Vol. 3, No. 10, October 2019


How to verify the validity and conformity of measuring instruments when inspecting suppliers (I)

A European buyer came to inspect a brake disc factory in China recently. During the tour he visited the R&D lab, incoming inspection lab, molding sand lab, chemical analysis lab at furnace, machining workshop, coating & packing area, etc. and carefully checked the green periodic calibration labels on the Link machine, hardness tester, tensile test machine, metallurgical analyzer, spectrum analyzer, electric scale, thermo probe, dial gauge, position gauge, automatic detector and coating thickness gauge. All instruments with current validity dates on the labels were considered OK, while those without labels or with expired validity dates on the labels were determined to be non-conformities. The validity and conformity of the instruments themselves meanwhile were not checked.

The calibration of the measuring instruments not only demonstrates a company’s capability in product quality control but also guarantees the long-term stability of the product quality. Every year, many international buyers of automobile spare parts would come to visit and inspect their suppliers in China for multiple times. The validity and conformity of the measuring instruments used by the supplier are naturally one of the key focuses during the inspections, but obviously it is not enough to just rely on the calibration labels.

Yet for international buyers not professionally trained in quality management, how the validity and conformity of the measuring instruments should be verified? In this article we would share our experience on what to watch for when checking the suppliers’ measuring instruments based on our years of practices assisting international buyers to manage the Chinese suppliers’ quality systems.

First we need to understand what the measuring instruments include and the differences between measuring tools and gauges.

Measuring instruments refer to the equipment that are used to determine the conformity of products, including general measuring instruments and special testing equipment. Instruments that are used for process parameter monitoring also include measuring equipment for safety, environmental protection as well as compliance.

Measuring tools are tools for measurements and calculations where the measured units and limits are directly displayed, such as ruler, electronic balance, protractor, and measuring cup.

Gauges are sample frames, sample plates and non-standard gauges including special test benches that are used in production, inspection and calibration to detect such dimensions as hole positions, peripheral shapes, relative positions of parts with complex shapes.

The differences between measuring tools and gauge are that measuring tools are universal measuring instrument whose data can be read directly, such as venire calipers, CMM (Coordinates Measuring Machine) and YVM (Quadratic Measurement), whereas gauges are instruments whose data cannot be read directly, such as jigs, fixture and gauge blocks. These gauges measure the part profiles or sides mainly through visual inspection, measuring meters, calipers, core bars, and plug pieces.

(To be continued)

By Felix SS YUAN


Auto A/C Compressors

The AC compressor is the central element of a vehicle air conditioning system. Its function is to compress and transport refrigerant vapor in the refrigeration system. The compressor provides pressure rise to the refrigerant to convert the vapor refrigerant into liquid refrigerant which in turn enables the further flow of the refrigerant through condenser, where it liquefies and moves to the expansion tube. The high-pressured liquid refrigerant turns into gas state after the liquid refrigerant expands and absorbs heat from the air, cooling the temperature in the process.

A. Based on working principles: Fixed displacement compressor, variable displacement compressor;
B. Based on working mode: Reciprocating, Rotary.

Primary failure modes
A. Abnormal Noises. If the AC compressor makes loud or weird noises, this may indicate that the electromagnetic clutchis damaged or severe wear and tear inside;
B. Leaking. Refrigerant fluid leaking is the most common issue in the A/C system;
C. If the compressor fails to operate, it is usually due to issues with the electric circuits.

Finished goods quality control points
Performance test, air tightness, installation dimension, interface specification, appearance, package.




Measurement Systems Analysis (MSA) is another Core Quality Tool for the implementation and maintenance of a Quality Management System (QMS) based on IATF 16949.

MSA is an experimental and mathematical method of determining how much the variation within the measurement process contributes to overall process variability. It is primarily used to determine the viability of an evaluation or measuring methodology for use on a specific part characteristic. There are five parameters to investigate in an MSA: Bias, Linearity, Stability, Repeatability and Reproducibility

MSA is widely practiced in the automotive industry.


Cost of raw materials:
Exchange rates:

USD/RMB: 1:7.0982

EUR/RMB: 1:7.8350

RUB/RMB: 1:0.1099

October 2019

The above information is for reference only


Notable Industry Events

Automechanika Shanghai 2019 will be held from the 3rd to 6th December 2019 in the National Exhibition and Convention Center (Shanghai). It’s Asia’s largest trade fair for automotive parts, accessories, equipment and services. The exhibition space will be 350,000 sqm, with 6,250 exhibitors and 140,000 visitors expected to attend this year.

The exhibition will cover Parts & Components, Electronics & Systems, Accessories & Customizing, Repair & Maintenance, REIFEN co-located zone, Alternative Drive Systems & Digital Solutions, Dealer & Workshop Management, Car Wash, Care & Reconditioning and many other fields.

The official website of the fair is:

Shentou as usual will exhibit at the Automechanika Shanghai 2019 and our booth numbers is 3E43. We look forward to meeting you there!

SHENTOU SUPPLY CHAIN MANAGEMENT CO. LTD. is a Shenzhen, China, based company serving international automotive clients in the implementation of their China strategies and programs. CHINA AUTOMOTIVE SUPPLIER QUALITY MANAGEMENT BRIEFING is a bi-monthly newsletter published by Shentou to address the specific and unique quality challenges and concerns international automotive companies face with suppliers in China. Comments are welcome at Click here to subscribe.

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