G-code output issue with Z-Height

Hi folks,
Am having an issue with Slicr G code output affecting the Z height. The skirt will print perfectly - but when the object is started the "Z" height mysteriously jumps from .3 mm to .9 :This initial inconsistency seems to remain throughout the G-code - that is to say the next layer is instructed at 1.2mm ( at .3mm layer height )
I can't see any problem in the settings - the issue is the same with any object I convert to gcode - skirt fine , then sudden 2 layer height jump for the remainder of the gcode.
Has anyone else experienced a similar phenomenon ?

As a workaround I have tried using the Z offset modifier to compensate the output by -.6 mm - then editing the resulting Gcode to change the skirt height back to correct values.

EDIT : I'm running 1.0.0RC2 version of slicr.

Edited 1 time(s). Last edit at 09/14/2014 08:05AM by genghisosmosis.

Sounds like you've got your first layer height set to 200% ("Print settings", "Layers and Perimeters", "First layer height")

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Waitaki 3D Printer

Not the case - however , I just found the problem !

From a previous job that required a raft the "raft" setting was set at two layers - even though "generate support material" was unticked it seems that having a value in here still affects the G-code output. Once I had reset the raft layer value to 0 , the G-code is correct.

Strange? I thought "generate support material" referred to bridging?

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Waitaki 3D Printer

I guess a raft is a kind of support material - however there is no mention of it in the manual.. It is under the "support material" option set so I assumed that simply clearing the checkbox for "support material" would turn off the raft option.

Its one less thing I have to worry about anyway !

You beat me to it - I had the same issue a long while ago that got me scratching my head until I realised that I had set raft layers without having a raft!

Dave