Extrusion width problem

Hi all,

I have a problem with extrusion width. I have a 0.4mm nozzle and layer height set to 0.2mm.
When slicing the 0.5mm thin wall, this gives a extrusion width in the gcode file of 0.67mm
I can calibrate it to come out in 0.67mm very well.

However... how can I make slic3r print the 0.5mm wall actually in 0.5mm and not 0.67mm?
When I set manual extrusion width to 200% (which is then 0.4mm) it prints the wall in 0.4mm, so there is no problem for the printer to print such thin perimeters....

Someone can help?
thanks!

The 200% applies to your layer height, not the nozzle size. With 0.2 height, if you want 0.5 extrusion width, you need to specify 250%.

Thanks, but I know that. The 200% where just a test to see if slic3r can print 0.4mm width walls.

When I manually set it to 0.4mm for example, then slicer prints all perimeters with 0.4mm regardless what there real width is. That cannot be correct...

Edited 1 time(s). Last edit at 10/31/2013 09:50AM by muelli.

What do you mean by the "real" width. You specify the layer height, and then you specify the extrusion width either as a real number or as a percentage of the layer height. Note that the nozzle size does not come into play in these calculations. In fact, if you ever used skeinforge, it doesn't even ask you the nozzle size. All extrusion commands specify the volume of plastic going into the extruder. Regardless of the nozzle size, that same volume must come out. the layer height and extrusion width define the cross section of your bead. The area of that cross section, together with the feed rate of the head must match the volume going into the extruder.

with "real width" I mean what is the width of the wall I measure with my calipers.

for testing I specified the extrusion width manually to 0.4mm and the 0.5mm thin wall came out as 0.4mm. slic3r does not slice the object to make it come out with 0.5mm walls as defined in the STL.
that is my problem, because then all dimensions in the CAD are not correct.
I create a testobject lets say 20x20x20mm cube with a 5mm hole trough it and the outer dimensions are OK but the hole comes out to small because the extrusion width is not correct. (in my opinion *g*)

Now I understand. Your walls in the STL are 0.5, but your extrusion width is 0.4 so slic3r does nothing to make up that last 0.1mm.

One of the areas where slic3r has issues is in thin walls. I've never tried to slice a wall that thin, but I have had walls that ended up hollow because slic3r did not fill them.

I think this is just a limit of both the hardware and software right now. The slicers try to get as close as possible to the actual measurements within the limits that they are working in. In a similar fashion, if you have an object height of X mm, it won't end up at exactly X mm if it's not a multiple of your layer height (taking into considerations what happens on the first layer). I think in these marginal situations, you just need to play around with slic3r parameters - like you've been doing - to get the results you want.

ok thanks, but that is bad news
right now I tried kisslicer but that tool has even more problems with the 0.5mm wall

Is there something that "just works"?

Use Skeinforge and pick a layer height and W/T value that gives a width of 0.5mm while keep the cross sectional area smaller than a 0.4mm circle.

With PLA it will extrude not much bigger than the nozzle so assume the maximum cross section is then 0.126mm^2. Since you want the width to be 0.5mm that gives a maximum height of 0.251mm

So you can use 0.25mm layers with W/T = 2 or 0.2mm with W/T = 2.5. Then don't forget to change the outline flow rate as described in the Mendel90 manual.

Any walls that are 0.5mm will then come out as 0.5mm but you can't print anything between 0.5mm and 1mm. Anything between 1mm and 1.5mm will have a gap. Anything above 1.5 will have two walls and infill.

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[www.hydraraptor.blogspot.com]

skeinforge is to complicated for me to understand.
I gave up on that

Kisslicer is the only one that adaptability changes the extrusion width and will print what ever width wall is input. It works really well but you have to figure out how to set it up correctly as it does not do anything for you (the name is deceiving as it is not simple it actually makes you manually set everything and you need to know how or you are stuck).

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Also 0.5mm walls is a bit thin with a 0.4mm nozzle. Slicers tend to work better when the minimum feature size is either twice the filament width or more than three times. It then just works as you two walls with a thickness appropriate to your nozzle and some infill in between. When printing something with feature sizes less than that you tend to have to design the object with the filament width in mind. That is why the filament width and layer height I use is defined in the Mendel90 config files and all parts are then made to be printable with those.

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[www.hydraraptor.blogspot.com]

Put another way - the part needs to be designed for the manufacturing process that is going to be used. There is no process that "just works". You always have to take the details of the process into account as you design the part.There is a practical feature size limit with this stuff. There's an even higher limit if you are picky about the accuracy of that feature.