AirBronto

What printer/hot end do you have? 25mm/sec at 1mm width and 0.8mm height seems really fast to me. You're extruding a ton of material at that speed. Unless you have a really powerful hot end I could see the sheer volume of material dropping the nozzle temperature. When the nozzle changes velocity, the extruded material isn't hot enough and gets pulled/separated from the lower level which gives you your rounded corners. I would set your print speed to something really low, like 5-10mm/sec and try again. If it looks better, your hotend probably just doesn't have enough thermal inertia to withstand the huge volume of material. At that point you can either print slower or print hotter.

I'm not sure if this is @iMattmax's problem or not, but I'm coming from Cura 3.6 and I installed 4.0.0 last night and I thought the Marketplace was missing too. I spent legitimately 10 minutes clicking every menu option I could see, closing and re-opening Cura, and trying everything I could think of to find it. It turns out that in the new UI, there's a new button at the top-right of the screen that says 'Marketplace,' and that's the only way to open the Marketplace menu.

Awesome, glad it you got it all figured out!

If you only print via SD then you probably don't have a graph of temperature data. Octoprint is super useful for stuff like that but if you don't have a raspberry pi then I guess you're out of luck. 20* drop when the fan comes on is way way way too much. Either your PIDs are incredibly fragile and even a tiny increase in airflow messes them up, or your fan duct is very wrong. Once you get a new duct on there I think your problem will just disappear. Some people recommend doing PID tuning at 50% fan, that way your PIDs are a little more aggressive than needs be with no fan, but they can handle more airflow without getting bogged down.

Can you post a picture of your temperature graph when the thermal runaway happens? I want to see if it looks like your heater is eventually going to get your nozzle to the right temp and your thermal runaway protection is just too aggressive, or if it looks like your fan is just overpowering your heater. Definitely check the airflow and the design of your duct, the air shouldn't be hitting/cooling the nozzle at all, it should only be hitting the freshly extruded material. In reality the turbulence from the duct will cause the nozzle to lose some heat, but it should be minimal. I can crank my fan up to 100% and my nozzle loses about 1 degree. Have you done a PID tune with Marlin yet? That can be another thing that could help, it could be that your firmware just doesn't have a good handle on how much power it takes to heat up your nozzle, and when the fan kicks on it gets knocked out of whack and can't keep up. A temperature graph screenshot would help troubleshoot that as well.

This sounds a bit like an X-Y problem. First off, your cooling fan should be angled in a way that it doesn't cool the nozzle very much. The cool air should hit right below the nozzle (so the brunt of the cooling effect hits the extruded filament). I would check to make sure it's angled properly. Also, if you're running marlin, I think it would make more sense to change your thermal runaway parameters. Really it would be as simple as updating the following settings in Configuration_adv.h: If you're getting this issue after you hit your print temperature but before you change temperature during a print: THERMAL_PROTECTION_PERIOD THERMAL_PROTECTION_HYSTERESIS If you're getting this after you change temperature mid-print: WATCH_TEMP_PERIOD WATCH_TEMP_INCREASE For me, I had to update my protection_period and hysteresis because I am running a larger nozzle so I push more material than my printer was originally designed for. I was regularly getting thermal runaways because the hotend was cooling down faster than my PIDs were expecting, and while they would eventually catch up, by that point it was too late and the thermal protection was triggered. I set my THERMAL_PROTECTION_PERIOD to 80 seconds, and my THERMAL_PROTECTION_HYSTERESIS to 3 degrees. I haven't had any thermal runaway issues since then.

Are you running Cura inside of a VM? I got this error when I was running Cura on a Windows guest in VirtualBox. I found a StackOverflow post that explained how to enable rudimentary OpenGL support, it worked for me, maybe this will help: StackOverflow OpenGL Fix

I just installed Cura 3.4.1 and 3.5.1 on a fresh Windows 10 virtual machine... and you're right! The settings changes in the 3.5.1 version did NOT go back and modify the changes in 3.4.1. I'm not sure what my earlier problem was, but it's not a problem anymore. Thanks! Now I can run 3.5.1 and test it without worrying about losing my 3.4.1 settings.

