Shenzhen HSJ Metal Fabrication Co., Ltd.
Shenzhen HSJ Metal Fabrication Co., Ltd.

Common Defects and Causes of Sheet Metal Stamping Process

Sheet metal stamping is a widely used manufacturing process that involves forming, bending, cutting, and deep drawing metal sheets to create various components for industries ranging from automotive to electronics. While sheet metal stamping is known for its efficiency and precision, it is not immune to defects that can compromise the quality of the final product. Understanding these defects is crucial for manufacturers to implement preventive measures and ensure the production of flawless sheet metal components.

Common Sheet Metal Stamping Defects

  • Tearing: Tearing occurs when excessive force is applied during the stamping process, causing the metal sheet to rupture or tear. This defect is often linked to improper tool design, inadequate lubrication, or incorrect material thickness.

  • Wrinkling: Wrinkling is characterized by folds or creases on the surface of the stamped metal. It is usually a result of insufficient tension between the metal sheet and the die, causing the material to fold instead of smoothly conforming to the die shape.

  • Springback: Springback happens when the metal sheet does not fully return to its original shape after the stamping process. This defect is more prevalent in materials with high elasticity and can be influenced by factors such as material properties, tooling design, and process parameters.

  • Buckling: Buckling occurs when the metal sheet collapses or deforms due to excessive compressive forces during stamping. Inadequate support, improper die clearance, or material inconsistency can contribute to this defect.

  • Edge Cracking: Edge cracking is the formation of cracks along the edges of the stamped metal. This defect is often caused by inadequate lubrication, excessive material hardness, or improper tooling design.

  • Die Marking: Die marking refers to the impressions or markings left on the surface of the stamped metal by the die. This defect can result from using a worn-out or improperly maintained die, leading to a compromised final product.

Common Defects In The Different Sheet Metal Stamping Steps

The three elements of sheet metal stamping: the reasonable stamping technology, advanced molds, and efficient stamping equipment. Stamping die is special process equipment for processing materials into parts (or semi-finished products) in stamping processing. There are sheet metal defects or we say defects in sheet metal forming of sheet metal stamping process, for example, burr defect in sheet metal. Sheet metal forming defects are not a rare phenomenon. As one of the most experienced sheet metal fabrication suppliers, HSJ has rich experience with common sheet metal stamping defects that might occur during the process and how to prevent them from happening. The following is an introduction to common defects and their causes in the sheet metal stamping process.

1. Stamping Defects When Blanking, Punching, Trimming

Defects: excessive burrs, deformation, surface scratches, size inconsistencies, few holes, etc.

1) The burr is too large → the gap between the convex and concave die is too large or too small; the cutting edge is worn; the guiding accuracy is poor; the position of the convex and concave die is not concentric, etc.

2) Deformation → The hole distance is too small; the pressure plate does not fit well with the concave mold surface; the gap is too large, etc.

3) Surface scratches → drag and pull during operation; the sheet material is scratched during the cutting process.

4) Inconsistent size → material loading is not in place; positioning device is damaged or loose, position shifting, etc.

5) Fewer holes → the punch are broken; the length of the punch is not enough.

2. Stamping Defects When Drawing

Defects: the flanging is not vertical, the flanging height is inconsistent, the flanging is rough, the flanging is cracked, etc.

1) Flanging is not vertical → the gap between the convex and concave molds is too large.

2) Inconsistent flanging height → uneven gap between convex and concave molds; inaccurate positioning; the inaccurate size of blanking parts.

3) Flanging and roughening → There are scars on the cutting edge; there are impurities on the surface of the part; the cutting edge hardness is too low.

4) Flanging crack → large burrs when trimming; the gap between the convex and concave molds is too small; there is a sudden change in the shape of the flanging.

3. Sheet Metal Bending Defects

Defects: unqualified sheet metal bending angle, cracked bending edge, step at bending R angle, etc.

1) The bending angle is unqualified → the gap between the convex and concave molds is too large, and the matching angle of the convex and concave molds does not match the thickness of the plate material.

2) The bending edge is broken → the gap between the punch and the die is too small; the bending angle is too small; the punching force is too large and the speed is too fast; the plate material is too hard.

3) The bending R angle has steps → the convex and concave die bending angle is too large; the outer R angle is too large; the bending force is too small.

Preventive Measures for Sheet Metal Stamping Defects

  • Proper Tooling Design:

    Ensuring that the stamping tools are designed with precision and accuracy is essential to minimize defects. This includes selecting the appropriate die clearance, maintaining proper clearances, and optimizing the tool geometry.

  • Material Selection:

    Choosing the right material for the specific application is crucial. Material properties, such as thickness and ductility, play a significant role in preventing defects. Understanding the behavior of the material under different conditions is essential for successful stamping.

  • Optimal Lubrication:

    Adequate lubrication is essential to reduce friction between the metal sheet and the stamping tool. Proper lubrication helps prevent tearing, wrinkling, and edge cracking, contributing to a smoother stamping process.

  • Controlled Process Parameters:

    Monitoring and controlling process parameters, such as press speed, feed rate, and temperature, are vital to prevent defects. Consistent and controlled conditions throughout the stamping process contribute to a higher-quality end product.

  • Regular Maintenance:

    Regular maintenance of stamping equipment, including dies, ensures that the tools are in optimal condition. This helps prevent die marking and other defects associated with worn-out or damaged tools.

Sheet metal stamping defects can be detrimental to the quality and functionality of the final product. Manufacturers must prioritize a holistic approach to prevent these defects by incorporating proper tooling design, material selection, lubrication, and process control. By understanding the root causes of common defects and implementing preventive measures, the sheet metal stamping process can consistently yield high-quality components for diverse industrial applications.

As one of the most professional China custom sheet metal fabrication suppliers, HSJ has specialized in custom metal fabrication. We can provide our customers with the highest-quality materials, the best technologies, and the most efficient welding processes. If you are looking for a reliable custom sheet metal fabrication supplier, don't hesitate to contact us.

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