Turn XYZ tube coordinates into bend data for fabrication. BS Tube currently displays LRA: Length, Rotation, and Angle. This guide explains the corresponding YBC terminology used by many tube benders, alongside the geometry and conventions to review before production.
BS Tube desktop converter with XYZ points, LRA bend rows, CLR values, and a 3D tube previewThe converter runs in the BS Tube Windows application, not in this web page.
What do XYZ coordinates represent?
XYZ describes the tube centerline in three-dimensional space. The ordered points describe the start, the theoretical intersections of adjacent straight centerlines, and the finish. A bend radius rounds each corner between the straight sections; a bend intersection is not a point on the curved tube surface.
Point order establishes the direction of travel through the part. Check the start end and finish end before comparing a coordinate table with a drawing or manufacturing setup.
From XYZ geometry to bend data
The conversion uses the ordered XYZ points and bend radii to calculate tangent locations, straight lengths, bend angles, and changes of bend plane. BS Tube presents the result as LRA rows beside the tube preview.
For a shop using YBC tube-bending coordinates, the next step is to relate those LRA quantities to the controller's feed, rotation, and bend-angle definitions. Matching the letters alone is not a machine-specific program conversion.
LRA and YBC tube-bending coordinates
LRA and YBC commonly describe corresponding quantities in a bend sequence. The BS Tube desktop application uses LRA labels; YBC here explains the terminology, not a separate display mode.
Common correspondence; verify the controller's definitions before using the values
BS Tube / LRA
YBC terminology
Meaning
L: Length
Y: Feed distance
The straight length before a bend. Between bends, BS Tube measures between tangent points, after allowing for both adjacent setbacks.
R: Rotation
B: Tube rotation
Rotation about the tube axis to orient the next bend plane relative to the preceding plane, in degrees.
A: Angle
C: Bend angle
The change in centerline direction through the bend, in degrees.
BS Tube's L values are individual straight lengths, not cumulative carriage positions. R describes relative rotation between bend planes. Some controllers instead expect absolute feed positions or accumulated rotations from a fixed zero. Clockwise/counterclockwise direction, sign conventions, starting references, and controller-specific definitions can also differ.
Check the required convention, units, and bend order in your machine documentation. A geometrically valid LRA table is not automatically a compatible YBC machine program; renaming columns does not resolve those differences.
CLR: Centerline Radius
CLR is the radius measured to the tube centerline, not the outside diameter. It is a separate geometry input, not another letter in LRA or YBC. CLR and bend angle determine the arc and tangent setbacks, which affect the calculated straight lengths.
A 90-degree bend example
Consider three XYZ points in INCH: (0, 0, 0), (10, 0, 0), and (10, 10, 0), with a 2-inch CLR at the middle point. Each straight segment meets at a theoretical corner 10 inches from an end.
Ideal centerline geometry, before manufacturing compensation
Quantity
Calculation
Result
Tangent setback at each side
CLR x tan(angle / 2)
2.000 in
Straight before the bend
10 - 2
8.000 in
Bend arc length
2 x pi / 2
3.142 in
Straight after the bend
10 - 2
8.000 in
Total centerline length
8 + pi + 8
19.142 in
There is one 90-degree bend and no change between bend planes in this example. The final straight is still part of the tube, even though it has no following bend.
Using the first bend plane as zero, the bend row is L = 8.000 in, R = 0 degrees, A = 90 degrees. Under the matching incremental convention, the corresponding terms are Y = 8.000 in, B = 0 degrees, C = 90 degrees. The remaining 8.000-inch straight is the end length, not another bend. This is a terminology example, not controller-ready output or a springback-compensated bend command.
Why changing CLR changes the straight lengths
Using a 3-inch CLR with those same XYZ intersection points moves each tangent point 3 inches from the corner. The straights become 7 inches each and the bend arc becomes 4.712 inches, for a total of 18.712 inches. The XYZ intersection coordinates remain unchanged, but the rounded centerline and its developed length change.
Adjacent bends must leave enough room for their tangent setbacks. Review geometry warnings instead of assuming any radius will fit. These are geometric lengths, not a prediction of material stretch or springback.
From coordinates to a reviewed tube path
Open XYZ / LRA in BS Tube and select INCH or Metric units.
Enter or import the ordered XYZ points and set the required CLR values.
Review the generated LRA rows and the tube in the viewer.
Confirm the starting end, bend direction, and rotation convention.
Review the XYZ/LRA report and verify the data against your manufacturing setup.
Both tables are editable. LRA-driven changes rebuild the XYZ data; review the resulting orientation and origin rather than expecting all original absolute coordinates to remain identical.
INCH, Metric, and machine conventions
Use consistent units for XYZ coordinates, straight lengths, and CLR. One inch equals 25.4 mm; bend angles and rotations remain angular values, not linear dimensions.
Before entering values at a bender, compare the start end, feed reference, rotation direction, and bend order with the reviewed tube preview. Confirm any tooling offsets or material compensation in the machine setup rather than treating geometric bend angles as compensated machine commands.
