Overlap and strip width
Overlap and strip width are important parameters in stamping process design, directly impacting material utilization, part quality, and die life. Overlap refers to the excess material on the strip, between stamping parts, and between the stamping parts and the strip edge. Its function is to ensure sufficient rigidity and strength of the strip during the stamping process, prevent deformation and deviation of the strip during feeding, and provide a positioning reference for the die positioning device. Strip width refers to the lateral dimension of the strip. It needs to be determined based on factors such as the size of the stamping part, the overlap value, and the feeding method to ensure that the strip can be smoothly fed into the die and the quality of the stamping part is guaranteed.
The overlap size has a significant impact on stamping production. Excessive overlap increases material consumption and reduces material utilization; too small an overlap results in insufficient rigidity and strength in the strip, making it prone to deformation and misalignment during the stamping process, affecting the quality of the stamped part and potentially even damaging the die. Therefore, the overlap value should be appropriately determined based on factors such as the part’s shape, size, material thickness, material properties, and feeding method. Generally speaking, a larger overlap value is recommended for thicker materials, poorer material plasticity, more complex part shapes, and manual feeding. Conversely, a smaller overlap value is recommended. For example, for 1mm thick mild steel sheet, when manually fed, the overlap between stamped parts is typically 1-1.5mm, and the overlap between the stamped part and the strip edge is typically 1.5-2mm.
The shape and position of the overlap will also affect the quality of the stamped parts and the utilization rate of the materials. The shape of the overlap should be as simple as possible, avoiding sharp corners and complex curves to reduce material waste and the difficulty of mold processing. The position of the overlap should be determined according to the shape of the stamped part and the feeding direction. Generally speaking, the overlap should be set in the non-working part of the stamped part to avoid affecting the performance of the stamped part. In continuous stamping, the overlap also needs to cooperate with the positioning device of the mold to ensure the correct feeding of the strip. For example, in a continuous mold using side blade positioning, the side blade will punch out a notch of a certain shape on the edge of the strip. The position of the overlap needs to be coordinated with the position of the side blade to ensure the accurate feeding distance of the strip.
The determination of strip width requires consideration of factors such as the lateral dimensions of the stamped part, the overlap value, the strip positioning method, and the feeding method. The basic formula for calculating strip width is: Strip width = maximum lateral dimension of the stamped part + 2 × overlap value + correction value. The correction value is set to take into account the width deviation of the strip during the rolling process and the offset during the feeding process, and is generally set to 0-2mm. In actual applications, the determination of strip width also needs to be adjusted according to the structure and positioning method of the mold. For example, for molds that use guide plates for positioning, the strip width should be 0.1-0.3mm smaller than the distance between the guide plates to ensure that the strip can be fed smoothly between the guide plates; for molds that use side blades for positioning, the strip width also needs to take into account the width of the side blade punching.
The layout of the strip also affects the strip width and material utilization. The layout of the strip refers to the arrangement of stamping parts on the strip. Common layouts include straight, diagonal, opposite, and mixed. Different layouts have different characteristics and applications. Straight is suitable for simple, small stampings, achieving high material utilization. Diagonal layout is suitable for stampings with complex shapes and sharp corners, reducing overlap and improving material utilization. Opposite layout is suitable for symmetrical stampings, fully utilizing the strip space and improving material utilization. Mixed layout is suitable for stampings of various shapes, improving strip utilization. When selecting a layout, it is necessary to comprehensively consider factors such as the stamping part’s shape, size, production batch, and material utilization to select the most appropriate layout.
In actual production, the overlap and strip width must be optimized and adjusted to improve material utilization and part quality. Computer-aided design (CAD) software can be used to design and optimize the layout, simulating material utilization and part quality under different overlap values and strip widths to select the optimal parameters. Furthermore, during the trial punching process, the overlap and strip width must be adjusted based on actual conditions. For example, if the dimensional accuracy of a stamped part fails to meet standards, this may be due to an inappropriate strip width or an undersized overlap, requiring adjustment. If material utilization is too low, the layout and overlap values must be optimized. Through continuous optimization and adjustment, material utilization can be maximized and production costs reduced while ensuring part quality.
