What are the specific requirements for the performance of machined parts?
Publish Time: 2024-08-21
The performance requirements of machined parts usually include the following aspects:
1. Dimensional accuracy
Dimensional tolerance control: The actual size of the part should be strictly controlled within the dimensional tolerance range specified in the design. For example, for a shaft part with a diameter of 50mm, its tolerance may be required to be within ±0.05mm to ensure the assembly accuracy with other matching parts.
Shape accuracy: including the flatness, roundness, cylindricity, etc. of the part. For example, the flatness requirement of a machined plane may be within 0.02mm/m to ensure that other parts installed on the plane can fit smoothly without shaking or gaps.
Position accuracy: such as parallelism, verticality, coaxiality, etc. For example, the coaxiality requirement of two mutually matching holes may be within ±0.03mm to ensure that the shaft installed in the hole can operate normally without eccentric wear.
2. Surface quality
Surface roughness: The surface of the part should have a suitable roughness to meet different use requirements. Generally speaking, the smaller the roughness value, the smoother the surface. For example, for the surface of sliding parts, the roughness may be required to be below Ra0.8μm to reduce friction and wear; while for some non-critical surfaces, the roughness requirements can be appropriately relaxed.
Surface hardness: The hardness of the surface of the parts can be improved by heat treatment, surface coating, etc., and its wear resistance and corrosion resistance can be enhanced. For example, for some parts that are subjected to high-load friction, such as gear surfaces, carburizing and quenching treatment can be performed to make their surface hardness reach HRC58-62 to increase their service life.
No surface defects: The surface of the parts should be free of defects such as cracks, sand holes, pores, scratches, etc., which may affect the strength, sealing and appearance quality of the parts. During the processing, strict quality control measures such as flaw detection and visual inspection are required to ensure that the surface quality of the parts meets the requirements.
III. Mechanical properties
Strength: The parts should have sufficient strength to withstand various loads during the working process without damage. Strength includes tensile strength, compressive strength, bending strength, etc. For example, for bolts that bear tensile loads, their tensile strength should meet the corresponding national standards to ensure that they will not break during the working process.
Hardness: Hardness is an indicator of the ability of parts to resist local deformation. Different parts need to have different hardness according to their use requirements. For example, parts such as cutting tools and molds require higher hardness to ensure their cutting performance and wear resistance; while some parts that bear impact loads require a combination of appropriate hardness and toughness.
Toughness: Parts should have a certain toughness to absorb energy when bearing impact loads and avoid brittle fracture. For example, for some parts used in harsh working environments, such as automobile suspension system parts, they need to have good toughness to ensure that they can withstand the impact of the road without breaking during driving.
Fatigue strength: For some parts that bear periodic loads, such as engine crankshafts, gears, etc., they need to have higher fatigue strength to ensure that they will not break due to fatigue during long-term work. The fatigue strength of parts can be improved through reasonable design, material selection and processing technology.
4. Physical properties
Density: The density of parts should meet the design requirements. For some applications with strict weight restrictions, such as the aerospace field, it is necessary to select materials with lower density and reduce the weight of parts as much as possible by optimizing the design and processing technology.
Thermal conductivity: For some parts that need to dissipate heat, such as engine cylinders, radiators, etc., they should have good thermal conductivity and be able to quickly transfer heat to ensure that the parts operate within the normal operating temperature range.
Conductivity: For some parts in electrical equipment, such as electrodes, wires, etc., they need to have good conductivity to ensure smooth transmission of current.
5. Other properties
Corrosion resistance: In some harsh working environments, such as humid, corrosive gas or liquid environments, parts should have good corrosion resistance. The corrosion resistance of parts can be improved by selecting corrosion-resistant materials, surface treatment (such as electroplating, spraying, etc.) or using protective coatings.
Sealing: For some parts that need to be sealed, such as valves, pump bodies, etc., they should have good sealing to prevent gas or liquid leakage. Through reasonable design, selection of appropriate sealing materials and processing technology, it can be ensured that the sealing of parts meets the requirements.
Machinability: The material of the parts should have good machinability and be easy to process using various machining methods. Machinability includes cutting performance, grinding performance, welding performance, etc. For example, some materials are easy to cut and have high processing efficiency, while other materials may require special processing technology and tools.
Assembling: Parts should be easy to assemble and should fit well with other parts. During the design and processing process, factors such as the assembly size, tolerance fit, and assembly method of the parts need to be considered to ensure that the parts can be assembled smoothly and can work normally after assembly.
