Additive Manufacturing Processes Vat Polymerization

Vat Polymerization

In vat polymerization a photopolymer is hardened by a laser light. A build platform is then raised inside a resin bath and a new layer is hardened. It is also called SLA or stereolithography and very close to DLP which is a similar technology.

SLA is used for things that need to be smooth or require a lot of detail. The technology is not really well suited for creating end use parts. For these applications part strength and heat deflection are generally not high enough. In the long run UV degrades the performance of parts making them yellowish and brittle. The process also requires manual removal of support material which raises the cost per part.

Having said that millions of hearing aids have been 3D printed with Envisiontec DLP machines and 3D Systems SLA machines. These have been cost effective and customized to the individual ear. In In The Ear hearing aids, 3D printing has disrupted the market significantly and the vast majority of these types of hearing aids are now 3D printed.

SLA is also used for jewelry. Lost wax methods are used in combination with 3D printed molds that are then cast. These can then be made into serial or unique pieces. Molds and high end prototypes are also made with SLA. In addition to 3D Systems and Envisiontec, Formlabs is shaking up the market with desktop SLA machines while Carbon entered with a splash with its CLIP technology, a refinement of SLA.

In the dental market SLA is used for large scale implementations of dental molds such as Invisalign which makes millions of molds with SLA each year.

The SLA materials themselves are photopolymers, resins with a light-activated component added to them. A wide range of these materials can be designed and made to a range of specifications including FDA approved ones.

For specialized applications such as casting and hearing aids, SLA shines as it can deliver a high throughput of parts to specified dimensions and high smoothness. In other applications adoption of the technology is lagging due to the limitations in the strength of the materials.


  • Smooth
  • Highly detailed
  • Millions of parts made


  • Parts have lower strength and heat deflection than other technologies

Main uses:

  • Hearing aids  
  • Dental
  • Jewelry

Additive Manufacturing can be used for a wide range of materials such as:






In filament there are a number of popular materials:







Besides Vat Polymerization there are other Additive Manufacturing technologies:


Powder Bed Fusion

Fused Deposition Modeling