VR3 Manufacturing Guidelines

Methods of Bending Tubes

• VR3 uses a semi-auto rotary draw or CNC mandrel tube bending when bending tubes primarily considering the cost and the bend geometry required.

  • Semi-Auto Rotary Draw

    • Essentially how a rotary draw works, is the tube is bent around a rotating bend die. This bend die is going to be fixed and matched with the centerline bend radii for each particular diameter of the tube.

    • A much cheaper option, but when used on a tube with a smaller bend radius and/or a thinner wall, the tube is more likely to show signs of flattening or deformation.

    • In comparison to mandrel bending, this is a much more cost-effective and faster process, better suited for larger radii and in areas where precision may not be as valued.

      

  • CNC Mandrel Tube Bending

    • This process works very similar to a rotary draw, with an additional component of a mandrel in the center of the tube used as a stabilizer when dealing with tubes with thinner walls and when forming tighter and exacting radii.

    • Although mandrel bending will reduce the risks of deformation, it is a much more expensive process as allows the tube to retain its shape and dimensions.

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Considerations

• When considering the bend radii, it must match the specs that VR3 has available.

  • Ex. A tighter radius will require a thicker wall due to the possibility of flattening or wrinkling in the bend of the tube.

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• Take into consideration the required bend lengths between tubes and end leg lengths. All things considered, the end length is more manageable given the provisions of extra length that VR3 will provide if end lengths are not reached but the length between bends is final.

Tube Thicknesses

Tube OD (in.)

• Tubes are measured using the outside diameter (OD) in comparison to pipes which are measured based on the inside diameter.

Centerline Bend Radii

• These are the particular bend constraints per the Tube OD but VR3 allows for inquiries if the tubes needed are not found on this chart.

• This centerline radius is the determining factor of the radius bend die which the bend is formed around. These radius bend dies are fixed and cannot be changed.

Min. Wall Thickness

• Given the possibility of deformation and other scenarios in which the tube may lose its shape, this minimum wall thickness provides the thinnest possible thickness to avoid possible issues.

Straight Length

• This addresses the constraints the machines have regarding bending the material. This particular length determines the minimum length between bends. There is another outdated chart that includes end length as well, which is generally 0.5” inches shorter than the minimum straight length but is a much easier constraint to deal with given the ability to trim ends.

Extra Considerations:

• Thicker Wall Tubes = Bent to Tighter Radii

• Thinner Wall Tubes = Larger Bend Radii and Limited Bend Angles