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Let's get back on subject. For the UM3 what could he have done to make one object print on one extruder and the other object print on the other extruder? And how could he have seen this in layer view?

It's barely HD (800X600). You can't connect to it through octoprint (pretty sure) but you can connect to it through any web browser. Also when connecting through a web browser the frame rate is much higher and the resolution is higher also (higher than other methods - you still only get 800X600). http://X.X.X.X:8080/?action=stream Change the Xs to your ip address for you UM3. Here is an actual size 800X600 screenshot of my UM3 at this moment (not printing this very moment):

Take it out and clean it. Mine had a few hairs in there blocking contact. First step is to remove the bottom front metal cover. Then remove the knob by pushing it out from behind. More info here:

In this photo of PLA the tension on the feeder was too low for the pattern on the left and a bit too high for the pattern on the right.

As a quick test - the UMO can pull about 10 pounds (5kg) of force. If it is pulling less than 5 pounds (2kg) it needs tweaking. Set the filament in the bowden so it is about half way. Hold the big gear in one hand and try to pull the filament out with the other. Also try lifting something of known and similar weight (like a few liters of water) for comparison. For example your printer should be able to "lift itself" meaning the force it can pull on the filament should be greater than the weight of the printer.

Ah! Okay I was able to duplicate the issue by checking the box "zoom towards mouse direction". Well turn that off! That's the whole problem. With that turned off it works much better. Having said that, I would love it if the cura engineers would make it so the orbit features pays attention to where the mouse is and orbits around where the mouse is instead of around the part. Same with the "+" keyboard key when zooming - that also ignores the position of the mouse even when I check the box mentioned in the first line of this post. Also I have a 3d mouse. I absolutely love my 3d mouse. It would be great if cura supported that.

Your bottom layer isn't squishing enough so the bottom layer appears underextruded and isn't sticking well. You need to move the nozzle closer to the print bed. If this is an Ultimaker then turn the 3 leveling screws about 1/2 turn CCW to move the bed up. Turn off any auto leveling if you have a UM3. When the first layer is going down watch it carefully and adjust the 3 screws by equal amounts (assuming you leveled the bed) until you have the bottom layer squished nicely. here's a video with probably much more detail than you want but it will make you a "make my part always stick" expert:

I'd look over all the retraction settings - I don't know the A8 but if the feeder is on the print head retraction should be no more than about 1mm and if the feeder is far away from the hot end and you have filament going through a bowden that connects the feeder to the hot end then retraction should be closer to 4mm. I mean the problem really seems to start suddenly when the retractions start. Also look at the part in layer view and I think cura has a way to show normal non-printing moves (blue lines) differently than retraction moves (lighter blue lines). Make sure to check the checkbox for showing "travels" when in layer view. You want only light blue (retraction) moves from one finger to the next. Darker blue would be expected within a given finger.

With power off I'd check all the pins that go into the arduino to make sure there aren't any bent ones. Also try removing the arduino board from the UM board and connecting to USB (which will power it up) and see if you can connect to the board that way using pronterface. Or try to connect to it in cura 15.* with and update the firmware from within cura. You want to figure out if the problem is with the arduino board or the green board. Hopefully it's just a loose connection and removing and re-inserting the arduino will fix your issue. If you have a windows machine and connect it to the arduino and you have the arduino driver installed you should hear that "ba da" sound where the second note is a higher pitch. Then in device manager you should see a usb device that popped in when you plugged it in and/or it should then appear as a COM port in the list of COM ports. If it appears in USB but not COM ports then you probably don't have the arduino driver installed.

You got EXP1 to EXP1 but did you get the red stripe the correct way round?

Look for pieces of wood dust. Find the assembly manual and look that over and take yours apart and look it over. It could be many things. Make sure the bearing rotates easily. Spring should be compressed to about 10mm when feeder is closed up.

Could you post a photo please? It usually takes several layers to go from infilled layers to solid layers because the bridging isn't perfect but 1.2mm should be enough.

What is your layer height here? Maybe try a bit thicker layers? Is the fan working? I'm not convinced it's underextrusion. maybe retraction settings or hardware issues. Maybe your layer height is simply too thin.

Was your fan on during the print? Turning the fan off might be good enough.

Well if you are getting sensor errors you probably have a bad sensor. I don't think there is any other explanation so I would concentrate on that. Regarding layer height - you shouldn't be restricted just because you happen to have a weak heater. But it might not be weak - it might simply be the sensor is bad. So if you aren't afraid of taking your head apart I would just order a sensor and see if that fixes it. If you don't want to have to take it apart twice then consider also buying a 40W heater and just change both at the same time. The way these sensors work - they are a pt100 chip that is indestructable and can handle 500C no problem. The trick is attaching this chip to the wires because it has to withstand 250C. So you can't use any kind of solder. So they crimp the wires to the pt100 and these get heated and cooled repeatedly and can eventually get somewhat loose. Often the sensor only fails above some seemingly arbitrary temperature because everything expands when it warms up.

