Objects too tall

Hi all,

I've been trying to tune my i3 and I'm pretty much there. Extrusion is on the whole good and when I print test pieces the X/Y are spot on. One issue I'm having and don't really know how to address is that all of my test pieces are coming in 0.48-0.50 mm too tall. The error doesn't seem to change with object height e.g. a 10mm test cube comes in at 10.50mm and a 20mm test cube comes in at 20.50mm so I don't think it's an issue with my z-axis steps calibration.

On the Z-Axis I'm using a capacitance based probe and auto-bed leveling. I have the negative offset configured in the Marlin firmware (~-3.2mm) which takes the nozzle down to about 0.1mm above the bed with the hotend cold as per the various setup guides I've read this should be about right. I don't have any issues with first layer adhesion and I get the same result with test parts printed at different bed locations so I'm pretty sure the glass is flat and the auto-level is working properly.

I'm at a bit of a loss as to what to look at next. Any suggestions?

Thanks,

JBFUK.

Any hints even?

I'm thinking it might have something to do with top solid layers.
Maybe slight over extrusion in n number of layers that eventually mounts to 0.50mm. You have same amount of top solid layers in each print?

Just thinking if it possible to set top solid layers to 95-98% and see if it has any effect?

That's good thinking but unfortunately two of the prints were single perimeter shells so no solid layers at all. Also I suspect I'm under-extruding based on testing and plan to bump up my E-steps buy a few clicks.

Ok, what is your layer height and what is your first layer height?

Layer height is 0.2mm with first layer of 0.3mm. I know it's tempting to put those two together and come to the conclusion that's where the 0.5mm comes from but that doesn't make sense. I'd expect it to be 0.1mm too tall if this was the issue wouldn't you? Why would it add another 0.2mm layer if it had already overshot the target height? Appreciate this could be the cause (e.g. could be a slic3r bug).

Nozzle is 0.4mm and I'm using a fixed 0.5mm width for perimeters (which are coming out spot on).

I'll change my first layer height to 0.2mm in the morning and see what the result is.

Edited 1 time(s). Last edit at 10/21/2016 03:32PM by JBFUK.

What does your slicer preview say about the height?

Is this object really 10mm or 20mm?

what happens if you turn off auto bed level?

First layer extrusion width 200% ? 150% ? 100% ??

What else is constant with every print?