The type of machine used (CNC lathe, three-axis CNC milling machine, or five-axis machining center) is usually determined based on the complexity of the part. The complexity, geometry, and size of the element influence the type of machine chosen, as well as tolerances, end use, and the type of material of the product. Typically, more complex parts require more attention during machining due to their design, specific dimensions, and requirements. Design engineers should strive to create as many simple, manufacturable parts as possible during the design process. The simpler the design, the easier and therefore cheaper it is to produce. Mechanical designers always wonder how to create designs that require fewer components while ensuring maximum efficiency. This allows to reduce costs while ensuring efficiency and higher productivity. CNC machines are used for machining metals and more. How to do it exactly? A CMM machine can help with this.
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 every manufacturing process. People use two methods for this purpose. One of them is the traditional method using a manual measuring tool or optical comparator. However, these tools require specialized knowledge and are prone to errors. The second is the use of 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 techniques. Measure the following dimensions:
- height,
- width
- depth in X, Y, and Z axes.
Depending on the complexity of the CMM, it can measure objects and record measurement data.
How to use a CMM measurement machine?
If we want to understand what CMM is, we also need to understand how it works. In this section, you will learn about the operation of CMM. CMMs have two general types of measurements. One type uses a contact mechanism (touch probe) to measure tool parts. The second type uses other methods, such as cameras or lasers as a measuring mechanism. The dimensions of the parts that it can measure also vary. Some models (automotive coordinate measuring machines) can measure parts larger than 10 m.
How does CMM work?
CMM does two things. It measures the physical geometry and dimensions of an object using a probe mounted on the machine's movable axis. It also tests the part to ensure it is the same as the modified design. CMM operates through the following steps. The part under examination is placed on the base of the coordinate machine. 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 could interfere with work. Above the plate of the coordinate machine, movable doors equipped with touch probes are also mounted. Then the CMM controls the part to align the probe along the X, Y, and Z axes. In this way, it replicates every aspect of the tested part.
While touching a point on the part being examined, the probe emits an electrical signal, which is mapped by the computer. By doing this consecutively for many points, you measure the part.
After the measurement is completed, the next phase is the analysis phase, after the probe captures the X, Y, and Z coordinates of the part. The information obtained from the analysis is constructed in terms of features. The operating mechanism is the same for coordinate machines using cameras or laser systems.
Benefits and limitations of the coordinate measuring machine
CMM should be an integral part of every manufacturing process. This is due to its enormous advantages, which outweigh its limitations. Nevertheless, we will discuss the strengths and weaknesses of this issue.
Benefits of using a coordinate measuring machine
- Saving time and money
Coordinate measuring machines are an integral part of the manufacturing process due to their speed and accuracy. The creation of complex tools has become commonplace in production, and coordinate machines are perfectly suited for measuring their dimensions. Ultimately, they reduce the costs and time of industrial production.
- Quality assurance
In contrast to traditional methods of machine part dimension analysis, coordinate measuring machines are the most reliable. They can digitally measure and analyze your parts, along with other services such as dimensional analysis, CAD comparison, tool certification, and reverse engineering. All of this is essential to ensure quality.
- The variety of probes and techniques ensures versatility
CMM is compatible with many types of tools and components. The complexity of the parts does not matter, as the CMM will measure it.
- Less operator involvement
CMMs are computer-controlled machines. Therefore, they reduce human involvement. This leads to a reduction in the number of operator errors, which can cause problems.
Disadvantages of using CMM
CMM machines significantly streamline manufacturing processes, while playing a key role in production. However, they also have certain limitations that need to be taken into account. Here are some of them:
- The probe must touch the surface
Every coordinate measuring machine using a probe operates on the same mechanism. For the probe to function, it must touch the surface of the part being measured. This is not a problem for very solid parts. However, for parts with fine or delicate finishes, repeated touching can degrade the quality of the product.
- Soft parts may cause damage
In the case of parts made of soft materials, such as rubber and elastomers, the use of a probe can cause them to collapse. There is a risk of creating errors that are visible during the analysis of numbers.
- Select the appropriate probe
Various types of probes are used in coordinate machines, and to achieve the best results, it is necessary to choose the right one. The choice of the right probe largely depends on the size of the part, the desired project, and the capabilities of the probe.
Factors affecting the complexity of parts
- Size of the part
The size itself does not determine the complexity of the part, but it can be a factor that influences it. Remember that sometimes larger flat parts are less demanding than smaller, more complex ones. The size of individual elements should also be taken into account, as it affects the size of the cutting tool used. Larger, fast cutting tools remove material faster, shortening the processing time.
- Part processing
The number of required operations, interventions, and checks also affects the complexity of the part. Depending on the geometry, finish, and tolerance, etc. the sequence of operations can be complex, time-consuming, and detailed. For example, a complex part may require many changes in position and human intervention. Sometimes the most suitable machine may be a five-axis machine or a milling lathe.
- Part tolerance
Part tolerances affect the choice of CNC machine used, as well as the cost and time of execution. The achievable tolerances are also influenced by the 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 machines, which increases costs.
Types of finishes
Below we present types of finishes:
- Shot blasting
Abrasive blasting involves removing any deposits or surface imperfections to achieve a more uniform, smooth surface. Spherical beads provide a consistent finish and are often used to achieve a matte finish. Finer elements are also available for a more satin or matte finish.
- Anodizing
Anodized finishes provide a specific coating resistant to wear and are often available in various colors. Anodizing is usually transparent, and the layers are often very thin, so CNC machine marks on the surface should be taken into account.
CMM inspection reports and machining of complex shapes
The control of a three-dimensional coordinate measuring machine (CMM) involves using a CMM to detect the size of parts to determine if they meet specific tolerance requirements. Coordinate measuring machines are used to measure the mass and properties of objects. CMM control will be required to measure more complex parts to ensure they meet specifications. Smooth surface finishes are checked at this stage to ensure they match drawings and designs. The CMM works with probes that measure points on the workpiece. Three axes form the coordinate system of the machine tool. The second system is the coordinate system of the part, in which three axes correspond to the features and reference points of the workpiece.
Benefits of CMM Inspection
CMM inspections are conducted as needed, and sometimes they are even mandatory. CMM inspection reports save time and reduce overall costs, ensuring that parts are manufactured exactly as they were designed. This guarantees high efficiency, and any design deviations or defects will be detected before shipment. Depending on the industry, deviations from the norm can be catastrophic (e.g. medical or aviation technology). This ultimate quality control provides certainty before creating parts and delivering them to customers. Computer numerical control devices and CNC machine tools have never been so accurate. Our company makes CNC technology and the CNC machining process even better, and metal machining is ensured, among other things, by precise tool positioning and properly applied types of control systems.