First layer issue

[pjfossee]

Hi guys. I've been having this "issue" ever since I started printing. Essentially my first layer seems to be extruded irregularly (see pic for an extreme example). I usually print with an initial 0.3mm layer height and while this issue is still present it is a bit less dramatic. In the picture I have it at 0.1mm initial layer height and as you can see there seems to be an odd pattern of underextrusion. I've printerd the same object with the exact same settings before and had the same issue but with the underextruded parts in a different area. I don't actually know that it's underextruded but I'm using it for lack of a better term. I'm sure the solution is obvious im just too much of a noob to realize it. I thought image.jpg maybe it was the glass but I don't think glass oscillates in its height like that. Maybe it does though I don't know. Any ideas?

[pjfossee]

Also, if it makes a difference, my layers are also randomly underextruded sometimes. The layers are just ever so slightly inset from the other layers. Sometimes they are wavy with underextruded area under every crest and over every trough of the wave.

[LambdaFF]

Hi,
Could we get a picture of the 1st layer in the previewer ? I'd also like to have material, temperature, speed and bed material / glue info.

It seems to me you are having a mix of several things :
1/ On the bottom right of the picture, the perimeters should all be making a 90° angle instead a few are making a rounded corner, right ? This indicates either too fast or no adhesion or both. Try slower with glue.
2/ The fact that your problem shows up on 0,1mm and not at 0,3mm initial layer tells me that probably your Z-offset is not set properly. For instance if the Z offset is 0,2mm think of it as this : in one case you try to put a 0,1mm layer in a 0,3mm gap (33% fill) in the other case you try to put a 0,3mm layer in a 0,5mm gap (60% fill).

I would advise to reset your Z offset.

[pjfossee]

Thanks for the reply.

Material - makerfarm black PLA
Temp - 215 Celsius
speed - 30mm/s on outer shell and bottom/top layers 40mm/s for inner shells and infill
bed material - hardware store glass
bad adhesive - hair spray (the kind Colin reccomends - fructis garnier extreme 5 or something)

Those lines in the bottom right should be at a right angle. They are apart of the brim though and not the actual part if that makes a difference.

I heard about z offset but couldn't find anthing for it in Cura. Is it somewhere in the marlin firmware? Also I do have this problem with 0.3mm layers but it is less severe and your explanation accounts for that. I assumed z-offset was automatically zero so If I leveled my bed perfectly then the slicer would raise the bed the exact height it needed off of the bed. I made sure I had my bed leveled so that the nozzle just made contact with the glass. I used a feeler guage to ensure that when the nozzle went up 0.1mm the glass didn't come up with it. So I think my bed leveling was good. But if z-offset isn't set at 0 normally then that could be the issue. But does it account for the pattern of it. If it were z offset wouldn't the whole bottom layer be underextruded? Thanks for the help. I really appreciate it!

[LambdaFF]

Look at the "probe calibration video" in here : http://printrbot.com/project/simple-metal/

Even if you don't have a probe, the general idea is the same, you need to use the M212, M500 & M501 commands to modifiy the Z offset.

Detailed info on the commands in here : http://reprap.org/wiki/G-code