Siemens SINUMERIK 840C - Manual (Page 258)

12.93 6 NC Machine Data (NC MD), NC Setting Data (NC SD)
6.5 Spindle-specific MD (spindle data)
The parameters for defining MD 455* and 456* can be taken from the table below.
Parameters for defining MD 455* and 456*
Parameter Symbol Meaning
Position control resolution b Reference unit for traversing path
Pulses per resolution
p Number of encoder pulses per
resolution
Pulse multiplication
f Pulse multiplication for HMS
measuring circuit module; MD 458*
Measuring gear
r1 /r2 Gear transmission ratio between
spindle and encoder
MD 455* = 4 • p • f • r2 Number of measuring system pulses per encoder revolution
including hardware multiplication; multiplied by r2
MD 456* =
360 • r1
b
Number of internally computed increments per encoder revolution;
multiplied by r1
If the values thus calculated are greater than the input limits, common factors must be
reduced.
Recommendation: Always reduce when possible, at least for values 100 000
Notes
• The position control resolution has been set to 0.5 x 10 -3 degrees for the spindle.
• If the spindle is allocated to a C axis (MD 461*), the C axis resolution is used for the
calculations (MD 1800*, 364*, 368*).
• The default values apply to the use of an SPC servo loop module and an encoder with
1024 pulses per revolution (see Example).
Examples
• Encoder mounted directly on the spindle; square pulse encoder and SPC servo loop
module
b
= 0.5 • 10 -3 degrees
p = 1024 pulses per revolution
f = 1 no pulse multiplication
r1 = 1 no measuring gear
r2 = 1
If the spindle performs one full revolution, the encoder generates 4 x 1024=4096 pulses.
If these factors are introduced into the formula:
MD 4550 = 4 096
MD 4560 = 720 000
Reduction by the common factor 128 yields:
MD 4550 = 32
MD 4560 = 5625
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 6–73
SINUMERIK 840C (IA)