gr5

That's very strange. I think it's a coincidence. I predict your problem still exists. If you get the error again - watch the calibration - the begining where it does the first two taps of the print bed (left and right core). It should stop right when it hits the glass. If it doesn't reach the glass or keeps going down long after it hits the glass then the sensor is faulty (keep radio noise sources 1 meter from the printer if possible - such as cell phones, laptops, transmitters). But if the taps look perfect and you still get this error then your cores really are probably different. Maybe the rubber gasket around the nozzle tips is lifting a core or maybe one of the cores is a little longer. The tolerance on this test I believe is +/- 0.5mm so if one core nozzle is 0.5mm longer then you get this error. Maybe try swapping out both cores with 2 others or at least swap out one of them. More often of course you get this error due to sensor issues.

I'm guessing you have cura 14.X or 13.X (from 2014 or 2013 respectively). The latest version is 4.8 which is what I slice your model on.

I have selected machine um2go so it will only print on a UM2 printer. What version of cura do you have?

Slices fine for me. Maybe you should post your project file - that will contain your printer settings, STL, profile, overrides, etc. Do "file" "save project..." and post that here.

Do you have the cura mesh tools plugin installed? That can fix a few mesh errors.

I thought if the initial layer height is 0.2mm and the bottom of the part is flat within 0.2mm then it the bottom most slice will be 0.2mm from the bottom of the part and it will slice fine. Right?

Maybe but I think it's backwards - I think prusa slicer automatically fixes many model errors. I really don't know which is true.

@mcmuffin6o GREAT QUESTION. Users can now do this! Up until a month or so ago only moderators could to it. It's two steps. First just under the topic click the "+" to "add tag". It's possibly you can only do that on your own topic (where you are first poster). I don't know. Click that and click "add tag" and choose SOLVED. Sometimes it's not available - it's possible you have to also mark it as a question first - I don't know. Or maybe parts of the forum don't allow marking it as solved. PART2 - while still in that dialog there is an option just below - a light blue button that says "item prefix". Push that button and choose SOLVED again. This adds the green tag to the topic which is visible much more easily on various screens on the forum.

Sorry I'm too lazy to open the STL but I think your print isn't quite flat on the bottom - the left sphere is sticking down slightly and it's printing that circle as a brim around the base (if you switch your color options in cura PREVIEW it will show skirt as a different color than the rest). One quick fix in cura is to lower the part down into the glass. But that is disabled by default so first go to cura preferences and uncheck the box "automatically drop models to the build plate". Then click on the part and use the move tool and set the Z value of the part to -0.1 or more until it prints the entire part on the bottom layer. Of course ideally you would have the bottom spheres perfectly lines up with the rest. I mean perfect within 0.01mm.

I could be wrong but isn't BLTOUCH an automated bed leveler? I'm talking about the UM2 which has no autlevel capability - just manual level. Once you get the manual level dialed in it stays. No need to level again. Probably ever. But I change nozzles a lot so I have to relevel a lot. I sell a set of nozzles that are the same length to 0.01mm but I'm too cheap to use it myself. I don't mind leveling. I do it on the fly while it prints the skirt.

The red lines in Cura are always touching "walls" in CAD. So yes there is still a wall there even though merged. The merge didn't work or it doesn't work the way you think it does. Maybe if you move the gears towards the cylinder 0.2mm and then merge again? I don't know CATIA at all. STL file contains just a list of unordered triangles. Any two consecutive triangles can be far apart in physical space. Anyway cura intersects a layer height with all those 3d triangles which gives you a set of lines in 2d space and then tries to figure out which lines go with which and makes loops. Each loop is an "island" to print with a red line outer and then green shell and then yellow infill. It's tricky when you have two walls on top of each other like you do but cura figured it out correctly. There's no way cura would put that red wall there unless there were triangles there. So CATIA didn't quite merge the teeth in properly.

I don't know what to say. It's not like Ultimaker spends a ton of money on parts. I seem to remember their Z nut in the UM2 was like $1 and someone said the $3 Z nuts were 10X better and Ultimaker should not be so cheap. But an Ender is a whole 'nother level of cheap I suppose and may use 1 cent limit switches instead of 5 cent limit switches (numbers grabbed from thin air). And 30 days is the low end. I've just never gone longer without changing nozzles.

