1 Introduction For each factory, the purchase of CNC machine tools is a considerable investment. In order to make the investment equipment play a key role in production and ensure that qualified parts are processed, it is crucial to recover costs as soon as possible.
Experience shows that more than 80% of the machine tools must be commissioned in the field before installation to meet their technical specifications. Therefore, when the new machine tool is accepted, verification is required to ensure that the machine tool can be installed at the beginning to ensure that it meets its technical specifications and the expected quality and efficiency.
In addition, experience has shown that 80% of the machine tools that have been put into production are in abnormally high-performance working conditions after a period of use, and even exceed their potential bearing capacity. Therefore, it is usually necessary to retest the new machine tool after it has been used for half a year. It can then be tested once a year. Regular inspection of machine tool errors and timely correction of pitch and backlash can effectively improve the accuracy of machine tools in production and use, improve the quality of parts processing, and do not produce waste, greatly improving the utilization of machine tools. In short, the timely disclosure of machine problems can avoid the loss of precision and destructive use of machine tools.
With the further promotion and application of numerical control technology, more and more numerical control machine tools use their own probe system to carry out workpiece and tool dimension detection and profile digitalization. To know that the realization of the above functions is closely related to the precision of the machine tool itself, if the accuracy of the machine tool is not calibrated on a regular basis, then it is impossible to accurately complete the above work.
Renishaw's ML10 laser interferometer linear displacement measurement software provides data analysis according to the following standards: BS4656 British Standard Three Machines; BS3800 British Machine Standards; ISO 230-2 International Standards; VDI/DGQ 3441 German Institute of Machine Tool Standards ; VDI 2617 German Institute of Engineers Three Test Machine Standards; NMTBA American Machine Tool Association Standards; GB10931-89 Chinese National Standards; ASME B89.1.12M American Society of Mechanical Engineers Standards; ASME B5.54 American Society of Mechanical Engineers Standards; E60-099 French Standards ;JISB2330 Japanese national standard.
2 Renishaw's advanced technology Renishaw UK is a global multinational company specializing in designing and manufacturing high-precision inspection instruments and equipment. The main products are coordinate measuring machines and probes for numerically-controlled machine tools, laser interferometers, ball bars, etc., which provide the pre-order (laser interferometer and ball-bar instrument) and sequence (machine-tool workpiece probes) for the machinery manufacturing industry. And a series of quality assurance methods for knife detection) and after-sequence (test and configuration of three measuring machines). All of her technologies and products are designed to ensure the accuracy of CNC machine tools, improve the performance of CNC machine tools, improve the efficiency of CNC machine tools, and ensure and improve the machining accuracy and quality of CNC machine tool manufacturing plants, and expand the market for finished products.
2.1ML10 Laser Interferometer
Renishaw ML10 laser interferometer provides a high-accuracy instrument for machine tool verification. It has high precision, up to ±1.1PPM (at 0-40°C), large measuring range (linear measurement length 40m, optional 80m), measurement Fast speed (60m/min), high resolution (0.001μm), good portability. Because Renishaw laser interferometer has automatic linear error compensation function, it can easily restore the precision of the machine tool and is welcomed by users.
In order to let everyone know more about the unique advantages of the ML10 laser interferometer in detecting the precision of CNC machine tools, the application of the ML10 laser interferometer in precision detection is highlighted below.
(1) Geometric accuracy detection can be used to detect straightness, verticality, pitch and yaw, flatness, parallelism, and so on.
(2) The detection of position accuracy and its automatic compensation can detect the positioning accuracy, repeat positioning accuracy, and micro-displacement accuracy of CNC machine tools. Using Renishaw ML10 laser interferometer can not only automatically measure the machine's error, but also can automatically compensate for its linear error through RS232 interface. It saves a lot of time compared with the usual compensation method and avoids manual calculation and manual numerical control. The operator error caused can be used to maximize the number of compensation points on the measured axis to achieve the best accuracy of the machine tool. In addition, the operator does not need to have the knowledge of machine parameters and compensation methods.
Currently, there are optional compensation software Fanuc, Siemens 800 series, UNM, Mazak, Mitsubishi, Cincinnati Acramatic, Heidenhain, Bosch, Allen-Bradley.
