Industrial measurement is a discipline that provides measurement technology support for product design, simulation, measurement, lofting, imitation, simulation, product quality control, and product motion state in all aspects of industrial production and scientific research. The measurement content is mainly based on the geometric quantity of the product, but also involves color, temperature, velocity and acceleration, and other physical quantities.
「 1. The connotation of precision measurement 」
Precision measurement technology is an integral part of industrial measurement technology, specifically industrial measurement with millimeter or higher accuracy. The development of modern industry has put forward higher requirements for the dimensional accuracy of products, especially for precision processing industries, such as precision screws, precision gears, precision worm gears, precision guide rails and precision bearings and other parts of the processing, the use of traditional measuring tools such as vernier calipers, micrometers and other traditional measuring tools have been unable to meet its measurement accuracy requirements. At the same time, with the increase of consumer demand for personalized products, manufacturing enterprises are faced with the requirements of increasing the types of product measurement, reducing the measurement batch, measuring speed, and storing measurement results for later quality data analysis and traceability, precision measurement technology has become an indispensable technology for enterprises to adapt to market competition. Moreover, with the development of artificial intelligence, machine learning, intelligent sensors, 5G and other technologies, online, automated, high-speed, and intelligent have become the main theme of current precision measurement systems and technologies. Therefore, precision measurement equipment needs to have a certain level of intelligence, such as after one measurement is completed, it can adaptively automatically and continuously measure the next batch of the same product, and automatically judge whether the product quality is qualified with the assistance of machine vision and other technologies. Furthermore, measurement is not only a judgment of product qualification, but also needs to be more widely integrated with quality analysis, processing and manufacturing, and design simulation, so as to achieve the purpose of quality driving productivity. The interaction of measurement data and quality analysis software can help enterprises achieve a more stable and reliable manufacturing process, ensure the stability of mass production, predict the trend of processing quality in advance, and adjust processing equipment, processing paths and even tools in time [ ]. As the eye of intelligent manufacturing, precision measurement not only plays a decisive role in product quality control, but also plays a decisive role in the level of manufacturing. At present, promoting intelligent manufacturing and digital transformation has become a development trend of enterprises, and the importance of precision measurement is self-evident.
Compared with traditional measurement equipment, intelligent measurement and measurement equipment is more complex, including mechanical, electrical, and soft multidisciplinary knowledge, covering radio frequency identification technology (RFID), machine vision, collaborative robots, online detection and management software systems and other fields, from the traditional manual testing to fully automated detection. The application of intelligent measurement equipment provides strong support for enterprise intelligent manufacturing. This section mainly introduces intelligent measuring equipment for geometric measurement, which involves the measurement of relevant parameters such as geometric dimensions, shapes and positions.
Intelligent measuring devices can measure geometric dimensions in a way that can be divided into tactile and non-contact measurements (Figure 1). Contact measurement method is a measurement method in which the sensor of the measuring instrument is in direct contact with the surface of the part to be measured. For example, the contact stylus moves along the surface of the workpiece and continuously obtains the measurement point data, which is also called scanning, and converts the collected shape data into discrete geometric point coordinate values through scanning, so as to complete the modeling of the surface shape of the object. It is characterized by high measurement reliability, high measurement accuracy and good repeatability. The disadvantage of contact measurement is that the measured contact force may deform the surface of the measuring instrument and part (such as soft surfaces), thus affecting the uncertainty of the measurement, so it is generally not suitable for the measurement of soft surfaces.
Figure 1 How intelligent measuring equipment measures geometric dimensions
Non-contact measurement is a measurement method in which the sensor of the measuring instrument and the surface of the measured part are not in direct contact, based on photoelectric, electromagnetic, ultrasonic and other technologies, in the case that the receiving element of the instrument is not in contact with the surface of the measured object, various external or internal data characteristics of the measured object can be obtained. The advantage of non-contact measurement is that the measuring sensor does not contact the surface of the measured object, does not cause any damage to the surface of the measured part, and is more suitable for the measurement of complex curved surfaces and soft surface parts. Non-contact measurements take the form of camera probe sensors, laser sensors or CT technology.
「 2. Precision Measuring Equipment 」
1) Coordinate measuring machine (CMM)
Coordinate measuring machining (CMM) (Figure 2) refers to an optical measuring instrument that can make three-way moving measurements in a three-way coordinate system, and can measure geometric shapes, lengths, and circumferential indexes. The measuring head of the coordinate measuring machine is divided into two types: contact and non-contact, and the commonly used probe is a contact probe, which has a wide range of applications, a variety of types, and convenient and flexible measurement. The disadvantage of CMM is that it has high requirements for the measurement environment, is not portable, and has a small measuring range.
