Slashee_the_Cow

When Cura loaded the preview, the fit on the bed, so that shouldn't be a problem.
 
Yep!
 
Open the gcode file in a text editor - a lot of slicers will put at either the top or bottom of the file what printer it was sliced for. But an Ender 3 is pretty standard as printers go, so unless they sliced it for something less common it should be alright. You can post the file here if you're not sure and we can have a look, or - just try it. It shouldn't be able to damage your printer or anything (the firmware should prevent that) but just keep an eye on it and if it doesn't look like the preview, cancel the print.

From the basic settings view just click the Show Custom button

Then just scroll down in the list until you get to the infill section:

 
If a box turns yellow when you enter a number, that's Cura's way of saying "this isn't recommended" but it won't stop you. If it turns red, that's Cura saying "I can't do this" and you probably won't be able to slice it.

This is a known bug. It should be fine in Cura 5.4.0 or if you are comfortable with running software that is not ready for release and contains its own bugs there is 5.7.0 pre-alpha you can you can try.

Are you trying to print through Cura from your computer over USB? You should be printing straight from a memory card in the printer.
 
USB printing in Cura is a legacy feature which is no longer supported and is a relic from the days when printers were too stupid to do anything but follow commands one at a time from a computer.

Can I be the smartarse in the room and say "just add a cube model to the scene, scale it to fit and put it in there?"
But that's alright. We have our own cubes. Use the support blocker tool, click somewhere on your model and it will add a support blocker. Now switch to the move tool, click the support blocker so only it is selected, then move it to the centre and scale it to fit inside your rectangle, up to the height you want.
 
Then we touch the magic "per model settings" button! 
Being a support blocker, it'll start as a "don't support overlaps" type:

If you want to fill the model so it's solid up to a certain height, with infill and then skin on top, just click the first button that turns it into a normal model!

Cura automatically combines models which intersect each other. So now it'll just be a filled in model with infill on the inside and skin layers on top!

It looks like it's overextruding at the Z seams. There's a bunch of ideas in here so read the whole thing before you try anything - and remember, small scale testing is your friend. In this case you really only need to print up to the height where there's a problem, because this is the sort of thing which could potentially disappear if you shrunk the whole thing.
(Don't worry, I'm sure you read all of my wisdom and most of my ramblings before doing anything 🙂)
 
 
Not sure I can give you a good answer on this one. My best guess is the route it takes to travel that corner might pick something up or is so short it can't retract properly.
This one I can definitely give you a good answer for: those white dots in the layer preview? That's where it starts a layer (or starts after having had to travel from somewhere else on the layer which there isn't a continuous route to from its previous position). Your settings have them sort of spread around the whole thing. I cover this topic (and it's definitely worth trying!) in a little bit.
 
If you want to try and address the overextrusion directly, you can try two opposite options:
Walls > Outer Wall Wipe Distance will make the nozzle continue slightly past a Z seam without extruding. The idea is if there's a small gap where it started whatever material is left in the nozzle gets to wipe it closed. Experimental > Enable Coasting will make it stop extruding slightly before a seam in case there's too much pressure in the nozzle and there'd still be some left by the time you get to the seam. In this case, I'd say "probably not". Although I've never used PP or a direct drive extruder bolted on after the fact, your retraction settings almost look like they're for a Bowden extruder - on my E3V3SE (comes with direct drive extruder as stock) the highest retraction I ever need to set it to is 3mm (for TPU, because its elasticity makes it so stringy) and I run it at 45mm/s - increasing the speed might help if your extruder can handle it.
 
Always a good idea to test that if you have overextrusion.
 
Maybe a good starting place -> Your settings have Z seams show up in all corners but only one corner is a problem? Set Walls > Z Seam Position to User Specified and then Walls > Z Seam Position to a corner which isn't the one you're having problems with. The problem might have something to do with travels so it might just move the problem to this corner but since all your seams will be on the same corner it'd be easier to fix (as in, by hand) when it's finished if it bothers you.

 
You can change relevant things like extrusion distance/speed, printing temperature, speed, etc., independently of the material you have selected. You can also create your own custom material which has all of these already set! Go to Preferences > Configure Cura... > Materials (in the left sidebar) > Create New (button in the top right). If you want to be able to change more settings for your material than it allows be default, then download the Material Settings plugin by the I-don't-know-how-he-does-it @ahoeben by clicking "Marketplace" at the top right and searching for material settings.

Slicing troubleshooting 101: play with settings until it looks right.

Ah! Sorry, misunderstood (I'm good at that).
 
