NCT Group 99M Selecting an Axis for Constant Surface Speed Control, Spindle Position Feedback

10 The Spindle Function

10.2.3 Selecting an Axis for Constant Surface Speed Control

The axis, which position the constant surface speed is calculated from, is selected by parameter 1182 AXIS. The logic axis number must be written at the parameter.

If other than the selected axis is to be used, the axis from which the constant surface speed is to be calculated can be specified by means of command

G96 P. Interpretation of address P:

P1: X, P2: Y, P3: Z,

P4: U, P5: V, P6: W,

P7: A, P8: B, P9: C

–The value set at address P is modal. After power on the control activates constant surface speed control to the axis set at parameter AXIS.

10.3 Spindle Position Feedback

In normal machining the NC will issue a speed command to the power amplifier of the spindle, proportional to the programmed speed (value specified at address S). Now this amplifier will be working in speed-control mode.

Some technological tasks may, however, require the spindle to be brought to a particular angular position. This is referred to as spindle positioning or indexing.

Prior to positioning, the NC will set the power amplifier of the spindle to position-controlled mode. In practice this means that the NC will not issue a speed command proportional to code S any more, instead, it will measure the position of the spindle by the use of an encoder mounted on the spindle, and will issue a command to the servo amplifier in accordance with the desired angular displacement (similar to the rest of controlled axes). This is the position feedback.

To be able to position the spindle on a particular machine, an encoder has to be mounted on the spindle and the power amplifier of the spindle must be capable of operation in position feedback mode as well.

10.4 Oriented Spindle Stop

The "spindle orientation" or the "oriented spindle stop" refers to the function of stopping the spindle in a particular angular position. This may be necessary, e.g., for an automatic tool change or for the execution of some drilling cycles. The possibility of orientation on a particular machine must be specified by parameter ORIENT1 in parameters. The command of spindle orientation is issued by function M19, but it may also be produced by some other function depending on the particular machine-tool. The orientation may be carried out in one of two different ways.

If the spindle cannot be used in position control mode, the orientation is feasible by turning the spindle to a proximity switch mounted on the machine.

If the spindle can be used in position control mode, command M19 will cause the control to return to the zero pulse of the spindle encoder. The control will automatically close the position control loop.

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