Siemens SINUMERIK 840C - Manual (Page 951)

12 Functional Descriptions 12.93
12.18.16 Examples
The hobbing machine functions are interrelated as follows:
C
(FA)
Y
(LA 3)
Z
(LA 2)
B
(LA 1)
The workpiece table axis (C) is the following axis; in this example, it is influenced by three
leading drives.
The following axis setpoint is calculated cyclically by means of the following logic equation:
u
dz
z
2
n
c
= n
b
·
z
0
z
2
+ v
z
· +v
y
·
u
dy
z
2
n
c
Speed of workpiece axis (C)
n
b
Speed of cutter spindle (B)
z
0
Number of hobbing operations
z
2
Number of teeth on workpiece
v
z
Feed velocity of axial axis (Z)
v
y
Feed velocity of tangential axis (Y)
u
dz
Axial differential constant
u
dy
Tangential differential constant
The first summand in the above equation determines the speed ratio between the workpiece
table and the cutter and therefore the number of teeth on the workpiece. The second
summand effects the requisite additional rotation of the C-axis for inclined gearing as a
function of the axial feed motion of the cutter to produce the tooth pitch. The third component
also makes allowance for additional rotation of the C-axis which compensates the tangential
motion of the cutter in relation to the workpiece. In this way, the tool can be evenly loaded
over its entire length.
The values z
0
, z
2
, u
dz
and u
dy
are dependent on workpiece and tool and are specified by the
NC user or in the part program.
The differential constants u
dz
and u
dy
make allowance for the workpiece tooth pitch and the
geometry of the cutter. The differential constants can be calculated in user-specific cycles.
12–176 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)