Fundamentals of approach and departure functions

Approach and departure functions allow you to avoid dwell marks on the workpiece because the tool gently approaches and departs from the contour.

Because the approach and departure functions encompass multiple path functions, you get shorter NC programs. The defined syntax elements APPR and DEP make it easier for you to find contours in the NC program.

Overview of the approach and departure functions

The APPR folder of theInsert NC function window contains the following functions:

Symbol

Function

Further information

APPR LT or APPR PLT

Use Cartesian or polar coordinates to approach a contour on a straight line with a tangential connection

APPR LN or APPR PLN

Use Cartesian or polar coordinates to approach a contour on a straight line perpendicular to the first contour point

APPR CT or APPR PCT

Use Cartesian or polar coordinates to approach a contour on a circular path with a tangential connection

APPR LCT or APPR PLCT

Use Cartesian or polar coordinates to approach a contour on a circular path with a tangential connection and a straight line

The DEP folder of the Insert NC function window contains the following functions:

Symbol

Function

Further information

DEP LT

Depart contour on a straight line with a tangential connection

DEP LN

Depart contour on a straight line perpendicular to the last contour point

DEP CT

Depart contour on a circular path with a tangential connection

DEP LCT or DEP PLCT

Use Cartesian or polar coordinates to depart a contour on a circular path with a tangential connection and a straight line

 
Tip

You can switch between entry of Cartesian and polar coordinates in the form or by pressing the P key.

Fundamentals of coordinate definitions

Approaching or departing a helix

The tool approaches and departs a helix in the extension of the helix by moving on a circular path that connects tangentially to the contour. Use the APPR CT and DEP CT functions for this.

Linear superimpositioning of a circular path

Positions for approach and departure

 
Notice
Danger of collision!
The control traverses from the current position (starting point PS) to the auxiliary point PH at the last feed rate entered. If you programmed FMAX in the last positioning block before the approach function, the control also approaches the auxiliary point PH at rapid traverse.
  1. Program a feed rate other than FMAX before the approach function

The control uses the following positions when approaching and departing a contour:

  • Starting point PS
  • The starting point PS is programmed prior to the approach function without radius compensation. The starting point is located outside of the contour.

  • Auxiliary point PH
  • Certain approach and departure functions require an additional auxiliary point PH. The control automatically calculates the auxiliary point using the entered information.

  • In order to determine the auxiliary point PH, the control requires a subsequent path function. If no path function follows, then the control stops the machining operation or simulation with an error message.

  • First contour point PA
  • Program the first contour point PA within the approach function, along with the radius compensation RR or RL.

  •  
    Tip

    If you program R0, then the control may stop the machining operation or simulation with an error message.

    This reaction is different from the behavior of the iTNC 530.

  • Last contour point PE
  • You program the last contour point PE with any path function.

  • End point PN
  • The position PN is located outside of the contour and arises from the information entered within the departure function. The departure function automatically cancels the radius compensation.

 
Notice
Danger of collision!
The control does not automatically check whether collisions can occur between the tool and the workpiece. Incorrect pre-positioning and incorrect auxiliary points PH can also lead to contour damage. There is danger of collision during the approach movement!
  1. Program a suitable pre-position
  2. Check the auxiliary point PH, the sequence and the contour with the aid of the graphic simulation

Definitions

Abbreviation

Definition

APPR (approach)

Approach function

DEP (departure)

Departure function

L (line)

Line segment

C (circle)

Circle

T (tangential)

Continuous, smooth transition

N (normal)

Perpendicular line