What I did:

Modified Skeinforge to be easier to use.

Deleted plugins that are not used anymore.

Made some setting easier to understand /set.

Put in some notes on the pages.

Creates a settings folder .SFACT in the skeinforge.py directory so your other SF is unaffected.

It is only valid for Stepper Extruders.

It is available at:

[github.com]]]>

Just done a small test print with the settings worked out earlier, left the Filament packing density alone. All looks really good now much better.

thanks all for the help]]>

>

> So if the filament packing density is reduced it

> will use less material on the fill and on the

> perimeter? It is set as 1 as the default setting

> by the looks of it

It's the other way around. Reducing the FPDR will increase the flow rate and use more material.]]>

> In SF 40 and 41, you set the flow rate equal to

> the feed rate and you set the diameter of you feed

> in the dimensions option to the measured diameter

> of your feed. If you have set your E steps per mm

> in the firmware to the calculated value for your

> extruder, then you just need to adjust the

> Filament Packing Density Ratio in dimensions to

> get the infill to come out right. SF does the

> volumetric calculations for you so that if you

> later change your layer thickness, perimeter fill

> over thickness ratio, or infill width over

> thickness ratio, it adjusts the flowrate

> accordingly so you still get properly filled

> objects.

>

> If you don't have the correct feed diameter, then

> the calculations in SF will be off and your

> objects won't be properly filled. Even if you've

> carefully measured and entered the correct

> diameter, if your feed quality is not good and the

> diameter varies with length, then your extruded

> filament will also vary proportionately and your

> print quality will suffer.

So if the filament packing density is reduced it will use less material on the fill and on the perimeter? It is set as 1 as the default setting by the looks of it]]>

> You use a workaround for something that is

> implemented already? :)

The difference is that I can adjust the first layer with one edit of the gcode without recrafting the stl. Zero height of the Z axis is a machine parameter, why would I have skeinforge compensate for it when G92 is designed for that long before your feature was implementated.]]>

> This is only valid of course if you have set up

> your Z-home to be exactly over (touching/barely

> touching) your printbed.

> If you have left some gap for safety (e.g 0.2mm)

> You should set that in Altitude. Set it to a

> negative value (-0.2 if your Z-home is 0.2mm above

> the bed). G-code will be generated for Z0.3. As

> you have already 0.2 gap beforehand, your

> nozzletip will now be at the correct position for

> extrusion.

>

I accomplish the same thing by doing a G92 Z0.2 after the G28 to account for the safety margin in start.gcode.]]>

If you don't have the correct feed diameter, then the calculations in SF will be off and your objects won't be properly filled. Even if you've carefully measured and entered the correct diameter, if your feed quality is not good and the diameter varies with length, then your extruded filament will also vary proportionately and your print quality will suffer.]]>

This is only valid of course if you have set up your Z-home to be exactly over (touching/barely touching) your printbed.

If you have left some gap for safety (e.g 0.2mm) You should set that in Altitude. Set it to a negative value (-0.2 if your Z-home is 0.2mm above the bed). G-code will be generated for Z0.3. As you have already 0.2 gap beforehand, your nozzletip will now be at the correct position for extrusion.

Note that there is also the setting under RAFT: operating nozzle lift over layer thickness (ratio). I have this one set to 0.5 so it does not affect my first layer height. And as far as I understand it has the same effect as the Additional heigt over layer thickness in BOTTOM.]]>

Thanks]]>

> Yep so have changed the settings in speed to match

> they are 0.5 and 0.39 and in carve I have layer

> thickness 0.4 and Perimeter width over thickness

> of 1.8

>

> in bottom I have a Height over layer of 0.4 and in

> fill I have Infill width over thickness of 1.5

>

> Hopefully get to test so point over the weekend

Can you confirm what I have ended up with here please?]]>

Also your description (at least to me) is as if it somhow approaches the topic from the result...

I prefer to see how Sf calculates fill. (as a rectangle) then calculate the error ratio to the Oval... Gives very good prints...

NoobMan: You are absolutely correct.. VRR is constant. Thanks for seeing that the error ratio is constant. If a few users could confirm that they get good prints with that ratio it could be calculated in SF automatically...]]>

And then ofc it makes total sense to be constant, because regardless what dimensions the rectangle has, it can fit a directly proportional oval inside it, and the ratio of oval/rectangle or empty_space/rectangle are always the same - regardless of the rectangle size.]]>

2) [www.ehow.com]]]>

[FCS=LH x EW] and [PCS=LH/2 x EW/2 x 3.14] therefore PCS = (FCS/4) * 3.14 therefore VRR = PCS/FCS = 3.14 / 4 = 0.7850 (constant)

Bottom line, i cant see the point to calculate VRR ever, since all variables in the formula cancel each other out, the VRR remains always constant regardless of inputs.

Could say from the start that VRR = a quarter of pi, tho i dont see its relevance for the sf math.

