00193407-02 HWWS SIPLACE Machine Accuracy EN.pdf - 第20页

© Siemens AG . . Änderungen vorbehalten SIPLACE Placement Systems Definition: to achieve a constant, clearly defined attribute , within specified parameters (tolerance limits). declaration of a capability value withou t …

SIPLACE

Placement Systems

Process capability, e.g. minimum C

=1,33 (4 Sigma specification)

¾ the Process Capability of the product is determined over a period of time.

¾ rather difficult to determine with component manufacturing.

¾ the so-called machine capability is only one precondition!

Process Capability index Cp, Cpk

The indices Cp (capability process) and Cpk describe the quality of a manufacturing process or

process step, which is assumed to be regular. The indices are calculated from the average standard

deviation of several samples.

The test is performed under realistic manufacturing conditions.

Cp: only dispersion in relation to the tolerance

Cpk: position of the process middle value in relation to the tolerance limits.

K: factor for centering of a process

Process Capability

SIPLACE

Placement Systems

Definition:

to achieve a constant, clearly defined attribute, within specified parameters (tolerance limits).

declaration of a capability value without a declaration of tolerance or specification limit is worthless !!!

… characteristic must be measure able and must be normal distributed

Cpk = Min (Cpk 1, Cpk 2),

means, the lowest value is only used for the Cpk

USL - LSL

6 x sigma

Cp =

3 x sigma

USL - offset

Cpk 1 =

3 x sigma

LSL - offset

Cpk 2 =

Process Capability

SIPLACE

Placement Systems

Exercise 1:

Calculate the Cm and Cmk value for a placement machine within a specification of 90 um at 4

Sigma with following indices:

standard distribution -18.5 um Cm value: ............................

offset - 21.0 um Cmk value: ...........................

Evaluate the result

Is the machine ... capable { not capable |

Exercise 2:

Calculate the Cm and Cmk value for the same placement machine within a specification of 135 um

at 6 sigma with following indices:

standard distribution -18.5 um Cm value: .............................

offset - 21.0 um Cmk value: .............................

Evaluate the result:

Is the machine ... capable { not capable |

Exercise 3:

Evaluate the results and compare it with the required specification

Exercise Maschine Capability