Shape distortion in long thin sections

Support & Troubleshooting
1

I print out a number of objects that have thin, planar areas (e.g., 100x10mm strips ranging from 0.1mm to 2mm thick). I have printed these in several resins (white, grey, black, tough) and I use a UV cure box with strips of 395nm UV 5050 surface-mount LEDs. I use Preform’s auto-support generation, so in general they are very generously supported.

In some cases, these objects begin to warp while still being printed. After printing, during cure, and after cooling down post cure, the warping becomes more pronounced. My (admittedly naive) impression is that the warping is due to internal tensions in the object: as the resin cures it shrinks internally and tension builds unevenly (parallel vs. perpendicular to the print layer?). If the object does not have thick enough walls, these tensions begin to warp the object.

In some cases I’ve been able to use axial bracing, and in other cases I can break up the solid expanse (by building it as a lattice instead of a solid wall). But this is not always possible.

I’ve experimented a little with object orientation during printing. If this is a matter of internal tensions, orientation of the layers seems like it might have a meaningful impact. Has anyone else found through their experience a layer orientation (presumably the plane of the object in relation to the plane of the build platform) that minimizes warping?

Thanks!

2

You are correct that there are internal stresses that can cause parts to warp. The easiest way to mitigate this is to orient parts in such a way as to limit stress in any one axis. A thin flat plane should be oriented at 45 degree angles in the X and Y to evenly distribute internal forces. You can also post-cure parts on support structures as parts that are fully post-cured won’t warp over time.

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I always cure these parts with supports in place. I’ve printed them straight across (along the wiper blade axis) and diagonally (x,y) across the platform. Of course they are also diagonally up the z axis. Since a single part may have multiple thin sections that are not parallel to each other (one might lie flat on z while another is at a 10 deg angle).

I’m trying a new print today with a part at 45 degrees x, y and z with even more supports, aimed at constraining warp.

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Are the parts dimensionally accurate before you cure? If so then check this out: Replacing Isopropyl Alcohol with Yellow Magic

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