MM upgrade. It is used to distinguish between a stock E3D hotend like the one that came with your MK2S.

Re: Blockage troubleshooting.

That makes sense, thank you.