**6. Outlook**

As the front-runner for high-resolution 3D printing, SLA retains substantial limitations due to the often high costs of this AM method, which are augmented further by slow printing velocities. Additionally, the fact that printing is only possible with one resin at a time severely restricts potential applications.

Trends toward faster manufacturing have already been set by the CLIP technology [44]. Other continuous DLP methods, where building platforms are raised at a constant rate during the printing process, have also been established [76]. For laser-SLA processes, illumination itself is a limiting factor in reducing printing times and different approaches to increase throughput are necessary. Using a broader scanning pattern for bulk features and applying more precise, narrow lines only in areas where the maximum resolution is required, such as for fine structures and at surfaces, is one method, which is already being implemented [93]. The development of hybrid systems of DLP and laser techniques is currently being investigated as well. Similarly, the inner area should be illuminated via pixel-based DLP, and only round surfaces drawn with the vector-based system of laser-SLA. This could further reduce printing times to rates comparable to DLP while maintaining high-accuracy of laser illumination [22].

Another method, which combines laser and DLP-SLA, addresses the compromise between build size and resolution in DLP. A proposition to retain small pixels and thereby highresolution even when printing large parts is to laterally stitch the projected images. If a layer has a cross-section exceeding the attainable size by the DMD, it can be divided into smaller areas, which are then illuminated one after the other [100]. This combination of scanning and projection-based illumination, also called large area projection micro SLA (LAPμLA) [101], can lead to the low-cost fabrication of cm-sized objects with a μm-range resolution [102].

Modification of available SLA systems to manufacture parts from multiple materials has been attempted. This usually includes a time consuming cleaning step between material changes. Thus, minimum feature sizes and resolution are no more comparable to conventional SLA than required printing time [103–105]. Nevertheless, after thorough investigation and development, these methods could help to further extend the application spectrum of SLA in the future.
