Problem with Repetier-Host pause function [SOLVED - sort-of]

I thought I'd have a go at setting up 'pause' on repetier-host, following the instructions on the website. I want to be able to change the filament halfway through a print on my Prusa i3 with RAMPS.

I put the following code in the pause script for this printer:

M83                              ; relative extruder moves
G1 E-1 F250	      ; retract filament 1mm
G91                               ; relative moves
G1 Z5 F300              ; raise nozzle 5mm
G90                              ; absolute moves
G1 X0 Y200 F2000   ; move head out of the way of the print

When I click on the pause button the hot-end lifts and moves to X0 Y200 correctly. When I click on resume the hot-end returns to the correct place, starts to move in the X-Y direction correctly, but the extruder tries to push filament through the hot-end very fast - much too fast for the nozzle so the filament gets stripped in the extruder.

Can anyone tell me if I'm doing anything wrong? Or is this a bug?

Many thanks.

Edited 2 time(s). Last edit at 02/12/2017 08:22AM by David J.

Well, I've localised the problem; it's caused by the first 2 lines of the code that relate to the extruder. If I comment them out the extruder restarts at the appropriate speed. My guess is that on restart Repetier-Host has the extruder in absolute mode, so tries to get from '-1' (or perhaps it's lost its extruder count) to whatever value it had stored before the pause command - hence the long and fast forward feed that results in stripped filament.

The problem is that I would like to retract the filament a small amount when pausing to reduce the amount of nozzle ooze...

I think you need a M82 after the E move, like

M83                              ; relative extruder moves
G1 E-1 F250	      ; retract filament 1mm
M82                        ;absalute extruder moves
G91                               ; relative moves
G1 Z5 F300              ; raise nozzle 5mm
G90                              ; absolute moves
G1 X0 Y200 F2000   ; move head out of the way of the print

I'll give that a try later...

UPDATE: That worked nicely - thanks!

My guess is that the M83 command left Repetier-Host with an undefined or unknown extruder position - anyway, it's working now.

Edited 1 time(s). Last edit at 02/12/2017 05:38AM by David J.