In order to qualify a tube shape, it is important to determine which characteristic of the tube is used to prove that the tube shape is good.

What are qualification attributes?

Example Qualification Attributes in VTube-LASER

Common Qualification Attributes for Tube Shapes

While some teams state specialized ways to qualify a tube, the most common attributes used in the industry are the tangent point and end point positions along the centerline of the tube. When you specify these two attributes, you can easily designate a consistent envelope tolerance for your part shapes, regardless of the lengths between bends, bend angles, the rotation angles, or even overall part size.

See these pages for information about the different configurations of VTube-LASER.

See Tangent Points - This is a very good way to qualify tube shapes.

See Typical Tangent Point Tolerances

See GD&T Tube Profile Envelopes

See XYZ Intersection Points - Not as good as tangent points because they exaggerate the deviations

See LRA Bender Data Tolerances - The worst way to qualify a tube shape

Applied to Gage R&R Tests

Gage R&R (Gage Repeatability & Reproducibility) is a method for evaluating your measuring system's suitability for measuring tube shapes.

When testing the system's ability to match the needs of your quality-control system, it is important to first determine the qualification attributes, then use only those attributes in the test.

Using the correct attributes for the Gage R&R test is critical for determining the measuring system's capability for qualifying a tube shape.