Knockng sound during printing


I don’t from which surface area the peeling process starts to produce noticeable noise but I guess it would also depend on the shape of the area as well as the material and even maybe the wear of the tank.

My gut feeling is that 750mm^2 may very well be enough for the peeling process to start producing noise.

Did you part printed successfully ?

In all cases this is not an issue, formlabs tested the peeling process by printing a 145x145x175 part, there is a photo of this somewhere in the forums.


My part printed kind of succesfully but I think the surface quality is worse than before the noise. I am using the standard gray material but my tray might be a little worn could this be the problem?


Can’t say for sure but half of the prints we do in grey generate noise during the peel operation and we have no issue with print quality after more than 8 liters and several trays used.


How often do you change tray?


The sound in that video is suction being released. The part you posted has a giant void in the center which if not vented will create a vacuum (and suction force) inside it every time the printer tries to pull it off the bottom of the tank. Play with a empty glass and a sink full of water and check out what happens when you dunk it in the water and pull it out in different orientations. To fix this you could add a vent hole or orient the part differently. This is also likely what is causing surface finish problems because when the part goes back down in the resin you are now pressurizing this void and the resin is squirting out around the interface of the object and the bottom of the tank while the laser is trying to cure it.

(Based on my experience and some educated guessing)


Ahh yea you can’t really see it but i actually have a hole going through the part so that it can’t create the suction you are talking about:


That should work. Another thing, if possible, set the part at a slight angle of up to 10 degrees. Any more and Preform will want supports on the sides. This way there is no chance of suction getting into the act. I use this method from time to time on large pieces.


I also have encountered this sound since the newer printers have been introduced. The original two printers I received were dark grey, and the last two printers have a gold-ish/platinum hue to them, and these are the printers making the sound when the tank or the wiper arm moves. I believe that this is the reason why I had an error occur when the arm stuck during a ‘clean sweep’ between layers, under the build plate. I just received a new printer last week and it makes the same noise. The original printers do not make that noise.
Here is the photo of both.


The new shell color was a cosmetic change and there aren’t any significant hardware differences between the two machines. There can be a few different causes for this knocking sound and over-compression or ‘cupping’ are some of the more common. If you’re able to upload your .form file, that would help to rule out a few causes.


I assumed it was a cosmetic change, but the sound did indeed start with the purchase of these newer machines with the ‘cosmetic’ changes. I have included 3 short videos showing the difference between our older form2 and the newest form 2. The 1st video has no sound when the wiper arm moves, only the build plate raising and lowering. The clicking sounds appears on the 2nd and 3rd video. The sound is faint on the 2nd video vs the 3rd.



I’m having a bit of trouble distinguishing the difference between the 1st video and the other two. I can hear a clicking sound in each of the videos but it’s tricky to gauge whether that’s background noise or coming from the printers. Are these each running the same Firmware and PreForm versions?


I have a newer recording of both machines side by side…hopefully you can hear the clicking of the newer vs older form2 versions.


Was the age od the vats the same on old vs. new, and did you run a print (or prints) on both prior to the print in the video?

Older vats, and vats that have been under resin long (and are mostly oxygen depleted) tend to cause more adhesion to parts, so offer more resistance to the peel.

Additionally, are both the old and the new unit running the same firmware? The peel changed dramatically about a year (?) ago and, i think, again, recently, to make it faster. Every iteration seems more and more violent to me (Formlabs keep claiming they’ve reduced the peel forces, though).


Yes, they were as close to being the same as I much as I know it to be possible. We usually order 2-4 resin tanks at the same time, same with resin cartridges. I use my vats until there is little to no ‘visible’ spaces showing on the tank printing surface, which is shown on 'my dashboard>materials. The noise that I here has little to do with the actual printing, but rather the step motor that moves the wiper arm. The noise begins when I start a new print job and the tank moves to start the warming process. I took the a few of the earlier videos at the start of a print job, and also during the print job.
Yes, all of the printers we have run the same firmware [rc1.16.7-12(14, Dec 2017)], except for the newest printer that we just received[rc1.13.5-101 (24 Apr 2017)]…I have yet to connect and update it.
The only issues that I have had with peel is when I use Dental Model resin, but I was advised to tweak how I position the models to reduce the force of the peel process between layers…and now I have no issues with unfinished print jobs. Of course I adjusted the settings that they recommended to reduce the amount of print time to a more acceptable time-frame.


Strange. Got no other ideas then.

@Formlabs - did the stepper drivers change between the old Form2 and the new Form2?


according to the Frew, they made no mechanical changes…only changed the outer housing, but purely cosmetic…?


Yeah, i think i’ve read the same.

Still, it occurred to me that maybe they’ve switched from Trinamic TMC2100 to TMC2130 and enabled StallGuard and that’s what’s causing the knocking sound somehow.


I have done a few prints on my Form2 and today is the first time I have had this clicking / banging noise.

Only thing new is the machine did a Firmware update this morning to match the new Preform SW.

I will change the resin and tank after this print and try something else to see if it is still happening.

Could it be FW related?


I’m having the same issue, and I also believe it appears since the last update.
But the sound has nothing to do with a big surface aera of the parts, I clearly see a metal bar jumping out of its track when the tank reach its maximum to the right.
the metal bar is here:


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