Summary

Geometry in GibbsCAM can be defined as Points, Lines, Arcs/Circles, or B-Splines. When geometry that appears to be a straight line is imported or extracted as a B-Spline, the geometry does not meet the criteria for a perfectly straight line within the current tolerance. Increasing the tolerance used during import or extraction may allow GibbsCAM to recognize the geometry as a Line instead of a B-Spline.


Table of Contents


Cause

GibbsCAM evaluates imported or extracted geometry according to the applicable tolerance. If the geometry is not mathematically recognized as a perfectly straight line within that tolerance, GibbsCAM may create it as a B-Spline instead.

The same principle applies to geometry that appears to be a perfect circle but does not meet the required tolerance.


Procedure

Step 1 - Display Geometry Labels

  1. Open the GibbsCAM file containing the geometry.

  2. Press Ctrl+L to turn on geometry labels.

  3. Alternatively, select View > Labels.

The labels identify the type of geometry:

  • P = Point

  • L = Line

  • C = Circle

  • B = B-Spline

Step 2 - Identify the Geometry Type

  1. Locate the geometry that is being identified as a B-Spline.

  2. Check the label displayed on the geometry.

A B label indicates that GibbsCAM has created the geometry as a B-Spline.

Step 3 - Increase the Tolerance

If the geometry is intended to be a Line but is being imported or extracted as a B-Spline:

  1. Increase the applicable geometry Tolerance.

  2. Re-import or re-extract the geometry.

  3. Turn on labels and check the geometry type again.


Expected Result

Geometry that meets the required tolerance is recognized as the appropriate geometry type. For example, geometry that is sufficiently close to a perfectly straight line may be imported or extracted as a Line rather than a B-Spline when an appropriate tolerance is used.


Additional Information

GibbsCAM Geometry Labels

Label

Geometry Type

P

Point

L

Line

C

Circle

B

B-Spline

A B-Spline does not necessarily indicate that the source geometry is incorrect. It means the geometry does not meet the criteria for the simpler geometry type at the tolerance being used.

Tolerance

Tolerance determines how closely imported or extracted geometry must conform to an ideal geometric definition. A line that is very slightly out of alignment may be treated as a B-Spline at a tight tolerance. Increasing the tolerance can allow GibbsCAM to treat the geometry as a straight Line.

The same concept applies to circles and other geometry.

Source: CAMCO Freshdesk article Lines Importing as B-Splines, article 70000686383.


Best Practices

  • Use Ctrl+L or View > Labels to verify the geometry type GibbsCAM created.

  • Review the applicable tolerance when geometry is unexpectedly recognized as a B-Spline.

  • Use a tolerance appropriate for the accuracy required by the part and manufacturing process.

  • Re-import or re-extract the geometry after changing the applicable tolerance.


Troubleshooting

  • Problem: A straight line from an imported or extracted model shows a B label.

Possible Causes

  • The geometry does not meet the definition of a perfectly straight line within the current tolerance.

Resolution

Increase the applicable tolerance and re-import or re-extract the geometry. Then turn on labels and verify the geometry type.

  • Problem: Geometry appears to be a circle but is imported as a B-Spline.

Possible Causes

  • The geometry is not mathematically recognized as a perfect circle within the current tolerance.

Resolution

Increase the applicable tolerance before importing or extracting the geometry again, then verify the geometry label.



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Keywords

Lines Importing as B-Splines, B-Spline, B-Splines, Line Geometry, Geometry Import, Geometry Extraction, Geometry Tolerance, Import Tolerance, Extract Tolerance, GibbsCAM Geometry, Geometry Labels, CAD Geometry