I'm not sure how feasible this is, but what would help me a lot is to have the ability to run different versions of the Cura applications completely in parallel with each other, sharing no files or profile settings at all. Like a lot of people, I've spent dozens of hours fine-tuning my 3.4.1 profile, dialing in well over 100 options and reconfiguring them for multiple nozzle sizes and materials. I tested the 3.5 beta (the beta versions seem to have their own paths for profiles and printers so I didn't have to worry about my production settings), but I refrained from updating to the 3.5 release because I was nervous about any process that modified/touched my profiles. I've made backups of them, but in previous versions (I believe it was going from 3.3 to 3.4), I had an issue where the upgraded software seemed to have changed my profiles just enough to cause strange issues when I tried to revert. I wish I could remember the details, but essentially updating to the new release version ended up hiding settings in the old version and I couldn't get them back even after uninstalling the new version. It also silently modified my starting GCODE for one of my machines, and reverted a few of my custom settings. Since I've made so many changes to so many settings, one or two misconfigurations could mean hours of work for me. My ideal scenario would be that when I download Cura 3.5 release, it copies everything like profiles, machines, and materials from my 3.4 folder into a 3.5 folder, and then only upgrades the newly copied files only (meaning that my original 3.4 profiles, machines and materials are completely unchanged by the upgrade). That way I could have 3.4 and 3.5 open at the same time for A/B testing, but I wouldn't have to worry about the 3.5 upgrade making small changes to my 3.4 install. I personally prefer the quick-release schedule because I like new features and enjoy tinkering with things. However, I'd like to be able to do it in a way that I can load up the new release, experiment freely with it, change any settings I want, enable new features, and then after I've completely messed everything up I can easily just say 'screw it,' open up my older version and know that everything is 100% unchanged, no reversion or backups or reconfiguration needed.

In case anyone finds this thread, smartavionic's PR was implemented in Cura 3.5 beta on 9/18/2018.

@smartavionics got it, thanks for going over that. I'll probably keep printing with interior walls first for now, but if things get bad I'll switch it back. Once more, thank you so much for adding this feature!

@smartavionics I just tested it out. It's perfect! It's exactly what I wanted, I was able to print a 3-wall thick print without any tiny-flow segments. It sped up the print, saved me material and the quality was exactly what I wanted. I have one question: on the tooltip for Minimum Flow, it says that "...you must print the outer wall before the inner walls." When I read that I was sad because I print inner walls first so the outer walls look nicer. Just to see what would happen, I unchecked "Outer walls before inner walls" and the model sliced exactly how I wanted it to. The model in Cura had the inner wall printed first, the second phantom inner wall was turned into travel moves, and then the two outer walls printed around it. I then sent it to my printer and everything seemed perfect, it printed the single inner wall, then the two outer walls without problems. Is there a reason that the outer walls have to be printed before the inner walls with this setting? Will this cause issues with other prints that I may not be seing in the test prints I did?

Oh man, it looks like this is release with CuraEngine PR 721 (wall_min_flow) in it! I am so excited, this was the last big issue I had with Cura. Thanks again to @smartavionics for creating the feature, and thanks to the Cura team for all your awesome work!

Cura has had an adaptive layer heights feature since I think 3.2.1. It's called Adaptive Layer Height, and you can also set the 'Infill Layer Thickness' to change the thickness of the interior infill line. I don't think you can setup variable line thickness manually within a given layer, but you can enable 'Fill Gaps Between Walls' to sort of do this automatically, but I've never had much luck with this setting so I leave it off.

That is extremely helpful, thank you! I found your PR on GitHub, it looks like it's exactly what I want. Fingers crossed that it gets implemented soon