2) PCS representation

I also honestly dont understand which area PCS is meant to represent either. [PCS=LH/2 x EW/2 x 3.14]. It feels like:

- either is 1/4 that rectangle*pi

- or its an attempt to a circular area (pi*R^2) where R^2 is meant like the product of LH&EW?

In either case i cant figure where does it come from. Maybe i dont have enough imagination tho.]]>

in bottom I have a Height over layer of 0.4 and in fill I have Infill width over thickness of 1.5

Hopefully get to test so point over the weekend]]>

This way you can get correct dimensions and watertight perimeters and full fills...

@Noobman: Nopheads blog post adresses the same issue.. He makes a few calculations different than I but the idea is the same...

SF calculates the extrusion volume as a rectangle of width and layer height. This works fine for the infill where there are lines next to each other and you can cram the plastic into rectangle shape to make it "watertight"

Unfortunately during print when you extrude perimeter first you have to rely on the surface tension and the viscosity of the extrudate to achieve any shape. (Without the surface tension and the high viscosity of molten filament the plastic would flow like water...)

What results is an oval. (sometimes an ellipse but oval is more useful in this place.. )

The area of an oval is height/2*width/2*pi... Thats what we use to get the ratio...

The VRR is constant as long as the shape (layer height/extrusionwidth) remains the same.. Basically we try to calculate the missing part in the rounded corners..

"FCS seems like layer_height^2 * aspect_ratio, which simplified looks like the area of the given W/H rectangle. "

FCS is calculated by SF as a rectangle..Its the base for the volumetric thing. (Although I changed it in my own version of SF to take the perimeter as base and I play with the infil...)

And you are right... I was in a hurry but dont think that I skipped something... And thank god this is not a nespaper as readers can actulally ask questions if they dont understand anything.]]>

> The first line gives you 0.72mm.

> Second line 0.288 mm2

> Third 0.226 mm2

> fourth : correct 0.785

>

> Your result is correct:

So do I need to adjust to get the result that is currently 0.785 to be almost the same as my nozzle at 0.5?

I think that's what your saying]]>

Third 0.226 mm2

fourth : correct 0.785

Your result is correct:]]>

But maybe i just dont understand it all.

FCS seems like layer_height^2 * aspect_ratio, which simplified looks like the area of the given W/H rectangle.

PCS dunno what it can be like that, i see a pi(), i see a division by 2 so maybe it was intended to be the area of a circle like = pi*R^2 where R=diameter/2. But like [LH/2 x EW/2 x 3.14], first part is 1/4 of the W/H rectangle and that multiplied with pi doesnt get me anywhere.

I think the writer was somewhat in a hurry and skipped something. I was working at a newspaper long time ago, and it was a habbit after one writes an article, some1 who has no clue about it reads it to give it "clear head". Its an interesting term which means the writer is involved in the stuff and may consider some parts self understood. Whereas some1 who has no clue about what is it, has its head clear - and will imediatelly point any areas that are unclear, or grey, or any curiosity that was not satisfied. I believe the above is a good example, though maybe i just overlooked something and its just me who doesnt understands. I found i understood this better when i was reading it [hydraraptor.blogspot.com] - i think its more or less around this topic.]]>

LH0.4*PWR1.8= 7.2

LH0.4*EW7.2= 2.88

LH/2*EW/2*3.14

0.4/2*7.2/2*3.14= 2.2608

PCS/FCS

2.2608/2.88=0.784

so going with a perimeter feedrate of 0.5 I get

0.5*VRR

0.5*0.784= 0.392

I have a 0.5 nozzle

If I have read this correctly I would set the perimeter flow rate to 0.39 then?]]>

Set your layerheight (LH) and Perimeter width over thickness ratio (PWR).

Multiply LH and PWR. That gives you your extrusion width in mm. (LH x PWR =EW)

Now calculate LH x EW = FCS (Fill x-section). that gives you the crosssection for the infill. This is the amount that SF calculates for volumetric dimension... It is the right amount for the infill... BUT: The primeter gets way too much extrudate this way. The volume for the perimeter would be:

LH/2 x EW/2 x 3.14 = PCS (Perimeter X-section).

Now get the ratio of PCS to FCS. (PCS / FCS = VRR (Volumetric reduction ratio..)

Set in SF- Speed: both extrusion and fill rate to same value. (50-50 maybe)

Set in Speed perimeter feedrate over operating feedrate ( to maybe 0.5 (so your perimeter is extruded slower and you get a better finish))

Now for the perimeter flowrate over operating flowrate multiply the PFROOFR with the VRR.. (Here 0.5 x VRR,)

Set it there...

You should be done...

You get good results if your nozzle x section ( (nozzle diameter/2)^2 x 3.14) is slightly or the same as your PCS...

Enjoy nice prints...]]>

Carve I have layer thickness 0.4 and Perimeter width over thickness 1.8

in Bottom I have Additional height over layer thickness 0.4

in Fill I have Infill width over thickness 1.5]]>