Uneven First Layer and Spotty Top Fill

Using a Rostock Mini Pro from 3D Printer Czar with 20 teeth pulleys (80 steps per mm), and an E3Dv6 hot end. Printing PLA at 190, 30mm perimeter and solid fill, 45mm infill. Using Elmers purple glue stick on a glass spring pan plate.

Using Rich Cattell's testing branch of Marlin, the auto-calibration takes between 8-9 iterations. First time (9 iterations) layer height (for a smaller object) was perfect. Second time (8 iterations) and I ended up shaving off 0.15mm from the printer height using M666 H158.85 (was 159.0 after calibration), though I might try going to 158.8.



The first layer photo was taken when the height was 158.95 and while not perfect, the whole object came out well enough for my needs. Though I am not sure how to go about compensating for the "bare" spots other than to keep lowering the height. At what point then does the rest of the print surface start creating issues?



The top fill photo shows the first of my three top layers and has a bunch of bridging (?) gaps in the layer. Is this normal? Any thoughts on what I need to change? I think you can also see some stringing issues in the photo, though it is not nearly as bad as in some of my other prints. I believe I am sitting at 0.5mm of retraction, possibly 45mm/sec.

I know more calibration is needed, I just wanted to try to print something interesting. All feedback and comments are appreciated.

The first photo shows classic signs of calibration not being quite right, as you suspected. If the second photo is meant to be doing solid infill, then it is under-extruding by a very large amount. Have you calibrated the extruder, and have you set the correct filament diameter in your slicing program?

0.5mm retraction in rather low for a Bowden extruder. I use 4 or 5mm.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yep, underextrusion. This can happen with any printer and is completely independent of delta calibration.

I did the 100mm extruder test to set the steps per mm but nothing beyond that. Filament diameter is correct.

Was working from memory on the retraction settings, turns out it was 2mm and 80mm/sec. Will try bumping it up to 3mm, though I am worried about creating a jam in the hot end if the retraction is to much.

It could be a simple case of your extruder gear slipping (lack of grip on the filament), or inadequate extruder temperature, or any number of other issues.

I have found in my case that the 100mm test did not yield usable values for e-steps/mm, so I just used a calibration object to determine correct values, this one:

[www.thingiverse.com]

Also note that I find myself forced to re-calibrate the extruder whenever I start a new spool of filament... Underextrusion really is a PITA to sort out sometimes.

Thanks for the link to the calibration object. I will read up on the instructions and try it out when I get some more time. Though I was wondering if the lack of extrusion in the previous photo might have been a bridging problem over the 20% infill? Just a random thought when printing tonight.

As for the retraction, bumped it from 2mm to 3mm and the difference was amazing, like 3-5 strings between two models. Bumped the retraction further to 3.2 and tried a different pair of models that were a lot more stringy at 2mm. Zero strings but it looks like I am getting blobs at the corner (or at least now they are visible).



There is one blob on the top middle corner (shiny spot), not really a big deal. But then a bunch of beads down the top left wall where the layers seem to have been "zippered" together.

Thanks for the suggestions everyone. Tonight is the happiest I have been with my printer to date.