Single Layer Misaligned?  

RE: Single Layer Misaligned?

I have also seen some "spot anomalies" on prints from my new MK4S, and am still observing it to watch for any predictability.

In your case, does it seem like the part has released from the print bed in that area where you see the malformation? As the part grows, particularly if you have internal geometry that causes the part to contract as it cools (i.e., solid layers), it can cause the edges of the part to release from the print bed. That can make the part warp upward, causing interference with layers above it. After a few more layers are applied, it usually settles back into its intended Z axis height, with a bit of "mushrooming" in the problem area. You can check this by shining a light from behind the part, and looking at it from the level of the print bed. If it has released from the steel sheet, you'll see light through the gap. I've experienced that more times than I can count. After getting over the frustration, it makes one seek to understand the art form more, and adjust variables to prevent it.

If your case is, in fact, a G-code glitch or something like that, I will watch this thread eagerly. 🙂

RE: Single Layer Misaligned?

I have had similar issues with my new MK4S.  A print would randomly produce a horizontal section with, what looks like, a missing layer.  It can range from a half-inch long to 2 or 3-inches long.  I can’t tell whether it’s a z-axis issue or an extruder issue.  I have spent about 20-hours (over 4 or 5 different sessions) with Prusa Chat with no real cause or solution.  The level of expertise varies depending on the tech. who connects with you.  Be careful, one tech suggested taking the printer apart and checking the z-rods to see if they were bent.  I thought that wasn’t practical and I felt if they were bent, ever print would have an issue…so use your judgement on their advise.

Here is what I gathered from Prusa:

1.) Yes, as mentioned above, the print partially lifting can cause an artifact that looks like the layer issues that you see in the photo and the model layer issue that I discussed.  You can look at the bottom of the print when done, and hold it up to the light at various angles and you can sometimes see a subtle texture variation that suggest the print partially popped off the bed…usually a corner.

2.) The issue could be a bug in Firmware.  If so, Prusa tech said to wait for next firmware update to see if it goes away.

3.) Could be a bad file.  In my case however, the same file can print with or without an issue…it’s very random.

I have been researching the web to see what I could find.  One thing I tried, and it seemed to work, so far anyway, is to replace the Prusa Flash Drive with a SanDisk USB 3.0 as I discovered that the drive reads & writes data to/from the printer and, sometimes it’s too slow or corrupted, so it can interrupt the gcode flow to the printer…causing a missed command, etc.  After 3 or 4 prints, I haven’t seen the issue return…in fact, unless it’s my imagination, my prints actually look slightly better.  I’m not getting too excited though, I’ll need to see many prints come out flawless before I think the issued solved.

I’m also considering gathering up my project files & associated photos of bad prints and sending it to Prusa Help email with my latest thoughts.  I’m essentially done with chat-support for now.  I’ve found the email support techs take their time and do a deeper dive, as opposed to the chat support.  I’m also hoping it expedites a bug fix, if, in fact, it is a bug.

That’s all I can add at this point.

If you update your flash drive, I’d appreciate hearing if it helped, or not.

I hope this helps

RE: Single Layer Misaligned?

I've been having the same thing after upgrading my MK3S to MK4, then still on MK4S. X or Y layer shift up to 3 inches.  I also went through all the mechanical checks with the techs, which seemed like the wrong debug path.  It really does seem like a firmware glitch.

RE: Single Layer Misaligned?

had something more drastic occur, started print, 

right off the bat, whole thing started 2 inches to the right, and did another shift and hit the edge about 2 min later. might try to factory reset see

any ideas would be great.

RE: Single Layer Misaligned?

Dan82,

Your comments validate some other glitches that I have seen, and I have suspected that the gcode file is getting corrupted somewhere. I've also seen missing sections of an outer perimeter. But more interestingly, I've seen a section of solid infill missing entirely. But it's clearly not a plugged nozzle or something like that — there will be a direct vector of extruded filament from the start of the empty zone to the end, where the infill picks up as expected. Here's the best illustration I have, where the glitch happened on the first layer, but it built up the layers on top of it as expected (this part was printed face-down).

I've now seen this on 4 or 5 prints, and will be reaching out to Prusa support to ask about it. I have "beamed" all of these files to the printer via Prusa Connect, so I was starting to wonder if the glitch was being introduced in the wifi transfer, and there aren't sufficient checksums in place to catch it. But your theory of a faulty USB stick makes sense, and I will find a good Sandisk stick to experiment with.

RE: Single Layer Misaligned?

I have the exact same feeling about Prusa Connect.  I did start copying files directly to the Prusa-usb via my pc and then plugging the Prusa-usb stick in mk4s.  I’ve never had any issues with this process but I’ve decided I cannot keep unplugging/plugging the usb stick, so I use Prusa connect to download/copy the file to printer via WiFi first…then I use mk4s onboard screen to tell it to print.  This is a subtle difference than the send to print option on prusaslicer, which seems to be doing too many things at once.  It seems better, though I’m still testing.