Test & measurement


Encoders H


aozhi Mechanical and Electrical (Haozhi), based in China, is an industry leader in direct-drive technology for machine tool


and robotics applications. Direct-drive (DD) motors are electric motors


that directly transmit power to the application without the use of mechanical reduction elements such as gears, pulleys, chains or belts. DD technology for linear motors and rotary


tables has matured in recent years. It has significantly improved the overall performance of machine tools, which has enabled corresponding improvements in the quality, speed and efficiency of production machining. These benefits help manufacturers to reduce machining times and to drive down costs. Haozhi builds direct-drive rotary (DDR) tables


and linear motors with integrated high- performance optical encoder systems from Renishaw, which give Haozhi products a substantial competitive advantage. Qun Lei, Vice president of Haozhi, explains


his company's role in the machine tool industry: “Haozhi initially focused on producing machine tool motor spindles and, after many years of hard work, we are now the global market leaders. We have launched a wide range of spindle products aimed at different industries — including the world's fastest motor spindle that operates at up to 400 krpm with a rotational accuracy of 6 µm. We also manufacture machine tool rotary tables and linear motors, and are developing gear reducers and robotic joint products to cater for the rapidly growing robotics market. We export primarily to Southeast Asia and a number of European countries.


52 Challenges


General market trends for DDR motors include higher position accuracy, increased reliability, and lower maintenance costs. In recent years, the use of direct-drive


rotary (DDR) table technology has expanded into automated manufacturing and light- machining applications. Rotary tables are usually deployed as either a


fourth or fifth axis on CNC machining centres for precision light manufacturing, such as the machining of mobile phone and tablet cases. Alternatively, rotary tables are used in indexing table modules for automated production lines. Many everyday consumer products require


parts that have been precision machined on rotary tables with excellent accuracy and motion control performance in order to produce the smooth surfaces required. The error budget of a motion control system,


such as a rotary table, is affected by factors related to the machine structure, individual mechanical components, transmission mechanisms and position encoders. Mechanical resonance is one of the most


common problems designers face when trying to maximise either the command response or dynamic stiffness of traditional rotary tables driven by worm gears. One


drive improvements in the performance of direct-drive motors


“We first came across Renishaw's advanced


metrology products more than a decade ago and have enjoyed working with them ever since. When we decided to begin developing rotary tables, we chose their optical encoders without any hesitation as we have the utmost confidence in Renishaw’s products.”


particular concern is the inertia mismatch between the load and the motor. DDR tables eliminate many of the mechanical


resonances associated with traditional rotary tables and enable the design of high-performance systems which are optimised for the speed and torque requirements of the application. For Haozhi, encoders are one of the most


critical components in their motion control products. Important encoder errors for rotary motors include sub-divisional error (SDE), jitter, installation error (which includes scale eccentricity), scale graduation error and the compliance of the coupling between the motor and the encoder rotary scale.


solution


Renishaw has a significant presence in the machine tool sector and has cultivated a successful relationship with Haozhi over many years. Haozhi has selected the RESOLUTE absolute


optical encoder series with RESA rings for its new family of rotary tables. “We first came across Renishaw's advanced


metrology products more than a decade ago and have enjoyed working with them ever since. When we decided to begin developing rotary tables, we chose their optical encoders without any hesitation as we have the utmost confidence in Renishaw's products. Our experience has shown that their optical encoders are easy to install and that our engineers are able to assemble them quickly. “Renishaw’s expert team also provides


outstanding aftersales service, and they helped with any issues that we encountered


January 2021 Instrumentation Monthly


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74