Sudden extreme Underextruding  

Re: Sudden extreme Underextruding

Hi Mathias.

I think I would reset the multiplier at 1.0 and increase the temperature instead. 1.5 is really too much.

All PETG are not the same, and it's possible that your PETG need higher temperature to reach the same viscosity as the PR PETG at this temperature. Do you have the print specification of your filament ?

Re: Sudden extreme Underextruding

Hi Christophe and thanks for sharing your thougths,

I started with 1.0 as it is Prusa PET standard and changed the Temperature settings to the Manufacturers recommendations. I then printed a Testcube and adjusted "flow" while printing. With that in mind i created gCode with extrusion Multipliers 1, 1.1, 1.2, 1.5 and 2. I printed all these cubes (just a few layers) and 1.5 was best of the five.

You can view the recommended settings for yourself (if you like) at
https://www.dasfilament.de/filament-spulen/petg-1-75-mm/174/petg-filament-1-75-mm-rubinrot?c=21
Recommended print temp is 230+-10°C, and Tom from Toms3D has the Filament listed with 230°C in his " Wall of Data" too (line 80).
https://docs.google.com/spreadsheets/d/1j9QazgoocuzHxg6qUXevq3dpAmmT2E87089FX6gRgWU/edit#gid=0
He also prints withe MK2 so the Values should be representativ.

From what i can tell it really flows already very well at 230°C and tuning it up to 240°C makes no noticeable difference.

I am currently using 230°C Nozzle and 75°C Bed Temperature coated with a thin layer of glue Stick to lower adheason and now somewhat helpless.

Re: Sudden extreme Underextruding

Then I'm out of idea.

Regarding the bed temperature with the PETG I have (RepRapper from a local store), I use a 55 °C for first layer and 60 °C for the following and have a good adhesion as well as a decent unsticking once the print is over, that's worth to try it.

Re: Sudden extreme Underextruding

I slept a nigth over it and thougth it could be a too low tention on the Extuder maybe slipping over the filament.
So i tigthent the Clamp untill i could hear the Extruder skipping (10mm washer to the underside of Screw) and then loosening it again untill the Skipping stopped (12mm washer to the underside of Screw). But that did not seem to help either.

I stumbled over this Thread
http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/pinda-probe-height-de-mystified--t2588.html#p20436
and measured my Distance between Nozzle and Bed afer an "Auto Home" to be 0.85mm (Measured with feeler gauge).

So i decided to redo the whole Pinda-Probe allingment and Z-Offset calibration. Peter aka PJR says that the Nozzle should be between 0.15 to 0.25 mm above the bed when The Printer has finished the "Auto-Home"-Command (if i getting him rigth there). After two hours i ended having a gap of about .35mm. Which introduces a new problem when calling the "Calibrate XYZ". The Nozzle touches now the bed on the Last Calibration point. I saw that while starting the "V2 Calibration gCode" but decided to let the print finish. I then saw that the line layed down was much fatter in the back than in the Front
So i tilt it over the Calibration Option "Bed Level Correct", +20µ in the Back and -20 in the Front and retried Like "vojtěch.b3" statesin Post#3 under
http://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/how-to-use-bed-level-correct--t1560.html
Now i wouldn't notice that the nozzle touches the Bed on the last Calibration Point if i did not already know. Something has clearly changed there. It was clearly visible before and now just mearly, if at all.

I did all this with PLA loaded to the Printer and the value for the "Live adjust Z" was -0.2mm. I got this value by assuming that the nozzle is lowered relativ from its "Home"-Position by the value entered under "Live-adjust Z". So in theorie the real Position is .35mm(measured) and the virtual Position is .15mm which leads to -0.2mm for the Offset Value. For PLA i got a nice line and was happy so i loaded the PETG again and had the same extreme underextruding again where i started yesterday. Settings where the "Prusa PET"-Standard with Slic3r.
I tried to print a cube 20x20x10mm and stopped the print when the printer was half throu and saying 0.5mm for higth in Display. I pulled of the "Cube" and measured it with my dial Calipers to be 0.8mm. 😯
Which lead me to further lower the nozzle to -0.35 which should be "Nozzle, touching the Bed" which gives me one nice clean even more perfect first layer as for PLA. 😯
Top (last layer)
?dl=0
Bottom (first layer)
?dl=0
For that one i used the "Fast" settings 240°C nozzle temp and 55°C Bed temp, as you suggested.

But that makes no sense at all to me. Why does this work? It seems that i missunderstood something. Can someone please tell me what i got wrong?

Re: Sudden extreme Underextruding

Matthias

Yes, it is getting a tad close when you get the nozzle set up as I have. I can hear the nozzle just tapping the bed at cal point 4, but the key is that the higher the probe whist passing calibration, the better the outcome - for me anyway. The bed should always be at working temps when running the 9-point cal and the nozzle should be well above the bed during pre-heat.

Peter

Re: Sudden extreme Underextruding

Okay that is somewhat good to hear. But that does not explain why i have to set the nozzle that deep. If my understanding is correct the nozzzle should now be at heigth 0mm when laying down the first layer. But thats not what happens. The total higth of the Cube is 10.05mm (should be 10) which is fine but not what one expect. Iwould expect squeezing the first layer so much that it is ttotally missing or ultra-thin. But no, i can see that it is layed down nicely.
I just don't understand why it is how it is and would really like to understand it.