A CMM machine is a coordinate measuring machine, which is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. A CMM machine can measure the dimensions, angles, and shapes of an object in three-dimensional space, using a coordinate system. A CMM machine can be used for quality control, inspection, reverse engineering, or design verification of various products and parts.
A CMM machine consists of three main components: a main structure, a probing system, and a data collection and reduction system. The main structure includes three axes of motion, which allow the probe to move along the X, Y, and Z directions. The probing system includes the probe and the sensor, which can be mechanical, optical, laser, or other types, depending on the application. The data collection and reduction system include the machine controller, the computer, and the software, which process the data from the probe and display the results.
It measures an object’s physical geometry, and dimension via the touching probe mounted on the machine’s moving axis. It also tests the parts to ascertain that it is the same as the corrected design. The CMM machine works via the following steps.
The part that is to be measured is placed on the CMM’s base. The base is the site of measurement, and it comes from a dense material that is stable and rigid. The stability and rigidity ensure that measurement is accurate irrespective of external forces that can disrupt the operation. Also mounted above the CMM plate is a movable gantry that is equipped with a touching probe. The CMM machine then controls the gantry to direct the probe along the X, Y, and Z axis. By doing so, it replicates every facet of the parts to be measured.
On touching a point of the part to be measured, the probe sends an electrical signal which the computer maps out. By doing so continuously with many points on the part, you will measure the part.
After the measurement, the next stage is the analysis stage, after the probe has captured the part’s X, Y, and Z coordinates. The information obtained is analyzed for the construction of features. The mechanism of action is the same for CMM machines that uses the camera or laser system.
CMM Machine Components
Knowing about a CMM machine also comes with understanding the functions of its components. Below are the important components of the CMM machine.
· Probe
Probes are the most popular and important component of a traditional CMM machine responsible for measuring action. Other CMM machines use optical light, cameras, lasers, etc.
Due to their nature, the probes’ tip comes from a rigid and stable material. It must also be temperature resistant such that the size won’t change when there is temperature alteration. Common materials used are ruby and zirconia. The tip can also be spherical or needle-like.
· Granite Table
A granite table is an important component of the CMM machine because it is very stable. It is also not affected by temperature, and when compared to other materials, the rate of wear and tear is lower. Granite is ideal for highly accurate measurement because its shape stays the same over time.
· Fixtures
Fixtures are also very important tools used as agents of stability and support in most manufacturing operations. They are components of the CMM machine and functions in fixing the parts into place. Fixing the part is required since a moving part can lead to errors in measurement. Other fixing tools available for use are the fixture plates, clamps, and magnets.
· Air Compressors and Dryers
Air compressors and dryers are common components of CMM machines such as the standard bridge or gantry-type CMMs.
· Software
The software is not a physical component but will be classified as a component. It is an important component that analyzes the probes or other sensitivity components.
Benefits & Limitations of Coordinate Measuring Machine
CMM machines should be an integral part of any production process. This is because of its huge advantages that outweigh the limitations. Nevertheless, we will discuss both in this section.
Benefits of Using a Coordinate Measuring Machine
Below is a wide range of reasons to use a CMM machine in your production workflow.
Save Time and Money
CMM machine is integral to the production flow because of its speed and accuracy. Production of complex tools is becoming rampant in the manufacturing industry, and the CMM machine is ideal for measuring their dimensions. Ultimately, they reduce production costs and time.
Quality Assurance Is Guaranteed
Unlike the conventional method of measuring machine parts’ dimensions, the CMM machine is the most reliable. It can digitally measure and analyze your part while providing other services such as dimensional analysis, CAD comparison, tool certifications and reverse engineers. This is all needed for quality assurance purpose.
Versatile with Multiple Probes and Techniques
CMM machine is compatible with many types of tools and components. It does not matter the complexity of the part since a CMM machine will measure it.
Less Operator Involvement
A CMM machine is a computer-controlled machine. Therefore, it reduces the involvement of human personnel. This reduction reduces operational error that can lead to problems.
Limitations of Using A Coordinate Measuring Machine
CMM machines definitely improve production workflow while playing a crucial role in manufacturing. However, it also has a few limitations that you should consider. Below are a few of its limitations.
The Probe Must Touch Surface
Every CMM machine using the probe has the same mechanism. For the probe to function, it must touch the surface of the part to be measured. This is not an issue for very durable parts. However, for parts with a fragile or delicate finish, consecutive touching can lead to parts deterioration.
Soft Parts Could Lead to Defects
For parts that comes from soft materials like rubbers and elastomers, using a probe can lead to the parts caving in. This will lead to error which is seen during digital analysis.
The Right Probe Must Be Selected
CMM machines use different types of probes, and for the best one, the right probe must be selected. Selecting the right probe depends largely on the part’s dimension, the design required, and the probe’ ability.
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