Hot Lithography

For the additive manufacturing of plastic parts, numerous different production technologies are available. Due to insufficient material properties or surface quality and precision, additively manufactured plastic parts have not made it from the position as design models and prototypes to the industrial production of technical or medical parts as well as products of everyday life. On one hand, good thermo-mechanical material properties like those of technical thermoplast (e.g. PP or ABS) are necessary as components for industrial applications. On the other hand, geometrical properties, such as low surface roughness like injection molded parts are crucial.

For producing parts with excellent surface quality, stereolithography processes (SLA) perform by far the best. However, the big disadvantage of these technologies are the traditional material systems. Classical photopolymers are brittle and have a low heat distortion temperature. Hence, they are subjected only to a limited extent for technical applications.

Cubicure’s newly developed photopolymers are exceedingly tough and have a high dimensional stability under heat. Those properties can be obtained through highly viscous and sticky raw materials, which cannot be processed in commercial SLA machine until now. Out of this, Cubicure developed its own additive manufacturing process, Hot Lithography, for the processing of those poorly flowable material systems.
The aim of Cubicure is the additive manufacturing of polymer parts with outstanding impact strength and heat deflection temperatures while at the same time, having the highest possible surface quality. During theoretical considerations about suitable chemical compounds for those photopolymer systems, it was evident that the resulting substances would be highly viscous at room temperature. From this, Cubicure started developing a special 3D-printing concept which is applicable for processing highly viscous chemicals.

The high-performance photopolymers developed by Cubicure are highly viscous or even solid substances which could not be processed in any commercial stereolithography production site until now. Due to strong temperature dependency of a fluids viscosity, a heated 3D-printing process was implemented. But, this process also needs to prevent the unintended overheating and thermally induced polymerization of the resins. Regarding the Cubicure 3D-printers processing technique, the exposure process, known out of SLA machines was combined with a special, newly developed and also heatable coating system.

The multiple patented technical solution of this process challenge was published under the name Hot Lithography. This technology enables the usage of high-molecular chemical substances for a high precision 3D-printing process for the first time and consequently, establishes parts with unexpected material quality.
The technology’s core is a specially developed and patented heating and coating mechanism which is capable of processing resins and pastes of the highest viscosity at operating temperatures up to 120°C.

Elevated temperatures do not only affect the viscosity of a resin, but also its stability and reactivity. Hence, a precise process handling and control is necessary to avoid unintended polymerization and consequently, the degradation of the material. Thus, the temperature of all process elements can be precisely controlled. The biggest challenge was the heating of the coated thin layer of raw material during the printing process. In either case, it is necessary to avoid temperature peaks and local overheating. The specially developed hot coating technology got patented.

For material exposure, a high precision laser-scanner-system is used. Available light wave lengths are 375 nm in the UV range and 405 nm in the visible blue range. The used wave length also allows the processing of filled and colored material systems as well as the printing of transparent and colorless parts.

“Hot Lithography” enables the additive processing of technically relevant plastics of highest precision for the first time!