Inverting extruder on start

Dear repetier,
i've anoter small problem with the firmware. Some times (this is the strange) on starting a job, the extruder first run on inverse side for a little time after then start to run on the right side. This happens when in the program there is the first G1 EXXX. For me he search the zero.
I've the g92 e0 and m82. This is a typical program start:

M107
M104 S220 ; set temperature
G28 ; home all axes
G90 ; use absolute coordinates
G21 ; set units to millimeters
G92 E0 ; reset extrusion distance
M82 ; use absolute distances for extrusion
G1 Z0.300 F7800.000
G1 X90.018 Y84.663
G1 F1800.000 E1.50000

made with slic3r.
The strange is that it happen only some times, (this time i've reinstlalled the firmware and seem all ok)
Thanks for any help
Francesco

Edited 1 time(s). Last edit at 06/25/2012 05:46PM by fralab.

With that start code and slicing with absolute e coordinates this should not happen. Make sure you have ops disabled, so it doesn't come from this side. When I had that problem it was always a g1 with lower e values, so it was always my fault sending the wrong commands. Never had it coming from the firmware.

---

Repetier-Software - the home of Repetier-Host (Windows, Linux and Mac OS X) and Repetier-Firmware.
Repetier-Server - the solution to control your printer from everywhere.
Visit us on Facebook and Twitter!

I not understand what is the problem, saturday and sunday i have a 30h print and yesterday i have this problem. In reality also saturday i incountred this problem but this magically disappeared on a restart.
Furthermore this mornig i can start the print whitout the anomal retraction of the filament on start, but after a bit (random) the printer stop and the host give no error. I have a doubt: i must change the eprom number when i reinstal the firmware?
To be honest, all problem was start when i tryed to install the version 0.7 of firmware, friday evening. Actually use 0.62.
In short i was a problem to upgrade the firmware, and then i reinstalled the old version (0.62) that work great for me. From this point i have a general instability of the system.
Can you help me to reset all the eprom values, an then restore my 0.62?
Very thanks
Francesco

Edited 2 time(s). Last edit at 06/26/2012 05:27AM by fralab.

Good hint. Did you read the upgrade instructions for the latest version ? There is a command you need to send when using eeprom with older version to correct eeprom configuration once. That parameter has indeed an effect on extruder retraction.

---

Repetier-Software - the home of Repetier-Host (Windows, Linux and Mac OS X) and Repetier-Firmware.
Repetier-Server - the solution to control your printer from everywhere.
Visit us on Facebook and Twitter!

Here is another possibility that would cause the behavior you describe. If you extrude just prior to starting a print, the extruder distance value will be at some positive number. If you then start the print with an e-axis value of zero, the extruder will spin in reverse until it reaches zero.

To get around this, I have the following in my start.gcode alteration file:

G1 Z0.2
G92 X0 Y0 Z0 E0

The first command (G1) lifts my nozzle slightly above the bed. I can adjust this height in the sliced gcode before I print, and if it's too high, or too low, I kill the job, make another adjustment, and re-start the print.

The second command (G92) sets all values to zero at the current position on all axes (X,Y,Z,E), so there is no return movement on E (or Z, which was moved +0.2)

Hi at all, and very thanks to all.
I've reinstalled te 0.62 firmware and changed the EEPROM_MODE entry. In this way seems that the printer work. Likely is true what write from repetier, the new value of extruder retraction stored in eeprom by 0.7 cause extruder retraction (and random freeze of comunication??).
For jcabrer, i'll use your start string in my program. Thanks.

Bye
Francesco