Extrusion Troubles

Hi all,

I've just finished building my printer and I'm working towards getting my first print out of it. My problem is that the extruder produces a correct (as far as I know) extrudate of melted plastic when it's away from the bed and manually command it to run, but when I attempt a print no significant amount of plastic leaves the nozzle and no more than little drops adhere to the bed.

My printer is as follows:
stock Prusa Mendel i2 with vanilla Wade extruder
0.9 degree steppers
glass, unheated bed with (currently) white masking tape coating
filament is white Reprapper 3.0mm PLA
e3d all metal hotend, 0.4mm nozzle
RAMPS 1.4 electronics running the latest Marlin firmware
Repetier host/Slic3r control software

Any ideas or things to check?

Note: I am not particularly confident in my Marlin settings, and I was hoping to be able to tune the printer by using printed objects for calibration.

You need to make sure your extruder is calibrated. If you tell Repetier to extrude 100mm you need to measure what goes in to see if it's exactly 100mm. I just measure 100mm on the filament and mark it with a pen, then tell repetier to extrude 100mm and see if the pen mark ends up where you measured from.

You were right, but even more so than you thought. I had calculated my extruder steps/mm wrong and the new value is about 20 times higher. It's not great at this point, but it's definitely printing something.

While we're on the subject, any ideas as to why plastic might just stop coming out of the extruder mid-print?

Well it's either gotten cold and solidified, or the extruder is not pushing it (slipping) or it's jammed (most likely from junk plastic with chunks of bad stuff in it.

So, you need to test each on it's own. If it were mine I would put it in open air and just extrude the heck out of it to see if it stops, and I would be watching the temp and the extruder to see if it stopped. It could be anything. Mine did this once as the heater wire connection was iffy and as it moved around it would disconnect and cool off then when it moved again it would connect and heat up again.