In the manufacturing process of small sheet metal accessories, determining the blanking clearance is a key factor affecting product quality, die life, and production efficiency. A reasonable blanking clearance not only ensures the cross-sectional quality of the accessories, reducing burrs and cracks, but also reduces die wear and extends its service life.
Setting this parameter requires comprehensive consideration of factors such as material properties, sheet thickness, precision requirements of small sheet metal accessories, and die structure. It is ultimately determined through a combination of theoretical calculations and practical adjustments.
Material properties are the fundamental basis for determining the blanking clearance. Different metal materials have significantly different mechanical properties. For example, low-carbon steel has good ductility, requiring a larger clearance during blanking to avoid excessive tearing; while stainless steel has high hardness, and a clearance that is too small can easily lead to die chipping, while a clearance that is too large may cause excessive burrs. For soft metals such as aluminum and copper, which have high fluidity, the blanking clearance needs to be smaller than that of steel to prevent excessive extrusion and deformation. Furthermore, the uniformity of material thickness also affects the clearance selection. If the sheet thickness fluctuates, the clearance must be designed based on the maximum thickness to avoid localized excessive clearance that could damage the die.
The relationship between sheet thickness and clearance follows a certain proportional principle. Generally, blanking clearance is positively correlated with sheet thickness; that is, the thicker the sheet, the larger the clearance required. This is because thicker plates have a larger deformation zone during blanking, requiring more space to release stress. Otherwise, secondary shearing can easily occur, leading to a decrease in cross-sectional quality. For small sheet metal accessories, due to the smaller sheet thickness, even small changes in clearance have a significant impact on the blanking effect, thus requiring more precise control. For example, the reasonable clearance for a 0.5mm thick low-carbon steel plate may be only 8%-12% of the plate thickness, while for a 2mm thick plate, the clearance may increase to 15%-20%.
The precision requirements of the accessories are an important reference for clearance adjustment. If the accessories have extremely high requirements for dimensional accuracy and surface roughness (such as the housing of precision electronic components), a smaller clearance is required to reduce burrs and corner collapse, but this will sacrifice some die life. If the precision requirements are moderate (such as ordinary structural parts), the clearance can be appropriately increased to extend the die life and reduce production costs. Furthermore, the complexity of the shape of small sheet metal accessories also affects clearance selection; complex shapes require smaller clearances to ensure synchronous blanking of all parts and avoid localized deformation.
The die structure and wear condition must be taken into account when adjusting the clearance. The punch and die of a die will wear down over time, causing the clearance to gradually increase. Therefore, the initial clearance setting should allow for wear tolerance. For example, for dies with a large expected production volume, the initial clearance can be slightly smaller than the theoretical value to compensate for later wear. Simultaneously, the guiding accuracy, rigidity, and cutting edge sharpness of the die also affect the clearance effect. High-precision guiding dies can use smaller clearances, while dies with insufficient rigidity need larger clearances to avoid chipping.
In actual production, the theoretical clearance needs to be verified and adjusted through trial punching. Due to factors such as batch differences in materials and fluctuations in equipment accuracy, theoretical calculations often need to be optimized based on on-site trial punching results. During trial punching, samples can be processed according to the theoretical clearance to observe the cross-sectional quality, burr height, and die wear. If the burrs are too large or the cross-section is torn, the clearance needs to be reduced; if the die wears too quickly or the punching force is too high, the clearance needs to be increased. Through multiple adjustments, the optimal clearance value that balances quality and efficiency is finally determined.
Environmental factors and operating procedures also affect the stability of the clearance. For example, excessively high punching speeds may cause the material to tear before it is fully deformed, requiring an increased clearance. Conversely, low temperatures may make the material brittle, necessitating a smaller clearance to prevent cracking. Furthermore, the operator's punching force and lubrication conditions can indirectly affect the clearance, thus requiring standardized operating procedures to ensure the stability of clearance parameters.
Determining the appropriate punching clearance for small sheet metal accessories requires a comprehensive assessment based on material properties, sheet thickness, precision requirements, die condition, and actual trial punching results. Through scientific setting and dynamic adjustment, both accessory quality and die life can be guaranteed, ensuring efficient and stable production.
