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Top 3 Differences Between Levelers and Straighteners

Roller Leveler

In the world of metal fabrication, precision and quality are paramount. Two essential machines, roller levelers and straighteners, play pivotal roles in achieving these goals. However, there is a persistent misunderstanding regarding these machines. While both aim to make metal parts flat and straight, their methods and outcomes differ significantly.

Roller Levelers vs. Straighteners: Top 3 Differences

Differences 1#: Processing Technology

  • Roller Levelers: Roller levelers primarily employ a series of rollers or rollers with adjustable settings. These rollers apply consistent pressure across the width of the material to gradually flatten and remove unevenness.
    Roller levelers can have various configurations, including two-roll, four-roll, or even multi-roll designs.
    A roller leveler can have up to 33 rollers. As the material goes through the series of rollers, stresses are removed and the desired flatness is achieved. The rollers underneath the main leveling rollers are backups for maximum rigidity and machine longevity.
  • Straighteners: Straighteners use rollers or bending rolls to reshape metal parts.
    They typically involve passing the material through rollers in multiple passes and adjusting the rolls to gradually correct any bends or distortions.
    Straighteners may have three or more rolls, depending on the complexity of the straightening task.

Differences 2#: Purpose

  • Roller Levelers: Roller Levelers(also called plate leveling machines) are designed to eliminate or significantly reduce internal stresses within metal sheets or parts. They are used to achieve uniform flatness and thickness throughout the material. Levelers are commonly used in industries where precision and uniformity are critical, such as manufacturing automotive body panels, steel processing, and metal fabrication.
  • Straighteners: The primary purpose of straighteners is to correct the shape of metal parts that have become bent, twisted, or distorted during manufacturing or handling. Straighteners aim to make the parts appear straight and free of visible deformations. They are not designed to eliminate internal stresses within the material.

Differences 3#: Applications

  • Roller Levelers:
    Roller levelers are suitable for a wide range of material thicknesses, from thin sheets to thicker plates.
    They are ideal for materials that require consistent flatness and low internal stresses, which is essential for subsequent processing steps like welding, cutting, or stamping.
  • Straighteners:
    Straighteners are commonly used in industries where the appearance and visual quality of the final product are critical, such as in the production of architectural components, furniture, or decorative metalwork.
    They are suitable for correcting minor to moderate deformations in metal parts, making them visually appealing and aesthetically pleasing.

The Role of a Straightener

A straightener, often a three- or four-roll bender, is a machine designed to correct the shape of metal parts. It’s a common misconception that passing a part through a straightener once will make it perfectly flat and stress-free. However, the reality is more complex.

  • Straightening Process: When using a straightener, a skilled operator may need to turn the part around and pass it through the machine multiple times. This process gradually bends and reshapes the part until it appears straight and flat to the naked eye.
  • Residual Stresses Remain: The crucial point of contention lies in the fact that even after multiple passes through a straightener, residual stresses within the material often persist. These internal stresses can be a ticking time bomb, especially when the metal part undergoes subsequent heating during the fabrication process.

Challenges with Simple Straightening

  • Multiple passes may be required.
  • Residual stresses often remain.
  • Parts may warp upon heating during fabrication.
AspectLevelersSimple Straighteners
PurposeLeveling metal parts to achieve flatness and reduce internal stresses.Correcting the shape of metal parts to make them appear flat and straight.
Internal Stress RemovalYes, removes or significantly reduces internal stresses.No, internal stresses often persist.
Heating During FabricationParts are less likely to warp due to reduced internal stresses.Parts may warp when heated due to remaining internal stresses.
Comparison of Roller Levelers and Simple Straighteners

The Hidden Challenge

While the parts may appear straight and flat after being processed through a simple straightener, they often conceal high internal stresses. These residual stresses become particularly problematic when the parts reach the welding stage of fabrication.

  • Welding and Residual Stresses: When metal parts with high internal stresses are welded together, a new set of challenges arises. The welding process introduces heat, causing the metal to expand and contract. If the internal stresses have not been adequately addressed, the parts can start to bow and deform during welding, leading to inaccuracies in the welds.
  • Ensuring Accuracy: Accuracy is critical in welding, especially when multiple parts need to be joined together seamlessly. Any deformation or bowing can compromise the structural integrity of the final product, leading to a cascade of issues downstream.


In the realm of metal fabrication, the distinction between plate leveling machines and straighteners is crucial. Levelers, with their ability to remove or significantly reduce internal stresses, play a pivotal role in ensuring that metal parts remain flat and stable, even when subjected to heating during fabrication. On the other hand, simple straighteners may make parts appear straight but often leave behind internal stresses that can wreak havoc during welding.

Understanding the limitations of straighteners and the benefits of levelers is essential for achieving high-quality, precise fabrication results. Investing in the right equipment and processes can make all the difference in avoiding the pitfalls of residual stresses and ensuring that metal parts remain flat, straight, and accurate throughout the entire manufacturing journey. In the end, the key lies in addressing internal stresses rather than merely pushing them around, ensuring that the final product meets the highest standards of excellence.