How to interpret ‘Width’ in the legend PrusaSlicer?  

RE: How to interpret ‘Width’ in the legend PrusaSlicer?

Without your Prusa Slicer project file its impossible to give a definitive answer.  As we don't even know what printer you are using, let alone what settings etc.  A PS 3mf project file has ALL the data required.  Much depends on if you are slicing with Arachne (the current default) or Classic.

However as a best guess, assuming you are using a profile anything like a standard Prusa one, if you look at the defined extrusion widths for a 0.4mm nozzle then external perimeters are often set at 0.45mm (so are normal perimeters).  So notionally one perimeter is generally going to be around 0.45mm thick.  2 perimeters which have to also overlap so they can stick together will be slightly under 0.9mm.  That is with Classic.  When you measure the real world thickness with a calliper of the part produced. 

The preview visualisation shows each extrusion individually, and Im guessing you have Arachne as the slicing engine.  That will try to dynamically adjust the extrusion to get closer to the desired model width.  Unlike classic which will just not print a section if the model is too thin for the extrusion width.  Note your bottom layers shade of green corresponds to about 0.45 which is what I would expect of a normal profiles 0.45mm

If you tried to print a box with a 0.4mm wall thickness using classic and detect thin walls =off then you wouldnt get any walls.  They would be too thin to slice.  If using Classic and you have Detect thin walls turned on then it would slice the walls but print them at a normal extrusion width, ie 0.45mm, so your walls would be 'over sized'.  Of course you can change the default extrusion width for your Print profile to 0.4 in such cases.
As mentioned before with Arachne it will dynamically try to reduce the extrusion width (within the bounds of the Arachne default settings).  As such a model with 0.4mm walls will get walls and they should be close to 0.4.  Assuming theres nothing else effecting extrusion such as a Speed profile.

With a desired model wall thickness of 0.8mm then Arachne will again try and select an extrusion width suitable, this time taking into account the overlap needs to 'try' and get your desired wall thickness.

This is why when calibrating for extrusion widths (such as fine tuning your extrusion multiplier for example) using a new filament or a change to your extruder hardware it is needed to change to Classic and not use Arachne.

RE: How to interpret ‘Width’ in the legend PrusaSlicer?

Thanks for the quick reply.

In the meantime, I re-read your advice about calibrating the extrusion multiplier - I must admit that it was only this time that I understood the intention of printing a simple cube with a single wall, and this is better than the model I have been using to date - which is a modelled empty cube with a bottom and a single wall....

Back to the topic of the post - I would just like to understand what the exact expected thickness of a double wall is.I am attaching the cube design for a standard print on MK4S.

I have a different printer but I print in PrusaSlicer and I am concerned to understand the problem - how to determine the expected wall thickness - no matter what printer it is printed on.

If possible, please let me know what the thickness of the double wall should be after printing a 20x20 mm cube with 0% filling, perimeters=2.

Standard printer MK4S, standard print settings for 0.20mm speed, generic PETG.Unfortunately I can't attach the 3mf file....

On the attached photo the project from 10 to 20mm is generated single wall but this thickness I can easily octalise using the legend - 0.45mm.

Regards

RE: How to interpret ‘Width’ in the legend PrusaSlicer?

Prusa Slicer tells you what the recommended object wall thickness is for various perimeter selections.  So with an extrusion width of 0.45mm the expected printed thickness for 2 perimeters is 0.86mm.  Those 2 extrusions of 0.45mm will be overlapped to give you a 0.86mm thick wall.  If you were to configure the extrusion width for exactly 0.4mm instead then 2 perimeters will be 0.76.  It gives you this info just below where you set your Perimeter count.  That text is dynamic, so if you adjust your extrusion widths the values will change accordingly.

If you want to attach ANYTHING besides pictures you must first zip them up.  The forum will just silently drop anything else which is why your cube or 3mf etc are not available.

RE: How to interpret ‘Width’ in the legend PrusaSlicer?

Thanks for the comprehensive reply.

I am glad I made the post out of curiosity.

Now I know what thickness to expect when calibrating the extrusion multiplier.

I also found out what the 'detect thin walls' function is for.and how to add files to an article.

I measure the walls with a micrometer - this is the quickest and safest way to calibrate, and the above information is important to me :-).

I wish cohesion and adhesion of layers on all your prints ;-).

Regards