Continuous Liquid Interface Production of 3D Objects: An Unconventional Technology and its Challenges and Opportunities

Abstract

The purpose of this paper is to understand and research literature on the “continuous liquid interface production (CLIP)” of 3D objects to address the current challenges. This proprietary technology was originally owned by EiPi Systems but is now being developed by Carbon 3D. Unlike conventional rapid prototyping of printing layer-by-layer to print 3D objects, CLIP is achieved with an oxygen-permeable window made of proprietary glass membrane and the ultraviolet image projection plane below it, which allows the continuous liquid interface to produce 3D objects where photo-polymerization is restricted between the window and the polymerizing part. This process eliminates the time requirement in between the layers resulting in the faster production of 3D objects with a resolution less than 100 microns. It is a known factor that the “supports” play a vital role in any liquid based 3D printing techniques and this does not change in CLIP. In addition to the parameters of support structure like shape, size, strength, ease of removability, surface finish after removal of supports etc, CLIP needs to deal with different types of materials. The support structure needs to be designed according to the respective material’s properties. There are two broad categories of the materials available from Carbon 3D, prototyping resins, and engineering resins. While the prototyping resin is used for the cosmetic models and the engineering resins are used for the practical applications. There are 6 types of engineering resins developed for the end user; of these, EPU and CE are more challenging to work with. EPU parts needs more supports and careful handling till the completion of post processing as the material is soft. CE parts are fragile and needs more systematic handling to complete the successful production. Although printing parts of EPU and CE is more time consuming when compared to the normal CLIP process, they are worth for their unmatched industrial applications. None of the existing 3D printing technologies offers this quality. The support structure, orientation and pot life are the influencing parameters for all resins. In this study, it is statistically proven that by optimizing the part orientation with respect to the slicing of each layer and customized supports; parts are built way better than before. The part orientation is optimized by ensuring each layer is supporting the subsequent layer and minimizing the islands. It is noticed that the results are always better by tilting the part 5 to 10 degrees in both X and Y axis in the build setup and this applies for most of the straight geometrical parts. For parts of specific geometry which can create a vacuum while pulling up the part needs to be oriented in a different way or create a re-closable air passage that can prevent the vacuum being created.