In the process of CNC machine tool machining parts, the selection of CNC tools is essential to the machining process. It is key to the process of making the parts. Choosing the right tool will not only affect the speed at which the part is machined. Choosing the right CNC tool reduces part distortion. In addition, it improves manufacturing quality and speeds up part machining. The right CNC tool also increases productivity and extends the life of tools and equipment. It reduces the number of tool changes and improves the efficiency and accuracy of CNC machines. This increases the competitiveness of the company’s products and ensures sustainable growth. In the next section, Yonglihao Machinery will show you how to choose the right tool for your CNC machine tool.
Table of Contents
Why Is It Important to Choose the Right CNC Cutting Tool?
Choosing the right cutting tool is an important part of CNC machining. Different tools have different functions and complex shapes in the cutting process. To get the best results, it is important to choose the right tool. When the right machine is used, the job is maximized and time is saved. Machining a part with the right tool also helps to ensure the finish of the part and reduces tool wear.
You may need to make sure that the design features you add to the part are made with standard tool sizes. For example, when you are designing holes in a part, make sure that you are using a drill bit that is widely available and of a standard size, not one that is too small or too large.
It also helps to use the same size holes whenever possible to ensure that the design features are the same. More importantly, if one knows how to use commonly used tools. Then the designer will be able to plan the geometry of the machined part well.
Standard Cutting Tools for CNC Machine Tools
There are many types of CNC machine tools, each with its own functions and characteristics. In the following, we will introduce the standard cutting tools for CNC machine tools:
CNC Milling Tools
In CNC milling, these tools are used to make many different parts. People also consider them as CNC cutting tools. CNC milling tools are very precise and accurate. Following are some of the common CNC cutting tools:
End Mills
End mills are common tools used for CNC milling. These CNC cutting tools can be used for many different purposes, much like a drill. They can be used to drill holes in materials to machine workpieces without holes. There are many types of end mills, each with a different number of tips or flutes.
Slitting Saws
A slitting saw is a CNC cutting tool that looks like a flat circle with a hole in the center and teeth on the outside. They are sometimes used with a mandrel, also known as a slicing or slotting miter. Slitting saws can cut more material in a smaller circle, which is useful for tasks such as severing or slotting.
Slab Mill
CNC tools known as slab mills or cutters cut flat objects. They only have serrated edges, and these are best suited for cutting workpieces of varying widths.
Face Mills
These CNC cutting tools have flat sides with replaceable diamond cutting edges. CNC face mills can only cut in a horizontal plane because the cutting edge is on the side. The main job of a face milling cutter is to cut workpieces into flat parts. One of the advantages of face milling cutters is that the cutting edge can be replaced. Therefore, it ensures longer tool life and working time.
Thread Milling Cutters
Threads can be cut using these CNC tools. While a tap is the tool used to create internal threads, a thread milling cutter performs much the same function as a tap. Thread milling cutters can work on both internal and external threads. You should use these tools when you need to cut hard materials or uneven parts.
Flying Shears
This is a CNC tool that has a rigid body and one or two cutting heads. The main job of a fly cutter is to cut wide or short cuts in the workpiece. However, it is better to use flying cutters with two cutting edges when machining. This is because they can handle larger portions of the workpiece.
External Radius Milling Cutter
This is a special type of CNC insert that has a semi-circular cutting edge. To add a radius to the outer edge of a pocket edge, an outside radius milling cutter is the perfect tool for the job. Machinists use these tools to smooth and level the edges of the workpiece, thus avoiding stress buildup and preventing sharp corners.
CNC Turning Tools
Lathes are usually used in conjunction with CNC turning tools. The lathe turns the workpiece at a high RPM while the tool cuts the workpiece into the desired shape. However, the shape of the workpiece is determined by the type of tool used and the way it is turned. These are the standard turning tools used by machinists for CNC work:
Chamfering Tools
Chamfering tools are used to remove burrs, chamfers, and sharp edges from finished parts. Their angled cutting surface removes sharp edges and makes the part look better.
Separation Tools
Many CNC machinists use a separating tool on their CNC lathe to remove material from the final part. The blade of this tool separates the end of the finished part from the rest of the material clamped to the CNC lathe chuck.
Boring Tools
Lathe boring bars are used to bore holes in products that have been drilled, tapped, or straightened. In most cases, these boring tools touch the workpiece only a little, making it easier to accurately ream the holes. However, it is important to note that these boring bars can chatter or vibrate, which can damage the surface finish of the workpiece.
Knurling Tools
Knurling tools are often used to add diamond, diagonal, or straight prongs or designs to the surface of a machined part. This can make the part look more aesthetically pleasing.
