Pencil Milling Part 2

By wrightj

In this post, I want to explain some of the options for working with Flow Cut.  I find that new users consistently struggle with understanding some of these options.

Max Concavity.JPGFirst up is Max Concavity.  It might be better to think of this as the maximum angle that Flow Cut will analyze for pencil milling.  If a cross section of the geometry shows a maximum angle greater than specified, the area will be ignored.  Maximum Angle is slightly misleading, because Flow Cut analyzes complex surfaces.  See the section view image for a better understanding.  I normally set Max Concavity to ~130° degrees, because the default setting is almost a flat surface.

Max Concavity Cross Section.JPG

Next item of discussion is Minimum Cut Length.  Pay attention, because you will see this option in other NX CAM dialogs.  Minimum Cut length is the shortest amount of cut material that Flow Cut should pay attention to.  For example, if Flow Cut found some geometry that qualified for Max Concavity it then checks to see if the area is long enough to actually matter.  I normally set this to 100% of the tool diameter.

Hookup Distance (I’ll ignore the obvious joke here) is a parameter that helps control excessive lifts and re-engages.  If two areas are chosen for machining, and they are less than the Hookup Distance away, then NX CAM will machine both areas as one contiguous area.

Remember, if you hover the cursor over most CAM dialog options, you will be rewarded with a picture that helps explain what the option does.  If you need more information about a dialog option, you can always press the F1 key for context-sensitive information.

Thanks for reading.

About the Author

Jim closeup 100x100.jpgJim has a Master’s degree in Business Administration from the University of Central Missouri. He has over 30 years of experience in the manufacturing industry, and over 25 years of experience in the CAD/CAM field. He serves as Field Support for Siemens PLM CAM products. Prior to his current role, he held stints as CNC Programmer, CAD/CAM Department Manager, CAD/CAM instructor, and Project Coordinator for Siemens PLM CAM software development.  He also made the Kessel Run in slightly over 18 parsecs.

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This article first appeared on the Siemens Digital Industries Software blog at