Print warping across one layer

I am printing 2 parts that go together. They are held together by a hinge on one side and a snap fit on the other side. As you can see in the attached picture.

Problem is the prints warp at one layer. I suppose it is because at this layer the print goes from a relatively small surface area to a large one. As you can see in the picture the flat area in the center is slightly slanted down when it should be horizontal. This effect on the layer throws off everything else. The tool works but the snap fit isn’t as nice as I would like. Any suggestions to fix this problem.

Additional info. I am printing with 3rd party resin, ApplyLabs Black. I have the resin in a old Tough cartridge and therefore printing as tough. I’ve had issues in the past printing in open mode and so print in old cartridges when possible for 3rd party resin.

I greatly appreciate any suggestions.

It looks like you printed with this flat surface parallel to the build platform. You’ll usually get better results if you print big, flat surfaces at a slight angle. That way each layer printed is just a little bigger than the previous one. When the surface is parallel to the build platform, the first layer is wide and thin and tends to move around, which can make things inaccurate.

What did auto-orient suggest for this part?

the reason you want to angle the print is easy to understand…
ALL resins shrink when going from liquid to solid.

when the laser has to cure a wide layer of resin, all of a sudden… each layer it lays down wants to shrink and CURL the previous layer as it shortens more in length than it does in thickness. Its not the first layer that is the only problem… each additional layer compounds the warpage.

The linear shrinkage over an inch or more of length is also enough to shear supports.

when you angle the critical surfaces to the build plane, you end up with a shorter initial layer- then you add a very slightly longer additional layer on top… and then each added layer is only slightly longer, reducing the curling forces applied to the layers already printed… by the time the longer cross sections are being laid down, you already have a wedge of harder resin that is now thick enough to resist warping under the stress… and each support has been connected essentially one at a time so that they are not pulling on each other during curing.

understanding HOW the printer works and the forces that printing entails will help you think more clearly about orientation and support layout and how to avoid the kinds of things that make for unsatisfactory results.

Thank you. I selected the orientation myself. So far we’ve been pretty successful not printing at angles. We’ve been doing this just for appearances and less clean up on supports.

I guess this is an instance where I’ll have to use the angle suggested Preform.

Giving the parts a 5-10° angle is sufficient to make wide planar surfaces easier to print, while still maintaining the advantages of printing at 0° : usually overhangs are not pronounced enough at 5-10° to be in need of supports.

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I like that, that’s a great idea, building the angles into the design. Thanks

That’s not what I intended to write, I meant : in PreForm, to orient the parts that you would print “straight” with a slight angle.

However your interpretation is also right : I am mostly doing engineering stuff and since we bought the Form2 I have often “designed for SLA” just like you would “design for manufacturing” with other disciplines (substractive manufacturing, injection molding, …). When beneficial we often give the parts huge radii, chamfers or drafts to accommodate the printing process even though those geometries would violate all common-sense for other means of production.

Ok, I read that wrong. But good to know that all you need is 5-10. Thanks

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