The type of machine used (CNC lathe, three-axis CNC milling machine, or five-axis machining center) is usually determined by the part’s complexity. The complexity, geometry, and size of the part affect the type of machine chosen and the product’s tolerances, end-use, and material type. Typically, more complex parts require more attention during machining due to their design, specific dimensions, and requirements. Design engineers should create as many simple, manufacturable parts as possible during the design process. The simpler the design, the easier and cheaper it is to manufacture. Mechanical designers are always thinking about creating designs requiring fewer components while ensuring maximum efficiency. This reduces costs while ensuring efficiency and higher productivity. CNC machines are used for metalworking and more. How do you do it accurately? A CMM machine can help.
What is a CMM machine?
Can CNC machining become even better with the help of CNC machines? Yes! Accurate geometry and physical dimensions are important in any manufacturing process. People use two methods to do this. One is the traditional method using a hand-held gauge or optical comparator. However, these tools require specialized knowledge and are prone to error. The other is to use a coordinate measuring machine. CMM stands for coordinate measuring machine. It is a tool that can measure the dimensions of machine parts/tools using coordinate measuring techniques. Measure the following dimensions:
- depth in X, Y, and Z axes.
- Depending on the complexity of the CMM, you can measure objects and record measurement data.
How to use a CMM measuring machine?
To learn a CMM, you must also understand how it works. In this section, you will learn what the CMM does. CMMs have two general types of measurement. One type uses a contact mechanism (touch probe) to measure a tool part. The other type uses other methods, such as cameras or lasers, as the measuring mechanism. The dimensions of the parts it can measure also vary. Some models (automotive CMMs) can measure parts larger than 10 meters.
How does the CMM work?
A CMM does two things. It measures an object’s physical geometry and dimensions using a probe mounted on a moving machine axis. It also tests the part to ensure it is the same as the modified design. CMM works through the following steps. The part to be tested is placed on the base of the CMM. The base is the measuring point and is made of stable and strong dense material. Stability and rigidity ensure measurement accuracy independent of external forces that can interfere with the work. A movable door equipped with touch probes is also mounted above the CMM plate. The CMM then controls the part to align the probe along the X, Y, and Z axes. In this way, it replicates every aspect of the part under test. When touching a point on the part under test, the probe emits an electrical signal that is mapped by the computer. By doing this sequentially for multiple points, you will measure the part. Once the measurement is complete, the next phase is the analysis phase, after the probe has captured the part’s X, Y, and Z coordinates. The information obtained from the analysis is constructed in terms of features. The operation mechanism is the same for CMMs using cameras or laser systems.
Benefits and limitations of a coordinate measuring machine
CMM should be an integral part of any manufacturing process. This is due to its significant advantages, which outweigh its limitations. Nonetheless, we will discuss the good and the bad points of it.
Saving time and money
Coordinate measuring machines are an integral part of manufacturing because of their speed and accuracy. Making complex tools is becoming commonplace in manufacturing, and CMMs are ideal for measuring their dimensions. Ultimately, they reduce the cost and time of industrial production.
Unlike traditional methods of analyzing the dimensions of machine parts, CMMs are the most reliable. They can digitally measure and explore your parts and other services such as dimensional analysis, CAD comparison, tool certification, and reverse engineering. All of these are essential for quality assurance.
A variety of probes and techniques provide versatility
CMM is compatible with many types of tools and components. Part complexity doesn’t matter because CMM will measure it.
Less operator involvement
CMMs are computer-controlled machines. As such, they reduce human involvement. This results in a reduction of operator errors that can cause problems.
Disadvantages of using CMMs
CMMs greatly improve manufacturing processes while playing a pivotal role in production. However, they also have some limitations that must be taken into account. Here are some of them:
The probe must touch the surface
Every coordinate measuring machine that uses a probe has the exact mechanism. For the probe to work, it must touch the surface of the measured part. For substantial parts, this is fine. However, for details with fine or delicate finishes, repeated touching can cause deterioration.
Soft parts can cause damage
For parts made of soft materials such as rubber and elastomers, using the probe can cause them to collapse. There is a risk of creating errors evident when analyzing the numbers.
Choose the right probe
Different types of probes are used in CMMs, and the right one must be chosen for the best results. Selecting the proper probe depends mainly on the size of the part, the desired design, and the probe’s capabilities.
Factors affecting part complexity
- Part size – Size alone does not determine part complexity, but it can be a factor that influences it. Remember that sometimes more significant flat parts are less demanding than smaller, more complex parts. Also, consider the size of the individual parts, as this affects the size of the cutting tool used. Larger, high-speed cutting tools remove material faster, reducing machining time.
- Machining of components – The number of operations, interventions, and inspections required also affects the part’s complexity. Depending on the geometry, finish, tolerances, etc., the sequence of operations can be complex, time-consuming, and detailed. For example, a complex part may require a lot of repositioning and human intervention. Sometimes a five-axis machine or a mill-turn machine may be the most suitable machine.
- Part tolerances – Part tolerances affect the choice of CNC machine used, cost, and lead time. Achievable tolerances are also affected by material, machining speed, and tooling. In short, the narrower the tolerance, the more expensive the part. Higher ones allow for greater precision but may also require additional processes, operations, tools, and machinery, which increases costs.
Types of finishes
The following are types of finishing:
Blasting involves the removal of any deposits or surface imperfections to produce a more uniform, smooth surface. Spherical beads provide a consistent finish and are often used to achieve a matte finish. Finer pieces are also available for a more satin or matte finish.
Anodized finishes provide a specific wear-resistant coating and are often available in a variety of colors. Anodizing is usually transparent, and the layers are often very thin, so CNC machine marks on the surface must be considered.
CMM inspection reports and machining complex shapes
Three-dimensional coordinate measuring machine (CMM) inspection involves using the CMM to detect the size of a part to determine if it meets specific tolerance requirements. CMMs are used to measure the mass and properties of objects. CMM inspection will be required to measure more complex parts to ensure they meet specifications. Smooth surface finishes are checked at this stage to make sure they match drawings and designs. The CMM works with probes that measure points on the workpiece. Three axes make up the machine tool’s coordinate system. The second system is the part coordinate system, in which the three axes correspond to features and reference points on the workpiece.
Benefits of CMM inspection
CMM inspections are performed as needed and are sometimes even mandatory. CMM inspection reports save time and reduce overhead costs by ensuring that parts are produced exactly as designed. This guarantees high efficiency, and any design deviations or defects will be detected before shipment. Depending on the industry, deviations from the standard can be catastrophic (e.g., medical or aerospace technology). This final quality control ensures that parts are created and delivered to customers. Computer numerical control equipment and CNC machine tools have never been so accurate. Our company makes CNC technology and the CNC machining process even better, and metalworking is ensured by, among other things, precise tool positioning and properly applied types of control systems.