All machine concepts have been developed to provide multi-functional options – turning, drilling and milling operations can now be carried out in sliding head machines through to 5-axis machining centers. Turning operations have used a machine axis to rotate the part around the component’s axis of symmetry.
Symmetrical features on non-symmetrical parts have used boring tools for parallel diameters on standard machining centers. However where contours are required normally circular interpolation by milling or a W-axis head has been required to generate the form.
A new machine development called interpolation turning has been developed for advanced machining centers and B axis multi-task machines. A turning operation can be carried out by interpolating with the X and Y axis in a circular direction and rotating the machine spindle in time with the rotational contour.
The circular movement can either increase or decrease in diameter to produce facing operations or be combined with the Z axis to produce a bore or outer diameter.
This method does not compete with the metal cutting efficiency of traditional boring or turning operations, however it does provide a viable option to interpolation with milling or W-axis facing heads. It should be considered for new machines where the components have symmetrical features on non-symmetrical components – e.g flanges, seal grooves and non-parallel bores.
The limitations of the method and machines are:
- The revolutions per minute – speed of the X, Y table feed
- Programming support – CAM cycles/post processors
- Spindle torque – as the spindle motor is rotating at a relatively low rpm the depth of cut of the turning operation should not be excessive
- Spindle interface – the coupling should be capable of transmitting a higher level of torque than normally required for milling operations. Steep taper 50 or Coromant Capto have superior torque transmission than HSK-A
The pictures show the difference in table movement between interpolation turning and the traditional way.