(3) Inspection accuracy and automatic compensation of the indexing accuracy of the digital turret Nowadays, the ML10 laser interferometer and the RX10 turntable reference can be used to automatically measure the rotary axis. It can perform automatic measurement at any angular position at any angular position with an accuracy of ±1. New international standards have recommended the use of this new technology. Compared with the traditional autocollimator and polyhedron method, it not only saves a lot of measurement time, but also obtains a complete rotary axis accuracy curve, knows every detail of its accuracy, and gives the statistical results processed according to relevant standards.
(4) Double-axis positioning accuracy detection and automatic compensation Renishaw's dual laser interferometer system can simultaneously measure large-scale gantry mobile CNC machine tools. The positioning accuracy of a certain axial movement by dual servos can also be passed through the RS232 interface. , Automatically compensate for the two-axis linearity error.
(5) Dynamic performance testing of CNC machine tools Using RENISHAW dynamic measurement and evaluation software, laser interferometers for machine tool vibration testing and analysis (FFT), dynamic analysis of ball screws, analysis of response characteristics of servo drive systems, dynamics of guide rails Characteristics (low-speed crawling) analysis, etc.
2.2QC10 ball bar instrument
In the precision testing of CNC machine tools, QC10 ball bar instrument and ML10 laser interferometer are two mutually complementary instruments, and they are indispensable. The ML10 laser interferometer focuses on the accuracy of the machine tool; the QC10 ballbar meter is mainly used to determine the cause of the machine's loss of accuracy and to diagnose the failure of the machine. However, compared with the ML10 laser interferometer, QC10 ballbar has not yet been understood by the majority of users. For this reason, the following will focus on the principle, function and application of QC10 ballbar.
2.2.1 What is a ball instrument
Renishaw QC10 ball bar is a tool for the rapid detection of two-axis linkage precision of CNC machine tools and failure analysis of machine tools. It consists of a high-precision displacement sensor mounted inside a retractable fiber rod. The sensor consists of two coils and a movable inner rod. The operating principle is similar to that of a displacement sensor using LVDT technology. When its length changes, the inner rod moves into the coil and the inductance changes. The detection circuit converts the inductive signal into a displacement signal with a resolution of 0.1 μm, which is transmitted to the PC through the interface. The accuracy of the laser interferometer is up to ±0.5μm (at 20°C).
The QC10 sensor detects changes in the machine's movement radius as the machine travels round the ballbar length by a predetermined program. Renishaw's QC10 analysis software can quickly change the machine's straightness, verticality, repeatability, and backlash. The ratio of each axis, for example, no match, servo performance, etc. is separated from the change in radius.
2.2.2 Main Functions
(1) Rapid calibration of machine tool accuracy grades By testing the machine tool with a ball bar at different feed rates, the operator can select the feed rate that meets the accuracy requirements of the machined workpiece to be processed, thereby avoiding the production of waste products.
(2) Quick diagnosis and analysis of machine tool faults and problems The ball bar instrument can quickly find out and analyze the problems of the machine tool, mainly check the backlash, the backlash of the screw, servo gain mismatch, verticality error, lead screw cycle. The performance of the error, such as the crash of the machine tool, can be detected by the ballbar and quickly tell the operator the accuracy of the machine tool and whether it can continue to use. In the ISO standard, methods for measuring the accuracy of a machine tool with a ball bar have been specified.
(3) Convenient maintenance and maintenance of the machine Tool ball bar can tell the user the accuracy of the machine tool, which can remind the maintenance engineer to pay attention to the problem of the machine tool and carry out preventive maintenance without causing major problems.
(4) Shortening the development cycle of the new machine tool Testing with a ball bar can analyze the influence of the selection of the machine's lubrication system, servo system, and bearing pairs on the accuracy of the machine tool. This will change the original design according to the test conditions, thus shortening the new machine tool development cycle.
(5) Convenient machine tool acceptance test For the machine tool manufacturer, the ball bar instrument can be used to rapidly test the machine tool and check whether the accuracy meets the design requirements. The ballbar is now recommended by international machine tool inspection standards such as ISO230 and ANSI B5.54. For the machine tool user's factory, the ball bar instrument can be used for machine tool acceptance test to replace the NAS test piece cutting, or after the ball bar instrument is used to detect the machine tool, the test piece can be cut.
2.2.3 Working Accuracy Detection
QC10 ball bar meter is a rapid (10 ~ 15min), convenient, and economical way to test the two-axis linkage performance of CNC machine tools, which can be used to replace the NAS test piece cutting accuracy.
