RESEARCH AND INNOVATION 11 Additive Manufacturing in tooling for hot stamping. State of the art Increasing demand of Ultra-High Strength Steel (UHSS) compo- nents in the automotive industry has led to hot stamping process becoming a focus of research. This process consists of two main steps. Firstly, the blank is heated above austenitization tempera- ture (>900 ̊C). Then, it is simultaneously stamped and quenched in an internally cooled tool set. The rapid cooling rate allows marten- sitic transformation to happen, which results in the part acquiring an ultra high strength up to 1500 MPa. This way, lighter compo- nents are attained without a decrease in car safety. In hot stamping, tools include cooling channels to treat the formed sheet and achieve higher cooling rates. The efficiency of the cooling channels determines the characteristics and cooling time of the final part. In fact, if they are not properly designed, hot spots might be generated in the stamping tools, leading to an inhomogeneous temperature distribution. This uneven distribution not only affects the final part, which might not acquire the required mechanical properties; but also reduces the life of the stamping tools conside- rably. The flexibility of the DED process in terms of the design of geometries allows such cooling system to be manufactured. Manufacturing of conformal cooling channels Hot stamping die manufacturing by DED technology has been long researched in the High Performance Manufacturing group and the capability of the process of both producing and repairing tool steel dies has been already demonstrated. In previous studies, the manufacturability of conformal cooling channels has been addres- sed by combining laser based DED and milling of AISI H13 tool steel. In addition, the performance of the channels has been com- pared to traditional straight ducts. Results show that DED enables to build defect free dies with different geometries, guaranteeing the required structural integrity and mechanical properties [4]. MsC and PhD students. With regard to cooling capacity, additively built up channels have the same performance as drilled channels. Nevertheless, thanks to keeping a constant distance between the cooling channel and the stamping surface, lower temperatures and more homogeneous temperature distributions of the conformal part are attained. Figure 1. (a) Manufactured part; (b) X-ray inspection. Impact of conformal cooling on process cycle time Parallel to the study of the manufacturability of conformal coo- ling channels, a thermal model of the hot stamping process, which enables the simulation of successive stamping operations, has been developed [5]. With the aid of this simulation tool, the ther- mal field generated in both the stamping tools and the part during the process have been evaluated. Besides, a comparison between traditionally manufactured and additively build-up tools has been established in which the effectivity of the conformal cooling chan- nels has been proved to be superior to that of dies with straight ducts. It is concluded that, in the case of stamping a B-pillar part, cycle time can be reduced by 3 s thanks to conformal cooling, leading to a 15% process performance increase. Besides, by approaching the channels to the stamping surface, further impro- vement can be achieved.