Deprag AST11-1 Operating Instruction Booklet page 117

MC
n.c.
NOK
OK
Power unit
Process ability index (C
Process capability coeffi-
cient (C )
pk
Process capability ex-
amination
see main controller
not connected – the named pin is not connected
not error free
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 t

C
p
6
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
(s)).
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 ver-
ify that
a) the process to be examined is processing with the recog-
nizable 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
117

lower_limi t

s

t lower_limi t
or

3 s

lower_limi t

3 s
- value for a screwdriver is 1.33
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
on limits of 4 Sigma
pk
Error contri-
bution
> 30%
~ 5%
3
60 ppm
1 ppm
0.6 ppm