Teacup / Gen7 : STEPS_PER_M_E means what?

I was initially under the impression STEPS_PER_M_E meant steps per meter of filament to extrude. For example - "how many steps to move 1m of my 3mm filament into the hot end?"

I'm assuming that must be wrong because when trying to test print - my printer pours out gobs of melted plastic rather than a fine line of extrusion.

So - is it actually "steps per meter of extrusion?" If so - I'm thinking of trying the following - tell me if I'm wrong:

114076 steps/m

0.9 degree stepper
16x micro-stepping
39/11 gear ratio (wades extruder)
7.035mm hobbed bolt diameter
1/9 area ratio (3mm filament, 1mm orifice)

400 steps/rev * 16 microstep * (39/11 gear ratio) * (1 rev / ([ 7.035mm * pi ]) * (1000 mm / 1m ) * (1/9 area ratio) = 114,076 steps/m ?

There are G-code generators which spit out code for what you described above and others, which want STEPS_PER_M for the filament extruded, the thin one coming out of the nozzle.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Another one is, some G-code compilers expect E to be absolute distances, others do relative distances.

If you see one or more "G92 E0" in your G-code, you have absolute E commands. Uncomment the #define E_ABSOLUTE in your config.h, then.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I think it is supposed to be meters of filament pushed into the extruder and NOT meters of extrusion coming out.

At least for me, I tried using slic3r and setting the E-codes to be relative, which yielded values on the order of 0.001
in the gcode file.

Definately seems like a measurement of plastic sucked in vs plastic squirted out.

And I believe that teacup wants the E values to be relative. I tried absolute and i got pulsed gobs, as if it was trying to squirt out more filament for some lines than for others (which is consistant with it wanting relative and getting absolute).

Without changing anything in the firmware if I then make slic3r produce a file containing relative E-codes I get almost no filament. Which is because all the E values are like 0.04.

I hope that helps... going to try calibrating my machine with steps per meter of filament sucked in and see if i can get a decent extrusion line.

I have a direct drive splined shaft pinch wheel extruder with 400 steps/rev and I came up with 33133 steps per meter of 3 mm filament (abs).

Works ok (no blobs) now. Oh and using relative E codes.

Quote

And I believe that teacup wants the E values to be relative.

Teacup can do both. As of last weekend, it supports M82/M83, too (on the Gen7 branch).

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

For what it's worth I'm using Skeinforge now & it seems to want *Filament* steps/m, not extrusion.

I ended up using 1,026,687 steps/m and it seems to work fairly well. I'm not sure what caused the earlier blobbing failure - must have been something else I fixed.

400 steps/rev x 16 microstep x 39/11 gear ratio x (1 / [ 7.035mm * pi ]) * 1000 mm/m = 1,026,687 steps/m