Dim3nsioneer

Die Lüfter laufen gleichmässig oder siehst Du da auch Unregelmässigkeiten? Das wäre jetzt sehr interessant, die beiden Lüfter-Duos mit einem LCR-Meter auszumessen. Aber ich nehme nicht an, dass Du sowas bei Dir rumstehen hast (ich leider auch nicht ).

This might happen if your z calibration is far off. Go to System->Maintenance->Calibration-> Calibrate z and give the machine a reasonable height for the second printcore.

I'm not sure if I get your issue correctly as there is no nozzle cleaning but a level switching on the second printcore. If this is your problem, i.e. the print head does not drive to the level switch correctly, you might want to try to re-calibrate it. There is an assistant for this in System->Maintenance->Calibration (first option) on the printer. In case I got you wrong, please post a short video. It might also be a good idea to get in touch with your Ultimaker reseller as driving into the clips is far from standard behavior and hints for an issue which might fall under waranty.

Not so far in Cura. But the flow behavior might be a bit different from one color to the other.

It might become a bit matt with time but there should not be deep scratches which could affect print quality.

I usually scratch it off with my fingernail. You can also remove the silicon ring from the core and brush the nozzle with a BRASS brush (not steel!).

@OlivierV: Did you check what the NFC reader test in the diagnostics menu (submenu of maintenance, submenu of system) says about that spool? Does it see the tag? Does it write "UNKNOWN" below the tag id?

Are acceleration control and / or jerk control activated with this printer in Cura? If yes, you may want to switch it off.

It's not that simple. Those users who print 1.75mm on their Ultimaker did in most cases some quite substantial changes to the printer (e.g. new feeder, different hotend, swap the Bowden tube). Please search the forum for reports and threads about such projects.

Let's test this. How would do you unclog a BB core in which you cannot insert any material from top far enough it gets soft?

Some spools have a hole diameter of 52-55mm, some a bit less. The latter can cause trouble with the material guide of the UM3. Even some UM spools (e.g. the spool used for TPU95A white without NFC tag) are affected. With a bit(!) of additional force they can be mounted.

The price including 19% VAT has indeed two digits in Germany and if you add some shipping charge the first digit is probably not a "1"... Depending on how urgently such a part is needed, it's still better than waiting for weeks for a cheaper part to arrive from China. @chrii: In case you are using a Robert feeder, you may also want to consider replacing the knurled UM part by an MK7.

I would avoid any "unnecessary" connectors.

Jetzt wäre eventuell noch hilfreich, diese Betrachtung bei einem Standard UM2+ mit der Standardfirmware zu machen. Das gäbe dann doch starke Hinweise darauf, in welchem Teil der Firmware die Probleme zu suchen sind.

In order to provide hard facts, here a result for the Ultimaker website by webpagetest.org. This service tests loading times of any website from a location of your choice (I've chosen Strassbourg in France as it is one of the closest to my place) and it is recommended by Google. https://www.webpagetest.org/result/170808_CV_QW9/

Metal doesn't bend

Nur so der Vollständigkeit halber: Die X/Y-Achsen sind alle gerade?

I use the one from @labern on my UM2 (dual version). It's advantage is the nice air guidance with low resistance, it's disadvantage is that the material comes pretty close to both nozzle and Olsson Block which leads to some deformations even as I printed it in PC.

Would you mind to post a picture of your print head from below (so we can see the nozzles)?

Would it be easier to simply use screw terminals or something to switch heaters and temp sensors instead of having to play with the software? I don't recommend to use switches for the pt100 and the heater. The PT100 would suffer from wrong measurement and the switch for the heater would have to sustain the 35W. If it is switched accidentially at full power it can be fused.

Ich habe gedacht "Hot Pull" und "Cold Pull" ist das gleiche bzw. meine ich das ich das irgendwo gelesen habe? Vom Mechanischen her ja, aber der Cold Pull wird bei tieferer Temperatur gezogen, so dass der Dreck mit dem Filament rauskommt. Der Hotpull reisst eigentlich immer durch und der Dreck bleibt drin; also ziemlich wirkungslos meiner Meinung nach.

You mean the temp2 and the heater2 connector? Yes. And I use Tinkerware 16.08.something.

You also might want to tag @swordriff directly for getting advise. Anyway, printing with a 0.25mm nozzle on an UM3 has to be considered as experimental, i.e. one has to find good settings by try-and-error.

I did this. And I spent quite some time to set up a machine profile for 1.75mm on extruder 2. But I cannot share it because I really had to do some very nasty hacks such as copying user settings from one PC to the other to get it working on the PC I wanted to have it. You have to create new json (for the machine and the extruders) and other configuration files. Unfortunately this is not very well documented atm. Most important thing to know is that it seems the property "material_diameter" is defined on the machine level instead of the extruder level (which is wrong imho). Further you have to define a 1.75mm material for your machine type and that's where I just got it running by accident and not by knowledge. Changing the existing generic 1.75mm PLA profile so it should also appear with the newly defined machine helped in my case on one PC but didn't work on the other. Copying the machine definition from the user settings got it working on the other computer. Maybe it's me being not clever enough for creating those files. In this case I want to ask the Cura devs to publish some kind of machine-profile-for-dummies(-like-me) guide.

Im Zweifelsfall bitte der englischen (neueren) Anleitung folgen. Ich empfehle für die Innenreinigung ausschliesslich Cold Pulls; Hot Pulls bringen meiner Meinung nach wenig bis gar nichts.