Deprag AST40-1 Operating Instruction Booklet page 147

OK
Power unit
Process ability index (C
Process capability
coefficient (C )
pk
Process capability
examination
Profibus
error free
Component for the motor control of the screwdriver
) C = total specific torque tolerance of the
p p
Connection: 6 Sigma (s).
This index just provides information about the spread angle of the
torque values.
upper_limi

C
p
Is defined as the minimum of:
upper_limi

1.)
C
pk
mean_value

2.)
C
pk
This index provides information about the placing as well as the
spreading of torque values.
The lower acceptable C
(corresponds to a calculation of the C
C / C
p pk
0.30
0.70
1.00
1.33
1.63
1.66
2.00
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.
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.
Industry bus for the control and data exchange with sequence
control.

t lower_limi t

6 s

t lower_limi t
or

3 s

lower_limi t

3 s
- value for a screwdriver is 1.33
pk
pk
within limit
Limit values
values
s
68.3
2s 95.4
3s
99.7
4s 99.994
4.891s
99.9999
5s 99.99994
6s 99.9999998
147
on limits of 4 Sigma (s)).
Error
contribution
> 30%
~ 5%
3
60 ppm
1 ppm
0.6 ppm