Optimizing PETG Layer Bonding Strength in Cura

I'm working on some small car interior trim clips that have to rely on layer to layer bonding strength. Filament is Inland PETG, printer is stock Ender 3 with Capricorn tubing.

When I run just one test print it functions well, but with the same settings when I run 21 they all break along the layers at about the same high stress point. If I set up Cura to run then in "One at A Time" mode I can only fit 4 on the bed at a time, and I'd like to print much larger groups.

I'm printing at 0.2mm, 17.5 mm/s, 255F / 70F, and pretty much all of the part is made of walls as it's pretty small (about 0.750" x 0.750").

What else can I do to optimize the layer to layer bond of the PETG? Thanks!

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I had a similar problem with a simple test print using PETG. I increased the nozzle temperature by five or ten degrees C. Slowing the print speed can also help in layer bonding. There's three parameters with which you can tinker, but change only one at a time to see how it affects the results. I think you might leave the temp at 255?C and check the other factors. 17.5 mm per second is half the speed I print, which leaves only cooling. Fan on or off? I believe I create the entire print with the fan off.

Yep, I've been leaving the fan off. There's no huge overhangs so I'm lucky in that regard.

At 255 F the stringing is acceptable, easy to clean up, but I expect it to get worse as I crank up the temp. But that was going to be my next step. I did a group of 9 and they seemed to have much better layer bonds. Still, the "One at a Time" thing may be the most reliable. I'll also revisit the design and see if I can add a bigger fillet in the area that's having trouble.

One thing I did find was that the Z-hop caused serious consistent stringing, and when I shut that off it dropped way down.

Can not speak on cura but if one works then I don't think your issue is cura. PETG is very particular about over all layer height. Starting height has to be perfect or you are in for trouble. Each layer change need to be correct as well. .03 too high and you can have bonding issues. Too close and your nozzle picks up much and knocks off parts.

In S3d if I have a small part that would be 3 perimeters and no infill, I use 1 perimeter an 100% infill. with one wall and 45 and -45 zig zag infill with 18-20% infill outline over lap you get a solid wall with much stronger bond the a bunch of single treads stacked next to each other. Not sure if you can do that in cura..

My guess from what I have read on this forum about Ender 3 is most of your problem is due to uneven bed height as it raises ..

Great tip regarding the 1 perimeter with 100% infill, with the alternating zig zag from, layer to layer. That will add alot of bonding strength. I was able to set that up in Cura.

I've been really happy with the Ender 3, though it's not a machine for average folks - not user friendly at all in setup or operation. It prints way better than my Da Vinci Jr could ever hope to though, due to the sloppy linear bearings on the Da Vinci and it's cheapo non-adjustable bed. I haven't tried printing anything really tall yet though on the Ender so can't speak to any uneven bed height issues.