Scraping/Grinding sound when LPU moves from right to left in between layers (Form 3/3B)

Hi everyone, I’ve never experienced this before and am a bit concerned.

I’m hearing a scraping/grinding noise when the LPU unit quickly moves from right to left when a layer is finished (or at the beginning of a layer?).

The video example below speaks a thousand words (or in this case, sounds):

Any ideas what’s going on?

A few things:

  • Using the Maintenance->Motor Moves interface, with the tank removed, the X and Z axis lead screws seem very smooth and fine. They sweep left and right and up and down without any abnormal sounds.

  • Mixer seems to be working fine

  • This is my second print using Clear resin on a brand new resin tank. Not sure if the sound happened on the first print, as I wasn’t monitoring it. But the first print was successful. When I aborted subsequent print when I heard the grinding, it appeared to be printing successfully up until I aborted it.

  • I wiped the underside of the tank and the LPU unit rollers with a small amount of isopropyl alcohol. I re-exported my STL file and re-generated it in Pre-Form. I updated to the latest Firmware (2.0.1) and Pre-Form (3.29.1). I re-booted the printer. I re-seated the build platform and resin tank.
    It seems to have gone down from a loud scrape to a gentler squeak, but sometimes becomes a scrape again.

  • I replaced the resin tank with a brand new resin tank. The first few layers (when the LPU unit seems to move slowly as it is building a raft), there is no sound. But eventually, the scraping sound occurred again.

  • I haven’t yet switched back to a different resin to see if the issue is specific to clear resin. (Seems weird that it would be resin-specific?)

  • Last thing I noticed is that the first resin tank’s film seems to have an obvious blemish near the right corner. It did not have this blemish when it was brand new. It must have experienced this scraping sound for at least 1+ hours (or way more if it was scraping throughout my entire first print). Something tells me this blemish is not a coincidence. This is why I don’t want to ignore the issue as it may be causing damage to my resin tanks:

Any advice would be greatly appreciated!

The X-axis screw may still need lubrication. Without a resin tank in place, there’s going to be less drag on the LPU and the screw will have an easier time moving it. And when a print is underway, I expect that drag goes up significantly.

A poorly (interestingly, under and over lubricated both do this) lubricated bearing (or ball screw) will exhibit “sticktion”. It doesn’t move smoothly. Force builds up until a threshold is reached and then the system “snaps” to a new position where the cycle repeats and the bearing “chatters”. That’s what it sounds like to me.

You cleaned the rollers and that eliminated some of the drag, the load on the screw was reduced and the sound got quieter. This is also consistent with “the screw needs some grease”.

If you’ve never cleaned and re-greased your lead screws, and you’ve had your printer any appreciable amount of time, it’s due. I suspect they all make this kind of noise at some point. Mine did.

There are instructions in the user support area. A specific type of grease is required.


@Randy_Cohen , thanks so much for your reply and taking the time to watch the video! Very interesting! I had pretty much dismissed the lead screws due to the Motor Moves testing I had done…but reading your observation, seems like the lead screw might very well be the issue.

Interestingly, my part appears to be printing correctly despite the sound, but as you mentioned, the lead screw is probably reaching its destination by overcoming the friction, but is screeching and/or jerky while trying to get there.

I will work on lubricating the lead screw as you mentioned and report back.

The motion system doesn’t miss steps unless the screw binds completely. But if it’s not at that point, when the stepper motor steps, the screw doesn’t move smoothly, it makes noise. But it still moves. My printer is located remote from my workstation. I will often prime the printer, fire off a job, and come back when it’s done printing. I don’t know how long my machine was making noise before I noticed. But I am pretty sure it’d been a while. I never noticed any degradation in the quality of my prints.

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On the right side, just under the tank tensioner, there is a plate like 2x10cm (i can’t remember exactly).
You’ll have to use a mirror to see it underneath, or your phone’s front camera.

Move your LPU to the left side (via Maintenance menu) and have a look on the right side in case this plate has been dislocated.

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Thank you both!

@Randy_Cohen , makes sense! I also print remotely these days so truth is I have no idea how long this has been going on for, although it’s likely very recent because I do swing by the room occasionally while it’s printing.

@agiorgitis thank you! I will take a look at that!

i got a photo for you, it’s from the underside. It stays in place with some clips

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Hi @FormFabricator9000,

I agree that lubricating the X-axis lead screw will most likely resolve the noise you encountered. With that said, the lead screw issue should be unrelated to the resin tank wear you noticed. For the tank, this looks to be a minor optical coupling issue, which can happen if one layer of the tank film is scratched or punctured. I’d recommend getting in touch with Support and sharing a photo of the tank to verify, but I would say most likely that we’d recommend no longer using this resin tank to minimize the chances of a potential resin spill.

Thank you @agiorgitis for the photo, I appreciate it!

Thank you @Jesse_K for the insight! I have a lead screw kit on the way, and Formlabs Support has graciously helped me out with the resin tank (which, like you said, should be unrelated to the lead screw noise and is just a coincidence).

I will report back once I have used the lead screw cleaning kit in case it is helpful to anyone else that comes by this thread.