Undercutting operations in NX CAM

This instruction shows how to create undercutting operations in NX. Two examples are shown: for planar and non-planar surfaces.


In NX CAM there is no dedicated undercutting operation. Most of the difficulties I faced in 3-axis undercutting were the following:

  • When the direction of cutting levels is bottom – up

undercutting 1_71

  • When a non-planar surface is manufactured

undercutting 2_41

Both of this the situations can be solved with the use of Surface Area or Streamline methods. These methods allow defining a toolpath along the edges of the model in any direction. It means that you can follow complex surface and define direction to bottom-up. Additionally, you can model your own surfaces to guide the toolpath.

Following examples show step-by-step instructions for both of the cases.

Example 1. Undercutting with bottom-up levels.

 Adjusting model for the CAM operation.

Before you start making an operation, consider which surface you would like to use for guiding. It has  to cover the required cutting area and its upper side has to be cut from the top side to the value, equal to the height of the cutter.

undercutting 1_72

  • In this example I will edit the model, I will start by wave linking it
  • Then I would select the Synchronous technology
  • Move face
  • I select the top and bottom levels, and move (the distance for moving the surfaces has to be equal to the height of the cutter)
  • Press OK

undercutting 1_2

Creating the surface operation.

  • Create a new surface area operation, do not define the part geometry.
  • In the method definition dialog set the drive surface
  • Define the direction as shown (you choose the side where toolpath starts and the direction of the first cut)
  • If required, switch the cutting side. Set the vector to the position as shown
  • Set the Cut Pattern to Zig

undercutting 1_31

  • Press OK.

Finalizing the operation.

  • Define the projection vector to be toward driveundercutting 1_4
  • Generate the toolpath (it should look similar to the one on the picture)

undercutting 1_5

  • If the toolpath looks fine, define the non-cutting moves
  • In this example I set the engage/retract to linear and transfer plane as an offset from the top surface
  • When operation is completed, hide the wave linked body

undercutting 1_7


In case you want to define multiple moves on one level, you can set the part geometry to the manufactured surface and use multilevel option in Cutting parameters.



Example 2. Undercutting for non-planar surface.

In this example a non-planar surface is manufactured, streamline method is used. Since no change is required to the surfaces, you can use the part geometry without changes.

Creating the surface operation.

  • Create a new surface operation and set method to Streamline
  • In the method definition dialog set the Flow Curves as shown
  • In this example I also set the Cut Pattern to spiral and different value for the stepover

undercutting 2_2

NOTE: It is recommended to test the operation with low stepover value, before setting the real value. The time for generating the toolpath can be significant.

  • Press OK for the method definition dialog

Finalizing the operation.

  • In the operation, set the Cut Area to the manufactured surface
  • Set the Projection vector to be Toward drive
  • Generate the operation

undercutting 2_4

If operation runs fine,  define the real values for stepover and check the engage/redact options.



This instruction shows the ways to reproduce the operations on simple examples. In real case scenario the manufactured surfaces are more complicated and they need to be completed in multiple operations. There are additional things that should be known when making such operations in 5-axis.

Have you experienced any issues when performing undercutting?

Leave a Reply