147
OK error
free
Power unit
Component for the motor control of the screwdriver
Process ability index (C
p
) C
p
= total specific torque tolerance of the
Connection: 6 Sigma (s).
This index just provides information about the spread angle of the
torque values.
s
t
lower_limi
t
upper_limi
C
p
6
Process capability
coefficient (C
pk
)
Is defined as the minimum of:
1.)
s
t
lower_limi
t
upper_limi
C
pk
3
or
2.)
s
t
lower_limi
mean_value
C
pk
3
This index provides information about the placing as well as the
spreading of torque values.
The lower acceptable C
pk
- value for a screwdriver is 1.33
(corresponds to a calculation of the C
pk
on limits of 4 Sigma (s)).
C
p
/ C
pk
Limit values
within limit
values
Error
contribution
0.30
s
68.3 >
30%
0.70
2s
95.4 ~
5%
1.00
3s
99.7 3
1.33
4s
99.994 60
ppm
1.63
4.891s
99.9999 1
ppm
1.66
5s
99.99994 0.6
ppm
2.00
6s
99.9999998
The mean value must not deviate from the target value by more
than 3%!!!
A correct statement about the process capability index is then no
longer possible.
Process capability
examination
Prior to using a processing device for the series production it is
possible to check if the requirements are met with sufficient safety.
It is the objective of the process capability examination to verify that
a) the process to be examined is processing with the recognizable
are legality. If legality is not recognizable then the process has
no defined capability. Especially then it is not permissible to
allocate a statistically calculated capability characteristic.
b) the process is able to produce the parts in the indicated
tolerances. The required documentation for this can only be
provided under point a) found legality.
The verification of the process ability must be done over a longer
time period. Random sampling is done in set intervals from the
running process and quality characteristics are recorded
(measured). The influence of the machines, the materials and the
operator are assumed by the process ability.
The basis of the analysis is the Gauss distribution curve.
Profibus
Industry bus for the control and data exchange with sequence
control.
