Link

I have looked into this a bit more and the constant similarity between this and when I have seen it is that the gaps appear at the layer start point, the wall lines are started from the same point due to the z alighment and this is the area the gaps start. It really goes seem like the other existent walls have shrunk and the new wall doesn't quite meet the existing. That may explain why rotating the model changes the behaviour as the z seam alignment will move. Would be worth trying to set the seam alignment to random and see if the gaps move. I also found that if I printed two models at the same time the issue went away, the print had to perform a retraction and move between parts which I assume changed either the wall print order and/or seam alignment position. I have seem this problem on both 0.6 and 0.4 nozzles too. And its constant in that it appears at the wall start point

I found another topic on this, same issue. Some ideas about the walls cooling and shrinking away from the other wall. I can relate toe this as when I had the problem I could see the gap get larger as the print cooled. I wonder whether S3D prints the walls in a different order and maybe that is the key difference ?, can you tell from the Gcode ?.

Glad the original issue is still ok, I can’t help but think there is some Cura quirk in here. Something doesn’t add up. Wish i knew what it was. I found this info on S3D website If lines are printed so thin that there's a gap when their shouldn't be, adjusting either Extrusion Width or Layer Height will NOT fix the problem. For example, if you have a 20% gap between walls that should be solid without a gap, and you make your Extrusion Width larger, your gap will still be 20%, but will now be a larger gap because the lines are now larger and further apart from each other (the print resolution is lower). You didn't get rid of the gap, you just enlarged the lines, and the line spacing, so the 20% gap appears wider, but is still there at 20%.Likewise, If lines are printed too thick and are overlapping each other, adjusting either Extrusion Width or Layer Height will NOT fix the problem. For example, if you have a 20% overlap between walls, and you make your Extrusion Width smaller, your overlap will still be 20%, but will now be a smaller overlap because your lines are now smaller and closer together (the print resolution is higher). You didn't get rid of the overlap, you just shrunk the lines, and the line spacing, so the 20% overlap appears thinner, but is still there at 20%.

Have you tried rotating the model, for some reason that stopped the gaps for me. That was def a Cura thing. Wish I knew what it was

That’s a pain, I have to admit I was surprised the line width worked as ‘in theory’ it shouldn’t as the slicer moves the lines to compensate for the extra width so the gaps ‘should’ remain (which they have). Have you checked the infil below the walls ?. Are you getting gaps on all layers or just the top ? Can you try another material, even a different colour of the same, just to rule out the material flow. I had some black pla which seemed to have such bad layer adhesion that I had gaps all the time, tried another filament and it was fine. Do you have a spare nozzle to swap and try that ? Also what is the ambient temperature in the room. I had some issues with gaps when the room was really cold. If you increase the temperature by 10 deg does it go ? Also try some cleaning filament. Ultimately either the plastic is not sticking to itself once laid down or you are slightly under extruding. It could be you have something in the nozzle, a small clog which needs to clear.

Thanks @CarloK, I have actually performed a few tests with both sets of firmware, Tinker with 0.95 and UM with 0.99 and the UM version has less fluctuation and holds a more stable temp during a print.

Thanks for providing these, it turns out the default nozzle PID values in the UM2+ Tinker firmware are actually the values from the 2 with the lower wattage heater. If anyone just uses the 2+ fiirmware as is you get pretty wild temp fluctuations. Might be worth updating the defaults in the 2+ tinker file to be the UM 2+ values ?. I have also noticed the K1 value is different in the Tinker confit for all printers compared to UM for all printers. UM state a K1 of 0.99 and Tinker has 0.95. This value is stated as the smoothing factor within the PID. Does anyone know what this does and does the difference matter ?

Many thanks. Do do you use PID in the bed or bang ? I have tried PID on the bed and it seems to make the LED's flicker slightly ?>, it is worth using ?, I don't see the temp jump much on the bed, but have read that PID on the bed is a good thing to use ? Cheers

Hi, Quick question regarding the PID tuning, are the default values good enough to use or should I run the PID auto tune for nozzle and bed ?, I am not sure if the defaults are the ones which we're in the UM firmware or are they older based on the TG firmware ?. Also do I need to specify a target temp for the PID (I had to do that with a Prusa machine I had a while back) and finally, what is Heater Time out ? Many thanks !

Hi @CarloK any news on the official release following testing ?, unfortunately I am not really in a position to run beta firmware as I leave prints unattended and don't feel too comfortable leaving it running on beta firmware for obvious reasons. many thanks

I read that UM feel it gives better detail, on my UM 2+ I get better results with 0.4 than I did with 0.35, I haven’t gone wider, maybe I will try it.

