Lulzbit Mini 2 First Layer Print issues

I am experiencing some issues with all filaments on the LulzBot Mini 2. The top of the print looks great, but the bottom always has a lip and stringing as seen in the photos. I have tried increasing the nozzle temp and bed temperature, but I do not know where to go from here. Would anyone be able to provide advice on removing the lip? Thank you.

Randall

Are you able to provide us with a picture of the first layer?


You can see the ridge on the bottom. The part is symmetrical across the XY plane. I cant find a reason to explain the hourglass shape/lip that occurs at the print bed.

Sorry, I meant more of a picture of the parts first layer. So removed from the bed and flipped so we can see the bottom of the print.

In Cura LE you can navigate to (from the menubar):

Extensions -> Post Processing -> Modify G-code

Then select

Add a script -> Pause at height or layer

Change the “Trigger” to “Layer no.” and type in the layer where you want it to stop.

It will complete the layer and wait for you before proceeding.

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This is a top down view of the bottom face of the print.

From this image, your nozzle is too high when printing the first layer.

The filament coming out is round – like a spaghetti noodle – but needs to be squished to have a flat bottom and the sides should press up neatly with each adjacent row of extruded filament (you should not gaps).

You can lower the Z-offset in the “Calibration” menu just a touch. The factory default offset for the standard SE 0.5mm printhead should be -1.2 … but this can get tweaked if changing printheads or even changing material types (some filaments need less “squish” than others).

I might lower this by .05 at a time until you get a good first layer. E.g. if you were at -1.2 then lower it to -1.25, etc. until you are happy with the first layer. Measure your first layer (or the “skirt”) to see how close the actual layer is to the layer height you set in the slicer.

A quick way to test is to slice this test part with a 0.25mm first layer height and print it.

30mm x .25mm test disk.stl (3.8 KB)

This is a very simple flat disk – 30mm diameter and just 0.25mm tall.

This part takes only about 1 minute to print (once the printer is done cleaning the nozzle and leveling the bed) – so you can do this in rapid succession until you are happy with accuracy and quality of the first layer height.

I’m also noticing what appears to be really bad stringing on the inside. Is that intended (part of your model)? Stringing can be a combination of retraction settings in the slicer and is also affected by printing temperature. Direct drive print-heads usually don’t need a big retraction value for most filaments – e.g. about 1mm is usually enough.

You can also use “combing” to help reduce this. “Combing” causes the slicer to perform non-printing moves that stay within the bounds of the printed part so that any oozing will happen inside the printed area (preferably within the infill) so that stringing isn’t visible.

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Thanks TheVirtualTim. When I looked into the settings, the z offset was set to -1.10. And lowering the value has made the print look better, though I am still trying to dial in the distance. The stringing is not intended, but I have not experience stringing with other prints. I have mostly been using Cura defaults for materials, but I will look into retraction settings and combing. Thank you for all the help.