Ultimate Guide to 3D Printing Thermosets

This article examines the difference between traditional SLA, DLP and 3SP for additive manufacturing in a large build envelope when high accuracy, repeatability, reliability and throughput are required.
​

---

After more than three decades of research and development, 3D printing is ready for prime time in manufacturing — production of high-value parts and mass customized products, in addition to prototypes, injection molding tooling, end-of-arm tooling and assembly jigs and fixtures.

In fact, a variety of manufacturers have been using 3D printing, also known as additive manufacturing, this way for years now, with more adopting the technology every day. In addition to manufacturers of all sizes, the range of production users also includes laboratories, hospitals and Hollywood studios.
​
Did you know, for example, that the global hearing aid industry has been mass producing custom hearing aids with 3D printers for more than a decade1? In recent years, dental laboratories have also been mass producing dental and orthodontic models, which require high XY accuracy and a smooth surface finish. This has eased the way for the mass production of clear thermoformed aligners for teeth straightening, in addition to other dental products. And in 2016, General Electric began mass production of metal fuel nozzle injectors for its LEAP jet engine using 28 additive manufacturing machines — validating the idea that 3D printing
isn’t just for prototypes anymore. 

The University of Michigan-Dearborn chose EnvisionTEC’s large frame 3SP technology to 3D print large parts for its Formula SAE Electric race car project. Watch the video at EnvisionTEC.com/automotive

Vat photopolymerization, in which a light source is used to selectively cure or harden photopolymer resins inside a vat or tray, has become a popular method of 3D printing among manufacturers for a variety of reasons.

For example, the photopolymer resins used during this process are also known as thermosetting plastics or thermosets, which strengthen during post-curing and hold their shape, even after reheating. This is in contrast to thermoplastics, which can be re-melted after being formed into a part. A wide range of thermoset materials are also available today with a variety of desirable properties, such as epoxies, which offer elasticity and exceptional chemical resistance, as well as biocompatible materials.
​
The vat photopolymerization category includes stereolithography (SLA), digital light processing (DLP) and a new method launched in 2013 called 3SP for scan, spin and selectively photocure. 3SP specializes in affordably building accurate parts with a smooth surface finish across a relatively large build envelope, where traditional SLA and DLP have challenges scaling up in size affordably. This allows for 3D printing of a single large part or a tray of smaller parts.
To understand why 3SP is so unique in its benefits, it’s critical to understand the limits of SLA and DLP. 

---

Understanding SLA vs. DLP

One of the earliest forms of 3D printing, SLA was patented in 1986 and commercialized by 3D Systems.
In SLA systems, a UV laser beam literally draws — lithography means “to write” — out a part into a vat of resin. Wherever the light hits resin, curing or hardening occurs. The laser beam can be positioned either above or directly below the vat, and each approach has its own pros and cons.

However, for most large manufacturing systems, the laser is typically positioned above the vat and curing takes place on the upper layer of resin in the vat or tray. This approach allows for the largest build envelopes and lower gravitational forces on the part being built. After each layer is built onto a build platform inside the vat, the platform is lowered in the Z axis so the next layer can be cured onto the part. 
​

Read More