Design of Multi-position Progressive Die Carrier
The design of carriers for multi-station progressive dies is a core technology for ensuring stable strip material feeding during continuous stamping. As a bridge connecting parts in each process, the carrier must possess sufficient strength and rigidity, while also providing a reliable reference for the positioning system. The rationality of carrier design directly impacts die stamping accuracy, production efficiency, and part quality. Therefore, targeted design is required based on part shape, material properties, and process schedule. Common carrier forms include edge carriers, intermediate carriers, bridge carriers, and hybrid carriers.
The edge carrier is the most widely used carrier type. Suitable for parts with sufficient excess material at the edge of the strip, the edge material on one or both sides of the strip is retained as a carrier to connect the various stamping stations. The edge width is determined by the material thickness and feeding method, generally ranging from 5-15mm. Thicker material increases the edge width. For example, for a 2mm thick mild steel strip, the edge width is 8-10mm; for a 0.5mm thick thin material, the edge width is 5-6mm. The edge carrier requires locating holes (3-6mm diameter) to serve as a reference for the guide pins. The spacing between the locating holes is equal to the feed distance, with an accuracy of ±0.01mm. To enhance the carrier strength, reinforcing ribs or indentations can be added to the edge material, especially for long parts, to prevent the carrier from bending during feeding.
Intermediate carriers are suitable for situations where parts are distributed in the middle of the strip and there is no margin at the edges. These carriers are formed by retaining connecting ribs between the parts. The width of the intermediate carrier is determined based on the part spacing and load-bearing capacity, generally 1/3-1/2 the minimum part spacing and no less than 3mm. The thickness of the connecting ribs can be the same as the part thickness or slightly thinner (10%-20% thinner) to reduce the difficulty of subsequent separation processes. For example, mobile phone connector parts use intermediate carriers with connecting ribs that are 3mm wide and 0.8mm thick (for part thickness of 1.0mm). This ensures carrier strength and facilitates final punching and separation. The positioning holes of the intermediate carrier must be located on the carrier’s symmetrical centerline to ensure positioning accuracy and prevent strip deviation.
A bridge carrier is a form of carrier with local connections. It is suitable for situations where parts have complex shapes and large spacing between parts. By setting bridge-shaped connecting ribs in local areas of the parts, connections between workstations are achieved. The length of the connecting ribs of the bridge carrier is generally 5-15mm, and the width is 3-8mm. The number is determined according to the size of the part, with 2-3 ribs set for small parts and 4-6 ribs set for large parts. For example, a car dashboard bracket part uses a bridge carrier, and 4 connecting ribs with a width of 5mm are set at the four corners of the part, which not only reduces the weight of the carrier but also ensures feeding stability. The bridge carrier should avoid setting connecting ribs in the key functional areas of the part to prevent affecting the accuracy of the part. The location of the connecting ribs should be selected on the non-matching surface of the part or the cut-off area for subsequent processing.
Hybrid carriers combine the advantages of both edge carriers and intermediate carriers, making them suitable for stamping large, complex parts. The edge carrier ensures overall feed accuracy, while the intermediate carrier enhances local connection strength. The design of the hybrid carrier requires coordinating the force distribution of the two carriers. The edge carrier bears the primary feed force, while the intermediate carrier assists in transmitting torque to prevent part twisting during the forming process. For example, washing machine inner drum parts in the home appliance industry utilize a hybrid carrier. The edge carriers on both sides are 12mm wide, with three 6mm-wide connecting ribs in the middle. These ribs share the deformation force during the drawing process, ensuring that the roundness error of the part is controlled within 0.1mm. The hybrid carrier’s positioning system utilizes positioning holes in both the edge carrier and the intermediate carrier, achieving dual positioning and improving anti-interference capabilities.
Verifying and optimizing the carrier’s strength is a crucial design step. Finite element analysis software (such as ANSYS or ABAQUS) must be used to simulate the carrier’s stresses during feeding and stamping to ensure that the maximum stress does not exceed the material’s yield strength. For high-strength materials (such as DP780), a safety factor of 1.5-2.0 is recommended for the carrier; for mild steel, a safety factor of 1.2-1.5 is recommended. Optimizing the carrier includes increasing local thickness, adding reinforcing ribs, and optimizing the distribution of connecting ribs. For example, designing the connecting ribs to a trapezoidal cross-section (with width gradually decreasing from base to tip) can reduce stress concentration. During the trial stamping phase, the carrier’s deformation should be observed. If bending or tearing occurs, the carrier’s size or structure should be adjusted until it meets the requirements for continuous stamping. Scientifically designed carriers ensure stable operation of multi-station progressive dies and guarantee high-quality production.
