Hi there. I have a problem where some of the layers in my print are not being printed correctly. It happens in the same place every time, and it’s also the same regardless of where it is positioned on the build plate. It doesn’t occur all the way around the model, so I’m almost 100% sure it’s not a Z-axis issue.
I think I’ve narrowed it down to something going wrong in the slicer. Image 1 shows the result with standard settings. Image 2 and 3 is after I made the following changes: Avoid crossing walls - enabled, resolution changed from 0.012 to 0.03, outer and inner wall speed set to 80 mm/s, temperature reduced from 220 to 205, and wipe while retracting - disabled. This improved the overall quality, but the errors are still there.
Image 4 shows the layer where the issue is most visible, and I’m almost certain it has something to do with retraction and unretraction (Seams). I’m still new to 3D printing and not very familiar with G-code and what it means, but there are three layers where unretraction occurs and it’s exactly where the problems appear on the model. I’ve tried placing seams manually, but it still creates those three layers in the same way.
I have found the slicer previews to potentially be very helpful in the diagnosis of such issues. Did you have a look at the flow, fan, speed and layer time previews yet? Frequently such type of issues show clearly in the previews, making diagnosis much easier.
flow, speed and layer time are all different to the rest of the model in the same area, so I can still not figure out what is wrong. if I change any of the setting, won’t this affect the whole model ?
If you move the slider down to those layers, are they comprised differently than the rest? I mean that the current view higher up looks like it has 1 wall, as well as a tiny gapfill that it creates at the outside of each “petal”
It could be that their particular size means that spot is perfect for 2walls to generate, or something along those lines. Investigate first - whats it look like?
An increased layer time for these particular layers leads to increased time for shrinkage of the these layers which, imo, would match the failure image.
What is a little strange, is that these longer print times seem to, counterintutively, also match a higher speed and flow.
While the lower defect does not show a “smoking gun” in this pic, the upper defect indicates the “slow down for overhang” to be active (blue arrows). However, it is also active on the layers below. Potentially, the “Ensure vertical shell thickness” is only active on this/these layers and the additional “lines” in the red oval are only present in this layer and not the layers above and below?
Before going further, it may make sense to also look at the fan speed preview. If it shows a clearly visible difference only for these layers, then I am currently on the wrong track
Otherwise, we will indeed need to equalize the layer times and indeed
In the past, I would have tried to tweak max flow and speed to get a more equalized cool down. Nowadays, I would try out the “Smoothing wall speed along Z (experimental)” (needs Developer mode to be enabled in Studio Preferences) or just increase the minimum layer time in the filaments fan settings.
I would play around a little with these settings (layer time, max flow and/or speed) and see what differences are visible in the previews (after having also checked the fan preview).
There are a few further observation from your first pic though. Kudos by the way for the high quality
Despite drying, there still does appear to be some stringing present (red ovals). If the drying time is too short, it can happen that only the outer part of a roll is dried. If that can be ruled out, it may help to enable wipe on retract in the filaments “Setting overrides”. It is rarely needed for PLA though.
Also, having experimented a bit with z-hop, I usually go without it these days. I have found it to make stringing thinner but more frequent. Wipe-on-retract is much more useful but that may just be my personal experience.
The blue circle on the other hand highlights what may be an undesired side effect of slowing down the print to achieve the minimum layer time. If the area is small, this setting just keeps the hot nozzle in the area needing cooling time for longer. In these cases, it is neccessary to force the nozzle away for a sufficient time by either, placing an additional object a fair distance away on the plate (either use a primitve of equal or greater height or clone the part) or to force a prime tower by enabling a smooth timelapse in the “Other” settings.
I hope that this is somewhat helpful, &
Yours,
Eno
PS: Is this a MakerWorld print? A good designer will usually have provided a well thought out print profile with pictures of real prints. Unfortunately, it is also these popular designs that attract a lot of copycat attention. Nowadays, it is not always easy to spot the difference.
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