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Behind the scenes of 3D measurement: Why can CMM measure the most difficult-to-reach surfaces?
In modern manufacturing and engineering, accurate measurement is key to ensuring product quality. A coordinate measuring machine (CMM) is a device specifically designed to measure the geometry of an object by using a probe to detect the position of various points on the object's surface. The unique design of these devices enables them to address surfaces that are difficult to reach with traditional measurements.
“A coordinate measuring machine can measure every detail of an object precisely at the micron level.”
CMMs use a variety of probe types, the most common being mechanical probes and laser sensors, but there are also other types such as optical probes and white light sensors. Depending on the machine, the probe position can be controlled manually by the operator, or automatically by a computer.
In a typical 3D "bridge" CMM, the probe moves along three orthogonal coordinate axes: X, Y, and Z. Each axis has a sensor that monitors the position of the probe along that axis, typically with micron accuracy.
When the probe touches a certain location on the object, the machine reads the position of each axis to obtain the three-dimensional coordinates of that point. This process can be repeated many times to generate a "point cloud" that describes the surface features of the measured object. These point cloud data can be further used, for example, to verify distances between features or to construct geometric features such as cylinders and faces for tolerance checking.
“CMMs offer unparalleled accuracy in engineering measurements and can easily handle a wide variety of shapes and surfaces.”
How does it work?
The operation of CMM covers multiple links, including the structure of the machine itself, the probe system and the data processing platform. These machines usually consist of three main parts: the machine body, the probe system, and the data collection system.
In the early days, CMM probes were mainly mechanical, but with the advancement of technology, the emergence of electronically triggered probes has greatly improved measurement accuracy. This type of probe can automatically send coordinate data to the computer when it detects the surface of an object, significantly reducing measurement errors caused by different operating methods.
In addition, the emergence of scanning probe systems has further improved measurement efficiency. This system can drag the probe on the surface, quickly acquire data, and generate a three-dimensional model, which not only improves the measurement speed, but also enhances the measurement accuracy. sex.
Diversity of CMM
CMMs are not limited to fixed devices; portable CMMs are becoming increasingly popular. Portable CMMs use either an articulated arm or an armless scanning system, enabling them to measure in different environments. Furthermore, with advancements in technology, the use of optical CMMs is also rising in the industry.
These portable devices are typically lightweight, easy to operate, and do not require a controlled environment to work, making them suitable for applications such as reverse engineering and rapid prototyping.
"With the popularity of portable CMMs, measurement accuracy has never been so accessible, whether in the factory or outdoors."
Standardization and Accuracy
To ensure the performance of a CMM, the ISO 10360 series of standards provides clear testing requirements. These standards specify the characteristics of probe systems as well as length measurement errors, helping users ensure reliable and accurate measurements.
The accuracy of a measurement is often assessed based on the uncertainty factor at a specific distance. For CMMs using touch probes, the probe's repeatability is typically accurate to within one micron, which is significant for many demanding applications.
Future Outlook
The development of CMM technology is not limited to traditional measurement methods. With the rise of non-contact scanning technology and micrometer measurement, multi-sensor measuring machines have appeared on the market. These devices not only increase measurement flexibility, but also meet the needs of different materials and shapes.
In general, CMM, as a precision measurement tool, is playing an indispensable role in modern manufacturing with its ever-increasing measurement accuracy and range. Against the backdrop of continued technological advancement, we cannot help but ask, what surprises and challenges will future measurement technology bring us?
