2. Solid Ground Curing (SGC)

Each object layer is defined by an optical mask corresponding to the CAD cross-section.

In Solid Ground Curing, also known as SGC, the first step in creating an object is to define the shape of each layer using a design created in CAD (Computer-Aided Design). An optical mask is created for each layer, which represents a cross-section of the final object. This mask guides the curing process, ensuring that only the areas meant to form solid parts will harden, while the rest remains liquid.

You can think of the optical mask like a stencil you might use for painting. When you hold a stencil over a surface and spray paint, only the areas exposed through the stencil get colored, while the rest remains untouched. In SGC, the liquid photopolymer behaves similarly, hardening only where the mask allows it to.

A thin layer of liquid photopolymer is spread, and the mask is placed over the surface.

Once the optical mask is ready, a thin layer of liquid photopolymer resin is spread evenly over the build platform. After that, the mask is carefully placed on top. The liquid resin will only solidify in the areas where the mask allows it, which is dictated by the designed cross-section. This process where the mask and the resin interact is crucial for accurately forming each layer of the object.

Imagine you are applying gel nail polish. You lay down a thin layer of the gel and then use a stencil to apply designs. The gel cures (hardens) only where the stencil has openings, leaving the rest of the area covered with liquid polish. Likewise, SGC ensures that only specific regions of the resin cure, leading to the desired shape.

The entire surface is cured simultaneously using a high-powered UV lamp—no laser scanning.

In Solid Ground Curing, instead of using a laser scanning method that focuses on curing point by point, a high-powered ultraviolet (UV) lamp is used to cure the entire surface area of the liquid resin at once. This means that as soon as the optical mask is applied, the UV light activates the curing process across the full layer, solidifying it instantly.

Think of how a large oven works when baking cookies. Instead of baking each cookie one at a time, the oven cooks multiple cookies at once, ensuring even heating throughout. Similarly, the UV lamp in SGC treats the entire layer simultaneously, allowing for faster production of the object.

Residual uncured resin is removed.

After the curing process is complete, any remaining uncured liquid resin that did not solidify is removed from the surface. This step is crucial to achieve the final finish of the part and ensure that only the intended solid areas remain. This residual removal can be done through careful washing or scraping, depending on the design complexity.

Imagine you are washing away the excess chocolate melted on top of a cake after it has been set. Just as you'd remove the extra chocolate that doesn't contribute to the overall cake design, in SGC, the leftover uncured resin is cleaned off to leave only the solid parts of the object.

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