HEIDENHAIN TNC 426, User Manual

Page: 184 / 502

158 6 Programming: Programming Contours
6.6 P
a
th Cont
ours—FK F
ree Cont
our Pr
ogr
a
mming
6.6 Path Contours—FK Free
Contour Programming
Fundamentals
Workpiece drawings that are not dimensioned for NC often contain
unconventional coordinate data that cannot be entered with the gray
path function keys. You may, for example, have only the following data
on a specific contour element:
n
Known coordinates on the contour element or in its proximity
n
Coordinate data that are referenced to another contour element
n
Directional data and data regarding the course of the contour
You can enter such dimensional data directly by using the FK free
contour programming function. The TNC derives the contour from the
known coordinate data and supports the programming dialog with the
interactive programming graphics. The figure to the upper right shows
a workpiece drawing for which FK programming is the most
convenient programming method.
If you wish to run FK programs on old TNC models, use the conversion
function (see “Converting an FK program into HEIDENHAIN
conversational format,” page 47).
The following prerequisites for FK programming
FK programming
The FK free contour programming feature can only be
used for programming contour elements that lie in the
working plane. The working plane is defined in the first
BLK FORM block of the part program.
You must enter all available data for every contour
element. Even the data that does not change must be
entered in every block - otherwise it will not be recognized.
Q parameters are permissible in all FK elements, except in
elements with relative references (e.g. RX or RAN), or in
elements that are referenced to other NC blocks.
If both FK blocks and conventional blocks are entered in a
program, the FK contour must be fully defined before you
can return to conventional programming.
The TNC needs a fixed point from which it can calculate
the contour elements. Use the gray path function keys to
program a position that contains both coordinates of the
working plane immediately before programming the FK
contour. Do not enter any Q parameters in this block.
If the first block of an FK contour is an FCT or FLT block,
you must program at least two NC block with the gray path
function keys to fully define the direction of contour
approach.
Do not program an FK contour immediately after an LBL
label.