Introduction to Types of Mechanical Finishing in CNC Machining

CNC machining methods involve physical interaction with the surface of the part to achieve the desired finish. nh rapid machining is one such machining manufacturer.These methods are versatile and are capable of producing a variety of surface effects from rough to mirrored. They are suitable for a wide range of materials, including metals, plastics, and composites, making them an integral part of the CNC machining process.

1.Milling and Turning

Milling and turning are the foundation of mechanical finishing in CNC machining. These processes not only shape the part, but also determine its final surface texture.

1. Technical Features: Both methods use cutting tools to remove material from the workpiece in a controlled manner, and accuracy and speed are critical. The choice between milling and turning usually depends on the geometry of the part: milling is suitable for complex shapes and features, while turning is suitable for cylindrical parts.
2. Materials and Applications: Milling and turning are commonly used for metals such as aluminum, steel, and brass, as well as plastics such as nylon and PEEK, and have a wide range of applications. From aerospace components that require tight tolerances to automotive parts that require durability and finish, these methods are essential.
3. Advantages and Disadvantages: The main advantages of milling and turning are their precision and versatility, which can achieve a wide range of surface finishes and part geometries. However, their limitations include tool wear, which can affect the quality of the finish over time, and the need for multiple setups for complex parts, which can increase production time and cost.

2.Grinding

Grinding is a finishing process that uses a grinding wheel to achieve an extremely smooth surface or precise geometry on a workpiece.

1. Technical Features: Grinding is characterized by its ability to achieve high precision and high surface quality, typically achieving a smooth surface of 0.1 μm Ra. Grinding is the preferred method for parts that require tight tolerances that cannot be achieved by milling and turning.
2. Materials and Applications: Grinding is suitable for hard materials such as hardened steel, ceramics and carbides, and is widely used in tool manufacturing, automotive and aerospace industries, all of which have high requirements for precision and surface integrity.
3. Advantages and Disadvantages: Grinding has unparalleled precision and surface quality, making it indispensable for many high-precision applications. The disadvantages are that grinding is relatively slow and the process is expensive due to wheel wear and maintenance.

3.Grinding

Grinding uses abrasives to smooth a surface, usually as a finishing step to remove minor imperfections left by previous machining processes.

1. Technical characteristics: Grinding is widely used and can adjust the grit size to provide a range of surface finishes from coarse to fine. It is often used in conjunction with other finishing processes to prepare surfaces for painting or coating.
2. Materials and applications: Grinding is suitable for a variety of materials, including wood, metal, and plastic. It is often used in the automotive and furniture industries to prepare surfaces for final finishing.
3. Advantages and disadvantages: The main advantages of grinding are that it is simple and effective in obtaining a smooth surface. However, grinding can be labor-intensive and time-consuming, especially for parts with complex geometries or that require an ultra-smooth surface.

4.Sandblasting

Sandblasting is a mechanical process that involves spraying a stream of abrasive glass beads at high speed onto the surface of a part. This operation effectively removes surface imperfections and creates a uniform matte surface, thereby enhancing the aesthetics and functional properties of the part.

1. Materials and Applications: Sandblasting is versatile and can be applied to a wide range of materials, including metals such as aluminum, steel, titanium, and plastics. It is commonly used in the automotive, aerospace, and electronics industries to prepare for painting, anodizing, or simply to improve appearance.
2. Advantages and Disadvantages: The main advantage of sandblasting is its ability to provide a consistent, aesthetically pleasing surface and can also mask minor surface defects. However, it is important to carefully control the sandblasting process to prevent material removal, which may change the dimensions of the part or introduce surface stresses.

5.Polishing

Polishing is a finishing process that uses abrasives or chemicals to achieve a high-gloss, mirror-like finish on the surface of a part. This method not only enhances the visual appeal of a part, but also reduces friction, improves cleanliness, and increases corrosion resistance.

1. Materials and Applications: This method is ideal for metals such as stainless steel, aluminum, and brass, and is widely used in the medical, food processing, and luxury industries, where a high level of surface finish is critical for both aesthetics and functionality.
2. Advantages and Disadvantages: The advantage of polishing is a smooth, reflective surface that enhances the visual appeal and performance characteristics of a part. However, polishing can be labor-intensive and time-consuming, especially for parts with complex geometries or where an extremely high finish is required.

6.Brushing

Brushing uses fine bristles or abrasive media to create a uniform, directional texture on the surface of a part. This method is particularly effective for highlighting the natural sheen of metal parts, but it cannot achieve the high gloss of polishing.

1. Materials and Applications: Applicable to a variety of metals, including aluminum, stainless steel, and copper, brushing is often used for architectural parts, consumer electronics, and automotive parts that require a satin effect.
2. Pros and Cons: The advantage of brushing is that it provides a consistent, beautiful surface that can hide fingerprints and minor imperfections. However, it may not be suitable for applications that require a non-directional surface finish or where surface smoothness is critical.

7.Tumble and Vibratory Polishing

Tumble and vibratory polishing are batch processes where parts are placed in a container filled with abrasive media and then the container is rotated (tumbled) or vibrated (vibratory polishing) to smooth and polish the parts. These methods are ideal for processing large quantities of small parts.

1. Materials and Applications: These processes are applicable to a variety of materials, including metals, plastics, and ceramics. They are particularly useful in the automotive, aerospace, and jewelry industries for deburring, grinding, and polishing parts.
2. Advantages and Disadvantages: The main advantage of tumble and vibratory polishing is their ability to efficiently complete large batches of parts simultaneously and provide a uniform surface finish. The main disadvantage is that contact between parts can occur, which can cause damage or deformation, especially for precision parts.

8.Sandblasting

Sandblasting is a versatile finishing process that involves pushing a stream of abrasive material against the surface of a part under high pressure. This method is very effective for cleaning, deburring, and finishing surfaces.

1. Materials and Applications: Sandblasting can be applied to a variety of materials, including metals, plastics, and composites. It is particularly useful for preparing surfaces for subsequent coatings, removing manufacturing residues, or creating specific surface textures. Common applications include automotive parts, aerospace components, and industrial machinery.
2. Advantages and Disadvantages: The main advantage of sandblasting is its ability to uniformly complete complex geometries and reach hard-to-reach areas. However, it requires careful selection of blasting media and parameters to avoid damaging the substrate or changing critical dimensions.

9.Vapor Polishing

Vapor polishing is a polishing technique that uses chemical vapors to melt the surface of a plastic part, resulting in a smooth, shiny surface. This method is particularly suitable for materials that are difficult to polish mechanically.

1. Materials and Applications: Vapor polishing is mainly used for thermoplastics such as polycarbonate, ABS and acrylic. It is well suited for applications that require optical clarity or high gloss, such as medical devices, automotive lights and display cases.
2. Advantages and Disadvantages: The advantage of vapor polishing is that a clear, smooth surface can be obtained without mechanical stress on the part. However, it involves the use of hazardous chemicals and requires strict safety measures and environmental control.

10.Knurling

Knurling is a process that creates a patterned texture on the surface of a part, usually for enhanced grip or aesthetics. It involves pressing a patterned tool against a rotating workpiece to form a tightly controlled uniform pattern.

1. Materials and Applications: Knurling is commonly used on metal parts, including aluminum, steel and brass. It is widely used in tool handles, control knobs and custom fasteners that require improved grip or decorative effects.
2. Advantages and Disadvantages: The main advantage of knurling is its ability to enhance the tactile feel of a part without significantly affecting its dimensional tolerances. However, knurling is limited to accessible rotationally symmetrical areas and may require additional finishing steps to remove any burrs or sharp edges created in the process.