Extruder setup woes

Hi, I have a problem with setting the extruder speed and, while I have followed the 'looking for help with calibrating E' thread, I haven't managed to cure the problem. I'm running Marlin via Pronterface from the 'Kliment-Printrun-edeb433' download and the latest download of Skeinforge but, when I try to set flowrate down from its default 210 to 30 which I have as feedrate, it won't allow me to set it below 50.
I am very new to 3d printing and completely confused by all the possible permutations in the software - even the 'simple' SFACT. I tried to find the settings file which JeffWilson posted so I could attach it to this message but all that appeared to be in that directory was a file called 'temperatures.csv' and, searching my computer, I only seem to be able to find .csv files created during runs of RepG .
My machine is a Prusa Mendel with Wades extruder and the hot end has a 0.4mm nozzle. The symptoms of my problem is that, as in JeffWilson's case, the extruder is running way too fast and skidding on the PLA filament. During one of the last print attempts I did change the value in the Pronterface Extruder speed box from the default of 300 to about 12 and, after a while, presumably when the arduino buffer refreshed, the extruder speed did drop but, if I'm going to have to juggle settings in both Skeinforge and Pronterface, that is getting even more confusing. I will say that I am not a complete novice at this type of thing as I have hung around the EMC2 community since it was first developed and have a couple of home built milling machines running successfully on that platform but this whole 3d printing game seems far more complicated.
I have attached an image showing the Skeinforge 'test.stl' file printed in clear PLA and the first stages of printing and Christmas Lego Man's body off Thingiverse. Maybe someone could suggest what is going wrong and what I should alter....

Thanks, Ian

bassman Wrote:
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> [...] the latest
> download of Skeinforge but, when I try to set
> flowrate down from its default 210 to 30 which I
> have as feedrate, it won't allow me to set it
> below 50.

Whar do you mean, it won't let you set it ? You're not allowed to click into the box and manually type the number in ?

What I mean is that when I click the down arrow adjacent to the box it will go down to 50, by which time the background of the box has turned yellow, and it will then go no further however much I click it... I don't suppose it makes any difference but I am running it on Linux - Ubuntu 11.04 to be precise..

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Thanks, Ian

Yes that's a sort of limitation system of skeinforge, telling you that this value is out of "normal" range - but its value is obsolete nowadays.
You can still manually enter a number in the box (and you need to do it often if you want to do something usefull with skeinforge).

Ok, I typed the figure in and ran a print of the thumbwheel which is on Thingiverse - it was relatively successful though the hex hole for the nut was slightly undersized. I then thought that I would be a bit experimental and upped the speed and feed to 50 as I know the machine is capable of much more than that. I also activated scale in Skeinforge and set it to 1.2. Now whenever I run the stl file through skeinforge and set it printing, the print head moves to the right start position and then the extruder runs rapidly backwards for several seconds and unloads all the filament!!! Dohhhh!!! I didn't change anything else and certainly nothing to do with the extruder but, even though I have closed down Pronterface, reset the printer, reloaded the file and even tried restarting the whole computer, I still get the same problem of unloaded filament. Do you think one reasonable print is its limit for the day??

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Thanks, Ian

Looking at the g-code file I see that straight after the initial positioning of the X and Y axes is a command G1 E5.0 . Since this is probably what is causing the extruder to unload all the filament, I suspect that the 'program' somewhere assumes that E has started at some value greater than 5.0. If this is the case, I can't see anywhere to zero E and I can't understand why the erroneous value should persist after the machine has been reset and the program shut down and restarted. Any ideas?
Pronterface doesn't seem to have any way to see or edit the g-code file so I don't suppose there is any way I could add in a G28 to zero E or something....

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Thanks, Ian

bassman Wrote:
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> Pronterface doesn't seem to have any way to see or
> edit the g-code file so I don't suppose there is
> any way I could add in a G28 to zero E or
> something....

Yes this is what the Start and end Gcodes are for. Find or create your start.gcode (start.gmc in SFact) and add G28 E0 to it.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

You can also type the command G28 E0 and send it in the command window on the bottom right. But, it should really be at the start of the g-code file.

I made the startup file and have G28 E0 as the first line of the g-code file but, for some reason I can't see, the extruder still does a reverse just before it tries to print. I can't see anything in the g-code file which could cause this - after the G28 E0 the next 'E' entry is a G1 E5.0 and then every 'E' entry is a number slightly larger than the previous one i.e. E5.058, E 5.085 etc... Is there some setting in Skeinforge (SFACT) I should be looking at or is there something in Pronterface which is overriding the g-code?

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Thanks, Ian

Does your extruder go in the right direction (forward) when you click on the extrude button in Pronterface? If it does, maybe you should upload the beginning portion of the g-code that's giving you problems.

Your line should be "G92 E0", this sets the extruder axis to zero. G28 is a homing command.

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