CNC Drilling Tools
Machinists use standard tools called CNC drills to drill holes in different-sized workpieces. In order to drill holes, these tools have grooves and cutting points. The grooves and cutting points get smaller over time. Most drills come in three different types, which are:
Center Drills
CNC machine tool machinists use a center drill bit to drill precise holes in a workpiece. Other drills are then used to drill the hole to a larger size. Machinists use a center drill bit to precisely drill small holes in a workpiece.
Twist Drill Bits
A twist drill is a circular drilling tool with holes that look like spirals or helixes. These CNC cutting tools are usually manufactured using high-speed steel (HSS). They can be used for general cutting, especially for drilling holes in metal, wood, and plastic workpieces.
Suction-jet Drills
CNC tools known as jet suction drills are often used to make holes in larger and deeper objects. Many times, machinists use these tools for deep-hole drilling.
Materials Used in CNC Cutting Tool Production
The optimum cutting speed and feed for CNC turning depends on the material used for CNC tools. In order to avoid inefficiencies in production, machinists usually say that they use CNC tools made of harder raw materials to cut the workpiece material. Some of the common CNC cutting tool materials are listed below:
Ceramics
Cutting ceramics are the hardest materials used to make CNC tools. These materials do not rust or melt, making them ideal for cutting the hardest workpieces. As with tools made with carbide, these cutting tools last longer. Cutting ceramics are very hard, but manufacturers don’t often use them for CNC machining tools because they chip easily.
Cemented Carbide
Since Cemented Carbide is made up of carbides and metals such as titanium. Cemented Carbide can therefore withstand higher temperatures compared to HSS. On the other hand, cracks or chips on the surface of the tool can shorten its service life. In addition, they do not last as long as HSS tools. Because of this, Cemented Carbide is used to make tools for finishing parts.
High-speed Steel
HSS consists of metals such as chromium, tungsten, and molybdenum. It is the best material for CNC machine tools because of its longer service life. HSS has a melting point of 600 degree Celsius and can withstand high-temperature heating. Therefore, it is better to use HSS CNC tools for heavy machining.
Carbon Steel
Carbon, silicon, and manganese are mixed together in this material. It is also less costly than other materials used in CNC machines. Unfortunately, this material, although much cheaper, does not last as long. The low melting point of carbon steel (200ºC) also means that this metal is not suitable for heavy-duty cutting. This is because carbon steel tools melt faster in heavy-duty applications. When cutting lightweight materials such as foam, plastics, and soft metals, machinists usually use carbon steel tools.
Factors to Consider When Choosing CNC Cutting Tools
In the process of CNC machining, tool selection can refer to the following key factors:
- Workpiece material: The workpiece material will determine the choice of tool material and geometric parameters of the cutting part. It also affects the machining accuracy of the final part and the functional performance of the product
- Nature of production: The nature of production here refers to the batch size of the part, mainly from the cost of processing to consider the impact of tool selection. For example, using special tools in mass production may be cost-effective. But, in single-piece or small-batch production, it’s better to use standard tools.
- Machining accuracy:Machining accuracy affects the type of finishing tool selection and structural shape. Such as the final processing of the hole according to the accuracy of the hole can be drilled, reamed drill, and other ways to process.
- Machining program: Different machining programs may choose different machining tools. For example, some large holes can be processed using drilling and reaming drills, can also be processed using a boring tool, you can also use a milling cutter for processing.
- Cutting parameters: Different materials require different cutting parameters. For example, when machining free-form surfaces, the cutting speed of a ball-end tool is zero. For this reason, ball-end tools are usually used for surface finishing.
- Workpiece size and shape: The size and shape of the workpiece also affect tool selection. For example, end mills process the edges of flat parts. To mill flat surfaces, use carbide insert milling cutters. For high-speed milling, convex or fluted cutters should be selected.
- Machining surface accuracy: Roughness affects tool shape and cutting dosage. For rough milling, use a coarse tooth cutter. For fine milling, use a fine tooth cutter. For rough surface or hole machining, use a corn milling cutter with carbide inserts.
Tool Configuration and Setup
In the general production process, setting up and installing good tools is crucial for producing parts. To complete multiple machining processes in a single clamping of the workpiece, shorten the auxiliary time, and reduce the error caused by installing the workpiece several times, an automatic tool changer can be used.
First, the machining tools should be mounted individually in standard tool holders. Then, after being pre-sized outside the machine, they are somehow placed in the tool magazine.
When changing tools, the first tool is picked up from the tool magazine. The tool changer then removes the tool from the magazine or spindle and replaces it. It loads the new tool into the spindle and puts the old tool back into the tool magazine. The tool magazine has a large capacity and can be mounted on the side or above the spindle housing.
