The so-called stereolithography was invented as early as 1983: It was discovered that certain types of polymers reacted to light rays and then solidified. This is the foundation for today's SLA technology, which is used to manufacture smaller components with high precision - for example, 1-to-1 prototypes for interiors, headlights or mechanical components. It took a good 20 years, however, until technology found its way into the industry. Not only were normal production methods such as using clay still cheaper, they were also faster and therefore more efficient. With the further development of stereolithography, the first economically affordable printers came onto the market around 2005, which were then slowly but surely adapted by the automotive industry.
SLA technology is indeed more expensive than FDM technology, which is based on melting solid plastic filament and subsequent application. The lithography process, however, is more accurate, requires less maintenance and is even suitable for incorporating printed parts into serial models. The parts, which are printed with this technique, are often as stable as their normally cast competitors.
Irrespective of which process is used, printing has reduced development costs enormously. The term rapid prototyping has established itself: Due to the fact that new designs were produced in a few hours instead of several weeks, new iterations could be reprinted much faster. The design process in the automotive industry has thus been significantly changed, even though many manufacturers still do not talk publicly about their prototyping process.