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The Importance of Understanding CNC Bender Rotation Directions


The "positive" direction for collet rotations in benders is NOT standardized for benders. It is important to understand how to determine rotation directions to avoid confusion through mirror-imaging parts accidentally.

  1. The direction of rotation can be indicated with a CW or CCW direction of rotation from the viewpoint of a viewer at the front of a bender looking toward the rear of the bender.
  2. When a bender collet rotates CCW to rotate positive, then it uses the American industry standard, the standard for our VTube and CNC Bender software. In this case, +90 would rotate the chuck 90 degrees CCW.
  3. When a bender collet rotates CW to rotate positive, it uses the non-American industry standard, the opposite of our software. In this case, +90 would rotate the chuck 90 degrees CW.

The engineering community uses a simple right-hand/left-hand rule to designate which way an axis spins positive:

This illustration demonstrates the RIGHT-HAND rule*

In this "right-hand rule" illustration:

  1. You are standing in the front of the bending, looking toward the back.
  2. Hold your right hand up in front of you.
  3. Point your thumb toward you.
  4. The arrow centerline is the centerline of the tube coming out of the collet.
  5. The direction of the curl of your fingers represents the direction of a positive rotation.
  6. Therefore, the right-hand rule indicates that positive rotates CCW.
  7. This is always the meaning of "positive" for rotations in our software.

Bobcad righthand rule2.png

European and Asian benders often follow the LEFT-HAND rule - which means that positive rotates CW. (To prove this, hold your left hand so that your thumb is pointing at you. What direction do your fingers curl?)

Bobcad lefthand rule2.png

Credit: The illustrations above are from the BobCAD-CAM site.