GB/T 18779.6-2020 in English
VALIDGeometrical product specifications(GPS)—Inspection by measurement of workpieces and measuring equipment—Part 6:Generalized decision rules for the acceptance and rejection of instruments and workpieces
- Issued on:2020-12-14
- Implemented on:2021-07-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$243.00
| Standard No: | GB/T 18779.6-2020 |
| Document status: | VALID |
| Title in English: | Geometrical product specifications(GPS)—Inspection by measurement of workpieces and measuring equipment—Part 6:Generalized decision rules for the acceptance and rejection of instruments and workpieces |
| Title in Chinese: | 产品几何技术规范（GPS） 工件与测量设备的测量检验 第6部分：仪器和工件接受/拒收的通用判定规则 |
| Language: | English |
| File Format: | Electronic (PDF) |
| Delivery: | Via email within 1~3 business days |
| Issued on: | 2020-12-14 |
| Implemented on: | 2021-07-01 |
| Chinese Classification: | J42-Measuring tool and instrument |
| Professional Classification: | GB-National Standard |
| Related Keywords: | strict acceptance rules
strict acceptance rule simple acceptance protection decision rules different decision rules |
| Related Topics: | Measuring equipment in
measurement inspection workpiece Acceptance of measuring instruments and equipment measuring instrument gps Measurement and inspection equipment Measuring and testing equipment Measure workpiece GBT18779.6 GBT18779.6-2020 Measuring equipment inspection |
《GB/T 18779.6-2020产品几何技术规范（GPS） 工件与测量设备的测量检验 第6部分：仪器和工件接受/拒收的通用判定规则》由TC240（全国产品几何技术规范标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Interpretation of the core content of the standard
GB/T 18779.6-2020, as an important part of the product geometry technical specification (GPS) system, expands the default judgment rules of GB/T 18779.1 and proposes economic optimization solutions that are suitable for different industrial scenarios. The standard introduces the concept of protection zone to construct a continuous judgment rule system from strict acceptance to loose acceptance.
Determination rule types and applications
| Determination rule type | Protection band setting | User risk | Applicable scenarios |
|---|---|---|---|
| Strict acceptance | Specification limit inward shift (positive protection band) | 0.00002(when Cp=1) | Safety-critical components |
| Simple acceptance | Protection band=0 | 0.00074(when Cp=1) | Conventional industrial parts |
| Relaxed acceptance | Specification limit outward shift (negative protection band) | 0.0455(when Cp=2/3) | Low-cost replacement parts |
Key technical parameters
The process capability index Cp and measurement capability index Cm defined in the standard are the key basis for selecting the judgment rule:
- Cp=T/(6σp): reflects the accuracy of the manufacturing process, σp is the standard deviation of the process distribution
- Cm=T/(4σm): characterizes the capability of the measurement system, σm is the measurement uncertainty
The example shows that when Cp=1 and Cm=4, the strict acceptance rule with 100%U protection band can reduce the probability of accepting defective products to 0.00002.
Economic decision model
The standard provides a systematic cost analysis method to quantify the economic benefits of different decision rules by constructing a profit matrix. Key elements include:
- Profit of accepting qualified products
- Cost of accepting unqualified products
- Loss of rejecting qualified products
- Cost of rejecting unqualified products
For safety-critical components (Example F), the cost of accepting unqualified products can be up to 50 times the production cost. At this time, strict acceptance rules can achieve the best economic benefits.
Implementation Suggestions
Suggestions in practical applications:
- Prioritize improving the Cp value by improving the manufacturing process
- The measurement system should meet the basic requirement of Cm≥4
- Safety-critical parts use ≥100%U protection belt
- Establish a written abnormal value handling procedure
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