NC fundamentals

Programmable axes

The programmable axes of the control are in accordance with the axis definitions specified in DIN 66217.

The programmable axes are designated as follows:

Main axis

Parallel axis

Rotary axis

X

U

A

Y

V

B

Z

W

C

 
Machine

Refer to your machine manual.

The number, designation and assignment of the programmable axes depend on the machine.

Your machine manufacturer can define further axes, such as PLC axes.

 
Tip

The TNC7 basic can move up to four axes simultaneously. If an NC block commands movement of more than four axes, the control displays an error message.

If the axis position does not change, you can nevertheless program more than four axes.

Designation of the axes of milling machines

The axes X, Y and Z on your machine are also designated as the main axis (1st axis), secondary axis (2nd axis) and tool axis. The main axis and secondary axis define the working plane.

The axes are associated as follows:

Main axis

Secondary axis

Tool axis

Working plane

X

Y

Z

XY, also UV, XV, UY

Y

Z

X

YZ, also WU, ZU, WX

Z

X

Y

ZX, also VW, YW, VZ

 
Machine

The control’s full range of functions is available only if the Z tool axis is used (e.g., PATTERN DEF).

Restricted use of the tool axes X and Y is possible when prepared and configured by the machine manufacturer.

Position encoders and reference marks

Fundamentals

The position of the machine axes is ascertained with position encoders. As a rule, linear axes are equipped with linear encoders. Rotary tables and rotary axes feature angle encoders.

The position encoders detect the positions of the tool or machine table by generating an electrical signal during movement of an axis. The control ascertains the position of the axis in the current reference system from this electrical signal.

Reference systems

Position encoders can measure these positions through different methods:

  • Absolutely
  • Incrementally

The control cannot determine the position of the axes while the power is interrupted. Absolute and incremental position encoders behave differently once power is restored.

Absolute position encoders

On absolute position encoders, every position on the encoder is uniquely identified. The control can thus immediately determine the association between the axis position and the coordinate system after a power interruption.

Incremental position encoders

Incremental position encoders need to find the distance between the current position and a reference mark in order to determine the actual position. Reference marks indicate a machine-based reference point. A reference mark must be traversed in order to determine the current position after a power interruption.

If the position encoders feature distance-coded reference marks, then you need to move the linear encoders of the axes by no more than 20 mm. On angle encoders this distance is no more than 20 °.

Axis reference run

Presets in the machine

The following table contains an overview of the presets in the machine or on the workpiece.

Icon

Preset

Machine datum

The machine datum is a fixed point defined in the machine configuration by the machine manufacturer.

The machine datum is the origin of the machine coordinate system M-CS.

Machine coordinate system M-CS

If you program M91 in an NC block, the defined values are referenced to the machine datum.

Traversing in the machine coordinate system M-CS with M91

M92 datum M92-ZP (zero point)

The M92 datum is a fixed point defined relative to the machine datum by the machine manufacturer in the machine configuration.

The M92 datum is the origin of the M92 coordinate system. If you program M92 in an NC block, the defined values are referenced to the M92 datum.

Traversing in the M92 coordinate system with M92

Tool change position

The tool change position is a fixed point defined relative to the machine datum by the machine manufacturer in the tool-change macro.

Reference point

The reference point is a fixed point for initializing position encoders.

Position encoders and reference marks

If the machine has incremental position encoders, the axes must traverse the reference point after booting.

Axis reference run

Workpiece preset

With the workpiece preset you define the origin of the workpiece coordinate system W-CS.

Workpiece coordinate system W-CS

The workpiece preset is defined in the active row of the preset table. You determine the workpiece preset with a 3D touch probe, for example.

Preset management

If no transformations are defined, the entries in the NC program refer to the workpiece preset.

Workpiece datum

You define the workpiece datum with transformations in the NC program, for example with TRANS DATUM or a datum table. The entries in the NC program refer to the workpiece datum. If no transformations are defined in the NC program, the workpiece datum corresponds to the workpiece preset.

If you tilt the working plane (#8 / #1-01-1), the workpiece datum is the point around which the workpiece is rotated.