I have a photo from ages ago of the settings in Slc3r for a Prusa I used to have, they also use a wider extrusion width than the nozzle !, interesting. Seems Cura is the only slicer to default to less than the nozzle I

Result !, however you shouldn’t really have to do that to fix it, Ultimaker run line widths of 0.35 and obviously don’t assume a gap will be present. Maybe there is a bug in Cura which means the width calculation gets messed up in some strange scenario ?. @smartavionics Will be best placed to comment on that. If if you have time go back to 0.4 width and check the infil setting I spoke about. Really interested to hear if it work ! ??

Have you tried with a 0.4 ?, can you reproduce the gaps ?

Yes I had the same thoughts about the line width, I increased mine from 0.35 to 0.4 as it gives me a nicer finish to overhangs but it made no difference to this gap issue when I had it. I don’t see how increasing the line width would help as Cura just compensates the spacing for the line width you specify, so the gap will be constant as I saw.

I have seen this issue also, and it seems to go as randomly as it arrived I had one issue where I was getting gaps when printing a horizontal line only in one part of the print, if I rotated the print (the now horizontal) line was fine with no gaps, simply put if I had a certain model in a certain orientation I would get a gap the same as you are seeing. I deleted my model in Fusion 360, remade it and re-sliced and it had no gaps regardless of orientation !. @smartavionics is a top man and really knows his stuff, but for my random gaps we never got to the bottom of it. As is said I rebuilt exactly the same model (and various test pieces) all with the same dimensions and none of them came out with gaps. We looked at Gcode and nothing jumped out I wish I know what it was, like you a tired overlap, more heat on the nozzle to correct potential under extrusion and nothing fixed it. However...... I spent a bit of time looking at where this occurred on some models and it looked like the top layer was sinking where there were gaps where the infil met the wall. In Cura you can have an extra line for skins which essentially makes the top skin ingress into the model more than the infil. In 3.5 there is an option to have 'extra infil wall count', make sure this is set to 1 (if extra skin wall count is also set to 1), this was you have a full supported top layer. Give that a try and see if it helps.

Thanks !, I don’t think it was your fault ?.

standard profileUM2_bridge-torture-test_50mm.3mf

thanks UM2_bridge-torture-test_50mm.3mf

There is a bug in that when you select 'bridge has multiple layers' this has no affect, essentially the bridge print Gcode is as though this option is always selected. You cannot for example change the fact that the fan turns off on the second layer (even if you set it to stay off it still turns off. I have checked the Gcode and its is identical with and without this setting enabled.

That would be slightly relevant if the only users of Cura were Ultimaker owners, and if what they released meant people could not use their printers !. Two points there, the vast majority of Cura users I bet aren’t only Ultimaker owners, and lets be honest, the only issue is here that (some ) people cannot use one version of Cura. It’s not like 3.4.1 doesn’t work !. There are some great additions in 3.5 but it’s not like 3.4.1 wasn’t useable !, far from it. Agree the software shouldn’t have bugs in it but UM are aware of this better than anyone and are fixing it. Ultimaker 2+ owners should be a lot more upset by the firmware which still hasn’t been fixed to correct the fact the material gets rammed into the hot end every time you change material !. I am a lot more concerned about a fix for this. Tbh I don’t get the stress over this issue when UM have acknowledge and are working on it !. Now UM team please release the 3.5 firmware for the 2+ ?

Might be some wires crossed here, you can download it however you like, it does the same thing. It when you actually start the install of the new version (in Mac at least) it asks if you want to upgrade/replace the old version or install another new one. This is what I am talking about. I pick install another and have both versions present. This have nothing to do with the download link or process to get the application file

when I move version I always make copies of all my profiles fist then install the new Cura version alongside the existeng. Install the new version as a clean version (don't upgrade the old one), then add the profiles you saved into the new version.), if for any reason the new is not good you have both the old one still intact and a backup of the profiles anyway. 3.5 has been fine for me, no issues at all. I am using latest Mac OS

I don't get why people are bashing the UM team here, this software is free !!!! and whilst anyone who works in software development knows you can't find every issue, it's how you deal with it when they come up. If the current version doesn't work for you (it works for most), then roll back to 3.4.1 whilst they fix it (which they are), the isolated nature of the people affected clearly shows that the UM team didn't just release any old software, not to mention it was in a released Beta phase for a while.

yes, very good point, I tend not to use hop so as you say it could well mark the already printed areas. So as an option would as you say be best. One other idea I had was it could be good to be able to define (as an option) what combing defines as the skin (in relation to combing), for example it if set 6 top and bottom layers for strength Cura calls each one skin, in terms of surface finish I am pro only worried about combing over the first 2 or 3 after that I am happy for the skin layers to be treated line infilled and can be combed over as the blobs won't show. Just a thought... thanks