gr5

Did you see the problem in layer view? Could it just be skipping that section? Thin walls sometimes dont' get printed. Try setting nozzle width/line width to 0.2 just to see what happens in layer view. You can certainly fudge it a bit - .3 line width with a .4mm nozzle will work. In cura 15.X it's critical to make the shell width a multiple of the nozzle width. If not it will ignore the nozzle width.

1) First of all you should not measure the temp sensor WHILE IT IS CONNECTED TO PCB. The electronics in the PCB will most likely mess up the measurement even if the power is off. If the power is on it will 100% guarantee measure wrong resistance. 2) Yes you can print without heated bed. Put blue tape on it. Clean the blue tape with alcohol using a tissue to remove the slippery waxy surface (you won't feel a huge difference - just do it - it makes a huge difference letting parts stick better). And then when you start the print immediately go to the TUNE menu and set the temp to 0C. Or you can set the temp to 0C in the material settings for the current material you have loaded e.g. PLA.

Hopefully some s3d expert like @neotko can help you.

An hour is kind of fast. 50mm/sec at .25mm layer height with a .4mm nozzle - multiply those 3 numbers and you get 5mm^3/sec. That's pushing it a bit. I don't like to go that fast. Try 30mm/sec with .2mm layers if you want it to look better. If you are really in a rush use a .6mm nozzle and .3mm layers at 30mm/sec.

I recommend tinkercad. It's free, on the web (so mac or pc is fine and even an ipad), and designed to be as simple as possible yet still very useful for moderately serious part design. You should also talk to some teachers here who have heavy experience with this sort of thing such as @Larum.

Are you talking about how the bottom layer isn't sticking to the glass but instead ending up no the nozzle? If so you need to move the glass closer to the nozzle. You can verify this by pushing up on the glass while printing the bottom layer. The quick fix is to just rotate the 3 bed leveling screws CCW to move the glass up closer to the nozzle. Or relevel but level with no paper so that the nozzle is touching the glass. Also heat the nozzle and clean the tip before leveling.

Small diameter nozzles for UM3 have been available for many months now from third parties. They are good quality. I'm biased of course as I am the main seller for USA. I have 0.1mm 0.15 and 0.25mm nozzles. I also have ruby nozzles in .25mm size. I love the .25mm nozzles. thegr5store.com

Which printer is this? Please set your profile settings to include which printer(s) you have. Check to see if the heater is working at all. Go to heat it up from the menu (again, what printer do you have) then look at it. Typically room temp is 20C to 25C. Then tell it to go to 100C and watch to see if it gets only up to say 50C or if it basically never goes above room temp. I suspect it never goes above room temp which means probably a loose wire somewhere. Please supply more information.

The firmware is available upon request. I have a copy somewhere. There are 2 firmwares: Marlin which runs on the white board inside the UM3 - that's on a arduino processor and most of Marlin is in github but I think the um3 version isn't on github right now. But I have it in a zip file somewhere and it's posted somewhere on this forum I think. Daid posted it so look at posts by Daid. Or just ask in a new topic. Explain your project also but make the title of the topic UM3 Firmware and I'll add a link to daid in it so he sees the post. The python code is all sitting on the UM3 easy to access if you own a UM3. I have that also in a zip file somewhere. Or again ask and some UM employee will probably post the current version.

More thoughts since you say you didn't load firmware: If one of the 4 wires is broken the servo will sometimes turn the wrong way or not at all and just hum and vibrate. You can reverse a stepper by swapping two of the wires in the connector. Swap the two wires in either twisted pair. In other words if green and black are twisted together then you can swap the positions of the green and black wire. This will reverse that stepper. Usually a paperclip can be used to push the correct tabs and get the connect pins out. then reverse them and slide them back in until they snap into place. No soldering needed.

It's really hard to say what the problem is. Best guess is that it's the little white teflon part in the head. 2 years old is quite old and if you haven't changed that part then it is time. I can think of several other problems. Best thing to do is to put in an olsson block. That way you can have the head back together and remove just the nozzle and then slide filament up through the block (while cold) to feel the friction in the head and slide it up further to feel the friction in the bowden. This helps eliminate a few issues. Also as soon as possible get an olsson block so you can open that when you have issues and also test the force needed to push filament. It could be your feeder gnurled sleeve is ground down to CF. It could be brittle filament that broke in the bowden and got stuck. It could be you have a nozzle clog like a piece of dust that keeps finding it's way into the nozzle tip. But I suspect the teflon part.

look through settings and allow Z position to go negative. Might be called something like "allow part to go below bed" or "disable auto z position". Something like that. Then click on the part in normal view. click the "move" icon to move your part and move it downward a tiny bit.

