Design of strip material spacing mechanism
The strip (or bar) spacing mechanism is the core device that ensures accurate strip feed distance during the continuous stamping process. Its function is to control the distance the strip is fed each time, ensuring that the stamping process at each workstation is carried out in the correct position. The spacing accuracy directly affects the dimensional consistency of the stamped parts and the service life of the mold. Therefore, the design of the spacing mechanism must select the appropriate structure and positioning method based on factors such as the precision requirements of the stamped parts, production batch, and feed speed. Common spacing mechanisms include stop pin spacing, side blade spacing, guide pin spacing, and servo feed spacing, each with its own scope of application and design characteristics.
The stop pin spacing mechanism is the simplest spacing method and is suitable for applications with low precision requirements (step tolerance ±0.1mm) and small production batches. Stop pins are categorized as fixed, movable, and starting. Fixed stop pins are mounted directly on the die or unloading plate and limit the feed distance by contacting the edge of the strip. Movable stop pins are spring-controlled, retracting as the strip is fed and popping out to prevent it from backing out. Starting stop pins are used for initial positioning of the strip, ensuring accurate stamping position at the first workstation. The working diameter of the stop pin is typically 5-10mm, and the head requires a rounded corner (R0.5-R1mm) to prevent scratching the strip. During design, the contact point between the stop pin and the strip edge should be located at the overlap of the strip to avoid affecting the shape of the stamped part. The height of the stop pin should be 1-2mm higher than the strip thickness to ensure reliable stoppage.
The side blade spacing mechanism achieves spacing by punching a notch of a certain width on the edge of the strip. It is suitable for continuous dies with high step accuracy requirements (±0.05mm). The length of the side blade is equal to the feeding pitch, and the width is determined according to the thickness of the strip, generally 1.5-2 times the thickness of the strip, to ensure that the notch after punching can cooperate with the subsequent stop block to achieve precise positioning. The side blades are divided into rectangular side blades, stepped side blades and pointed side blades. Rectangular side blades are suitable for ordinary strips, stepped side blades can reduce the punching force, and pointed side blades are suitable for strips with narrow overlaps. The fitting clearance between the side blade and the die must be consistent with the blanking clearance. The edge of the notch after punching should be flat and free of burrs, otherwise it will affect the spacing accuracy. In order to prevent the waste material punched by the side blade from affecting the feeding, a waste discharge channel must be set under the die. The channel width must be 2-3mm larger than the side blade width.
Guide pin spacing mechanisms are typically used in conjunction with side cutting edges or stop pins to achieve highly accurate spacing (step tolerance ±0.01-±0.03mm), making them suitable for the production of precision stamped parts. Guide pins are mounted on the punch mounting plate and inserted into locating holes in the strip ( punched in a previous process) during the stamping process, mechanically correcting strip positional deviations. The guide pin’s diameter is 0.01-0.02mm smaller than the locating hole, and its head is conical (60° angle) for smooth insertion. The head length should be 1-2mm greater than the strip thickness to ensure effective guidance. During design, guide pins should be positioned as close to the stamping station as possible to minimize the accumulation of positioning errors. For multi-station progressive dies, guide pins should be installed at each station, forming a continuous positioning correction system. The synchronization of the guide pin and the punch must be strictly controlled to ensure that the guiding action is completed before the stamping action, preventing strip displacement during stamping.
The servo feeder distance-fixing mechanism is the most automated distance-fixing method. It uses a servo motor to drive the feed roller or clamp, achieving digital control of the step distance. Its distance accuracy can reach ±0.01mm, making it suitable for high-speed, high-precision strip stamping production lines. The core of the servo feeder mechanism is a servo motor and ball screw (or synchronous belt) drive system. The feed distance and speed are controlled by a PLC, allowing real-time adjustment of the step distance to compensate for stretching or shrinkage of the strip. The feed roller diameter is selected based on the strip thickness. Thin materials (≤1mm) require a 50-80mm diameter, while thick materials (>1mm) require a 100-150mm diameter. The roller surface should be knurled or sprayed with a wear-resistant coating to increase friction with the strip. The servo feeder mechanism must be strictly synchronized with the stamping action of the die, using an encoder for position feedback to ensure that feeding is complete before stamping begins to avoid interference.
The design of the spacing mechanism needs to take into account the elastic deformation of the strip and the feeding resistance. For high-strength strips (such as high-strength steel plates), the force of the spacing mechanism needs to be appropriately increased. For example, the punching force of the side blade needs to be increased by 20%-30% compared to ordinary strips to prevent incomplete punching from affecting the spacing. During the continuous drawing process, the strip will change in length due to plastic deformation. The spacing mechanism needs to be equipped with a compensation function, such as adding a tension sensor to the servo feeding system to adjust the step distance in real time to compensate for the stretching of the material. The maintenance of the spacing mechanism is also crucial. The waste and oil stains on the stop pins and side blades need to be cleaned regularly, and the wear of the guide pins needs to be checked to ensure the long-term stability of the spacing accuracy. By rationally selecting the type of spacing mechanism and optimizing the design parameters, it is possible to improve production efficiency and mold life while ensuring the accuracy of stamping parts.
