An introduction to the application and development of lower-die technology for thick-plate bending in press brakes—save this now!

What are the applications and developments of the lower-die process for thick-plate bending in press brakes according to bending standards? Let’s briefly analyze this together below.

The material thickness typically defined as “medium-to-thick plate” in our industry generally ranges from 4 to 15 mm. For commercial-vehicle manufacturers, the processing of frame components made from medium-to-thick plate mainly encompasses cold bending, CNC punching, stamping, press braking, and blanking/cutting. Among these processes, the standard die-based press-braking technique for thick plates has been in use for many years and has now reached a mature stage. Moreover, driven by industry trends, this process is progressively evolving toward greater automation, intelligence, and digitalization, giving rise to a wide array of innovative die designs, process methodologies, and inspection methods for press braking.

Compared with traditional bending processes, it has achieved significant breakthroughs in terms of efficiency, precision, operational complexity, labor intensity, and manufacturing costs. Moreover, when contrasted with other machining technologies, bending offers a shorter production preparation cycle and lower costs, making it highly favored by a wide range of enterprises due to its flexible processing capabilities. It is foreseeable that this flexible manufacturing technology will continue to evolve and find broader applications.

Medium- and thick-plate bending refers to the process of altering the angle of conventional sheet metal or plate components, such as bending a plate into V-shaped or L-shaped configurations. Currently, for our frame-type bent parts, the primary method for manufacturing frame connection plates is punch press bending. Among our main products, V-shaped and L-shaped thick-plate connection plates are predominant, with 500L steel being the most commonly used material. The tensile strength typically ranges from 500 to 750 MPa. Due to the material properties and thickness characteristics of medium- and thick-plate stock, individual part weights generally fall within the 10–35 kg range, while the width and length of the blanks vary considerably depending on the product design. This poses significant challenges in terms of processing efficiency, cost, and the physical workload of operators. Many of these parts serve as load-bearing and connecting components, demanding high dimensional accuracy; therefore, careful planning of the initial bending process layout is essential.

What are the key considerations for the lower die when following the bending standards for thick plates on a press brake? Let’s take a brief look at this together below.

When bending small- or long-sized sheet metal, care must be taken to avoid safety hazards caused by contact between the workpiece and the die or machine frame.

During the bending process using the standard lower die for thick-plate bending, no personnel other than authorized staff are permitted to remain in the press brake area to ensure worker safety. Workers must not place their hands or any other part of their body between the upper and lower dies of the press brake. The dies must be inspected regularly for looseness or potential displacement to ensure they are securely fastened and to prevent accidents. If a malfunction occurs in the press brake system or an emergency situation arises, the emergency stop button must be pressed; if the press brake does not stop, the root cause must be identified and the fault rectified before the machine can be restarted.

The selection of the bending angle is, of course, closely related to the product requirements. Generally speaking, when using a die for a 90° bend, the intermediate angle should be set larger than the angles at the two ends; in some cases, this may result in a tighter fit, which can be adjusted by tweaking the screws on the machine. Once the adjustment is made, as long as the product’s market demand remains unchanged, no further modifications to the process parameters should be undertaken. During the bending operation, use the pressure gauge to obtain an accurate pressure reading and then adjust the pressure accordingly.