Manual impeller manufacturing in NX CAM, 4 axis mill-turn

This entry is part 4 of 4 in the series "Impeller manufacturing" NX CAM training 3-5 axis

NX CAM multi-axis has a potential to save resources by making complex parts in 4 axis instead of 5 axis. This example shows the process for making a CNC toolpath for an impeller on a mill-turn machine (with simultaneous 4 axis). It will be useful for practicing skills in multi-axis milling and for CNC programmers who support mill-turn machines.

NX CAM multiaxis, 4 axis

Acknowledgement: Thanks to Mech Kamalraj for providing the model.

Why replace 5 axis with 4 axis.

Quite many geometries, which are made in 5axis can actually be made in 4 axis. In case it is a complex turn-mill part (like impeller) it can make sense to manufacture it in one single setup on a turn-mill machine. This can replace the (quite commonly used) process, when the workpiece is done on a lathe and then is sent to 5 axis milling machine. The possibility to select methods, gives more flexibility in production planning, that potentially can result in savings.

“Interpolate vector” gives flexible axis definition.

Here I describe the method, which is mainly based on the use of Interpolate vector axis position. It involves quite a lot of manual work and requires basic understanding of multiaxis. Technique is similar to what was shown in previously for 5 axis, with some corrections for 4 axis. Roughing is done similar to 3 axis rouging tutorial.

Step-by-step instruction.

In my example of 5 axis I was defining the vector to be perpendicular to view. In this case we do it in the same way, but we only rotate model in 4 axis. Normally the rotation axis of a turn-mill part is Z.

  • Use F8 to align the view
  • Use axis rotation (put mouse to the right or left side when rotation is on)

Axis rotation

Check the model.

First of all, rotate the model around Z axis, and find out if all zones are reachable on 4 axis machine.

Define Surface area parameters

  • Start a new multi-axis operation with Surface Area drive method
  • Specify the Drive surface
NX CAM multiaxis, 4 axis

The selected surface is shown with yellow

  • Specify the Cut direction 
  • Set the method Cut Pattern to Zig
  • Press Display under Preview (the preview should look similar to one on the picture)

NX CAM multiaxis, 4 axis


  • Press OK

Defining multi-axis options.

  • The projection vector can be kept as Tool Axis (default)
  • Set the axis to Interpolate vector (Interpolate vector dialog opens)
  • Rotate the model around the Z axis until you see that a zone next to the vector will not cause the collision

NX CAM multiaxis, 4 axis

  • Repeat the actions for all system vectors
  • If required, add new points and set directions (for this impeller I needed 2 more)

NX CAM multiaxis, 4 axis


  • Set Interpolation method to Smooth
  • Press OK
  • Generate the operation


Coming soon.


In case the correct rotation is followed, the operation would perform the correct 4 axis movements.

When making similar geometry, consider the following:

  • In some impeller geometries, you can reach all areas in 4 axis, but you would require a smaller tool (compared to 5 axis). That means that sometimes 5 axis operations are more productive.
  • The surface finish can be worse (again, compared to 5 axis), because in many cases 4 axis would not allow keeping a constant angle to the surface.

NX CAM multiaxis, 4 axis


Did you experience problems when moving from 5 to 4 axis? In what kind of parts?


  1. Hello Andres,
    I was doing impellers on Hermle C40 with Heidenhain controller, some time ago. Covered the 4 axis impellers when delivering multiaxis training to a customer. Not sure I member which turn-mill machine was used.
    For postprocessors I can recommend the free materials here:

    There is also a Siemens training for NX postbulder, but it have to be purchased from them.

    In general, I can recommend ordering a postrocessor from a well trusted Siemens partner in your area.

    Hope it can help you.

  2. so what about post process? what kind of machine you have? , do you have tutorial about nx postbuilder?

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