Ultimaker did a test around 10 years ago on those limit switches and found them consistent to better than 0.01mm (one hundredth!). My memory of the accuracy could be wrong but I remember they were really surprised at how consistent they were. These were cheap limit switches from China most likely. Also the Z height in an Ultimaker printer after leveling stays consistent for over a month. I only have to relevel if I change a nozzle. I'm not bragging - just saying it's probably not the switch exactly but some other mechanical thing that is inconsistent. Or maybe Ultimaker was just lucky with their limit switches and Ender unlucky. But I suspect it's not the switch itself but something around the switch.

Ah!!! I just looked at my printer. So you click the upper left button where it says "nylon" or "pla" or whatever. Then - this is where you missed my instructions - you click the "..." in the upper right corner. Do not click any of the 3 obvious buttons. Ever. I haven't clicked those in years. The obvious ones are LOAD UNLOAD CHANGE. I never use those. It's fine to use those. I just happen to have a different work flow. Instead I use the functions in the ... menu. One allows you to choose material type (like PLA). The other allows you to MOVE the material to purge out any of the previous filament.

What test extrusion? I don't know what you are doing. I think there is an option to "change material". I haven't used that in several years. I just slide the filament in and out manually and select the material the way I described above. Then I use "move" to make sure I purge out any of the previous material still left in the core. Then I print. I don't do "change material". I'm not even sure if that's the right name for the option.

Larger nozzles also have less friction for the filament to pass through. Typical nozzle pressures are very high. The difficult part for the extruder is not the speed but the force. So 5mm^3/sec might be the limit on a 0.4mm nozzle for your feeder but with a 0.8mm nozzle it has 4X the area and so it can print 4X faster with the same feeder force. In other words with a 1mm nozzle, 20mm^3/sec is doable with a typical feeder. So you do not need to slow down the print speed with larger nozzles. Make the line width match the nozzle and if the nozzle is twice as wide I like to make the layer height also twice as high.

There are also lots of free tools out there that might be able to fix this if this isn't your model. I've never had to fix this particular problem but I'm guessing that meshmixer and meshlab both can probably fix this issue.

It's an issue with your model - not cura. Your model is specifically defining the teeth as separate parts with a wall between. Go back to CAD and try to merge the teeth into the rest of the part. What CAD are you using?

Cura takes 3d model files such as STL and outputs gcode. You can't take gcode as an input. Cura will take gcode as an input but only to DISPLAY it. You need the original model. Almoast always an STL file.

To manually select just scroll through the choices until you find tough PLA. Tap it once and then tap the blue "confirm" button. To get to the choices you click on the left/center menu. Then in upper left (if left core) click the material and then in the upper right click the "..." and select the material there.

Oh I found this: if using blender - here's how to fix your model I went into edit mode with the object in Blender 2.83 and pressed "a" which selects all faces / vertices / edges, depending on what select mode you are in. The entire object should be highlighted. I then went to "Mesh" (see images), went to the "Normals" section, and selected "Recalculate Outside". This probably will not fix any edges that are not merged, but it will fix the faces that are inverted on the object.

So I looked at your STL file. The normals are all messed up. There is a Cura plugin that fixes normals - I tried it and it worked great on your model. blender is one of those programs that let you reverse the normals (put the walls inside-out) which confuses cura. Here's how to fix them in Cura (but there are also ways to fix them in blender but I don't know much about blender). In the upper right corner of Cura click "marketplace" and make sure you are on the "plugins" tab and install "Mesh Tools". Then restart Cura. Now right click on your model, choose "mesh tools" and first choose "check mesh", then "fix model normals"

In cura click "File" in the top left corner. It's a menu item. Then "save..." for older Cura and "Save project..." for newer cura. Please post that file.

@GregValiant - you've got an Ender, right? What do you think? Is the bed faulty or is the nozzle too far from the bed?

That looks like sketchup. It's easy (much too easy) to have the normals backwards in sketchup. Notice how some walls are white and some are gray? Right click on the gray ones (in sketchup) and select "reverse faces". Once you fixed them all, export to STL again and it should be fine. More info here: https://i.materialise.com/blog/3d-printing-with-sketchup/ Also labern reccomends these plugins: cleanup3 (may be 4 now) Solid inspector.