Underside texture issues

We’re having some strange issues with the texture on the underside of flat surfaces on our Form 4L. This surface was printed at ~45 degrees:

But we see this issue on surfaces printed flat too. I understand that ideally, flat surfaces would be printed vertically like this:

But that’s not really feasible for cube-shaped parts, as the most you can tilt any face is 45 degrees. Adding more supports doesn’t seem to help either, and we end up with these rings around the support touch points (image from another print/model which was printed at a ~15 degree angle):

We’re seeing this issue with both Black V5 and Tough 2000 V1.1, although the rings around the supports don’t seem as bad on Black V5.

The parts were printed on a Form 4L and washed with Formlabs Washing Solution in a Form Wash L for 10 minutes, before being left to soak in water for 60 seconds and dried with an air compressor. They were also cured in a Form Cure L using the Tough 2000 V1.1 profile (although these issues are visible before curing).

Does anyone know what is happening here? I sadly don’t have the PreForm file for either of these models, but here’s the STL for the first one (it’s a wall thickness test):

depth_test_v2.stl (1.9 MB)

Thanks!

hello @jwfortx,
Thanks for posting about these concerns. I shared these photos internally, and we’re curious about some of the details. Ultimately, we’d love to be in contact directly with our Services team so we can help get those prints looking great. I took a glance at your account, and it doesn’t look like you reached out to us yet about it. You can do so through our Contact Support site.

While I’ve got you here, in your photo of the clear support marks, is that dimpling convex, concave or pretty flush with the surface?

Your first photo, and your comments below, reflect our best practices for Model Orientation. As each model is unique, it doesn’t always get to be a perfect orientation, and I understand the challenges with cubes.

Those lines are peel artifacts due to the peel forces between layers and models being under supported. Large surface areas and places where surface area increases are susceptible to high peel forces, which can create a suction effect. The suction prevents a layer from properly peeling off the bottom of the resin tank, leaving horizontal lines in a printed part. Layers between support touchpoints, where the part is less supported, are less resilient to high peel forces. As a result, the location of the peel artifacts tend to correspond to support placement.


The model here is supported at a 15 degree angle on both axis, and full supports. There is always the desire to use less supports, so experimenting with what works best for you is understandable.

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