I can't help but notice there's a ton of travel moves between model, support, and other bits of model:

Are you having any problems with stringing or anything? If the filament is getting pulled away before it fully sets that could explain it.
 
<looks through settings>
Okay, I think you're accelerating waaaaaay too fast. If I enable travel acceleration settings it defaults to 5000mm/s² which I'm guessing is what it will default to without manually setting it. My Ender-3 V3 SE can accelerate at 4000mm/s² and when I let it do that it's actually pulled parts of the model with it sometimes. And since it doesn't always respect the speeds Cura puts into the gcode, I actually had to turn down the maximum acceleration on the printer's control panel.
 
Your print acceleration is also set to 1500mm/s² for the most part. I don't know much about the specific PLA you're using but it's generally only high speed PLA which is designed to go down properly at that sort of acceleration. And since you're printing at 45mm/s, I don't think it's high speed PLA 😉
 
Personally for my stuff I set the acceleration for all the print moves to 500mm/s² and the travel acceleration to 1000mm/s². It doesn't actually add that much time to most prints (and even if it does, slow print > failed print).
 
<continues looking through settings>
20mm/s jerk?!?!??!?!!?? *does dramatic fake fainting, collapsing to the ground*
For most prints I use 8mm/s, tops. If it's got intricate details or I'm worried about stability, I take it down to 4. Jerk is how much the speed can change instantly on a corner (because in an ideal world you smoothly come to a stop and move off in the next direction, but in the real world that results in a blob in the corner). Higher can cause significant vibrations in the printer (on some printers, so bad you get some layer shift), but it also means that when a printer goes round a corner or finishes a section it can pull the filament with it because corners require a bit more adherence than the rest of the print or else it'll just dragged along by the print head.
 
Okay, that's it for the settings, the rest looks pretty normal. I would like to make a suggestion or two:
Create a modifier mesh - add a support blocker, move and scale it so that it covers the top part of your model:

Click the Per Model Settings button on the left, set it to Modify settings for overlaps (third option) and increase the number of walls:

This will make the insides of the bits which stick up solid walls instead of having a little bit of infill (without adding extra walls around the main area):

A lot better for adhesion and easier for it to print than tiny bits of infill. Support > Support Structure to Tree: Saves you a bit of filament and more importantly, doesn't scar the model by sitting on it to use it as a base:
Walls > Wall Ordering to Inside To Outside. The first part of each layer to go down is the most likely to have problems. Sweep it under the proverbial rug 😉 Hope that gives you some cud to chew on. Hopefully some of it works 🙂

Howdy!
 
Slowing down the print would help: you're extruding about four times as much filament (by volume) than a 0.4mm nozzle. The hot end needs to be able to heat it all the way through as it flows through. Slowing down the print = lower flow rate = more time spent in hot end. You might also want to increase your print temperature a bit to compensate.
 
Correct! It's not the right way. The right way is to change the setting Walls > Horizontal Expansion. Increasing the flow rate doesn't really guarantee "wider lines" either, especially on a print like this (where there are so few lines, and they're not constrained by walls).
 
I think I can see the problem in the photos. It is a bit related to the layer height though. Let's take a zoom in on the slice preview:

Okay, that's a bit more polygonal than real life, but put (hopefully) simply, the nozzle doesn't extrude the filament in this shape: └─┘
It extrudes it in this shape: O (since it's a round nozzle).
So essentially each layer is a little donut rather than a little cylinder. Increasing the flow can help a little, since there's a little bit that can trickle down (also helped if you slow down the print).
It's also present if you use a 0.4mm nozzle to print 0.2mm layers, just a lot less noticeable because the gaps are smaller:

 
Don't feel so bad. I've never done it either. I'll just tag @GregValiant who gives a great explanation of stuff like this.

I actually don't think it's the printer, it's how Cura is slicing it - those distances probably aren't considered far enough to be worth retracting the filament for, meaning even if it isn't extruding during a travel, it'll probably lay down a string (if you could upload the gcode file produced, it would be possible to verify this, if you could upload the Cura project entirely - get it ready to print in Cura then go to File > Save Project and upload the .3mf here - that always gives us the best chance possible of figuring it out.
 
You also don't say what printer you're using - if you have a Bowden extruder this might be a hopeless cause, but that doesn't mean we can't try. If you have a direct drive extruder, your results are likely to be better.
 
(You might have to make all settings visible for this, I don't know how many will show up by default).
Go to Travel > Enable Retraction and make sure it's on.
Make sure Retraction Distance and Retraction Speed are set to the appropriate values (depends on your printer and material).
Set Retraction Minimum Travel to something really tiny, like 0.01mm, to force it to retract on every move.
Also set Minimum Extrusion Distance Window to something 1mm or so that it won't reach its usual retraction limit.
 
