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What are the factors that affect the bending accuracy of CNC press brakes?

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When using a CNC press brake to bend workpieces, it is common for the bending accuracy to not meet the required standards. As operators, we need to have good judgment, and consider the following four main factors:

CNC press brakes

1. Material Factors

Flatness of the reference surface: The flatness of the reference surface of the sheet metal, whether the material’s stress is evenly distributed, and whether the thickness of the material is consistent—all these factors impact the accuracy of the press brake. Uneven reference surfaces and inconsistent material thickness can cause uneven bending. Therefore, the thickness, quality, and shape of the sheet metal are very important.

Residual stress in sheet metal: Residual stress generated during the production of metal sheet (such as steel, aluminum, copper, etc.) can affect the deformation during the bending process, leading to accuracy issues.

Material properties: Different metals (such as steel, aluminum, copper, etc.) have varying bending properties and physical characteristics. For example, certain alloys may be more prone to plastic deformation or stress concentration, which can affect the final bending accuracy. In addition, surface contamination, rust, or coatings on the material may interfere with the contact between the mold and the workpiece, thereby affecting accuracy.

Temperature variation: Temperature changes can lead to the expansion or contraction of metal materials, especially in large-scale bending operations. Variations in the temperature of the machine structure, mold, and sheet metal can cause small dimensional deviations. Special attention must be paid to temperature control when operating the press brake in high or low-temperature environments.

2. Die Factors

Accuracy of the upper and lower dies: If the dimensions of the upper and lower dies do not meet the required standards or are severely worn, bending accuracy will be affected.

Lower die compensation system: The precision of the lower die compensation device and its compatibility with the machine frame design are also important. If the compensation system is inaccurate or does not match the machine frame, it can lead to uneven distribution of bending force, affecting accuracy.

CNC press brakes

3. Mechanical Factors

Linear accuracy of the slide clamping points (Y-axis, X-axis): If the slide’s linearity is inaccurate, it will lead to unbalanced movement of the slide, thus affecting bending accuracy.

Repeat positioning accuracy and arbitrary positioning accuracy of Y1 and Y2: If the positioning accuracy is insufficient, the size and angle of the bent workpieces may not be consistent.

Strength and precision of the machine frame and slide: The stability and strength of the frame affect the rigidity of the entire bending process. If the frame is unstable, the slide may fail to maintain an accurate motion path, thus compromising accuracy.

Repeat positioning accuracy and arbitrary positioning accuracy of the backgauge system (X-direction, R-direction): The backgauge system plays an important role in controlling the position of the workpiece. If the backgauge system is inaccurate, it will lead to incorrect positioning of the workpiece and affect the bending precision.

4. Human Factors

Consistency of the operator’s pushing force: The operator’s left and right pushing force on the sheet metal should be consistent. Any variation in the force applied can lead to uneven bending, affecting the final precision.

The above are the four main factors that affect the bending accuracy of CNC press brakes. In addition, as the CNC press brake is used over time, mechanical components such as slides, bearings, and guide rails will gradually wear down, which can lead to inaccuracies in movement and, consequently, affect bending precision. Furthermore, failures in hydraulic pumps, cylinders, or valves can cause pressure instability, which in turn affects the bending force and ultimately impacts accuracy. Therefore, regular maintenance and replacement of worn parts are essential to maintaining the press brake’s precision. To improve bending accuracy, operators need to consider these factors comprehensively and take appropriate optimization measures.

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I'm Jackson Cao, founder of prima-press, with over 30 years in the sheet metal industry. Our goal is to deliver valuable content related to sheet metal processing to a wider audience. Don't hesitate to get in touch—I'm delighted to offer top-tier service and products. Welcome to a world of premium sheet metal expertise!

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