Well which is it - heater error or temp sensor error? They are completely different. Heater error is when it can't heat the nozzle up more than a given amount in a given time. Sensor error would imply the sensor is giving seriously wrong readings (0V or 5V). If you get the second error then something is loose - I'd remove the sensor cables from under the printer, connect to an ohm meter, and jiggle the wiring at the connector there and at the nozzle area. You might have to replace it. However, I'm guessing you only get heater error and what you describe makes sense. Heater error is when it's putting in full power and the darn nozzle just won't heat up any more. This could happen with .3mm layer heights and 0.8mm nozzle. It wouldn't happen on the first layer as it's printing slower so less plastic to melt per second. Also the fan doesn't come on until the second or third layer which makes the heater have to work even harder. So if it's only heater error then you probably want to beef up your heater. UM used to sell 25W heaters with their printers but the value was all over the place and I saw one even as low as 18W. So I'd replace that with a 35W heater (which I think is what comes with the UM2+). You can get one from 3dsolex or any Ultimaker reseller. 3dsolex also has 40W and 50W heaters. Or you could consider getting the plus upgrade. It's expensive but you'll probably really like it.

No need. Except when I just put my bed back together I skip right over that part. It's just to make sure that when you actually do the "true" leveling it doesn't hit any of the clips or scratch the glass. Autoleveling is just a bad idea overall. It's going to result in the bottom cm or so of your part with varying corrections. So your part will be less accurate than without this feature. For example if your bed has a .3mm tilt to it, then your final print will have a .3mm tilt on the bottom layer. Add to this that lots of things can confuse the feature (like some filament on the tip of a nozzle that is above the expected melting temp because now you have pla in but the stuff on the tip is higher temp). When UM gets 9 point or higher autoleveling that compensates for curved glass - THEN it will be a useful feature. For now it only compensates for tilted planes.

@hoegge I watched the video. I couldn't duplicate that crazy behavior. When I rotate it ALWAYS rotates about the center of the print bed. So if my part is in the middle (like your benchy) then rotate works fine. But if I put my part in a corner then it sucks - just like your video. How do you zoom? How do you rotate? I rotate with right-click-drag. Do you have some other way to rotate? I don't have a mouse wheel or middle mouse button so I zoom with the plus key: "+". It doesn't matter where my mouse is when I zoom in that way - this might be a key to why we see different results.

I just looked at the code. What I think @ctbeke means is that as soon as a layer_height is thin enough to satisfy the above formula, the algorithm stops trying to make the layer thinner. Also looking at the code he got it backwards - "steepest_slope_in_layer" appears to actually be flattest slope in layer. Another way to look at it: adaptive-layer-height = threshold * tan(flattest_slope_in_layer) (but it never goes outside the min and max layer heights) I think. Did I get that right @ctbeke? cool feature by the way! I'm pretty sure that's right. It's just that instead of doing the simple formula above the algorithm is trying different layer heights - getting thinner and thinner until it satisfies the first formula above. I think more complexity should be added to the algorithm - the algorithm should distinguish sloped overhangs from sloped top surfaces - I know right now it just deals with a huge list of triangles in 3 dimensions but still - it should know which ones are top and which are underside surfaces and have different minimum_layer_heights for the two types because you don't want to add extra layers for overhangs. You only want to add extra layers for top surfaces. Adding thinner layers for top surfaces makes the stair-step pattern disappear. Adding more layers for overhangs makes the quality go to hell.

@chuck-yanke Here is a quick summary of the problem: Ultimaker and many (but not all) printer's stepper drivers are implemented such that every 15th and 16th step is very weak and the stepper usually doesn't move on those. So if it is moving smoothly it moves steps 1 through 14 then pauses for two steps and then suddenly moves 3 steps on the next cycle (back to the first step). This causes very very tiny stair-steps in your print and is most noticable on large flattish surfaces that are not parallel (but are almost parallel) to x,y,z planes. For example this is invisible on most cylinders, cubes, boxes, gears, chamfers, holes... It's invisible on almost all parts. Unless you rotate your cube by 1 degree from being parallel with X axis. It's visible on parts like "benchy" which is cartoonish and none of the planes are parallel to anything. So on Benchy's walls which are slightly not vertical and slightly not parallel it's visible. It can also be visible as repeating horizontal layer lines because sometimes the Z steps more and sometimes less depending. For what I print - mostly mechanical stuff - it doesn't matter. For artistic, organic stuff like an animal - which has no large flattish surfaces - it doesn't matter. For certain parts it matters. The tl-smoother adds a diode which makes it so the stepper has to up it's voltage. This really helps the 15th and 16th steps get more power - more oomph. The tradeoff is the stepper driver has to work harder and gets a bit hotter. No one seems to know how much hotter so it's not clear if you need to add heat sinks/fans or not. Most people do not and most people seem fine and happy. If the stepper drivers overheat their built in circuit turns off for a few milliseconds and you get lost steps in your prints - it's very obvious. But no hardware will get damaged - instead your print will be ruined. In my opinion it's a waste to put the tl-smoother on the E axis (extruder) because it won't help the quality of your print (in my opnion) and also because that is the stepper that is working the hardest and most likely to overheat as well. That is why most of these tl-smoother kits only have 3 cables for 3 steppers.

