Difference between revisions of "The Limitations of Qualifying Tube Shapes using Bender Data"
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It's easy to visually demonstrate the limitation of using bender data to tell us if a part shape falls within the tolerance envelope.<br><br> | It's easy to visually demonstrate the limitation of using bender data to tell us if a part shape falls within the tolerance envelope.<br><br> | ||
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+ | '''INSIDE THE ENVELOPES: QUALIFIES'''<br><br> | ||
+ | Compare the two aligned parts on the image. The white tube is the MASTER. The pink tube is the MEASURED ALIGNED. The blue transparent cylinders that surround the tube are the TOLERANCE ENVELOPES. The tube shape must be within each straight's tolerance envelope to be considered a good shape - or a shape that qualifies.<br><br> | ||
+ | This first part has 4 inch straights for every straight. (See the LRA data above.)<br><br> | ||
+ | All the centerlines fall within within the tolerance envelope as defined by the Tangent Grid. The "T1 dev" column values are TANGENT 1 DEVIATIONS, and the "T2 dev" column values are TANGENT 2 DEVIATIONS.<br><br> | ||
+ | The tangent points are where the straights meet the bend arcs along the centerline. | ||
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+ | [[image:VTL image 4 inch straights.png|500px]]<br><br> | ||
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+ | '''OUTSIDE THE ENVELOPES: DOES NOT QUALIFY'''<br><br> | ||
+ | This second alignment image shows the part with IDENTICAL ANGLES - but the two middle straights are lengthened to 10 inches between bends.<br><br> | ||
+ | You can see red cells in the Tangent point/Midpoint grid, and yellow tolerance envelopes where the pink is breaking through.<br><br> | ||
+ | The part is no longer within tolerance - even though all the angle deviations are identical between the two parts.<br><br> | ||
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+ | [[image:VTL image 4 inch and 10 inch straights.png|500px]]<br><br> | ||
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+ | == Example 2 == | ||
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+ | In this example, you will see a part with a short straight with two tolerance envelopes.<br><br> | ||
+ | Both parts are the same - and they have some easy-to-see deviation in the bender data. However, one is acceptable, and the other part is not.</td> | ||
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Revision as of 15:41, 29 March 2018
This page explains the major limitations of using bender data for qualifying tube shapes.
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Contents |
What is Bender Data?
Bender data is the data used to setup tube bending machines. Usually, bender data has at three major columns of data - the LENGTH between bends, ROTATION planes between bends, and BEND ANGLE columns. These columns can be used to define the shape of a tube and setup a tube bender.
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The Limitations of Bender Data for Qualifying Tube Shapes
The tube fabrication industry rarely uses bender data to qualify part shapes for a very good reason. |
Illustration of the LimitationLook at the bender data on the right. The two sets are not the same because I've made the MEASURED rotations to be exactly one degree away from MASTER data rotations. |
Visually Demonstrate the Problem of Qualifying with Angles
Unless you can perform 3D trigonometry mentally on-the-fly, the answer to the question above isn't obvious. Even if we make a guess, we can't accurately guess at what tolerance envelope value the part would be considered acceptable. |
INSIDE THE ENVELOPES: QUALIFIES |
OUTSIDE THE ENVELOPES: DOES NOT QUALIFY |
Example 2
In this example, you will see a part with a short straight with two tolerance envelopes. |
INSIDE THE ENVELOPES: QUALIFIES |
OUTSIDE THE ENVELOPES: DOES NOT QUALIFY |
The Best Data for Qualification
The best data for qualification is centerline TANGENT POINT and MIDPOINT data in the Inspection Data menu and in the Reports menu. |