That lifts the right core up and down. Core needs to be up when printing with left core and down when printing with right core. You want it in the "down" (rearward) position when loading and unloading. I mean you don't have a choice: it must be in the down position.

Oh and don't lower the temp during printing. That makes it not stick to itself as well.

Well if the pva doesn't stick to the glass then that's a different problem and easily fixed. But I'm guessing from the photos that the main problem is humidity. That was my thought before I read any of your text. Do you have an electric oven you can use to dry the PVA in? First find the softening temp of PVA. it's quite cool - maybe 50C? I truly forget, sorry. Don't let the oven get over that temp. Put the PVA in for a few hours. Then when you are done printing with it make sure you put it in a sealed bag with dessicant. Buy some of that rechargable dessicant that you can heat or microwave back to dry again and redry the dessicant when it changes color per directions.

What error? I don't see an error. Do you mean it's not supporting the overhang maybe? Do you want support? Did you enable support in cura? Try turning off brim and skirt as that may be confusing the support. Or is it some other error?

Absolutely - this is common as well. I would start by removing them and cleaning them with WD40 and drying them thoroughly and see if this helps. Also it could be that the 2 rods are not quite parallel and loosening the bearings, then sliding bed up and down a bit and re-tightening the bearings to the bed will fix it. If not contact your reseller or get some better quality ones if you are still under warranty. They are only about 15€ I think if you get them through a 3rd party. Neotko posted somewhere else in this forum I think where to get good ones.

That's very helpful. The lack of yellow is expected. Red is the outer most shell. Green is the next 3 shells. Yellow is anything not covered by those shells. Get it? it's exactly what you would expect. Those small areas however don't look so good. It looks like probably underextrusion. Looking at the other settings I recommend you leave travel speed alone (or maybe increase to 150mm/sec) and then display ALL the speeds. Click on the gear and make them all visible. Then set them all to 30mm/sec. I know it will take almost twice as long to print but the quality should be significantly better and will probalby fix the underextrusion you are seeing. If you want to do a quick test (I would want to) then I would click on the object to print in "normal view" and move it downwards under the bed until only those final areas to print are visible - maybe just the top 1cm of the part. Then print that as a test at 30mm/sec and it should look great. Speed changes are bad on bowden printers as it can take quite a while for the pressure to balance out. And on these tiny little portions of the print it doesn't have time to equalize pressure. Lowering the speed helps a lot with this. If you really want to save time consider thicker layers but keep speed at 30 to 35mm/sec.

Well I'm starting to get these again. I rarely use my UM2 now because of this but eventually I will have to fix this. I'm thinking of swapping the display board between 2 of my printers and seeing if the problem moves or stays. I'll put that on my todo list right now - it should happen by the fall. For now though I have 5 printers and having one "down" is annoying but I can get by. I use my um2go the most! I love that little guy.

People have tried that. But then you get a bit of play at the flat spot and it's not as obvious what the problem is. Overall people who have tried it both ways usually say not having the flat is better.

Good stuff! I'd love to see more "developer mode" tricks added to David B's already useful postings that he made right when the UM3 came out.

If you decide to modify the firmware on the UM3 I recommend you come back here and post your changes on github somewhere and ask for the developers to incorporate your additions.

This is a common problem. It looks like it is only tilting in the X direction so you only have to fix the X axis. There are 5 or 6 pulleys (I think 2 of them are connected so I think 5) and you have to tighten the set screws in all 5 (or 6) of them. The most important one is the one on the motor and that's the hardest to get to but I can usually get to it without taking the motor out. If you can't get to that one, then remove the right rear metal cover - it's held on by I think only 2 screws. Then you can remove 4 screws if you need to take the motor out. But if you have a long hex driver you can get it without taking anything apart. Tighten the hell out of these set screws. I mean if you are using a L shaped allen wrench your fingers should hurt a little after. the tool should actually twist slightly. Really really tight. That will fix this issue. Sometimes called "layer shifting". Sometimes called "tilted prints".

The most likely issue is that you have the wrong firmware. The UM2 rotates one direction for feeding and the UM2+ and um2go rotate the other. Could you have loaded the um2+ firmware on a um2 or vice versa?

Can you post a video? I think it's normal but won't know unless we can hear it. I suggest you post it on youtube and then add a link to this thread.