Sliced Print Incorrect Height (Dual Extruder?)

[azza]

Hi,

I have an issue in Kisslicer version 1.5 Beta 1 which is proving hard to diagnose.
Prusa i3 machine modified to have dual bowden extruders.
I have this issue where prints are coming out under scaled but only in the Z axis, so they are effectively squashed.
Everything has been calibrated and rechecked.
The weird thing is that the same stl sliced a while back prints normal. So I can take that gcode file and a new slice of the same thing and get different results!
So that suggests a software problem.
A calibration cube prints fine, as I've just about everything else I try. So I thought it was just an isolated thing.
But I've just managed to reproduce it with another random stl.

The only thing that I've really worked out and it might be a coincidence is that it seems to be when I only use extruder 1.
This is what I reproduced the issue with:

http://www.thingiverse.com/thing:257911

I've attached a photo to illustrate what I mean.

[Mikk36]

Could you also post the gcode file, which has the issue?

[azza]

Hi,

I have attached a gcode example.
I did load this up in a visualisation tool and the model appeared to have the correct height etc.
I'm kind of at a loss as to what is going on. I thought it was me resetting the gcode prefix, select extruder settings etc.
But it just happens on some slices and seems to coincide with just using extruder 1 only.

If I print using both extruders e.g. one for support material or two colours then everything works fine.

Aaron

[PenskeGuy]

Well, that's just weird. What happens if you select Extruder 2 only?

[azza]

I've been printing everything using extruder 2 and it always works.

Reading through the gcode it seems to be setting the correct layer heights in .2mm increments so my only conclusion now is that there is a bug in the marlin firmware.

I just came across this:

https://github.com/MarlinFirmware/Marlin/issues/1916

It sounds like the opposite of my problem, my layers look like they're getting squished. Seems to be more noticeable with ABS where the print head is just driving through the print digging a hole.

[azza]

Pulling the latest source code for Marlin appears to have solved the issue.
https://github.com/MarlinFirmware/Marlin

But I seemed to have swapped one really bad bug for another really bad bug.. the homing is broken, at least I've discovered a work around in the meantime.