I'm relatively new to 3D printing, and am a bit out of my depth at the moment. I got a Wanhao Duplicator i3 Plus (Monoprice branded) about a month ago, and have had mixed success with printing on it. I had some early successes, and got some pretty decent prints of a bunch of upgrade parts for the printer; z-brace, belt tensioners, sturdier pulley mounts, etc. I was using a roll of Amazon Basics 1.75mm Black PETG. It popped and crackled constantly (even after drying), but still produced pretty good results.

The problems really started when my new order of filament showed up last week. I got Sunlu PETG, and have been having major problems getting consistent prints. I'll get a great print one time, and the next will fail horribly, just a few layers in (once the print gets past the solid bottom layers and into the infill. I've linked a few pictures to illustrate my point.

https://imgur.com /a/nPvLTvc

The first 2 images are the more successful prints. They're definitely not perfect by a long shot, but pretty good, considering I'm still tweaking the slicer settings. The 3rd image is one of many failed prints. It was printed with exactly the same slicer settings as the first 2. I'm using Cura 4.6 with tweaked default settings for PETG. It seems to go wrong when it gets to large sections of infill, but that's not always the case, as the first 2 images have plenty of infill.

I've tried tweaking just about every setting I can, and I just can't seem to get any sort of consistent result. I've raised and lowered hotend temp, fan speeds, retraction, print speeds, extrusion multipliers. None of it really had any positive effect on print quality. I've even tried different slicers (mostly Prusa Slicer) with even worse results.

I want to eventually switch to Prusa Slicer, but one problem at a time. My one "successful" print with Prusa Slicer managed to produc this simultaneously under- and over-extruded, blobby, pitted, poorly-adhered monstrosity: It's really quite impressively bad. I'm honestly not sure how the print event managed to finish. But, as i said, this is a problem for another day. One thing at a time.

https://imgur.com/a/n27BtwX

Any help would be greatly appreciated.

--Aaron.