Depending on your material and extruder, this might grind it up a bit, so the results could be subpar because of that (it'll end up at an uneven thickness) but while I've never done anything that tiny, I have done this sort of thing and a decent PLA can stand up to a bit.

I'll get to the how (or at least my best guess at it) in a second, but first a warning:
 
You shouldn't. Only materials which are designed to be printed that fast, like high speed PLA, should be printed that fast. Most spools of filament will have details on the side of the idea printing settings for them, and I've found your average PLA tends to say about 65mm/s. If you're printing too fast the material won't have nearly enough time to set and it'll end up being dragged behind the nozzle (or just pulled out of position in general). It almost certainly will negatively affect your print results.
 
My Ender-3 V3 SE can print at up to 250mm/s and accelerate at up to 4000mm/s². Even printing at a slower speed, with the fan on full bore, sometimes the acceleration when it finishes a move and does a travel move can pull the filament with it resulting in the model being stretched out at that point. I never have the acceleration set to over 1000mm/s² to prevent this (and sometimes it ignore the values in the gcode file so I had to lower the maximums in the control panel of the printer).
 
Good quality print > fast print.
 
Okay, now if you're really sure you want to print as fast as possible:
By default when you set Speed > Print Speed it will do infill at that speed and everything else at half of that. You may have to enable showing all settings to get it to show up, but you'd need to change all the values to the full speed. Turn on Speed > Enable Acceleration Control and set it all to as high as your printer is capable of. You might have to look up the specs on Creality's website (although in the case of the E3V3SE it's not that simple - the website says 5000mm/s², the manual says 2500mm/s² and the printer itself reports 4000mm/s²). Turn on Speed > Enable Jerk Control and set that - there isn't really a maximum figure to go by. It's how much the speed is allowed to change instantly at a corner - the higher the speed, the less it has to decelerate, but it also negatively affects adhesion (which is often at its worst at corners because it needs to set before the nozzle starts dragging it in a different direction. It also has the risk of causing vibrations which if they're bad enough can move one of the stepper motors a step or two causing layer shift (where it starts printing layers slightly off from where it had been printing all the others). For my setup the "yellow zone" is anything above 50mm/s but the default is 8mm/s and if I'm doing something which might wobble or requires high precision I'll turn it down to 4mm/s. And a couple of things to bear in mind if it's not increasing the F values in the gcode file:
Ignore the F values on G1 moves which only have an E value. That's just setting the extrusion rate, or retracting/unretracting. 250mm/s is fast enough to cross the bed in literally less than a second. In many cases, there's only so fast it can go because it'll reach the end of the move before it can accelerate to the maximum speed, given it'll have to slow down at the end, so there's no point setting the feed rate (the F values in moves in gcode) any higher than that. If I may close with a screenshot from the page on Creality's website for your printer:

You're most likely doing typical printing yourself.

Generally the softer a material is, the worse it handles getting support off (you should see some of the stuff I've printed in TPU - not only is it practically impossible to remove all the support, but it's so soft you can't even file the left overs off).
 
Try disabling Support > Enable Support Interface. Your support density is high enough that bridging the gaps should be easy and it's a lot easier to remove a few lines of support than a whole grid of interface.
 
You could also try printing it on its side, like this:

The visual scarring from the support is much less visible on vertical (or angled, like towards the bottom) surfaces. If you're going to do it this way just make sure you're not printing too fast and your acceleration and jerk are reasonably low or else it'll wobble and fall over, but the flaps on the sides will add stability and looking at your project file your acceleration and jerk are at nice safe levels.

Before we get to settings: You have to make this thicker. Something one layer thick probably won't survive coming off the print bed. You don't need to change the model, just select your model, open the scale tool in Cura, turn off Uniform Scaling and increase the Z height to give it some thickness:

(Even 2mm is not really very thick, but I wouldn't even consider going below 1mm, pull out a ruler and you'll see).
 
Okay, on to settings (you might have to make all settings visible or search for some of these):
Quality > Line Width to whatever the narrowest you can pull off is. Most printers come with a 0.4mm nozzle and I find I can go down to a line width of 0.26mm reliably with that. Quality > Initial Layer Line Width to 100%. I think that's the default, but you should just double check. Okay, now the one that actually matters: Experimental > Slicing Tolerance to Exclusive. That guarantees that Cura will always round in favour of making holes to match a model. With all of those, you get this:

Cura doesn't use M221 to set the flow rate - it calculates the extrusion lengths and takes the flow rate into account, so they're in the E values of the G1 moves.
 
