## 1 Introduction  
Steel forming is widely used in various industries because it allows for the production of lightweight and strong parts. Bending technology is very widespread [1], which allows the shaping of blanks into desired forms and angles. The components produced by bending form a significant part of steel sheet products. When designing bent parts, it is necessary to respect technological principles [2], which help ensure a quality end product and minimise problems during the manufacturing process. The appropriate material must be selected for the required strength, corrosion resistance, and other specific properties of the component. Appropriate bending radius, bending orientation relative to the rolling direction of the blank, etc. should be selected. Springback affects the final shape of the bent part and the resulting precision of the part [3; 4; 5; 6; 7]. The amount of springback after bending is affected by the radius of the bend, the material, the thickness of the material to be bent, the speed of the bend, and the temperature of the workpiece. Finite element simulations [8; 9; 10] allow for the analysis of stresses and deformations in the material during the forming process and minimise undesirable phenomena such as material springback. For the simulation of sheet metal forming processes, it is important to know their formability [11; 12; 13], which can be expressed by forming limit diagrams. These data are crucial for the development of correct material models in simulation programs. The method of deformation networks can be used for the analysis of material deformations during surface forming [14; 15; 16]. This method is important for the design of forming processes and tool optimisation. Unfilled or reinforced plastic materials can be used to produce bending tools that are loaded at low stress and therefore the life of the tool is sufficient [17; 18; 19]. For plastic tools,the production time and cost are low, whereas the yield stress and Young's modulus are considerably lower than those for steel tools. These cost-effective tools are suitable for small-batch industrial production. Another alternative is to use a flexible punch with natural rubber, silicone rubber, or polyurethane rubber. Polyurethane, which is also commonly known as urethane, turned out to be the most suitable for metal-forming applications. Rubber pads in this method may be constructed either solidly or laminated. A laminated pad comprises sheets of rubber placed on top of each other. The advantage they have is that the working surface can be restored simply by turning the top layer over or replacing it. Tools can be made of inexpensive, easy-to-machine materials due to the hydrostatic pressure exerted on them. Parts with an excellent surface finish can be formed as no tool marks are created. Also, in this kind of forming process, set-up time is considerably shorter as no lining-up of tools is necessary. However, the rubber pad forming process has certain disadvantages. The rubber pad has a limited lifetime that depends on the severity of the forming in combination with the pressure level. When rubber is used as the pressure-carrying medium, a lack of sufficient forming pressure results in parts with less sharpness, which may require subsequent hand work. The production rate is relatively slow [20; 21; 22]. In sheet metal bending, rigid metallic tools are the most commonly used [23; 24]. Bending tools should be made of material with sufficient hardness and strength to withstand pressure and wear during material forming. The bending tools are designed to minimise the springback of the formed material [25; 26]. The optimal bending radii, bending angles, and tool geometries are selected. When producing large quantities of parts, it is important to increase the useful life of the tool to achieve production efficiency and minimise costs.