Case Study: Hybrid Measuring System Combines Gear and 3D Coordinate Metrology
15.06.15 - Flexibility and precision in quality assurance are especially demanded by companies whose products have a high degree of individualization. Even for large parts these attributes are very important.
For this reason and to fulfill the requirements of customers from the fields of mining, wind energy and railway transportation, the American-Chinese joint venture Chongqing Xinxing Tongyong Drivetrain Co. Ltd. integrated a LH 2600 Hybrid into their quality assurance process. This measuring system allows the measurement of gears, shafts, prismatic parts and surface parameters – without extensive reclamping of the large components.
Development and production of large gears is the main business of Chongqing Xinxing Tongyong Drivetrain Co. Ltd.. The focus is on components such as shafts, drive shafts, herringbone gearing and cylindrical gears. Xinxing Tongyong Drivetrain continually invests in machining centers and measuring systems, so their processes are always state-of-the-art.
Measurement Principals of Gear and 3D Coordinate Metrology
In 2011 an LH Hybrid type measuring system was installed in the quality assurance department. The design of this measuring system is unique. The basic machine is built as bridge type measuring machine. A rotary table is integrated into the massive granite base plate. This enables the combination of gear and 3D gear metrology. Furthermore the LH Hybrid is characterized by a retractable tailstock. So besides the measurement of different types of gears, prismatic parts and shafts can be measured between centers. The LH Hybrid at Xinxing Tongyong Drivetrain is additionally equipped with a sensor for measurement of roughness and determination of surface parameters.
The project to purchase the measuring system at Xinxing Tongyong Drivetrain was coordinated by Mr. Yang Xiaoping, Manager of Quality Assurance. The main criterion for selection of the measuring system was the requirement that all types of gears in the product portfolio have to be measured precisely and reliably. Furthermore measurement of prismatic parts such as the housings of turbines and generators and the evaluation of form and position tolerances have to be carried out easily.
After a long selection process Yang Xiaoping came to the conclusion that the LH Hybrid series measuring systems from WENZEL are the only ones to fulfill their expectations and requirements economically. The only alternative discussed was a solution with two measuring systems, but this would have meant that the investment would have been significantly higher. Part of it caused by a larger measuring room which would have had to be built. Furthermore the users would have to be trained on both measuring systems and the maintenance costs would have doubled.
The Investment Has Paid Off
„The past years, in which we have the LH 2600 Hybrid in operation, showed that we made a very good decision”, explains Yang Xiaoping. “The measuring system reduced the required floor space, saves time and costs for machine maintenance and contributes the fast and precise testing of our large gears and housings.”
The investment in the LH Hybrid paid off doubly as the measuring system is used for contract measurements, too. Already in June 2011, one month after the machine was put into operation a manufacturer of railway components from Chongqing contacted the company. The subject was a very complex measurement task which required the highest precision. Based on the successful completion of the project with the LH Hybrid, contract measurement became part of the product portfolio of Xinxing Tongyong Drivetrain.
„The quality of the LH Hybrid showed in the measurement of grounded gears,” says Yang Xiaoping. “Our production team got an order from a large company in Chongqing to grind gears. The high precision measurements with the LH Hybrid were successfully carried out. This has proven our approach to establish contract measurement as a product of our company.”
Two Proven Measuring Softwares for Challenging Measurement Tasks
The LH Hybrid combines the world of 3D coordinate metrology with the world of gear metrology. For ideal access to the measuring object the basic machine is designed as a typical 3D coordinate measuring machine of bridge type design. This enables it among other things to measure large scale housings completely and easily. To additionally fulfill the requirements of gear metrology a rotary table is integrated into the massive granite base plate. This allows the measurement of gears according to gearing principles.
To fulfill the demanding measurement tasks of 3D coordinate and gear metrology the measurement system is equipped with two software packages. The software package TGear is used for the measurement of the different gears. Its modular design enables the adaption to different measurement tasks of e.g. bevel gears, shafts, worm gears, rotors and other rotationally symmetrical parts. The creation of measuring programs is done by input of gear parameters into an input mask. The proven measuring software Metrosoft CM is used for the field of 3D coordinate measurements. The software offers extensive functionality for the measurement and analysis of geometrical dimensions and the evaluation of form and position tolerances.
Helpful Functionality for the Daily Life in Metrology
Yang Xiaoping and his team are enthusiastic. “The combination of the two measuring procedures helps us to create precise and reliable measuring results fast.” Some functions have proven themselves as very helpful in daily life in metrology:
Roughness measurement
The application is very user friendly as the measuring object is already fixed and aligned. So the roughness measurement can be carried out directly after the gear measurement has been finished. Therefore the measuring probe is exchanged for a roughness sensor and the measurement procedure can then be executed in CNC mode. The measuring positions are identical with those for the measurement of profile and lead. In 2012 planetary wheels have been produced for a customer from the field of wind energy. They required a surface roughness of Ra = 0.4 µm. For this project many tests with different grinding wheels and machining process parameters were necessary. The roughness tests with LH 2600 Hybrid allowed a time-saving completion of the project with the required accuracy of the measurements.
Profile measurements of cylindrical gears
The specifications of the VDI/VDE 2612 guide lines are explicitly implemented into the software TGear. For the evaluation of the pressure angle different evaluation areas can be defined according to the analysis requirements. With this functionality the requirements of a German customer concerning the evaluations were fulfilled. This included that for the evaluation of the pressure angle the evaluation areas needed to be extended to the nominal tip circle. For the evaluation of the spiral angle the evaluation area had to be extended to the nominal tooth width.
Scanning of root rounding
The functionality for scanning the root rounding allows the evaluation of the tooth root radius, tooth root rounding and the tooth surface involute. This enables the precise analysis of the condition of the gear after gear hobbing and the grinding so reliable evaluations, which provide information about the correct form of the hob cutter can be carried out.
Twist Analysis
Using the functionality for twist analysis within the gear measuring software TGear, profile and lead can be analyzed at different positions distributed across the complete tooth. Based on this measurement the twist can be determined along with conclusions about the hardening distortion.
Future-Oriented Invested
At the present time gears with a maximum diameter of 1500 mm can be produced. However the LH 2600 Hybrid allows the measurement of gears with a maximum diameter of 2600 mm. So the measuring system will enable Xinxing Tongyong Drivetrain to analyze gears even when production capacities are expanded. Based on a constantly increasing customer base and production volume the LH 2600 Hybrid is operated in a three shift operation since May 2013.
