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Extrusion width ratio

Posted by TinHead 
Extrusion width ratio
February 23, 2012 05:33AM
Hi Sound,

When setting extrusion width ratio to 0 slic3r generates the following output at the beginning of the Gcode file:

; generated by Slic3r 0.6.0 on 2012-02-23 at 15:13:17

; layer_height = 0.2
; perimeters = 3
; solid_layers = 3
; fill_density = 0.5
; nozzle_diameter = 0.35
; filament_diameter = 3.0
; perimeter_speed = 30
; infill_speed = 30
; travel_speed = 100
; extrusion_width_ratio = 0
; scale = 1
; single wall width = 0.49mm

While looking for a way to calibrate my Prusa to get the best results I have found the procedure you posted on one of the issues for Slic3r:

Quote

This is a calibration procedure for Slic3r:

Set your layer height to 0.2mm and your extrusion width ratio to 2. This should give extrusion threads with a 0.4mm width.

Then take a cube, slice it with 1 perimeter, 0 solid layers and 0 fill density. It will print like a hollow calibration piece.

Then you can measure the width of a wall and check whether it matches the expected 0.4mm. If not, reduce or increase the amount of plastic using the Extrusion Multiplier.

If you do that, let me know your results: I'm very interested in them.

My first question is, if a setting of 2 should yield 0.4 mm width for 0.2 mm layer height how come that letting the extrusion width ration on auto yields 0.49 mm width for 0.2 mm?

I have done the procedure and I found that to get 0.4 mm width for 0.2 mm height I need to set the ratio to 1.7, and I have done so with better results, but Sublime pointed out in one post that my extruder steps per mm are incorrectly setup if I need to adjust the ratio.

I just rechecked my esteps and I pretty much hit extrude 10mm and get 10mm of filament pulled in ... so I'm puzzled about this.

So my second question is: what is the correct approach?

Thanks!
Re: Extrusion width ratio
February 23, 2012 05:42AM
@TinHead, perhaps you're confusing the Extrusion Multiplier setting with the Extrusion Width Ratio setting? Tweak the former, and leave the latter to zero.
Re: Extrusion width ratio
February 23, 2012 05:48AM
Oh indeed, I did, I did ! That makes that part clear thanks!

How about the layer width? why 0.49?
Re: Extrusion width ratio
February 23, 2012 06:53AM
@TinHead, it's the result of the automatic internal calculation.
Re: Extrusion width ratio
February 23, 2012 07:08AM
I don't want to be annoying so ignore this if it's stupid.

Yes I understand that it is an outcome of the internal calculation.

But it does not change with the layer height, for 0.1 mm layer height I still get the same width of 0.49 for a 0.35 mm nozzle.

I mean if this is intentional and it is how it's supposed to work ... well fine with me.

But if I mess with the Extrusion Width Ratio (yes I mean Extrusion Width Ratio this time) I do get smaller width, so smaller width is possible which in turn means you can get a better horizontal resolution at smaller layer heights, and this would be really useful no?

Edited 1 time(s). Last edit at 02/23/2012 07:10AM by TinHead.
Re: Extrusion width ratio
February 23, 2012 09:49AM
Extrusion Width Ratio is placed under the advanced options, so it's not necessary to change it at all and you shouldn't do it only if you really need a particular extrusion width. Just be careful not to set it to a smaller extrusion width than your nozzle size: the results are undefined in that case.
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