VTube Intersection Point Tolerances
Important Note About the Limitations of Using XYZ Intersection Point Deviations To Qualify a Part Shape
Before describing the intersection point tolerances, it is important to note that XYZ tangent points (not discussed on this page) are the preferred points to use for tube shape qualification. The reason is because intersection points are not as good as tangent points for tube-shape qualification. Here is why:
- Intersection deviations tend to exaggerate the deviations mathematically.
- The reason why they exaggerate the deviation is because they are not as close to OD wall in the straight as tangent points are.
- The higher the bend angle at an intersection, the further the intersection points are from the actual part - which means that the deviation exaggeration is greater as the bend angles increase. Tangent points don't have this problem, because they are always closely connected to the straight sections of the tube shape.
See What are Centerline Tangent Points and Why Are They Important in VTube-LASER? for more information about tangent point deviations.
A Visual Example of the Problem With Using Intersection Points for Qualification
See these two images to help understand the problem with using intersection points for qualification.
The two tangents show 0.054 and 0.046 inches in deviation. However, the intersection points are separated by 0.322 inches.
The intersection deviation is 6 times larger than the profile deviation of the tube. However, it is easy to see that the part falls well within the envelopes (the transparent blue cylinders) that are formed by the tangent deviations. Intersection deviations do not act as a good representative of the actual profile deviation.
Why Include Intersection Deviations in the VTube Interface?
The only reason we include intersection point deviations in reports because some customers require them for part qualification.
How the XYZ Intersection Deviation Tolerances Work
The XYZ intersection deviation tolerances allow you to quickly qualify a part using +/- tolerances to the intersection points.
The intersection tolerances are based on values are that follow the three axes in a coordinate system. Since the tolerances measure along the axes, these tolerances can be positive or negative to also indicate a direction.
XYZ Intersection Deviations
The XYZ intersection deviation tolerances are are compared to the XYZ deviations as shown in the model in this screen image.
The 0.013" value is the straight-line distance measured directly from the master to the corresponding measured points.
Set the Default Tolerance in Part Setup Menu
You can set the default tolerance in the Part Setup menu. Scroll down to row 34.
Set the Default Tolerance in General Setup Menu
You can set the default tolerance in the Inspection Data General Setup menu. (This is for version 2.5 and newer.)
Set the Default Tolerance in Inspection Data Menu
You can set the default tolerance in the Inspection Data menu by entering a Default Tolerance at the top and pressing the Set button.
Set the Tolerances in Inspection Data Grids
Click on the Change Grid Setup button until you see the tolerances in the grid like we show in the image on the right.
Set the Tolerances in Expanded Windows
Setting All The Tolerances At The Same Time
The screen images on the right show an example of before and after changes made to an entire column:
XYZ Intersection +/- Tolerance Values in Printed Reports
The XYZ Intersection deviation values can be included in reports: