Start script

[Ian84]

I have set up the start script to prime and nozzel right on the edge of the bed, so to not have to run a skirt to prime...

It has proven to work well, but randomly... The extruder motor turns the wrong way... Instead of pushing... It will pull for the whole duration. Of the prime process when it lays down filiment into the bed....

Meaning for 2 good prints then, it will reverse... Then good... Then.... Good and good.... Then reverse.... Etc... Very Unpredictable.... But you notice it right away..
The only way out is to, release the spring on extruder and push by hand.... Which can lead to a blob start point on your print... As you are regulating flow by your hand pressure as you manually push..

Once the start script is finished the ext will work as normal to print... Which doesn't work as the filiment is already pulled out!

It is random... I can't seems to find out what is causing this? Any insight?

I will post the script shortly.

Cheers.

[Ian84]

any input to the above?

here is the start script:

M106 S255 ; enable FAN
G28 ; home all axes
G1 Z0.20 ; move print head up
G1 Y0.5 X110 F500.0 ; move out of print volume
G1 X10.0 E9 F500.0 ; start purge line
G1 Y1.0.5 F500.0 E9 F500.0
G1 X60.0 E12.5 F500.0 ; finish purge line

[dkightley]

What you're describing looks very much like an electrical issue.

I wouldn't be surprised as if there's a break in one of the wires supplying the motor...and most of the time the break is closed until there#s a disturbance, when it separates...and the motor will tend to run in one direction only. Another disturbance to the wiring....and the contact makes, and the motor runs correctly.

The break could be anywhere......a bad connection in the plug, to the crimped connector, anywhere along the wiring run. You need to carefully exercise the wiring along its run until either you separate the ends permanently....or are able to open & close the gap at will!

If this only happens when the extruder is priming, then it's probably because the extruder head is stretching the wiring to one of its extremes.....which will be a clue!

[Ian84]

Thanks for your Input. I have the wanhao I3 mini, it's a bowden style. Extruder motor is fixed inside the tower only print bed moves to the extreme front.

And yes only happens on script priming runs.

Hmmm...... Thinking....

[gavatron3000]

i had a similar behaviour when i didnt use relative moves for the extruder, when the start script ends it will call the extruder to 0mm and due to it being absolute is will reverse the extruder as youve stated

[Ian84]

Couldn't fully understand your explanation, care to explain it for a noob and also what is the solution ? add or edit the script ?

Cheers.

[gavatron3000]

use relative extrusion moves, it is in the profile settings as a tick box under the gcode tab.
if your set to absolute extrusion whats happening is your start script is being executed and your extruder is moving to 12.5mm by the end of the script, when the script ends the slicer puts E0 at the start of the print, your extruder will reverse to 0mm.
i recommend using relative extrusion but if you dont want to a work around is to add G92 E0 to the start and end of your start script.