Influence of perimeter to G1 Code distances

I have made a squre model of 10mm size. the siz3r configuration is change to no top/button layer, no infill and only 1 Perimeter. (it looks like square fence).
Default extrusion width=0 / repetier Host Extruder diameter 0.4
Now I can easily check the G1 movements.
I have change the nozzle diameter in Slic3r from 0.4, 0.5, 0.6 ,0.7 but the movement stays always the same: 4.905mm from the center.
Also when I changes of the diameter in the Host Extruder the value does not change.
That means the G1 code move the nozzle 9.810mm for one side of the square.

I do not understand, why the nozzle diameter has no influence to G1 movements?
(a thicker nozzle diameter should make a thicker perimeter, and therefore the G1-movement should be smaller - or is this a wrong theses)
What factor does influence the value of the G1 code ?

Any help is welcome! Thanks

Now i checked further and find out it depends on the layer height:
0.1 mm G1:4.952mm = 9.904 (theoretical 10mm)
0.2 mm G1:4.905mm = 9.810
0.4 mm G1:4.810mm = 9.620
I am surprised about this dependency!
Is there an explanation?
Depends the perimeter diameter only on the layer height?

What does then the nozzle diameter influence? Is it the speed for extruder?
So with Nozzle diameter 0.4:
X-4.952 Y-4.953 E6.04983
and with Nozzle 0.8:
X-4.952 Y-4.953 E6.07648
So only a very small difference!
(for doubling the nozzle diameter only a small difference)

My basic interest is: the dimensions of my parts do not fit outside dimension 0.1-0.2 too big and boreholes 0.1-0.2 too small.
So my idea is that the diameter of the perimeter is in reality bigger than slic3r calculates ...

Extrusion width is determined by the quantity of plastic deposited per mm and the layer height. Think about it - the amount extruded per mm will determine the volume of plastic per mm. The width will thus equal volume per mm divided by height.

Dave

@dmould: in General I agree with you. But still I do not understand the details: "default extrusion width" and "Layer height" define "plastic quantity" - that is clear.
And plastic quantity is defined by the extruder speed E in G1.
If I leave layer height unchanged, then only the "default extrusion width" influences plastic quantity,
But the "default extrusion width" does not influence the extruder speed - it is always the same value.

If I change the nozzle diameter:
extrusion width 0.4 / layer heigth 0.2/ nozzle 0.4
G1 X-4.905 Y-4.905 E6.14459
extrusion width 0.4 / layer heigth 0.2/ nozzle 0.8
G1 X-4.905 Y-4.905 E6.19739
the extruder speed is slightly increased aprx 0.8% but the nozzle is doubled?!

Does the the "Extrusion multiplier" increase the quantity of plastic?
(but it has no influence to the G1-Code)

Do you know anything that changes the distance of the first perimeter to the edge of the part?
example: outside part lenght 10mm / perimeter G1-Code 9.81mm / I need 9.75mm?

Georg

Edited 1 time(s). Last edit at 01/06/2015 01:57PM by Georg99.

Apart from "Default extrusion width", have you also tried "Perimeters" on the same "Extrusion width" section on "Advanced" "Print Settings"?

Let aside nozzle diameter. It is not used in determining the extrusion. And be aware that "default" will be overwritten by a more specific extrusion width if not set to 0.
However, if you really want to control the dimensions, set all extrusion width manually to a value of your choice, but not less than the actual nozzle diameter (though it might work) - you can set it larger than the nozzle diameter, but the result will depend on the actual construction of the tip of the nozzle.

Extrusion multiplier will influence the amount of plastic, but the effects might not be the desired ones (e.g. you may get some overextrusion. Have you read this [reprap.org]?

Quote
Georg99
@dmould: in General I agree with you. But still I do not understand the details: "default extrusion width" and "Layer height" define "plastic quantity" - that is clear.
And plastic quantity is defined by the extruder speed E in G1.
If I leave layer height unchanged, then only the "default extrusion width" influences plastic quantity,
But the "default extrusion width" does not influence the extruder speed - it is always the same value.

