gr5

Probably a loose wire at the connection to the bed. Slightly loose such that the resistance is 10(?) ohms higher than reality. Jiggle those wires - see if one comes out. Check the resistance in reality when it's reading 88C (but cut power and remove cable at bottom of printer first).

You can print larger. You aren't supplying any photos or strong evidence of non-planar glass or non-planar rods/gantry so first I'm going to assume that the problem is your parts aren't sticking well and by the time you get to the 30th layer the part is peeling off the bed. Not sticking. This is easily fixed. But you have to ask how to fix that issue. Alternatively you are correct and your gantry is warped enough to cause problems. Please print just the skirt of a large print and photograph the skirt. If you are right there should be areas of the skirt that are overly squished (transparent) and other areas that aren't squished enough (ropy) and areas that are perfect (pancake). One fix is of course to increase your bottom layer thickness. This is one of the reasons bottom layer is typically .3mm (much thicker than the others). But there are other solutions. Both of these problems (large parts warping off bed and inconsistent bottom level) are fixable and can be dealt with. Lets confirm which problem you have first (maybe you have both but I want to see the bottom layer skirt only first).

Is 1mm the outside diameter or the inside diameter? Inside diameter of 1mm is easy. You can with practice get it perfectly repeatable. Outside diameter of 1mm would be hard to do. Also what do you mean buy erosion resistant? typical 3d printing materials can withstand erosion by water only but add sand or almost any solid into the mix and I don't know of any 3d printed materials that can handle it. It's just plastic.

@nallath - is this parameter highlighted above simply sent as a gcode at the start of the print? Or is it used only to estimate print times? Or is it used for both things?

If you slice with s3d you set the filament diameter in the slicer. If you slice with cura and you tell it you have a UM2 series printer or UMO+ then normally the filament diameter is set on the printer itself. You can do it in the materials menu system and save it permanently for your PLA filament or you can do it live from the TUNE menu after you start the print (during warm up is a good time). In CURA in the machine settings you can switch to REPRAP mode in which case material settings like nozzle/bed temperatures and filament diameter will appear. When you load a gcode file, UM2 marlin knows if it's a normal gcode file versus one sliced in "ultigcode" mode meaning it leaves out those settings from the gcode.

I don't see the problem. Maybe zoom in to the "problem" area? You can print vertical things with no support. You can tilt that vertical to 45 degrees from vertical and still - no support needed - you will get a perfect surface. You can tilt further to 60 degrees from vertical. Now the surface is getting a bit rough but still the quality is probably better than if you added support and then broke off the support. You can tilt further to 75 degrees and now the quality is definitely getting worse but still about the same as if you had support so why waste time printing support? You can tilt further to 80 degrees from vertical (10 degrees from horizontal) at this point it will still print but you will have much better results with support. If you tilt further to 85 degrees from vertical (5 degrees from horizontal) now you definitely want support. In summary you don't need support for surfaces tilted only 45 degrees from vertical. Cura has advanced settings that let you change this angle.

I don't recommend printing 1.75 without some small modifications. 3dsolex sells a nice 1.75mm conversion kit. I've tried it and it works fine. But there's no reason that I know of to go to 1.75mm. All the filament types you might want to print are available in 3mm. Onto your other question. The thing that makes the Ultimaker somewhat unique is that the feeder and hot end are separated out with the bowden tube in between. This has pros and cons. The main pro is that you get better quality prints because the print head is so light weight that Marlin firmware doesn't slow the head down much on corners so you get equal/even flow from the extruder (a problem if you slow down too much on corners - it over extrudes when it slows down). But the bowden has cons as well. One of them is that it's difficult to print ninjaflex (as far as I know that's the most flexible material out there). It's like pushing a string through that bowden. But it works. You have to get the "plus" (um2+ or um2ext+) or the UMO or you have to switch out feeders to use the iRoberti feeder (free/open 3d printed feeder for um2 printers). Also you have to print about 5X slower and 20C hotter and you have to add drops of oil to the filament. But it works fine. I've printed many things with ninjaflex. Slightly stiffer flexible materials are even easier to print. TPE is similar to ninjaflex (or maybe the same thing?).

There is a SAVE command somewhere in the material settings I think. This should save the settings to the eeprom for retrieval on power up. If not there try among the "MOTION SETTTINGS". The save command there should save everything to the eeprom I think probably including the material settings.

Play and backlash are the same thing. You can look the word backlash up on wikipedia. From the top view I would say you have play. I'm not sure if it is serious enough to cause the problem the you show ("misalignment") but maybe. So fix the play first. Here is something that describes why you get the pattern you have on your top layer where you have 2 lines close together and then a gap: https://ultimaker.com/en/community/2872-some-calibration-photographs#reply-16137 Play is usually caused by loose belts - usually the belt connected to the motor. It can also be caused by belts too tight (too much friction). What kind of printer is this? It can be caused by the head being a bit loose (see if you can push the nozzle around without the belts moving). Or the endcaps on a UMO can be too tight (try loosening 4 of the 8).

No. I mean it's possible but crazy hard to do as its compiled and compressed so it would take months by an expert decompiler.

I'm guessing backlash/play. I'd like to see an overhead view to be sure. On more photo zoomed in on part of your part please. If it's play then it would shift on certain layers because it's going clockwise versus counter clockwise.

Glenn? Bad link?

Bend the fans in a bit. With power off push the head to extremes. The black plastic head should hit the black plastic side block before the fan hits the wall. Maybe take a photo or google photos of um2 head.

