Mount P.,Mount PrintMore wrote:Why is it important to set the filament parameters in the FFF? What about the extrusion process is handled differently from a mathematical perspective if you set a filament diameter and extrusion multiplier in the slicing parameters versus using the override at run time? This is a question I've posted before at somepoint and the responses I got at the time led me to believe this wasn't an issue.
I tend to run copies of the same files over and over or in various colors, so I very much like not having to recreate my gcode files just because I put on a new roll. I literally run these calibration parts, take the measurements, write the override I want to use on the side of the spool with a Sharpie, and then swap around spools at will while running off various parts.
I'll get some pictures of the test patches and post them soon. Perhaps that will help spur some further discussion.
Your question prompted me to "shut up and do the test". So I took a model, sliced it with my usual extrusion multiplier (0.94), then ONLY changed the extrusion multiplier (this time to 1.10) and sliced again, and compared selected regions of the two G-code files. Here are some snippets from right at a layer change:
ExtMult = 0.94:
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; layer 48, Z = 9.58 G0 X76.37 Y98.13 F12000 G0 Z9.51 F1200 G1 E-0.05 F1000 G92 E0 G1 X76.37 Y126.13 E0.9192 F3150 G1 X104.63 Y126.13 E1.8469 G1 X104.63 Y118.13 E2.1095 G1 X108.37 Y118.13 E2.2323 G1 X108.37 Y127.241 E2.5314 G1 X116.63 Y127.241 E2.8025 G1 X116.63 Y118.13 E3.1016 G1 X124.37 Y118.13 E3.3557 G1 X124.37 Y156.87 E4.6275 G1 X105.63 Y156.87 E5.2426 G1 X105.63 Y126.87 E6.2275 G1 X75.63 Y126.87 E7.2123 G1 X75.63 Y98.14 E8.1555 G0 X75.63 Y98.13 F3150 G0 X76.37 Y98.13 F3150 G92 E0 G1 E-0.6 F1000 G0 X115 Y130.869 F12000 G1 E-0.05 F1000 G92 E0 G1 X114.644 Y130.886 E0.0117 F3150
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; layer 48, Z = 9.58 G0 X76.37 Y98.13 F12000 G0 Z9.51 F1200 G1 E-0.05 F1000 G92 E0 G1 X76.37 Y126.13 E1.0756 F3150 G1 X104.63 Y126.13 E2.1613 G1 X104.63 Y118.13 E2.4686 G1 X108.37 Y118.13 E2.6123 G1 X108.37 Y127.241 E2.9622 G1 X116.63 Y127.241 E3.2796 G1 X116.63 Y118.13 E3.6296 G1 X124.37 Y118.13 E3.9269 G1 X124.37 Y156.87 E5.4151 G1 X105.63 Y156.87 E6.135 G1 X105.63 Y126.87 E7.2875 G1 X75.63 Y126.87 E8.4399 G1 X75.63 Y98.14 E9.5436 G0 X75.63 Y98.13 F3150 G0 X76.37 Y98.13 F3150 G92 E0 G1 E-0.6 F1000 G0 X115 Y130.869 F12000 G1 E-0.05 F1000 G92 E0 G1 X114.644 Y130.886 E0.0137 F3150
So, as far as I can tell from this simple experiment, you are absolutely right: no, it doesn't appear to make any difference whether you adjust the extrusion multiplier when slicing or online with the knob in the machine control panel. But that's assuming what the online override does. Sorry, I'm not THAT good a C programmer to pick through the firmware and figure out what the M-code for the extrusion multiplier override actually does!