P1S Maintenance: What is causing this Screeching sound?

Bambu Lab P Series Troubleshooting
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I am using a P1S printer and it was due for maintenance, mainly because I noticed some layer shifts around the same z-height.

The most striking issue I noticed was a screeching sound when driving the build plate up and down the z-axis, so I lubricated the lead screws. However, the screeching noise did not go away and did not tone down either. I cleaned the screws with paper towels and re-lubricated them stronger than before, but nothing changed.

Video Link to demonstrate the screeching sound

The noise is much stronger when driving the build plate down than when driving it up.

I wonder if I have to clean or lubricate these vertical rods that are running parallel to the lead screws too, but I never saw anybody do any maintenance on them so I wanted to ask here how to do it before working on them.

Lead_Screw_Side_Rod
Lead_Screw_Side_Rod937Ă—1665 151 KB

Other than that, does anybody have an idea what might cause my screeching sound and how to fix it?

Thanks in advance

Edit: For your info, here is also an image of the layer shifts I was concerned about

20260220_182257
20260220_1822571920Ă—3412 219 KB

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Look at this link and watch the video:

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The link @LarryCnAZ posted is spot on. My P1S was speaking in the Z axis the last time I performed maintenance. It was the idler pulley on the botton of the print for the Z belt. A few drops of lube and all is well.

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Those rods should be oiled, just like the Y-axis rods. The oil not only lubricates, but also provides rust protection. Instructions are here:

The idler pulley is a likely supect for the noise. Something about that sound says “I’m rotating”.

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