Cracking sound at release from FEP film

[Sven]

Hi!

I recently built my own DLP based bottom-up printer using a FlexVat consisting of a original DuPont FEP/Teflon film (50um). There's no extra acrylic in between and just the highly tightened film itself. I have no special peel mechanism but only the Z-axis movement. My prints come out well after many failures. After reading in this forum I was able to fix the issues. However, I still have sounds during release which I think are strange.

Is is normal that the release from the printed object off the FEP film makes a kind of cracking sound? The loudness depends heavenly on the area to be released.
The film gets pulled up like 3mm before its released. I thought Teflon FEP film has a special coating so nothing adheres to it!?

Is that sound related to too much exposure or any other issue? I cannot find good videos on the net including great audio.
Might that become better with a peel mechanism like here: https://www.youtube.com/watch?v=-K0bb5_Pjkw (around 0:50)?

Resin: Fun To Do Standard Blend in black.
Object: http://www.thingiverse.com/thing:291323 (scaled down a bit)

Thanks,
Sven

[mUVe 3D Admin]

Sven,

Are you doing a tilting peel? Usually that takes a large amount of the stress out of the job. Also the FEP needs to be stretched very tight like a drum in order to work. Ideally it will actually stretch the material as you pull it into place. The stretching will ensure the bottom stays as flat as possible and that it releases properly.

mUVe 3D Support

[Sven]

Hi!

At the moment there is no tilting peel mechanism. My plan is to integrate one in a later version of the printer. For the moment I need to life without it.

My FEP is already tight - maybe not tight enough. I'll check again and re-tighten it.

I now also reduced my exposure time for some tests. It's getting better now... I'll check back again after the changes!

Thanks,

Sven

[Sven]

Just as a small reply:

I re-tightened the FEP and decreased the exposure time by half. Sounds are gone now - even without special peel system and only Z-axis movements

Thanks,

Sven