Filament length calculation

Hi,
I am using slic3r for a project in chemistry:
Printing a 0.1 mm layer on a 100*100 mm surface

I am using a syringe to apply my material (silica gel), it should apply 1 mL, 1000 mm3

The inner diameter of the syringe is 4.7 mm so the length to apply should be 58 mm.
But in slic3r, if I enter 4.7 mm as diameter in the filament setting, once I load the gcode in pronterface, it says that it will use 6.4 mm instead of 58. I must input a diameter of 1.55 mm to get a correct value.

There must be a parameter I am missing, and I will really appreciate a little help on this on, I put my config file in attach as well as the stl.

Dimitri

So looks like total length is being divided by 10. The original calculated length should have been 64mm - the additional 6mm is due to the fact that the infill overlaps the perimeter a little and other factors. A syringe that extrudes a tenth the volume per mm would be 1.49mm diameter ( 4.7 / sqrt10 ), which ties in with what you found.

The question however is whether Slic3r output the wrong length, or pronterface read it incorrectly. Look at the G-code in a text editor and find the total filament length there (commented near the end of the file), which will tell you whether the error is with Slic3r or pronterface. The main concern is whether Slic3r is correctly calculating the length to extrude for each move and the error is only in the total, or whether the extrusions are also out in which case the print will be wrong.

Dave

Well, I am actually using the gcode with the 1.55 filament diameter and the syringe output the desired 1 mL.
I looked inside each gcode and I can confirm that pronterface read the good value for the filament length, in the comment and with the last G1 value (G1 X99.647 Y99.859 E6.40988 and G1 X99.647 Y99.859 E58.93623).

I select the overlap infill/perimeters at 0% in slic3r and looked at all parameters that could play here but don't see any.
I also put the first layer extrusion width at 100% to remove any bias.

Andddd I just manage to get it output the good value...
I had a value of 0 for the bottom layer, when this value is 1, the length calculated is correct, I don't understand though.

DImitri

Sounds like it was doing low percentage infill.

Just spotted on your ini file that you had set 0 solid bottom layers. However your infill was set to 100% so it shouldn't have mattered ...

Dave

I come back on this one a few days later,

I now tried to apply several layers and it looks like the slicing is only strange for the first layer, the next layers with a height of 0.1mm will apply the desired 58 mm. I changed the value of the first layer extrusion width ( in print setting -> advanced) by trial and error, I get the targeted 58 mm in the gcode with a percentage of 730%.

I first tried with 906 % (58 / 6.4) but the values was wrong so trial and error did the job. I have no idea where this value of 730 % comes from but I can work with this setting.

If I put a bottom layer, the path of the first layer is not the same than the other layers, much narrower, but the 58 mm are here with 100 % as first layer extrusion width. Once again, strange behavior for the first layer.

Dimitri