Various industrial metrology fields, including automotive parts measurement, mold measurement, gear measurement, hardware measurement, electronic measurement, blade measurement, machinery manufacturing, etc.
Figure 2 CMM (Source: Hexagon)
2) Articulated arm measuring machine
The articulated arm measuring machine (Figure 3) is a portable contact measuring instrument in which the articulated arm has 6 or 7 degrees of freedom and can be rotated flexibly, simulating the movement of the human arm for contact with the point to be measured at different positions in space. The probe functions the same as the coordinate measuring machine. Some manufacturers attach small structured light scanners to their probes to enable fast scanning of workpieces, combining the advantages of contact and non-contact systems.
It can complete dimensional inspection, point cloud scanning, etc.
Figure 3 Articulated arm measuring machine (Source: Hexagon)
3) Laser tracker
The laser tracker (Figure 4) is an instrument that uses laser as a ranging means with a reflective target, which is equipped with a goniometric mechanism rotating around two axes to form a complete spherical coordinate measurement system. It can be used to measure stationary targets, track and measure moving targets or a combination thereof.
It can easily and accurately complete tasks such as large-size and oversized tooling measurement and parts matching.
Figure 4 Laser tracker (Source: Hexagon)
4) Digital photogrammetry
Photographic measuring equipment (Figure 5) is a way to continuously take pictures of objects with industrial cameras, and then use image processing software and technology to analyze the photographs taken to calculate the size of the measured object. Photogenic measurement systems provide a high-speed, 3D photogenic measurement solution.
Fast data acquisition and complex workshop site environment.
Figure 5 Photographic measurement equipment (Source: Hexagon)
5) Optical three-dimensional measurement equipment
A three-dimensional optical measuring system is a system that uses a beam of light for measurement, which has the advantage of non-contact. This system, also known as three-dimensional blue light scanner, is divided into three-dimensional blue light scanner, laser three-dimensional scanner, CT tomography scanner, etc. according to different sensing methods (Figure 6).
Suitable for full-scale 3D digital inspection of the geometry of the object to be measured, the 3D scanner has industrial-grade high accuracy and high stability, and can still provide high-precision measurement data in harsh environments.
Figure 6 Optical 3D measurement equipment (Source: Hexagon)
6) Composite image measuring machine
The composite image measuring instrument (Figure 7) is to complete the measurement of all types of features of the workpiece on the same equipment, avoiding secondary clamping on different equipment, saving the time of loading and unloading and the investment of multiple equipment. The application of composite sensor measurement technology to achieve fast optical measurement and contact scanning measurement to improve detection efficiency.
Measurement of small, thin, soft, complex shaped parts.
Figure 7 Composite image measuring instrument
7) On-machine measuring equipment
On-machine measurement is to take the machine tool hardware as the carrier, with the corresponding measurement tools (hardware includes: machine tool probe, machine tool setter, etc.; The software includes macro programs, special 3D measurement software, etc.), and during the workpiece machining process, the measurement of geometric features is carried out on the machine tool in real time, and the subsequent process improvement is guided according to the inspection results (Figure 8).
Processing equipment such as milling machines, machining centers and lathes.
Figure 8 On-machine measurement equipment
8) Gap profile surface measurement equipment
Profile measurement and 3D surface inspection are possible, and it is a handheld non-contact measurement. It can meet a range of manufacturing quality requirements from product development and manufacturing to repair and maintenance (Figure 9).
Applications in automotive, railway, steel and aerospace industries such as clearance and face difference measurement between body and door, wheel profile inspection, brake disc measurement, wheel spacing measurement, wheel wear inspection and track wear inspection, etc.
Figure 9 Gap profile surface measurement equipment
9) Machine tool high-precision calibration compensation equipment
It is mainly used to provide calibration compensation, can perform accurate and complete geometric analysis, continuously monitor and achieve the improvement of the accuracy of machine tools and coordinate measuring machines, and can be used in machine tool design and calibration, calibration of measuring instruments, electronics/automotive/aerospace and other industries and research fields (Figure 10).
Calibration of machine tools for high accuracy guarantees.
Figure 10 High-precision calibration compensation equipment for machine tools
Source: Wisdom Garden