Newbie: Mendel moves but does not extrude while printing.

We are trying to make our first print on a Mendel kit.
The extruder prints a filament when commanded to "Extrude" but does not extrude while printing.
The extruder circuit is on. The carriage just moves without depositing.
Have we simply missed a tick in a box or resetting values?
We are using Python and Skeinforge as described in the Reprap manual.
See attached monitor photo:

Regards, Extrudeboy

We've now printed a different STL file and it does now print intermittently, sometimes in gushes of molten PLA and sometimes nothing at all. Do I have to take apart my printer head and clear the Bowden tube or are there more probable fixes to try first?

I think that you're saying that the extruder motor is turning, but little to no filiment comes out, or when it does it's in blobs, correct?

Does your extruder use teeth to drive the filiment into the hotend? Check the groves between the teeth of the drive wheel. I had a similar problem, and the root cause was the grooves between the teeth of the drive were jammed with PLA. I used the tip of an exacto knife blade to clear the spaces. Also, if you're using translucent filiment, the PLA can appear clear in small amounts against dark surfaces - so check carefully.

I believe that the PLA deposited on my printer when I had the printhead too close to the build plate and the filiment slipped against the drive teeth.

Hello and thanks for your response, the large extruder drive cog seems to get stuck and a little manual assistance sometimes gets it moving.
But this causes large intermitent deposits rather than fine filament.
we've tried turning up the potentiometer for the E-drive motor without improvement.
I also noticed the printer window keeps stating "echo: too long extrusion prevented".
(See second attached photo)

I notice that you're slicing in what I call pronterface. I had experinced some problems with slilcing in pronterface, so I started using Slic3r directly with better results - could have just been me however.

Also, trust me, clean the teeth. I saw the same behavior as you - related to speed of extrustion????

Also have you calibrated the printer? extruding directly from Pronterface seems different than extrusion associated with printing which takes into account several parameters to determine feedrates.

Holy smokes look at the length of filament for that print "7978352.5131mm"! That's not right. Look in your configuration.h and tell us how many steps per mm you have configured for your extruder. Did you do a calibration?

-Jay

Thanks Jay, yes 8km of filament is ridiculous!
We hadn't completely calibrated. We had hoped the Reprap kit was ready to run.
We have checked what we can using Reprap wiki calibration but we can't find "configuration.h"
Where do we find the settings on Pronterface?

Update: we have solved the E motor problem: it had too much current. It now extrudes as we print but far too much.
This is great news because physically the machine works, however we are still unable to find "configuration.h" to slow it down.

pronterface is host software. I am talking about either sprinter or marlin firmware. Means you will need Arduino to change the code, recompile and upload to the Arduino Mega.