@cjs - I have not modded my UM3 other than to print the ultiwedge from youmagine (not really a mod) and I use 3dsolex cores instead of standard cores (disclaimer - I sell them in my store). But what does a tl-smoother have to do with auto leveling? Nothing as far as I am concerned. tl-smoother just increases the power of the stepper a bit every 15th and 16th step such that the stepper moves the proper distance on all 16 microsteps and not 14 out of the 16 micro steps.

If you really want you can program the AA core to think it's a BB core. UM seems to think it will clog more easily but like kman says - what do you have to lose? If you want to disassemble your core to get at the nozzle more easily or to swap nozzles (with what though?) then here is a video instructing you how to do this that I created: If you want to make your AA cores think they are BB (otherwise the printer refuses to send PVA through it) then here are instructions: Frist put your UM3 into developer mode - it's in the menus on the UM3. Your machine needs to be on your network (wifi or ethernet) if it isn't already. Once it's on the network it will show the IP address at the top of the main screen. Next you need ssh which is built into linux and Macintosh terminal but not windows. For windows I recommend putty: https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html In putty you don't type the "ssh" part but just put the ultimaker@111.222.333.444 part and click "open". ssh ultimaker@1.2.3.4 (don't enter 1.2.3.4 - enter the ip address listed on your UM3) username/password: ultimaker/ultimaker (much easier than root/ultimaker as it takes you straight into the utility to do sendgcode) Choose the type and size from the list below - T0 is left slot and T1 is right slot so before running any of these make sure the core you want to program is in the left slot if it will be AA and in the right slot if it will be BB After programming the core, slide it out and back into the slot at which point the UM3 will re-read the eeprom and realize it's new state. The software that does X,Y,Z offset calibrations for a core goes by serial number and that can't be changed so you shouldn't lose any calibration data when you do the below changes. AA 0.4 sendgcode M151 T0 A8 D7800000000004141 sendgcode M151 T0 A16 D20302E3400000000 BB 0.4 sendgcode M151 T1 A8 D7800000000004242 sendgcode M151 T1 A16 D20302E3400000000 AA 0.8 sendgcode M151 T0 A8 D7800000000004141 sendgcode M151 T0 A16 D20302E3800000000 BB 0.8 sendgcode M151 T1 A8 D7800000000004242 sendgcode M151 T1 A16 D20302E3800000000 AA 0.25 sendgcode M151 T0 A8 D7800000000004141 sendgcode M151 T0 A16 D20302E3235000000 BB 0.25 sendgcode M151 T1 A8 D7800000000004242 sendgcode M151 T1 A16 D20302E3235000000 AA 0.4 sendgcode M151 T0 A8 D7800000000004141 sendgcode M151 T0 A16 D20302E3400000000 BB 0.4 sendgcode M151 T1 A8 D7800000000004242 sendgcode M151 T1 A16 D20302E3400000000 AA 0.6 sendgcode M151 T0 A8 D7800000000004141 sendgcode M151 T0 A16 D20302E3600000000 BB 0.6 sendgcode M151 T1 A8 D7800000000004242 sendgcode M151 T1 A16 D20302E3600000000 AA 0.8 sendgcode M151 T0 A8 D7800000000004141 sendgcode M151 T0 A16 D20302E3800000000 BB 0.8 sendgcode M151 T1 A8 D7800000000004242 sendgcode M151 T1 A16 D20302E3800000000

How did you "make them all 0.8mm thick"? Is there a free program that this guy can use to do that?

Wow! This is a great question. Maybe Erin knows. The firmware is here: http://software.ultimaker.com/jedi/releases/ But that somehow "knows" which type of machine you have. Maybe it's a jumper or something. @fbrc8-erin @Daid @neotko @nallath - do one of you know how to tell a UM3 that it is not an extended? I'm going to guess you will have to put it in developer mode and ssh into the machine (in dev mode it tells you the ip address). Do you know how to use ssh @rasmus? If not I can send you instructions. username is root, password is ultimaker. But I don't know what to do after that.

Those walls appear to be infinitely thin. You need to make them thicker - I recommend 0.5mm minimum 1mm even better. At 0.5mm walls this thing will be pretty delicate. At infinitely thin walls, well, there's nothing to print.