Research On Virtual Digital Indexing Head And Its Correlative Technology

Indexing heads, which provide high-accuracy angular standard, have been widely used in machining. The traditional digital indexing heads display measurement results by separated digital readout box, which results in the following shortcomings: lack of flexibility, too relying on the hard work of the operator, difficult to interface with other instruments, and too hard to be used in automatic measurement. With the development of technology and industry, more requirements of the automatization and flexibility of machine equipments are emerged. Developing instruments that are easy to interface with computers, reconstruct measurement functions with virtual instrument technology, and develop more powerful data analyzing software, which will benefit to the combination of measurement process and manufacture process, is the trend of the instrument development. In this case, designing a virtual digital indexing head, which is flexible and can be easily interfaced with computers, is worthy and significant.In addition, combining with sensors and accessories, indexing heads can be used to measure form errors. Measurement and assessment of form errors are very important to manufacture, because they are committed steps of product quality test and machining accuracy control. Roundness and cylindricity are two of the most widely used tolerances, because most of workpieces contain round or cylindrical fraction. However, no method of assessing roundness and cylindricity, which not only meets the definitions of the national standards but also are the rapid and concision properties possessed, has been found.In this paper, the principle of a virtual digital readout for grating transducers based on Complex Programmable Logic Device (CPLD) and Universal Serial Bus (USB) technology is proposed, which use USB to communicate the hardware circuit and computer and take the functions of the traditional digital readout on computer screen, including displaying, presetting, zero clearing, format transition, storing and so on. The results of analysis show that the indication error of the system is smaller than±0.432um as the relative movement speed of the gratings is less than 0.3m/s, which can be used to interrogate and display the data of the grating transducer.On the base of virtual digital readout for grating transducers, the principle of a virtual digital indexing head is proposed, which is consisted of a digital indexing head with two grating transducers, a virtual digital readout system, and a virtual digital...