extruder questions.....

question: how much filament should my hotend put out (and how fast?) for 10mm going in?

details:
I'm trying to get my extruder ser properly, first, I've got .5mm tip (filament comes out at .6mm or so?) using 1.75mm ABS filament on a J-head hotend. I ran the extruder (without the j-head attached) and ran 100mm of filament through. It came out to something like 700 steps (m92 e700 (oh, using marlin, btw)). anyways, with the hot end attached, if I run it at 700 steps, it jams up pretty quick. (I've gone up to 260C but I'm still not sure that's flowing as well as it should? So I donno if my temp reading is off, or what...)

Make sure steps/mm is correct.

The way I do it is take hot end off, tell it to feed 20mm.
Measure what was actually fed carefully. (I put a mark on filament and measure with calipers)
Multiple your current (set in firmware) steps/mm X 20mm (feed instruction) and divide the result by the length of filament actually fed.
That number is your new steps/mm figure.
Repeat and adjust as required.

Well, you will still have to feed the filament with the hotend and nozzle attached to get a final reading. The forces involved in the extruder will have a marked influence on the amount fed. Mark your filament somewhere to measure at least 50mm of feed, then, when hitting the extrude button, watch the mark and observe that there is no stalling of the filament as its fed. Measure the amount fed and adjust your firmware accordingly. Once that's correct you will need to tune your "extrusion multiplier" by printing the .5mm cube.

It shouldn't affect it much, but yes - repeat when your hot end is fitted.

I guess skipped mentioning some of the steps in the first post, I did do all that, and I come up with 615 (to be exact), and the filament still seemed to back up. I cut it in half, and it seems to be running fine now?! may still need a little fine tuning (filament speedwise), but other than that, it's starting to look like I might actually get this thing working!

I have to fine tune the extruder multiplier!? ok, I've seen this in slic3r but never really thought much about it... when/why/where/how does this change the print? I mean, why would I want it more than one if I'm adjusting the filament feed rate, where does this come in to play?

It affects the amount of plastic used on a print. If you print the 0.5mm hollow calibration cube and measure one of the sides you will know how much is being extruded. For example, if the sides measure, say, 1.1mm thick then you are extruding too much plastic leading to blobs etc. The cube is printed at 0.5mm for a reason - it is supposed to measure 0.5mm. Have a look at the link below and follow the process then you'll be good.

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