## 1 Introduction  
Additive manufacturing (AM) has generated increasing interest in recent years and is currently undergoing tremendous development. The possibility of creating customised and complex parts in a relatively short time makes AM a very interesting manufacturing process on an industrial level. Therefore, this technology serves as a complement and extension of conventional subtractive manufacturing technologies [1; 2; 3]. More and more companies are using this technology in their production processes, as in many cases, it considerably reduces costs and times compared to those of other conventional manufacturing techniques [4; 5; 6; 7; 8; 9]. Despite these advantages, AM, compared to other manufacturing processes, is a very recent technology and in certain aspects, still requires further maturity. The main technological challenge is still to improve the ability to obtain parts that are functional and can be used in industrial sectors [10]. This is why the technology is constantly evolving. This can be seen in the efforts made in recent years to develop specific regulations for implementing AM as a general manufacturing process [6; 11]. Although it should be noted that in certain aspects, such as metrology, this technology still lags far behind the development of other more consolidated processes. AM is very useful when low production volumes, high design complexity, and frequent design changes are required, as it offers the possibility of producing complex parts, overcoming the design limitations of traditional manufacturing methods [5; 7] and becoming a highly virtualised process. For this reason, the starting point of any AM process is considered to be the design of the part to be manufactured, from which a geometric information exchange model is obtained. One of the most widely used interchange formats in AM is STL (Standard Tessellation Language), developed in 1986 together with the stereolithography and has since become a standard, although there are formats that offer more features, such as the AMF (additive manufacturing file) format [12; 13]. The STL format performs a decomposition of the modelled surface geometry by discretising it into flat tessellated triangles that share their edges to form a mesh [14]. In this way, an approximation is made to the designed model and if the goal is to reduce the approximation error committed when discretising the model, the density of the facets or faces of the mesh is increased. This increases the resolution of the mesh, although this entails an increase in the information contained in the file and therefore, an increase in the file's post-processing time. Therefore, the meshing process must be optimised to improve processing times [12; 13; 14; 15]. This is very important in the case of AM, as a non-optimised STL file can lead to increased pre-processing time or geometric errors in the final parts caused by approximation errors. Although this effect will be more determinant in those AM processes in which a high quality of the parts is sought or in those where it is possible to obtain more precise details, as in the case of VAT photopolymerisation processes. In these processes, a liquid photopolymer is selectively cured inside a tank by the action of a light source, usually ultraviolet, which activates polymerisation [13; 16]. When the resin is exposed to the curing light, photoinitiators release species that act as catalysts for the formation of chains between monomers and oligomers. The chemical-thermal process of chain formation is irreversible, and the prototypes cannot return to their liquid form. Using this principle, consecutive layers of resin are gradually fabricated from a 3D model [17]. The low layer thicknesses used in this process, together with the high lateral accuracies, make it one of the polymer AM processes from which the highest quality is obtained [18; 19]. In recent years, the use of this technology has undergone a major expansion, with the number of studies carried out on this process doubling.