Design of progressive die for card punching and blanking
Progressive die design for card punching and blanking is a highly efficient forming technology for various card types (such as bank cards, membership cards, and time cards). It continuously completes the punching (positioning holes and functional holes) and blanking processes within a single die, achieving a production rate of 300-500 pieces/minute with a dimensional accuracy of ±0.05mm. It is suitable for processing plastic cards such as PVC and PET, as well as thin steel sheets (0.1-0.5mm thick). Compared to single-stage dies, progressive dies reduce process cycles and improve hole positioning accuracy (hole pitch tolerance <0.03mm). Initially, the number of stations should be determined based on the card size (typically 85.5mm × 54mm) and hole distribution. Typically, three to four stations are used: the first station punches the positioning holes, the second the functional holes (such as magnetic stripe holes and chip holes), the third the blanking, and the fourth (optional) inspection.
The die structure consists of upper and lower die bases, a punch assembly, a die assembly, a feed mechanism, a positioning device, and a discharge device. The punch is designed according to the hole profile. The punch is made of high-speed steel W18Cr4V, hardened to HRC 62-65, with a cutting edge diameter tolerance of IT6. For a φ2mm hole, the punch diameter is set to φ2-0.01mm to ensure precise hole dimensions. The blanking punch conforms to the card shape and is made of Cr12MoV, hardened to HRC 58-62, with a cutting edge sharpness of Ra 0.8μm or less. The die is a monolithic structure made of cemented carbide (WC-Co) with a hardness of HRA 89-91. The clearance between the punch and die is 5%-8% of the material thickness. For 0.3mm thick PVC cards, the clearance is set to 0.015-0.024mm to reduce burrs.
The feeding and positioning system is the core of the progressive die. A servo motor-driven roller feeder offers a feed step accuracy of ±0.01mm. A high-precision ball screw controls the feed speed, synchronized with the stamping frequency (300-500 strokes/minute). The positioning system utilizes guide pins in conjunction with positioning holes, with one set of guide pins installed for every two workstations. The diameter of the guide pins is 0.01-0.02mm smaller than the positioning holes, ensuring a card positioning error of less than 0.02mm at each workstation. For plastic cards, a tension control device is installed along the feed path to maintain a stable material tension of 5-10N to prevent card deformation.
The unloading and waste removal systems must accommodate high-speed production. Each station is equipped with a flexible unloading plate, powered by polyurethane rubber. The unloading force is 8% to 12% of the punching force, ensuring smooth card removal from the punch. Punched waste is discharged through a waste hole at the bottom of the die. The hole diameter is 0.5 to 1mm larger than the waste material and is tilted at a 10° to 15° angle to facilitate the flow of waste into a collection bin. After the cards are dropped, they are transported to the next processing step by a conveyor belt. The conveyor belt speed is matched to the drop frequency to prevent card accumulation.
Commissioning and maintenance must ensure high-speed stability. During mold trials, a high-speed camera is used to capture the punching process, analyzing card warping or hole offset. The feed pitch is then adjusted (±0.005mm each time) until acceptable. An image measuring instrument is used to inspect card size and hole position, with 50 pieces inspected per hour, and a pass rate of ≥99.5%. During routine maintenance, the punching punch is replaced every 100,000 pieces, and the die edge is inspected for wear (reground if wear exceeds 0.01mm). The feed roller is cleaned weekly to remove surface oil and debris, and the guide pin is inspected every 50,000 pieces to ensure accurate fit with the locating holes. The mold must be equipped with an overload protection device that automatically shuts down when the punching force exceeds 10% of the set value to prevent damage.