# Measurement

Measurement is the systematic assignment of a number or value to a characteristic of an object or event. The value can be compared with other objects or events for scientific usages. The range and scope and the corresponding applications of measurement are dependent on the context and disciplines. In the field of natural sciences and western engineering, measurement values do not apply to nominal properties of objects.

In the machine tool usages, people use CMM system to do measurement for accuracy and precision limits, such as work pieces, tooling objects, tilting angles, etc. There are 2D and 3D measurements and in the present article we will take a look of 3D CMM measurement. In the industrial usages, a 3D coordinate measuring machine is also called 3D CMM machine. This is a coordinate measuring machine, and is a device that measures the geometry of physical items by sensing discrete points on the surface of the targeted item with a probe.

## Detecting Probes

There are many different types of probes which are adopted in CMMs, including mechanical, optical, laser, and even white light. Based on the machine models, the probe position may be manually controlled by an onsite operator or it may also be computer controlled based on the programs. In practice, CMMs typically specify a probe's position in terms of the displacement from a reference position in a three-dimensional Cartesian coordinate system, which are with XYZ axes as designed.

## Axes and Measurement

In order to move the detecting probe along the X, Y, and Z axes, many machine tools also allow the probe angle to be managed to allow measurement of surfaces that would otherwise be unreachable. In the machine tool industry, the CMM equipment is widely used to do precision measurement for the work piece as well as other objects, so to achieve the intended accurate processing within the intended standards. 3D rather than 2D CMM is widely accepted in the machine tool industry, and the deployment of CMM in the grinding is very common for the purpose of precision finishing.

Machine tools are the most fundamental capital goods for manufacturing, and for manufacturers the critical role that determines the final output of the end products is precision standard. The quality of the machine tool, as this reason, is the key point of the quality of the manufacturers’ final end products. The inventory of machine tools varies from case to case. This is dependent on the request of customer. After the invention of the machining centers and the programmed controlling system, the standards of machining become more and more rigid compared with the standards in the NC era.

## CNC and CMM

There are many machine tool systems that can be connected and coordinated with CMM devices. Besides the CNC machining centers, there are also CNC turning centers, CNC milling machines, CNC tapping and milling centers, CNC drilling and milling centers, etc. that can work with the CMM. Those machines, though not as versatile as machining centers, are also very strong in machining all kinds of work pieces with complicated profiling shapes.

The coordination with the CMM machine may not be always built-in but rather, may be other kinds of integrations. Currently, many machine tool manufacturers tend to integrate CMM devices into their machine tools, applying a wider field of precision standards to the machine tool sector. Machining centers, either vertical or horizontal, are powerful in all kinds of heavy cutting duties especially if the machining centers are designed with double column structure frame. Therefore, in the era of Industry 4.0, all kinds of machine tools are evolving towards the form with more versatile functionalities.

## Roughness Measuring

Grinding is a type of abrasive cutting that needs CMM to perform during processing if high precision is needed. For grinding machines such as external grinding and internal grinding machines, the role of an built-in installed CMM machine is very helpful.

In the metal working industry, there are a wide variety of grinding machines, and roll grinders are very efficient for many kinds of grinding processes. A roll grinder is a powered grinding tool or machine tool that used for grinding process, which is a common type of machining that utilizes abrasive wheel or wheels as the cutting means for processing. Each grain of abrasive on the wheel's surface cuts a small chip from the work pieces through shear deformation manner.

There is a huge number of grinding machine classifications due to the complicated grinding mechanisms that are all different from one another. Those grinding measures are invented based on the industrial demands. Regarding the grinder inventory, there are belt grinder, bench grinder, cylindrical grinder, surface grinder, tool & cutter grinder, jig grinder, gear grinder, die grinder, angle grinder, and roll grinder, just to name a few.

Cylindrical grinder includes both the types that use centers and the center-less types. A cylindrical grinder may have multiple grinding wheels for different purposes. For the CMM measurement to be applied, onsite workers have to know how and where to work the probe onto the targeted point.

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