What on earth is going on with the extrusion multiplier?

[dammitcoetzee]

I'm really confused by the extrusion multiplier. I have tuned my extruder to give me exactly 10mm of filament using this tool http://hackaday.com/2016/01/27/3d-print ... with-ease/ .

It's within .25mm over 100mm, it's really exact. I'm using atomic filament, it's the most dimensionally accurate you can buy, period. I have the filament diameter set properly.

So why am I getting consistently too much dang plastic from simplify? How do I calibrate this? More importantly, why should I calibrate this if my e-steps are set perfectly.

I thought I would be able to set my extrusion multiplier to 1.0, print a single wall calibration cube to get my "natural" extrusion width at my speed and layer height, and get perfect plastic prints. Instead I'm glooping all over the place with too much plastic, too much infill, and terrible bottoms and tops. What is this number?

Please don't link me to the tuning section. It's useless. It just tells me to adjust my extrusion multiplier without giving me a metric to measure against. Pointless.

[CompoundCarl]

The way that plastic is extruded in free air is different than how it's going to be extruded when you're actually printing on the bed. So personally, I don't bother calibrating with free air extrusions, I just print objects on the bed and adjust the extrusion multiplier until I'm getting the correct amount of plastic that I need.

I determine my steps/mm values just my looking at the gearing ratio of the extruder.

So you can use whatever method you wish, but you will eventually have to pick one of those parameters to tweak once you actually start printing to make sure you are getting the correct amount of plastic.