It's generally quicker for the printer to adjust to different flow rates than using M221 commands, especially when you're changing it frequently (like if you use different flow rates for different types of the print, i.e. infill, walls, support).

The problem is that PETG is sort of stringy compared to PLA so instead of oozing out a bit after it comes out of the nozzle it just gets laid down in the line it was printed.
 
A couple of suggestions:
Turn on Top/Bottom > Enable Ironing and then make Iron Only Highest Layer (it'll appear when you enable ironing) is turned off. Ironing runs the nozzle over a surface letting out a small trickle designed to fill any gaps.
Increase Material > Top/Bottom Flow. I haven't tried this so I wouldn't know what value you'd want but 110% might be a good place to start. This will extrude more material than is needed to print the line which hopefully might expand and fill the gaps.

You're silly not to upgrade. At the very least use the release version of 5.5 if you don't want to use the latest version.
 
Rafts aren't used much these days (relic from a bygone era when proper bed adhesion was nigh impossible) but if your build plate always warps, that's a fair enough reason.
 
The main setting for a stronger connection would be Build Plate Adhesion > Raft Air Gap. Normally it puts a layer (at least) of space between your print and the raft to make it easier to remove (i.e. it just does an empty layer then starts doing your print... sounds wrong but hey, it works, like there's an air gap by default between support interface and a model).
Initial Layer Z Overlap lowers the layers of your model (except the first one above the raft) a little bit to sort of force your model to squish onto the raft but you don't want to set that too high (like, one layer height, tops, but it's not something I've tested so I don't know what's ideal, I think the default is half a layer).

Yep! Just go to Extensions > Post Processing > Modify G-Code, and in the window that pops up click the Add a script button, then choose "ChangeAtZ" from the list. You can set it to trigger at either a certain height or a certain layer number, and it can change the speed.
 
I think if you just want it to change travel speed, you need to set both Change Speed to your travel speed and Change Print Speed to your print speed, but I haven't tried it myself.
 
There's also the "Limit X-Y Accel/Jerk" script, which lets you pick a layer (or pick a start and end layer for it to gradually go down and after the end layer will just stay low). This doesn't change travel speed but it lets you lower the acceleration and jerk rates, the idea is for a bed slinger printer (a printer that moves its bed on at least one axis) as things get taller, it lowers the chance that your model will wobble from side to side.

Unfortunately I'm not sure there is a way using the AppImage (since you can't edit it). Playing around I found you can do it by renaming (or deleting) C:\Program Files\UltiMaker Cura 5.6.0\share\cura\resources\images\cura.png on Windows. Excuse me while I go make a picture of pixel art cows in a paddock to replace it with.
 
As far as I'm aware there aren't any command line options for Cura (running either the binary in Windows or the AppImage in Linux. You could submit a feature request though.
 
I've yet to find a distro with an up to date version in its repos. My beloved OpenSUSE Tumbleweed is only up to 4.13.0 😕

Based on your image and text, I meant it as literally and honestly as I do that I'm going to get myself a piece of mudcake in an hour or two (I buy the giant ones from Costco, cut them up and freeze them).
 
Here's what it looks like if you have normal top/bottom settings and choose a concentric infill:

That gives each hole a concentric top, which gives you those long lines (along the Y axis in that picture) in midair, which exactly what you don't want.
 
But if we make the whole thing skin (FWIW I set Top/Bottom Thickness to 64mm because it's a round number (I like round numbers) which is more than half the model height (the important part):

It slices the whole thing like it would slice the circular top or bottom, not treating each individual hole cover as its own concentric fill. The downside of this approach, however, is that it makes the whole thing solid, because there's no infill in skin. That increases material use and print time (I'm not sure if those are important factors to you).
 
Fortunately I had a flash of inspiration: skin expansion!

That's with Top/Bottom > Skin Expand Distance set to 2mm (technically any value above half the distance between holes should work, but going over doesn't matter). Now instead of treating the top of each hole as a bit of skin, the skin has expanded enough that it fills that layer so it can print it as a full concentric pattern!
 
Important note: You'll need to change your infill pattern to something else. Concentric infill here will add next to no strength.
 
It'll do that for however many layers you have Top/Bottom > Bottom Thickness > Bottom Layers (and its counterpart for top layers). By default that's four layers each, so it's doing twelve layers of infill total. If you'd prefer a bit more infill, just lower the top and bottom layers but assign values to Top/Bottom > Top Surface Skin Layers (how many layers it will do on the top) and Top/Bottom > Bottom Thickness > Initial Bottom Layers. By default they'll follow the normal number of layers but if you wanted to for example reduce it to two layers above and below the holes for more infill you can still have enough layers for a decent top and bottom.
 
