tomnagel

@geert_2, I think you can use this method on an UM3 as well. However, I see no benefits. If you position your print head in a corner according to instructions, it's virtually impossible to break or bend anything.

@neotko No, missing steps is an entirely different mechanism. What I'm talking about with microslip happens in the pinch. The same phenomenon happens in cars: the distance covered with one wheel rotation of a car is dependent on the forces between the road and the wheel. So when accelerating, there is a high force between road and tire, and one wheel rotation gives a smaller traveled distance then when cruising at constant speed when the forces are (much) lower. Back to filament transport: even though the knurled wheel "bites" into the filament, the same effect is there. You can even see it: look with a magnifying glass to the teeth marks on a piece of filament: the distance between the teeth marks decreases when the extruders forces go up. A guy called "Nophead" reported on this effect already in 2009. He has photos of the teethmarks somewhere on his site, but unfortunately I can't find the exact page.

@kmanstudios Thank you for sharing your experiences, and summing it all up. I'd like to make a few additions: * I don't think that it is necessary to clean out a well maintained BB core before storing it. I say "well maintained", because maybe in your case, the thing was already almost clogged when you put it away. I think even in the case the PVA in the core gets moist, the printer will push that out during the next time it primes. Absorbing moisture only makes the filament soft, which is an entirely different thing than (thermal) degradation. Of course I'm not saying that cleaning it before storage is a bad thing, but I think it is not worth the trouble. * We have done a large test with 22 printers for more than 2000h. All with different preventive maintenance intervals. Our conclusion (yet to be published, so consider this a preview): the advised cleaning interval is 400h. Reason: during normal use, there is some build-up of degraded PVA on the inner sides of the nozzle. Even the printers which we gave *no* preventive maintenance stayed open, but the build-up will increase the chances of clogging when you have an incident, and probably the flow resistance increases as well, though this was not measured. This research concluded 400h was the optimal interval. * Just by trying, we found that for some reason, clear PolyCarbonate (PC) works very well for cleaning the BB core. In many cases, the brown build-up is extruded when PC is pushed through the nozzle, while PLA is just extruded and leaves the brown stuff behind. Hot pulls at 270degC, cold pull at 135degC. * Last but not least a remark about hot pulls: timing is of the essence. To be able to "fish out" the clog or dirt, you need to press the filament in the print core not too long and not too short. Too long will melt too much of your stick, and all the molten stuff stays inside including the dirt. Too short, and your stick has not become soft and sticky enough. You will learn by doing, but 1-2secs covers it I think.

Not perse worse, just different. And different behaviour of a subsystem creates different behavior in the total system, which could be, in combination with the Cura default profiles, suboptimal. Every feeder has something I call microslip, with which I mean that the amount of filament that is transported per revolution of the motor depends on the force on this same filament. In the UM2+/UM3 feeder, this microslip is probably more than in the Bondtech feeder, because that feeder grips the filament on both sides. Some people might say that therefore the Bondtech is superior. But that is not always true. A somewhat higher microslip yields a more 'forgiving' feeder, which could be beneficial in the first layer for example. And there can be other differences, I don't know. Anyway, the default Cura profiles are tuned towards the UM feeder, and not towards other feeders. So if you are a user who wants 'no hassle', stay away from non-UM 'upgrades'. If you have special needs, and are willing to invest a lot of time optimising your system, go ahead.

If it behaves differently than the UM3 feeder, the standard Cura printing profiles won't be optimal anymore. If it behaves the same, then it's not worth $400. It very much depends on what you are looking for. In general, the UM3 feeder performs well, but in certain cases the Bondtech feeder will be better. But you will have to optimise the slicer settings yourself.

The pattern is always printed without the calibration. If you want to see the result of the calibration, try printing a dual material object.

Please be aware that Active Leveling also measures the Z-offset between nozzle 1 and 2. It does so more accurately than most users can.

Yes, features are being built into Cura to use the 0.4mm and 0.8mm print core in one print. And actually, with different layer heights. This is already possible with the current version of Cura (infill thickness). The limitation is that the thicker layers should be a multiple of the thinner layers. But the next version of Cura will enable you to choose the extruder per feature. So then, you can print the inside of a model with a thicker nozzle and thicker layers, and the outside of the model in high detail (thin nozzle, thin layers). For most models, this will greatly decrease printing time. Bu it also enables you to print the skin of an object with "special material" (bronzefill, woodfill etc) and the inside with plain/cheap stuff.

