Extruder or Z Axis Issue?

Source: https://kevinakasam.com/ (Information from Kevin Discord Server posted by kevin)

I always recommend printing two test cubes that differ only in size. This helps distinguish between extrusion/extruder issues and Z-axis problems. Because the extruder rotates, patterns can appear in sync with its rotation, which may look like Z-axis issues, similar to the patterns shown in the attached image.

The well-known XYZ calibration cube works, but the letters can sometimes introduce artifacts (you’ve probably noticed differences in the print above and below the letters). A regular cube would be better. Print it with your standard settings—a solid cube with three walls, top and bottom layers, 20% infill, and normal cooling. Avoid hollow cubes, as they can introduce other variables like temperature deformation, insufficient cooling, or poor wall and infill overlap, which impact print quality. A normal print will give you more realistic results.

After printing, you might be pleased with the outcome or frustrated if it doesn't look right. If there’s a visible pattern, don’t automatically assume it’s due to a Z-axis issue. As mentioned, the extruder can also cause regular patterns, especially with simple shapes where each layer is identical. To figure out whether it’s a Z-axis problem, you need to change something that would affect an extruder-induced pattern. The simplest way to do this is to print another cube of a different size (e.g., 20mm to 30mm). Changing only the size can help reveal the source of the issue.

Once you’ve printed both cubes, compare them. If the pattern is the same in both (regardless of size), it's likely a Z-axis problem. However, if the pattern shifts or changes in frequency between the cubes, it's more likely an issue with the extruder.

Both cubes show no visible pattern or the artifacts don’t appear consistently:

The artifacts are most likely due to extrusion inconsistencies, such as an improperly tuned flow rate or extrusion multiplier (check out this tuning guide: https://ellis3dp.com/Print-Tuning-Guide/articles/index_tuning.html). It could also be caused by poor filament quality, where variations in diameter lead to inconsistent extrusion.

Both cubes show a pattern that aligns:

If the artifacts appear at the same height on both prints, it suggests an issue with the Z-axis mechanics. Think of your Z-axis like a railway—if the artifacts occur at the same height repeatedly, something along that "railway" is causing the issue. This could be something as simple as dust on the V-wheels or a dent in the wheels themselves. It might also be eccentric motion, like wobbling from a leadscrew, a damaged bearing, or poor-quality pulleys. Although Z-artifacts caused by the drive system are rare in belt-driven Z-axis setups, it's worth checking the V-slot profiles, V-wheels, or linear rails for any damage. Belts are generally too soft to cause Z-artifacts, unlike a hardened steel leadscrew, which is why many people move away from them. So in this case, check if your bearings are intact, the belt isn’t damaged, and the pulleys are round and running smoothly.

Both cubes show a pattern that doesn’t align:

This one is trickier. While it rules out Z-axis issues, it doesn’t guarantee the problem lies with the extruder. It's most likely the extruder, but other factors—like too much resistance in the filament path or spool issues—can also cause similar patterns. You can often identify extruder problems by looking for diagonal lines on prints with more complex shapes, like figurines.

So, what might be causing these issues? Several things. Mirage has made quite a few videos on what seems like Z-wobble but is actually extruder or filament artifacts (https://www.youtube.com/@MirageC/search?query=wobble). Typically, it's an issue with the extruder gears or how they rotate. Ideally, they should rotate in a perfect cycle to ensure consistent filament feed, but that’s often not the case, especially with lower-end hardware. Small adjustments, like tweaking the idler tension or reducing backlash between the motor and extruder gears, can help. If your extruder hardware comes from a less reputable source, the hardware itself could be the issue. Even after addressing wobble-like issues, problems with the extruder gears can persist.