I would also like to give you the award for "model which takes the longest to slice, under 20,000 verts". That is both a joke and the truth (the best kind of joke).

I don't seem to have the same trouble @GregValiant does with PETG. I've never needed to use additional adhesion, though it could be a build plate thing - I have whatever powder coated (I think) metal thing that comes stock with the Ender-3 V3 SE and I think he has a glass plate, I've never needed to do anything to the bed, only need to add adhesion in Cura for very thin parts or things with a very small base of support and never had trouble with warping. It does need to run quite hot (I run my bed at 80, but I'm not sure if it actually gets any higher).
 
I will also respectfully disagree about the "maximum retraction" part of it, although it could be different if you use a Bowden extruder. PETG is stringy so does need more retraction, but for example, with my direct drive extruder, I retract PLA 0.8mm, PETG 2mm and TPU 3mm. You don't want to over-retract if you can avoid it (the gears in the extruder can grind up the filament a bit and you might not have the nozzle pressure required for filament to start flowing immediately) but it's really a case of trial and error to find out what works best for you (remember: small scale testing is your friend, don't print a big thing five different times).

In one at a time mode, even if the models don't physically overlap in the Z direction, Cura dedicates the footprint of the model, plus the size of the print head around it, on the build plate to that model, and no other model can be in that area (to prevent the print head crashing into an existing model when doing another).
 
I don't think it's possible to change the behaviour, it's a built in mechanism in Cura to so that it doesn't produce gcode which might damage a printer.
 
Most of the time, multicolour prints (on a single extruder printer) are done by doing a certain number of layers in each colour and then pausing to change filament for the next colour.
 
If doing it that way doesn't work for you, then the best way to do it is to print them separately and glue them together (if you're just printing PLA, cyanoacrylate - regular old superglue - works very well).
 
I don't recommend this (in fact I recommend against it, unless you really know what you're doing), but you could align them, delete the top one, slice, undo the delete and delete the other one and slice, and then take all the layers from the second file (not the startup or end g-code) and place them after all the layers of the first file but before the end gcode, and insert an M100 pause at the start of the layers for the upper model so you can change filament.

I'm not sure it's a problem with anything you've done, it could just be the file got corrupted (unless you can repeat the problem by doing the same setup and saving it, in which case my first stop would be my last bit about simplifying the model).
 
I've done some somewhat insane prints that have gone nearly the top of the build volume, and I don't want the bed's movement or vibration from the print head to affect the model, so I have to go slow. Slow print > failed print.
 
Oh, and TPU. The TPU I usually work with I've found prints best at about 20mm/s. But that's just because the filament is so loose and stringy (you can actually grab a bit of filament and stretch it like a rubber band) that it needs to go slow so it has time to set and adhere to the filament around it or else the print head will just pull it along.
 
Correct (unfortunately): Cura can view gcode but it can't edit it like that (I don't know of any programs that can). Small, individual corrections can be done in a text editor but not things like moving whole objects around.
 
It's not so much about the duplication - it's easy enough for a 3MF file to say "place 1 copy of this model here, place 1 copy there, place 1 copy over there, and the last one here" without having to duplicate the model. 2GB is pretty unwieldy but that in itself shouldn't cause a problem (but unless you have a professional quality machine it's likely far more detail than you could print yourself).
 
You can use a program like Microsoft's free 3D Builder app (which is actually pretty good) on Windows to "simplify" the model, reducing the number of triangles in it, without really affecting the overall look (as long as you don't go too extreme) which will result in a much smaller file which programs are much happier to work with (especially if you don't have a ton of RAM).

This really belongs in the "Improve your 3D prints" section of the forum, not the Cura one.

(Line width view, but travels shown).
 
Walls > Wall Transitioning Threshold Angle to 15°.
Just have to find the right angle for your model. If you see any off bits just try increasing that about a degree at a time.
You might have to turn settings visibility up to "expert" or "all" to see it, or you can search for it.
 
The difference between "normal" and "both" for Surface Mode is that Both (or Surface) will close loops of any triangles (STLs are comprised entirely of triangles) in the model which don't actually get closed. Normal ignores them because they're not valid parts of a model.

In my definition, I have
        "machine_max_feedrate_z": { "default_value": 2 },
        "speed_z_hop": {"default<needs to be underscore instead of space>value": 2},