A small addition here: the glass must be *low enough*, but does not have to be in the lowest position. Before leveling, the glass moves upwards at high speed. When it starts the probing process, it switches to the low speed (with a humming sound). At the start of this, there should be at least 0.5mm between the glass and the nozzle. So you could aim at 1mm or so. The drawback of a lower position is that active leveling takes longer, ans does not increase reliability or accuracy. For the highest reliability and accuracy: clean the nozzle, and clean the glass plate. Please note that at the probing points on your glass plate, small amounts of plastic may accumulate, which ruins the accuracy of the probes.

Sorry, I don't think cleaning the contacts can help in this case. Dirty contacts will only increase resistance, and the resetting behavior points at a too low resistance. My guess is that your AA print core is faulty. Your reseller will be able to help you.

This is definiteky not a known problem. Are you using a recent version of Cura? Your print profilies could be faulty, consider a reinstall action of Cura. And then manually remove the folder with the profiles (which one, @ahouben?) And after so many failed prints, could your nozzle be clogged? Try cleaning it using the cold pull method (aka atomic method) https://ultimaker.com/en/resources/23132-clogged-print-core

Just to be sure: what do you mean with the z-seam? Is it the vertical line in your picture? I'm just triggered by your remark that you get this with 2 different slicers. If you mean the horizontal line in your picture, that might be a problem with your z-bearings.

I have to correct @kmanstudios here, a hot pull with PLA is (meant to be) done at 230 degrees. Insert the plastic, wait 1-2 seconds and pull it out. The timing is of the essence here, because if you wait too long, too much of the inserted plastic was molten, and you are not able to pull the dirt out! If you wait too short, the plastic has no time to melt. see also this support page. So: bring the hot end to 230, and start "fishing" with hot pulls. Please report back your result. I will help you further if necessary.

Looks like the heater in the second AA core draws too much current, which makes the power supply cut power. If you have a multimeter at hand, you can measure the electrical resistance of the heater. It should be typically 23 Ohm (21.9 - 25.6Ohm) And if you reinsert the BB core and force active leveling (which heats up both print cores), this does not happen?

What printer are you using, with what firmware? If What does the printer do right before printing this first line? Did it prime? If you print the biggest object that your buildplate can fit, the brim will be big as well. That enables you to see if the line width normalizes within say, 20 seconds, or that it keeps being too wide. In the first case, it is a startup issue, in the latter case there is some error in the extrusion rate.

I think you did not answer this question: "When you take out the PLA during hot-pull, is the tip melted? That is hugely important. If you have material stuck in your cold zone the hot and cold pulls will never work." I don't understand why you cannot extrude material after you punctured the clog with a needle. To which temperature did you heat up the hot end? Did you use polycarbonate for the hot pulls and the cold pulls?

Did you contact your reseller already? They will certainly be able to help you.

I don't think there's a way to tell Cura where to start the fill pattern. I think it has to do with temperatures going to equilibrium in your printer. Not so much in the print head, but the bed and the frame. If you'd like to experiment a little, use the preheat function in Cura, or set the temperature of the bed manually 15 minutes before start.

You probably want to know the nozzle material. It is brass, just like the 0.4mm.

The XY calibration is only to accurately align the left and the right nozzle. If your circles are oval shaped, I think it's usually a problem with your short belts. Look for the Ultimaker troubleshooting guide from 3DVerkstan.

Were there any special characters in your file name? like German umlaut? That goes wrong somewhere iin embedded. Will be solved.

The latter

Keeping the PVA dry is definitely the most important advice. I'm not sure that this is also necessary for the bb core, I don't think that is necessary, but it certainly won't hurt.

Please read my comments in https://ultimaker.com/en/community/49459-clogged-bb-core?page=1&sort=#reply-180561

I heard that the ptfe tubes are less stiff. If that is true, building up tension will take longer, which would be a clear drawback. Also I like the fact that the current Bowden tubes are transparent.