Difference between revisions of "What are Centerline Tangent Points and Why Are They Important in VTube-LASER?"

Reading the T1d, MP, T2d Chart

• Back to VTube-LASER

The Tangent chart is represented by a grid of straights for each row with tangent points and midpoints for each straight:

• T1d = Tangent 1 Deviation
• MPd = Midpoint Deviation
• T2d = Tangent 2 Deviation
  
  

Technically a tangent point is the point where any straight meets any bend. These are considered the best points for qualifying a tube shape because the are the points that most closely approximate the walls of a tube gauge.

The two end points are an exception to the technical tangent definition given above. There is no bend attached to these points. But these points (T1d in straight 1, and T2d in the last straight) still have value in determining if the part is the correct shape, so it is convenient to include them in this chart and grid - even though they are not really tangents.

The general rule is this: If the tangent points are within tolerance, then it follows that the shape of the part - based on the straights - fits well enough inside the tolerance envelope in order to qualify. In GD&T, this is often referred to as the centerline profile.

The chart is represented by a grid of straights for each row, and critical inspection points along each straight:

• T1d = Tangent 1 Deviation
• MPd = Midpoint Deviation
• T2d = Tangent 2 Deviation

Technically a tangent point is the point where the straight meets the bend. These are considered the best points for qualifying a tube shape because they most closely approximate a profile gauge. The only exception are the points at the end - where no bend is attached. But these points (T1d in straight 1, and T2d in the last straight) still have value in determining if the part is the correct shape.

If the tangent points are within tolerance, then it follows that the shape of the part - based on the straights - fits well enough inside the restricted path or envelope in order to qualify. In GD&T, this is often referred to as the centerline profile.

• A tight qualification is 1 millimeter. It is much more challenging to measure the end scan with a tight tolerance. Keep in mind that tube deformation will make tight tolerance end scans more challenging.
  
  

• A much easier / quicker qualification is to increase the value to much high number - like 25 millimeters. (Many customers use 25 millimeters to avoid this qualification from occuring completely - and making end scans much easier.)
  
  

Set the default value by clearing the VTube project, then changing the value, then saving the setup to the default file in the System Options - Project Setup menu.