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Flat areas are thick in middle, thin/curled at edges

I print a lot of model railroad parts with large flat areas (2-3" square up to 3" x 5.5") but each part, regardless of resin or layer thickness (Clear or GreyPro), is much thicker in the center and thins out as you reach the edges. Everything is printed at 50um and there is no post-cure UV treatment because, even for 1 minute duration, parts will curl due (likely) to varying thicknesses and material stresses being relieved differently.

I use the PreForm default for density of supports with tips at .15mm, mini-rafts and 2 mm above raft. Because these parts will be used as mold patterns and represent steel sheets/plates, they must be parallel to the platform. I’ve tested a couple smaller pieces at 10 degree tilt in 1 axis and this problem goes away but even a minimal stairstepping can’t be tolerated.

Are there advanced settings in PreForm that can be tweaked to correct this problem? Several years ago, I used to buy Prototherm SLAs from a service bureau who printed parts on a Viper and those flat parts had the same cross sectional thickness end to end so I know it can be done but not sure if it’s possible with Form3.


Thanks so much for reaching out! The best way to print models with large, flat areas is to tilt them at an angle—45 degrees tends to work best. By printing your model at an angle, you are reducing the surface area of each layer while also decreasing the amount of contact the print has with the tank. This means that the print is subject to less force as the build platform raises with every layer—thereby decreasing the chances of curling and increasing your success rate.

If the “stair-stepping” is an issue, you can try printing at a higher resolution—the Form 3 can print at a resolution of down to 25 microns! In my experience, printing at this resolution makes layer lines and “stair-stepping” nearly invisible.

While there are not any advanced settings in PreForm specifically targeting this issue, I’d recommend reaching out to our support team if you’re still struggling to print these parts. They’ll be able to provide you with more advice for your specific models!

Thanks for the reply. As I stated in the original post, I’ve tried 10 degrees tilt and the super-thick, dish-shaped center that tapers to the ends was much better. I use Grey Pro often which only allows 50 micron layers.

I’ve successfully printed similar parts standing vertically to the platform which nearly eliminates layers and all of the thick center but increases build time dramatically. This may be the only way to reduce layering to an acceptable level and eliminate the thick center. I will contact FormLabs about this.

Based on FL feedback, I adopted a full raft for parts with large, flat areas and increased the density to 1.5. I’ve printed 2 parts measuring about 1.5" x 4" long in Clear V4, .001" layers and have no warpage or thick/thin/curled areas. The part’s thickness, including the .40mm raft and setting the bottom of the part at 2.0mm, was less than .100". So far, so good.