In the precision stamping of speaker short circuit ring stretched copper, determining the blanking clearance is a crucial step affecting part quality, die life, and production efficiency. The blanking clearance refers to the dimensional difference between the cutting edges of the punch and die; its rationality directly determines the cross-sectional quality, dimensional accuracy, and die wear rate. For materials like speaker short circuit ring stretched copper, which have excellent ductility but low hardness, the clearance value must be determined comprehensively based on material properties, part requirements, and process conditions.
Speaker short circuit ring stretched copper has strong plastic deformation capabilities, and excessive material compression can easily occur during blanking if the clearance is too small. When the clearance is less than a reasonable range, the dual compression effect of the punch and die on the material intensifies. While the bright band may increase, the fracture zone is significantly shortened, and the burrs appear as cracks and increase in volume. Simultaneously, an excessively small clearance exacerbates frictional wear on the die cutting edges, leading to increased blanking and unloading forces. This not only increases energy consumption but may also cause die jamming or chipping. For parts like speaker short circuit rings that require high dimensional accuracy, an excessively small clearance can also reduce dimensional stability due to increased material elastic recovery, affecting assembly accuracy.
If the blanking clearance is too large, the fracture zone of the speaker short circuit ring stretched copper will expand due to increased tensile stress, resulting in a shortened bright band, increased collapse angle, significantly increased burr height, and a rougher morphology. This cross-sectional quality defect directly affects the conductivity and mechanical strength of the short circuit ring, and may even lead to a short circuit risk due to burr detachment. Furthermore, an excessively large clearance reduces the dimensional accuracy of the part, especially for thinner speaker short circuit ring stretched copper materials. An excessively large clearance can easily lead to an oversized punch diameter or an undersized blanking size, exceeding tolerance limits. Regarding die life, an excessively large clearance accelerates cutting edge wear, but compared to an excessively small clearance, the wear rate is usually slower, although the decline in part quality is more pronounced.
The determination of a reasonable blanking clearance should be based on the principle of "overlapping upper and lower cracks," meaning that the cracks generated by the punch and die cutting edges during blanking should be on the same straight line to avoid secondary shearing or tearing of the material. For speaker short circuit ring stretched copper materials, the reasonable clearance range usually needs to be determined through experimental optimization, generally falling within a small percentage range of the material thickness. When selecting a blanking clearance, if the part requires high cross-sectional quality, such as a high proportion of bright bands and minimal burrs, a smaller clearance should be preferred. If die life and reduced punching force are prioritized, the clearance can be appropriately increased. For example, when punching a thin speaker short circuit ring (stretched copper), if a smooth, burr-free edge is required, the clearance can be controlled close to the lower limit. For parts with greater thickness or moderate dimensional accuracy requirements, a middle value can be selected to balance quality and efficiency.
Die manufacturing precision is crucial for achieving the correct blanking clearance. High-precision die machining and assembly ensure uniform clearance distribution, avoiding quality fluctuations caused by excessively large or small local clearances. For example, when using wire EDM, the clearance between the punch and die needs to be compensated by considering the electrode wire diameter, discharge gap, and grinding amount to ensure the actual clearance does not exceed the maximum initial clearance value. Furthermore, the precision of the die guiding system also affects clearance stability; high-precision guide pillars and bushings effectively reduce offset during the punching process, ensuring clearance consistency.
Trial die testing is a key step in verifying the rationality of the blanking clearance. The suitability of the clearance can be determined by observing the cross-sectional quality, dimensional accuracy, and working condition of the stamped part. If the bright band accounts for about one-third of the sheet thickness, burrs and warping are small, and unloading and pushing are smooth, the clearance is basically reasonable. If the sheet can easily detach from the punch without using an unloading spring, or if the sheet punched into the die easily falls through the sprue hole, the clearance may be too large. Conversely, if unloading is difficult or the die shows abnormal wear, the clearance is too small. For precision parts such as speaker short-circuit rings, actual assembly testing is required to verify dimensional accuracy and performance stability, and fine-tuning of the clearance may be necessary.
