I'm attempting to print this print-in-place bag clip (in the 80 and 100 sizes). Early prints came out well, except that my persistent elephant foot resulted in locking the hinge.

Oddly, a few days ago I printed four simultaneous copies of this print in place wall hook with the same filament and settings (before adjusting the initial layer and line width) and they required almost no "exercising" after printing to hinge freely from the stop to latched closed. The hinge design on these is simpler, without the "easy printing without steep overhangs feature" (using no-support-needed slopes); instead, the lower casing of the hinge acts as supports for the pin and its flange, which then acts as supports for the upper casing.

I'm printing in Amazon Basics PLA, nozzle at 200 °C, bed at 55 °C. I level the bed with a 0.08 mm feeler gauge after homing and jogging the Z axis to 0.075 mm, and I adjust pretty tight, so I'm setting effectively zero clearance. I've adjusted my settings in Cura 4.10.0 (0.2 mm overall layer height, 0.4 mm line width) as follows: Initial Layer Horizontal Expansion -0.3 mm, Initial Layer Line Width 90%, Initial Layer Height 0.3 mm, Wall Line Width 0.35 mm in order to attempt to correct elephant foot without losing bed adhesion (printing on the uncoated side of a Creality borosilicate glass bed using a glue stick wash), and I'm getting good first layers, but by the third layer, even with the reduced line width, the hinge parts are fusing.

With this particular Thing, the option exists to open the object in FreeCAD and adjust a "hinge tolerance" parameter to give the hinge larger clearances, but I understand from this question and its answers that this problem occurring in the second and third layers is likely a Z travel problem, my first few layers not being as high as the printer's firmware thinks they are -- and there doesn't seem to be a way to "taper off" the line width and flow level adjustments that can be applied to the first layer, as opposed to "second layer has same settings as layer 122." There's also the possibility of slicing the part upside down, so the critical clearances aren't in the bottom 3-4 layers, but this design might not permit that to work.

Pursuant to that, I've tightened the eccentric wheels on both uprights to the point I can barely slip the wheel when the gantry is restrained, but without any change in the way the hinge gaps fill in on layers 2 and 3.

So: how can I correct this second and third layer expansion so my print-in-place parts will work correctly?

Edit: This doesn't seem like a long time, but it's been rather humid here recently, so it's possible this excessive expansion is related to moisture in the filament. I ran out the filament spool I was using (unsealed about two weeks ago) and opened a new spool of the same brand/type: Amazon Basics PLA -- and started getting a good print with only common elephant foot amelioration (small negative horizontal expansion in initial layer). The print failed for a seemingly unrelated reason, but I should be able to try again soon.

Edit 2: After correcting a loose thermistor that was causing thermal runaways, I was able to complete a print with the fresher filament (after a week of continued humid weather), and did get a better print -- in that I was able to break the lightly fused hinge loose and get a bag clip that works as intended. I'm still seeing considerable expansion in layers 2 and 3, which aren't accessible to "initial layer" settings that would otherwise ameliorate elephant foot, but with four layers for both bottom and top skin, I'm seeing no expansion at the top (as has been suggested as the cause due to overextrusion of bottom skin).

Edit 3: most recently, I've gotten a successful print by adjusting the "horizontal expansion" in the slicer -- giving -0.1 mm in initial layer, and -0.05 mm for the rest of the part. This doesn't eliminate the layer expansion, but does reduce the hinge fusing to the point I can break the parts free after the print completes. I continue to doubt pressure from the interior of the layer could cause this; I've watched these layers print, and the three lines of the wall print first, inside to outside, followed by a fourth line forming the border of the skin fill, and then the skin fill. The wall lines, then, ought to be well adhered and cooled by the time the skin layer starts to fill in.

  • $\begingroup$ Do you perhaps just have overextrusion? Once you get past the solid bottom layers, it will mostly disappear into infill zone, but it will accumulate for the first few layers with nowhere for it to go. $\endgroup$ Aug 8 at 15:19
  • $\begingroup$ @R..GitHubSTOPHELPINGICE But wouldn't I see that as a reverse elephant foot in the equal number of solid layers at the top? Those layers have no visible expansion. For that matter, the walls print before the solid fill on the bottom layers, so they should be stuck to previous layer and at least partially cooled before the fill goes in. $\endgroup$
    – Zeiss Ikon
    Aug 8 at 17:26
  • $\begingroup$ Only if you have sufficiently many top layers. The first one sags roughly a whole layer, allowing for a lot of excess material in the subsequent ones. $\endgroup$ Aug 8 at 18:02
  • $\begingroup$ @R..GitHubSTOPHELPINGICE I normally run 4 layers both top and bottom. I suppose I could try cutting extrusion to 95% and see if it's better. $\endgroup$
    – Zeiss Ikon
    Aug 9 at 10:59
  • $\begingroup$ @Kezat As tagged, it's an Ender 3. Not V2 or Pro; the cheap one. $\endgroup$
    – Zeiss Ikon
    Aug 9 at 11:01

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