The CNC machine has an automatic tool changer with a tool magazine. It has only one spindle in the spindle box. The parts of the spindle must be tough to meet the needs of precision machining. In addition, the tool magazine contains many tools. This allows multi-process machining of complex parts. The adaptability and efficiency of the machine tool is greatly improved. Automatic tool change systems with tool magazines are suitable for CNC drilling centers and machining centers.
Advanced Tool Selection Strategies
In CNC machining, tools are considered a critical component of the production process. The general selection principles for critical tools are ease of installation, ease of adjustment, robustness, and machining accuracy. To meet the machining requirements, choose a shorter shank. This will improve tool rigidity. When selecting the tool, the size of the tool should be adapted to the surface size of the workpiece to be machined.
For roughing non-smooth surfaces or hole surfaces, you can use carbide insert milling cutters. For certain 3D surfaces and variable beveled contours, you can use spherical, ring, taper, and trapezoidal cutters, among others. In the surface processing, should be selected ball tool, and the radius of the ball tool should be less than the minimum curvature radius of the surface. The end-cutting speed of a ball-ended tool is zero. To ensure accuracy, the cutting rows are very close to each other. In terms of surface quality and cutting efficiency, flat-end tools are superior to ball-end tools. Therefore, after ensuring the machining accuracy, then select the flat-end tool for roughing or finishing.
Tool selection also needs to be adjusted according to specific machining tasks. In high-volume production, you can pick high-quality tools with good wear resistance. These tools may cost more. But, they can greatly cut the overall machining costs by boosting quality and efficiency.
Maintenance & Care for CNC Tools
The maintenance of CNC tools is also an important part of the machining process. In the whole process of machining parts, the need to do as well as possible in the following areas:
- Regularly clean the tool: In the production process, the surface of the tool is easy to adhere to the cutting fluid, oil and metal shavings, and other impurities, these impurities will not only affect the cutting performance of the tool but also may cause damage to the machine tool. Therefore, the tool should be cleaned regularly to keep its surface clean.
- Regularly check tools for wear and replace them as appropriate: You can use the number of times a tool is used or the length of time it is on the job to plan a tool replacement cycle so that it can be replaced promptly.
- Reasonable storage by the requirements: Store knives in a dry, ventilated, dust-free place. Avoid direct sunlight and moisture. At the same time, tools should be categorized and stored to avoid confusion and damage. Good maintenance and preventive measures are therefore important. They prolong tool life and also improve the quality of parts machining.
Conclusion
Metal-cutting tool materials are now categorized into five main groups. They are high-speed steel, cemented carbide, ceramics, cubic boron nitride, and polycrystalline diamond. When turning or milling high-strength steel, titanium alloy, and stainless steel parts, it is recommended that you use carbide tools with better wear resistance.
- In the roughing stage, hard, imprecise tools should be used to remove excess parts of the blank material.
- During the semi-finishing and finishing stages, durable, precision tools are used to ensure the accuracy and quality of the part.
Use the least accurate tools in the roughing stage and the most accurate tools in the finishing stage. If roughing and finishing selection of the same tool, it is recommended that roughing selection of finishing eliminated from the tool, because finishing eliminated most of the tool wear for the edge of the slight wear, coating wear repair light, continue to use will affect the machining quality of the finishing process, but the impact on the roughing is small.
Nowadays, CNC tooling is rapidly evolving and changing. More and more tool types are coming. When we choose tools, we need to keep learning new tooling knowledge and mastering new cutting technology. Yonglihao Machinery has lots of experience and expertise in the industry. It can provide you with the best solutions. For more information, please feel free to contact us, we will be happy to serve you.
FAQ
What are the signs that a CNC tool needs replacement?
In CNC machining, when we find that tools are worn, parts are oversized, machining efficiency becomes lower, and the surface finish of the machined parts is reduced, we may need to change tools to ensure that the quality of the parts machined meets the requirements of the drawings.
How do different CNC cutting tools impact the final product quality?
The tool’s geometry, material, and how it’s made directly determine the part’s accuracy and surface quality. Different CNC cutting tools have different impacts on the final product’s quality. For example, a high-precision tool can ensure that the part’s dimensions and shapes are within the allowed range. High-quality tool materials can reduce wear in machining and ensure a good surface finish.
Can the same CNC tools be used for different materials?
Yes, the same tool can be used for different materials because some lathe tools are universal. For example, carbide tools are suitable for ferrous and non-ferrous workpieces. However, some cannot. For example, HSS lathe tools only work for soft materials, like aluminum.