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    6 Sheet Metal Rolling Defects and How to Avoid Them

    6 Sheet Metal Rolling Defects and How to Avoid Them

    What are common sheet metal rolling defects?

    1. Impurities
    2. Edge cracks
    3. Alligator cracks
    4. Wavy edges
    5. Zipper cracks
    6. Center buckling

    Sheet metal is a diverse material. It can be processed by many different tools and machines and manipulated into a wide variety of shapes. They form a large majority of products we use daily. For example, sheet metal components make up your HVAC system, your refrigerator, your metal roofs and doors, and much more.

    As such, the sheet metal manufacturing process is an important one. However, many problems can occur when processing this material, particularly in the rolling procedure. In this article, we’ll cover all the potential sheet metal rolling defects you can encounter, and how you can avoid them.

    Impurities

    Prior to using your rolling machine, you may notice that your sheet metal has surface impurities. These may be due to mishandling of sheet metal during transport or storage, or from previous processing.

    Here are a few impurities your sheet metal could have:

    • Imperfections — Such as dust, rust, and scratches.
    • Lap — When a corner or fin of the sheet metal is folded over but not welded to the surface.
    • Mill shearing — These look like feather-like laps, caused by mill defects.
    • Scabs — Patches of loose metal and debris that have been pressed onto the surface of the sheet metal.
    • Seams — Open lines that appear along with the sheet metal, caused by the presence of metal scales.

    These defects can be smoothed out of the sheet metal before proceeding to roll. Some methods you could use are grinding with air chisels or grinders, burning with a torch to remove scabs and debris, or others.

    Edge Cracks

    Edge Cracks

    During the rolling process, the sheet metal may come off the machine with cracks along its edges. This defect is called edge cracks and happens when there are high tensile stresses. High tensile stresses occur from uneven heating, uneven rolling, or excess quenching.

    To avoid this, ensure that the rolling process is adjusted to the strength and thickness of the workpiece. Using edge rolls can also help in achieving uniform, faultless sheet metal pieces. Trimming can also remove any edge cracks that occur despite your adjustments.

    Alligator Cracks

    Your sheet metal workpiece may also split into separate pieces during rolling. The opened section of slabs may resemble an open alligator mouth — hence the name. This can happen if your machine is pressing down too hard or causing too much friction on the sheet metal, causing it to react strangely.

    It can also happen when the metal content of the sheet metal is not uniform, such as having too much carbon content in one area, which causes metallurgical weakness.

    To resolve this, you could use cambering. Otherwise, try eliminating the load that causes deflection and friction. Go for less weight and tension. You could also use a larger diameter roller and thicker materials.

    Wavy Edges

    Wavy Edges

    Another common sheet rolling defect is wavy edges. Your workpiece can become thinner on the edges and thicker in the middle, creating wavy, uneven edges. This may happen when there is a deflection involved under the load in a rolling machine.

    You could use hydraulic jacks to prevent wavy edges. Using jacks will help control the elasticity and deformation of the sheet metal as per your requirements. Using smaller diameter rolls will also help in preventing wavy edges.

    Zipper Cracks

    Small cracks may also appear in the middle of your workpiece. This phenomenon is called zipper cracks and can be caused by the bending of the sheet metal under high rolling pressure. This causes stress to build up towards the center, creating small bumps and waves along the workpiece.

    Cambering is an effective technique in preventing zipper cracks. By using this method, you can provide a slightly larger diameter at the center of your sheet metal, which offsets the tension built up by the pressure of your rolling machine.

    Center Buckling

    Center Buckling

    Center buckling is a defect where there appear to be multiple “humps” along the center length of your workpiece. This defect can happen when the roll pressures across the face of the sheet metal are not equal. This creates unbalanced stretching and rolling, leaving ripples across the sheet metal’s surface.

    Switching to crowned rollers is a possible solution for center buckles. The roll’s shape and curvature can counter the effect of deflection, which means there is less risk of deforming your sheet metal.

    Key Takeaway

    Resolving and preventing the common sheet metal rolling defects can be tricky — with many methods such as cambering, crowned rollers, hydraulic jacks, and much more, beginners may have trouble fulfilling their sheet metal project on their own.

    But, with reliable manufacturers — like Regan Industrial Sales, Inc. — you’ll be able to avoid the hassle of dealing with sheet metal rolling defects altogether. With our years of experience combined with advanced equipment and techniques, we are committed to providing high-quality sheet metal products to our customers. Contact us today to learn more about our manufacturing services.