If I change the nozzle diameter:
extrusion width 0.4 / layer heigth 0.2/ nozzle 0.4
G1 X-4.905 Y-4.905 E6.14459
extrusion width 0.4 / layer heigth 0.2/ nozzle 0.8
G1 X-4.905 Y-4.905 E6.19739
the extruder speed is slightly increased aprx 0.8% but the nozzle is doubled?!
Georg

You have described the facts correctly, but have then changed the wrong variable. The same volume of plastic must be extruded from a 0.4mm nozzle at a height of 0.2mm to get an extrusion width of 0.4mm as is needed to get the same height & width from a 0.8mm nozzle - the nozzle diameter you set makes pretty much no difference to the G-code (the small difference you see is probably only due to the fact that the extrusion profile is a flattened circle rather than a rectangle, and the nozzle diameter affects the curvature of the sides). It has to be the same because volume=length*height*width and you have set the length, width and height the same for both nozzle diameters - the height (0.2mm) is constrained by the gap between the nozzle and the previous layer, the length of the move is the same, the width set for the extrusion (0.4mm) is the same and so the volume must also be the same. The nozzle diameter affects mainly the range of widths and print speeds that will in practice print satisfactorily. In a perfect World a 1mm nozzle would stretch the plastic it is extruding to make a track 0.4mm wide, and a 0.2mm nozzle pushing the same volume of plastic over the same height & distance would result in the extruded plastic being forced to move sideways as it exits to form exactly the same 0.4mm wide trail. In practice however neither would result in a well shaped extrusion, so there is only a limited range of extrusion widths that will print satisfactorily from a given size of nozzle.

Try changing the extrusion width required instead of the (irrelevant) nozzle diameter, and you will see a proportionate change in volume (filament extrusion length). Of course, if you leave the extrusion width as "auto" (by entering a value of zero), Slicer will compute a suitable extrusion width to use based upon the nozzle diameter and so you will get different G code (the extrusion width Slic3r chooses can be found in the commented header of the G code file it produces).

As an aside, I'm not sure whether your reference to extruder speed rather than extruded volume was a mis-type. The E parameter in the G-code is the length of filament and hence represents the volume of plastic extruded over the distance of the move, it is not (directly) the extruder speed. The extruder speed is determined in the printer controller's firmware rather than the G code, based upon not only that E parameter but also the speed of the XY move (which is not constant due to the application of acceleration).

Dave

@Dave, thanks for your explanations! You are right I misunderstood the E value ... (learning never stops - thanks for the tip with extruder sizes in the comments).
I made endless testparts, so I started to look directly at the G-code.

Do I understand you right: the geometry G1 code will alwayse be same - I must work on the thickness of the perimeter that comes out of the nozzle.

(my standard with the result 10mm in the model become 10.1mm in the part)
0 = default extrusion and nozzle=0.4
; perimeters extrusion width = 0.19mm
; infill extrusion width = 0.67mm
; solid infill extrusion width = 0.67mm
; top infill extrusion width = 0.35mm
G1 X-4.905 Y-4.905 E6.14459

changing the 0 from default extrusion width to 0.35
; perimeters extrusion width = 0.19mm
; infill extrusion width = 0.35mm
; solid infill extrusion width = 0.35mm
; top infill extrusion width = 0.35mm
G1 X-4.905 Y-4.905 E6.14459

0 = default extrusion and nozzle=0.6
; perimeters extrusion width = 0.19mm
; infill extrusion width = 1.46mm
; solid infill extrusion width = 1.02mm
; top infill extrusion width = 0.35mm
--> minimal increasing to E (the opposite what I want)
G1 X-4.905 Y-4.905 E6.25649

0 = default extrusion and nozzle=0.3
; perimeters extrusion width = 0.19mm
; infill extrusion width = 0.37mm
; solid infill extrusion width = 0.37mm
; top infill extrusion width = 0.35mm
--> minimal increasing to E (compared to default=0 - still bigger)
G1 X-4.905 Y-4.905 E6.19709

0 = default extrusion and nozzle=0.2
; perimeters extrusion width = 0.19mm
; infill extrusion width = 0.21mm
; solid infill extrusion width = 0.21mm
; top infill extrusion width = 0.35mm
now E is shorter 0.4% - I need at least 1% (it is for sure not linear)
G1 X-4.905 Y-4.905 E6.11819

Hmm ... I am confused - what is your proposal to make E smaller?! (nozzle 0.1 does not work)

BTW: I tried the CURA-Engine. Their geometry code for the 10x10 part ist G1 X-4.900 Y-4.900.
So the geometry code is a little bit smaller!
In the moment the cura-code is closer for the dimensions on my machine. (but still not 100%)

Edited 1 time(s). Last edit at 01/08/2015 02:31AM by Georg99.

Don't use default extrusion width 'auto'. This should be set to a value which will work with your hotend/nozzle. e.g. 0.4mm for a 0.4mm nozzle.

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