In modern production, CNC (Computer Numerical Control) machines are widely used. These are computer-controlled tools designed to perform precise movements in repeatable patterns. They were introduced to the industry in the 1940s and 1950s. As highly precise machines, they are used in various machining operations. Although CNC machining is very similar to 3D printing, the main differences are high precision, advanced speed, and cost. Generally speaking, CNC machines are a better choice for more precise, efficient, and high-quality projects. There are various types of CNC tools, and manufacturers mostly use them for projects requiring high precision and accuracy, hence it is important to choose the right machine for a given project. However, before we discuss these tools, let's take a closer look at the different types of CNC.
Types of CNC machines for cutting plastics and others
Essentially, there are five broad categories of CNC machines, depending on the type of machine, precision, and nature of the project. These are:
- CNC milling machine
This is probably the most popular type on the market. A specific program in alphanumeric form is translated to a CNC milling machine (computer numerical control). In these machining operations, a programming language called G-code is used. After programming, the rotating cutting tool cuts the sheet into various shapes and sizes. Unlike other manually operated milling machines, CNC milling offers much greater precision.
- CNC Router
Similar to most manually operated plotters, CNC equivalents can cut materials such as wood, plastic, steel, aluminum, foam, and composites. However, with the use of CNC, you will be able to cut more prototype models and advanced shapes of materials. Just like with a CNC mill, a Router works with digital computer controllers to produce more parts in less time, thereby increasing productivity. Typically, industrial CNC routers have 3-axis machines, but in technical and highly complex machining operations, 4-axis, 5-axis, and even 6-axis machines are used.
- CNC Lathe
Using a different programming language, these machines can perform more precise cuts. They are rotary machines that precisely cut, shape in three dimensions, and form materials. These machines are ideal for producing spherical or cylindrical objects.
- Plasma Cutting Machine
CNC plasma cutters are used for cutting heavy metals, such as steel. They operate on the principle of converting gas into plasma, which is blown out at high speed through the cutter. Properly heated plasma will melt almost any metal cut by the machine, and the high pressure obtained in the process of using the cutter blows out any metal debris at the cutting site.
- EDM Machine
EDM machines can be either virtual machines or wire machines. They use electrical discharges to cut sheet metal. As a result, they create materials of specific shapes and sizes.
In addition to these five types, there are also other kinds of CNC machines available on the market. With the emergence of these machines, production has become easier, as it is possible to create more precise and accurate designs in the shortest possible time.
CNC Tool
Cutting tools have existed since ancient times. They are one of the oldest inventions in human history, and those we use today have radically changed. They are associated with the use of various types of saws. Originally, we made them from stone, so the current, metal tools have gained great value in the field of production. Although all cutting tools serve the same purpose, cutting material, their applications are highly diversified.
Essentially, for a cutting tool to be effective, it must meet certain criteria:
- It must be 30% to 50% harder than the material it is working with.
- It has high thermal conductivity.
- It has a low friction coefficient.
- Chemically inert and stable.
In practice, CNC tools perform various cutting operations. Before you can consider which one to use for a specific operation, you need to know what materials the manufacturer used to make the tool. Based on this material, cutting tools are divided into:
- Carbon steel tools
These cutting tools are inexpensive and primarily designed for low-speed work. They contain 0.6 - 1.5% carbon, as well as small amounts of manganese and silicon. They are mainly used in twist drills, forming tools, milling cutters, and lathes.
- High-speed steel (HSS)
It is made of high-carbon steel and an appropriate amount of alloying elements such as chromium, tungsten, and molybdenum. This combination increases hardness, wear resistance, and durability. It ensures higher efficiency in removing metals and other materials.
- Ceramics
These chemically inert tools are corrosion-resistant and are even ten times faster than HSS. The ceramic material is usually made of aluminum oxide and silicon nitride. In projects that require the highest quality finishing operations, this type of material is often used.
- Carbide
Designed for high-speed operation, these tools made of cemented carbides are extremely hard and can withstand temperatures up to 1000 degrees Celsius. They are typically made of tantalum, titanium, and tungsten. They are also used in operations requiring high-quality surface finish.
CNC Cutting Tools
CNC cutting tools are available in various shapes and sizes for different milling and turning operations. Besides, the object should be machined using the appropriate software and mills. Some CNC mills include:
- End mill - A rotary cutting tool that can be used to remove material. Although they are very similar to drills, end mills are used for more general machining operations. Unlike drills, which cut into the material axially, end mills are side cutting tools that can cut in any direction. Due to their design, some end mills cannot cut material axially. Generally speaking, end mills have various types of tips, each depending on the desired end product. Different types of end mill tips include:
- Ball nose end mills: perfect for working with 3D contours, ball nose end mills have a rounded tip for excellent curved surfaces.
- V-groove end mills: these tools make a V-shaped cut. V-bits can be 90o or 60o, depending on the angle of the recess required by the material. Although they are commonly used for engraving signs on materials, they are perfect for projects requiring perfectly sharp edges.
- Cylindrical-end mills with a straight groove: these CNC cutting tools are general-purpose tools that provide excellent edge quality.
- Downcut and Upcut type mills: these spiral tools allow for a smooth surface finish by transferring chip remnants downwards or a rough surface finish by transferring remnants upwards and away from the designated area.
- The basic structure of the end mill includes a groove (spiral groove), cutting edge (tooth), diameter, shank, cutting length, and the total length of the tool.
Before we proceed to machining, remember the necessity of designing the cut in advance, maintaining the thermal stability of the material.
CNC Drills
Below we present drills and knives used for cutting with the CNC method
Twist drills: These CNC rotary cutters have two grooves and two cutting edges. Thanks to their unique design, the coolant quickly reaches the cutting point. Manufacturers often use these cutting tools to lower production costs and perform finishing operations at the highest level. The twist drill consists of three main parts: the shank, the body, and the tip.
Flying scissor blade: These single-edged knives on milling machines are of general use, providing excellent surface finish. The CNC mill passes through the material surface, rotating in the direction of the clock hands, making the material surface smooth and flat. They are intended for CNC engineers looking for excellent, precise finishing.
Coolants and cooling-lubricating fluids during cutting
They are usually not used in CNC cutting tools. Coolant-lubricating fluids remove chips from the cutting area. They also provide additional benefits, such as:
- They reduce thermal distortions of the workpiece.
- They improve the tool's lifespan.
- They improve the surface finish.
- Tool holders usually keep CNC cutting tools in place before they are installed on the CNC machine.
Why is it worth choosing the right CNC tool?
Machining plays a key role in the quality of your project. CNC cutting differs from traditional cutting techniques in many aspects. Although CNC machines are expensive to purchase, the wide spectrum of applications for computer-controlled machines cannot be overlooked. In fact, the quality of your project depends on the type of cutting tool used. The industrial world is highly competitive, and manufacturers and end users, on their way to success, must create top-quality products through proper planning and precise cutting. Since knives are the basis of professional design, special attention should be paid to those minor details that can make your project better or worse. Higher productivity, high precision, accuracy, and machining efficiency are the driving forces required to produce first-class products. You can easily achieve these advantages of CNC cutting, having the right cutting tools, and a solid understanding of CNC cutting tools is the first step to success in a competitive industry.