Well when I switch back to 1.75mm filament (I switched to 3mm this past weekend for other tests) I will try printing something with lots of retractions.

What? Screen shot or photo of your part please?

This may sound like a stupid question but other's had this problem - sometimes the power cable isn't quite all the way plugged into the printer (it kind of snaps) because the circuit board is sometimes pushed a little to the side so it's a very very tight fit with the power cable. One person said he had to push with about 100 pounds (50kg) of force to get the cable in! I'm surprised he didn't break anything. The fix is to loosen the 4 screws slightly that hold the PCB in place, center the plug, then retighten. I have to tell you personally when I see zero lights on the board that's fantastic news because power problems are the easiest to solve. Either power is not getting to the board at all (just check the voltage on the board right at the connector) or it's not making it through the first power converter (a chip that converts the 24V to ... I forget - either 5V or 12V. I think 12V). It's most likely the power connector but #2 most likely is that power converter chip. It's a large chip with 3 leads. I can show you where if you think you have the wherewithall to replace it.

So I finally installed and tried out my own kit about a month ago and printed about 30 things with it over the month. I tried it with the 3mm bowden tube and a special only-one-on-the-planet 2mm bowden tube and there was no improvement with the smaller bowden tube. I also installed the iRoberti feeder. I feel that is crucial. When I tried it with my "original" black feeder it could barely touch the filament. I had to loosen the 4 screws and push the motor closer to the filament but even then it didn't have a good grip. With just the bowden that comes with the printer and the minimum 1.75 conversion (and iRoberti feeder) it worked great for me. The minimum kit comes with an Olsson block drilled to 1.75 instead of 3mm and a teflon part also drilled to 1.75 instead of 3mm. I used regular 3mm nozzles and it worked great. You won't be able to do cold pulls with the 3mm nozzles and 1.75mm filament but it didn't matter for me. no clogs during the month and if there had been any I would try my nozzle cleaner tool or just remove the nozzle and burn it clean in flame. @Myrightfoot is right in that you have to tell the printer the new filament diameter of course.

Oh! I forgot the photo to show you the jumper:

The PCB is probably getting too hot. I recommend removing the cover over the PCB (none of my machines have had the cover in a year) and then also adding a fan blowing under your printer a bit. You can tilt the printer by putting one side on a book or something to get better air flow. The printer will print fine upside down or sideways or any orientation so don't worry about that aspect. Just don't tip it so much it accidentally falls over with a bang.

There are 2 possibilities: 1) wrong firmware or new bug in firmware (maybe this is a new bug, maybe you downloaded um2go firmware with wrong distances) 2) z microstepping jumper fell off. #1 is simpler - just get this version of firmware which is better anyway and I'm sure it works: https://github.com/TinkerGnome/Ultimaker2Marlin/releases #2 requires removing the 4 screws that hold the board in. Again. Yuk. Easily take you 10 minutes. Change the circled jumper. It will half or double the number of steps/mm for the Z axis. I don't remember if the jumper is supposed to be there or not. Note that you can also set steps/mm manually in the tinkerMarlin software (which is in step 1). It really doesn't matter that much if you go for 8 microsteps or 16 microsteps as long as it agrees with the steps/mm in the firmware. Back to #1 - note that there are many "positions" in Marln - one for the distance from home at bottom to nozzle at top, and other distances. It could be that the um2go value somehow got in the um2 normal build.

Put it in the freezer. REally. After 20 minutes take it out and immediately try to remove the part (before the part or glass warm up). It might just fall off (I'm always surprised when it does - I never learn). Usually though I use a putty knife with one corner sharpened razor thin. Glass is tough - usually only diamond will scratch glass. It's the printed part you are more likely to damage.

Only during first layer. The remaining layers are put down after moving the Z axis an exact amount e.g. .2mm and so will be perfect. It's only the first layer that is affected by the 3 leveling screws.

Before you start worrying about cura - you want to make sure Marlin knows where (0,0) is and which way your limit switches go (normally open versus normally closed), which way to step to move the head towards home and which way to move it away from home. You can set all these things in some of the marlin builders. Since you have UM2 board you need a Marlin compatible with that. If you are uncomfortable with building Marlin you probably don't have to. Instead you can just reverse the 2 wires on either twisted pair on a stepper to reverse the direction. Anyway the first thing you want to do after you hook up a stepper is to install pronterface which you can get for free here: http://koti.kapsi.fi/~kliment/printrun/ Hook up your computer with pronterface to the UM2 circuit board with a USB. There will be lots of values you can update using pronterface such as "steps/mm" and you can view those values before you move an axis. Before you home any axis try moving it a small amount. STart with 1mm then 10mm and see if it is correct distance. If not adjust steps/mm values. If wrong direction adjust by swapping wires as I said. Then test limit switches using pronterface and by pusing on the switch. See if it works. Only after doing that for x,y,z do you try the home command. From pronterface you can also test that the PT100 temp sensors are working. If they aren't you can't really do anything with the printer as Marlin shuts you down/blocks you from doing much of anything.

If the belts are too tight you can get backlash due to friction. But lets not worry about that yet - get the model looking perfect in slice view before working on hardware issues like belts.

what? wait! stop! Did you ever look at slice view in cura? If it looks bad in slice view then changing flow rate isn't going to make a difference. Also changing nozzle size isn't likely to do anything unless you change shell size also to be a multiple of nozzle size. Again, did you look in slice view? Don't waste your time printing when you can check it in slice view in a few seconds.