yellowshark

… oh by the way circular geometry will NOT be accurate, easily out by 3/400microns. You need to compensate within your 3D model dims to get circles right.

With a new printer you should easily hit 100 microns and quite frankly 50 microns at worst. As @Smithy says standard settings will not do it for you. Smithy mentions some fancy expansion settings there which I have never used, are they available in 2.7 I wonder? Don't know what slicing tolerance is but I am sure Smithy will be correct. My maxim is slow and cool and a filament you know you can rely on. I have two PLA filaments that I turn to when dimensional accuracy is important. I go for 30mm/s and nothing more than 190; probably less if I were using 0.15 layer height. Cannot recall what I use for outer before inner walls as my notes are on another PC. I have a sneaky feeling that I did a comparative test and found no difference but Cura help does suggest outer before inner can help accuracy. All the notes above will help but you will need probably need to do some of your own testing to get there. I do not know what testing Ultimaker do on each machine before shipment for this area - you could send a question to Support. Ultimately if you cannot get to your target, which should be at least 100 microns then you might want to start playing with your e-steps settings in the firmware. Quite easy actually as long as you have some idea on what you are doing when playing with firmware and take it easy.

Hi Sean, I take you point but do not understand why that corner would be 85d rather than 90d. Are you saying that Cura does not slice 90d corners correctly? Or of course your modelling software.

Thanks @smartavionics, that makes complete sense now🙂

Confused, if you have drawn a square then surely by definition each corner will be as sharp as the other 3 and they will all be 90d. Or am I missing something obvious that is going to embarrass me😵

I am trying to use DesignSpark instead of Solidworks (for this particular job) and this should be so easy but blowed if I can work out how. I am in Sketch mode and have drawn a number of interconnected lines and want to go back and change the length of a particular line - but how? I can select the line and see its length at the bottom of the screen, on the right hand side but I cannot change that displayed figure. How do I get a box displayed that will allow me to change it? If I do change it will the connected line(s) automatically remain connected and move with the changed dimension?

Good point, I had not thought of that aspect.

I am not aware of being able to control this by software, someone else may. The normal method has been via your printer e-steps in the firmware. Easy to do but if you do want to change firmware settings you need to be sure on what you are doing and take it carefully. A bit like playing with the registry on a Windows computer!

Big corners: Printing outer wall before inner walls and walls before infill can both help with dimensional accuracy. Also print as cool as possible. Do not forget that even if your extrusion looks OK, the printer is slowing down as it goes into the corner and then accelerating away, if you are hotter than you need to be then you could be getting slight over-extrusion at the corners increasing the dimension. Go as cool as you can until you see under extrusion then add 5 degrees. As @Smithy says the slower you go the better it will be. If dimensional accuracy is important for me on a job then I will never go faster than 30mm/s. You are 200 microns out and you should be able to hit a maximum of 50 microns, especially with a nice new 5S 🙂

… plus also if you start varying the speed up and down at the top, you risk getting artefacts on the outer wall as the pressure keeps adjusting.

personally I am not sure what the problem is; just add a layer or reduce the top layers speed; if you are printing fast enough so that the first of the top layers does not print well over the infill then you would probably want to reduce the speed of the top layers anyway to ensure a quality surface finish. I have not used it but you could also use the option Gradual Infill Steps which, as I read it, seems to increase the infill density as you approach the top layers - indeed this may be a very good solution. But it is not a problem I have ever had as I always make sure I define enough top layers, which of course varies with layer thickness, to get a quality surface.

No I meant not digging the needle point into to wall of nozzle, you can push it in as far as you want. I have always done it with the extruder removed otherwise you cannot see if there is anything there.

… if you drop the nozzle into some boiling water first you will find that helps.

Well I have done that a couple of times over the years and it has not caused me a problem. I guess the main point is to scrape off the filament not dig the needle into the nozzle.

Can you not just cut the filament towards the end and feed in filament from a new spool directly behind/touching the existing filament being pulled through the Bowden?

Ah, well I am not sure where you are now with the retraction setting but it was 2mm which seems awfully short to me. But I am talking about 2.85 PLA and I do not know if that needs different settings. It may just be that you are not retracting enough so when the printing starts on the next layer you are over-extruding. Probably worth trying say 5.5 unless you know it needs to be shorter for 1.75/ABS. I am not sure but I have never seen your symptoms before. It could be cooling but I do not understand why the problem is localised if it is.

This is all very strange! I would definitely set minimum layer time to 10 secs. OK so on layer change it starts on one of the rear corners; is it the right hand side I.e. the side with the mess? I am just wondering if it travels direct to the mess area and the previous filament has not had time to cool before you come along and print more filament, so we are not looking at under-extrusion but just a simple mess; clutching at straws here! Are you able to print PLA too. It might be interesting/helpful to see a PLA version.

Do not know why that is happening; on my printer with 2.7 it prints top left down to bottom right. But hey bottom left to top right is still ok, yes?

A bug, you must be joking that is how it should print. So you fix it for people who print all at once but screw up something that worked perfectly for all those people that print one at a time. great design and coding I think not. So are you going to fix it for us. I will not be moving to 3.n.n because I cannot - I need that functionality. Paah

Good to make progress. Did you use the same settings for the round piece that you used for the square piece., Can you send us the stl and, as @Smithy requested, the project file if possible?

I do not know if this has changed since 2.7 but Cura prints in reverse order of the models loaded. So to get this right load each copy of the model individually. Position the first copy in the right front position, the next to the left and rear of the first copy and so on heading back to the left rear position.

OK firstly, you say it worked before upgrade but not now. I assume you are printing the same model with same settings (as far as you know) and the same filament, otherwise the statement is not really valid. Assuming yes, have you compared the 3.6.0 and the prior version settings in detail - I mean every single setting whether you use /change them or not- to see if something has changed that you were not aware of. It looks like a very small piece - do you have your minimum layer time set to a minimum of 10 seconds? What width of filament are you using - is that what is defined in your Cura settings? What is your setting for flow %? Is it right that all the model parts in your 4th picture were printed before you upgraded to 3.6.0? What is your z-alignment setting? If it is not random is the new layer starting in the area where the possible under-extrusion is happening?

Impossible to say without knowing all your printer speeds and layer height. I will assume your line width is set to 0.4 and wall width a multiple of that, although they should not affect under/over extrusion unless there is serious variation. Are you using 1.75 filament?

I agree with @Smithy entirely except maybe for the zits but I have never printed abs so I could be wrong. I am happy to print too but I will have to drop the temp for PLA

Set all your print speeds to the same figure, i.e. infill walls skin print speed, leave travel speed alone. Personally, whilst you are trying to debug this, I would use 30mm/s. Set flow to 100%. Set all your line widths and nozzle size to 0.4, or if you have measured your line width printed then set it to that. E.G. at 0.4 my nozzle prints 0.45 so all my relevant settings and my design are based on 0.45. Set your wall thickness to a multiple of your nozzle size/line width. Print as cool as possible.