## 1 Introduction
[24] studied the design of molds considering their thermal analysis and corresponding thermal gradients in the mold and parts. In view of the developed study, it was possible to conclude that there is a greater shrinkage probability of parts in places closer to cooling channels, when compared to other regions of the mold. Thus, the localized cooling of the part may be subject to the main warpage effect, due to these thermal gradients. Thus, if thermal analyzes are carried out, which, through thermal simulation, allows the identification of the existence, type and location of thermal gradients that are developed for a part, it is possible to act on the mold design to avoid the appearance of warpage. The design of ejection systems for molded parts was also the subject of research [25]. To this end, a new procedure was developed that was capable of automatically creating the layout and measuring the necessary ejection pins according to the 3D model of the part to be molded. This algorithm is based on the analysis of the difference in thickness between each node-mesh pair, locating the zones with thickness variation. Thus, the areas where the ejectors can be placed are identified, as well as their size and shape. The same team of researchers recently published another work [26], now showing the development of an algorithm capable of automatically generating cooling channels. In this case, in addition to recognizing part topology, the algorithm needed to consider the amount of heat was to be transferred, as well as the corresponding places, designing and dimensioning the cooling system so that heat was drained from the part uniformly, avoiding the above-listed defects. The plastic injection molding industry has continued to innovate and respond to the growing demand of consumers in terms of functionality, comfort and product innovation; injection cycles were grouped, enabling what is known as multi-material injection molding. Usually, in the first stage, a thermoplastic is injected, and then an elastomer is often injected to give the part new functionality or to increase its wearing comfort. This technique brings new challenges, due to the need for compatibility between the injected materials and the corresponding thermal cycles. To make this possible, there must be different cavities. The first cavity enables the molding of the first material, usually more rigid (thermoplastic or thermosetting); and the second cavity enables the introduction of the first part that is already molded, having the necessary free space for the molding of the second material, which is normally compliant. There are several ways to move from the first to the second phase, with some technological progress in the meantime. Initially, the first molded parts had to be transferred from one initial cavity to another (where the second material/molding was performed) [26]. Technology has evolved and rotating molds are now common; they are provided with the necessary cavities and movements that make multi-material injection molding possible without having to extract the first molded partsfrom the cavity where they were made. Clearly, this situation depends on the geometry of the part that is obtained. Currently, there are essentially three possible techniques for making multi-material injection molding: cavity transfer, removable core, and sliding core methods [27]. The cavity transfer technique is less demanding in terms of mold design; on the contrary, it requires a precise handling system for the initially molded parts. The removable core technique does not require manipulation of the parts, as it is only required that the core move. However, the use of this technique has limitations in terms of the geometry to which it can be applied. In the sliding core method, the entire cavity of the part is extracted from the initial mold volume and sliding cores are purposefully placed inside the mold to restrict or activate flows in certain zones.