# KIN_TYP_3 - four-axis kinematics with double spindle head (top spindle)

## Kinematic structure

The kinematic structure of the machine consists of 3 translatory axes and 1 rotary axis in the tool (double spindle head).

The KIN_TYP_4 selects the bottom spindle.

Axis configuration in the NC channel
Axis identifier | X, Y, Z, B
Axis index | 0, 1, 2, 3
Kinematic structure
| Tool axes | Workpiece axes
NC axes | X, Y, Z, B | -

Kinematic structure of the 4-axis milling machine with double spindle head

The top figure shows the structure of the milling head for the zero position of the B axis. It features 2 spindles (referred to in this document as top and bottom spindle irrespective of the current position of the B axis) so that 2 tools can be clamped rotated by 180° relative to each other.

A command in the NC program allows selection of the two spindles or which of the 2 tools is currently active.

If the top spindle is active, the programmed value for the B axis must be changed as follows:

bM=bM+180°

Thus, changing spindles means rotating the B axis through an angle of 180° and translatory shifts of all 3 linear axes. This is due to the geometry constants when RTCP is active.

Side view and front view of the double spindle head (upper spindle)

## Offset data of kinematics

HD offset | param[i] | Description | Unit
HD1 | 0 | Offset tool holding device to rotation point B axis | 10 E-4 mm
HD2 | 1 | Y offset tool head | 10 E-4 mm
HD3 | 2 | X offset from tool holding device to B axis | 10 E-4 mm