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Quality Management in the Bosch Group | Technical Statistics 9. Machine and Process Capability 3. Edition, 01.07.2004 2. Edition 29.07.1991 1. Edition 11.04.1990 The minimum requirements given in this manual for capability and performance indices are valid at the time of publication (edition date). In case of conflict, the requirements of QSP0402 are binding and take precedence over this manual.  2004 Robert Bosch GmbH -2- Machine and Process Capability Table of Contents Page 1. Introdu
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  9. Machine and Process Capability Quality Management in the Bosch Group | Technical Statistics  - 2 - 3. Edition, 01.07.2004 2. Edition 29.07.19911. Edition 11.04.1990The minimum requirements given in this manual for capability and performance indices arevalid at the time of publication (edition date). In case of conflict, the requirements of QSP0402are binding and take precedence over this manual. ©  2004 Robert Bosch GmbH  - 3 - Machine and Process CapabilityTable of Contents Page1. Introduction............................................................................................................................... 42. Terms......................................................................................................................................... 43. Flow Chart for Machine and Process Capability Study............................................................ 64. Machine Capability Study......................................................................................................... 74.1 A Machine Capability Study in Detail ............................................................................ 84.2 Data Evaluation............................................................................................................... 94.2.1 Study of Temporal Stability.................................................................................. 94.2.2 Standard Method................................................................................................... 94.2.3 Manual Calculation Procedure............................................................................ 114.3 Machine Capability Study with Reduced Expense........................................................ 125. Process Capability Study......................................................................................................... 145.1 Procedure....................................................................................................................... 145.2 Data Evaluation (Standard Method).............................................................................. 145.2.1 Studying the Process Stability (Analysis of Variance and F Test)..................... 145.2.2 Studying the Statistical Distribution................................................................... 155.2.3 Calculating Process Capability Indices............................................................... 155.3 Data Evaluation (Manual Calculation Procedure)......................................................... 165.3.1 Studying the Process Stability ............................................................................ 165.3.2 Studying the Statistical Distribution................................................................... 165.3.3 Calculating Process Capability Indices............................................................... 166. Interpretation of Capability Indices......................................................................................... 186.1 Relation between Capability Index and Fraction Nonconforming................................ 186.2 Effect of the Sample Size.............................................................................................. 196.3 Effect of the Measurement System................................................................................ 197. Capability Indices for Qualitative Characteristics................................................................... 208. Report of Capability or Performance Indices.......................................................................... 209. Methods for Calculating Capability Indices............................................................................ 219.1 Method M1.................................................................................................................... 219.2 Method M2.................................................................................................................... 229.3 Method M3 (Range Method)......................................................................................... 229.4 Method M4 (Quantile Method)..................................................................................... 2310. Distribution Models .............................................................................................................. 2410.1 Distributions from the Johnson Family....................................................................... 2410.2 Extended Normal Distribution..................................................................................... 2511. Examples............................................................................................................................... 2612. Capability Indices for Two-Dimensional Characteristics ..................................................... 3013. Forms..................................................................................................................................... 3114. Abbreviations........................................................................................................................ 3715. References............................................................................................................................. 39Index............................................................................................................................................ 40  - 4 - 1. Introduction Suitable methods must be applied for monitoring, and where applicable, measurement of  processes. “These methods shall demonstrate the ability of the processes to achieve plannedresults. When planned results are not achieved, correction and corrective action shall be taken,as appropriate, to ensure conformity of the product.” (see [2])Examples of characteristics to assess the process performance or capability are or include thefollowing: ã   Capability indices ã   Response time ã   Cycle time or throughput ã   Reliability and safety ã   Rate of yield ã   Effectiveness and efficiency ã   Use of suitable technology ã   Avoidance and reduction of waste ã   Costs 2. Terms Process This document deals exclusively with production and assembly processes. A process is under-stood as a series of activities or procedures in which raw materials or pre-machined parts or components are further processed to generate a finished product.The definition in the standard [1] is as follows: “Set of interrelated or interacting activitieswhich transforms inputs into outputs.” Capability Studies A process capability study (Process analysis, see [3]) is performed for a new or changed production process (including assembly) in order to verify the (preliminary) process capabilityor performance and to obtain additional inputs for controlling the process (see [3]).References [10] and [11] distinguish between long-term and short-term studies. In a short-termstudy (e.g., machine capability study), characteristics of products manufactured in one con-tinuous production run are evaluated. A long-term study evaluates parts manufactured over alonger time-span which is representative of the variation encountered in series production. Capability and Performance Indices Quantitative measures for evaluating capability include the machine and process capability or  process performance indices (see [4]). These must achieve or surpass the specified minimumvalues.The minimum requirements given in this manual for capability and performance indices arevalid at the time of publication (edition date). In case of conflict, the requirements of QSP0402are binding and take precedence over this manual. Higher minimum requirements for processcapability or performance may exist for special characteristics, or may be specified internally ona product-by-product basis. Machine Capability Study The machine capability study is a short-term study with the sole aim of discovering themachine-specific effects on the production process.
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