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As a core component in the precision transmission field, the accuracy, stability, and service life of ball screws directly depend on the control of every detail in the production process. From a piece of ordinary steel to a finished product capable of micron-level transmission, ball screws undergo multiple rigorous production procedures. Today, we will take you into the ball screw production workshop, revealing the complete process from raw material selection to finished product inspection, and showing how high-precision ball screws are "born."
I. Source Control: Raw Material Selection and Pretreatment to Lay a Solid Quality Foundation
High-quality products start with premium raw materials. Ball screws have extremely high requirements for the material, purity, and mechanical properties of raw materials. Currently, the mainstream raw materials for ball screws are high-carbon chromium bearing steel (such as GCr15) or alloy structural steel (such as 40CrNiMoA). This type of steel has excellent hardness, wear resistance, and toughness, which can meet the needs of long-term high-speed operation of ball screws.
In the raw material selection stage, we strictly check the impurity content and mechanical properties of raw materials through spectral analysis, hardness testing, and other methods to ensure that each batch of steel meets the standards. After selection, the raw materials enter the pretreatment stage, including heat treatment processes such as forging, normalizing, and annealing. Among them, forging can refine grains and improve the density and strength of the steel; subsequent normalizing and annealing can reduce internal stress in the steel, improve machinability, and lay the foundation for subsequent precision machining.
II. Core Machining: From Rough Machining to Precision Machining, Gradually Approaching Accurate Dimensions
After pretreatment, the steel enters the core machining stage, which is divided into rough machining and precision machining steps to gradually process the steel into a ball screw blank that meets the design requirements.
1. Rough Machining: Removing Redundancy and Outlining the Basic Contour
The core purpose of rough machining is to quickly remove excess parts of the raw material and initially process the basic structures such as the shaft diameter and thread contour of the screw. The main processes include turning and milling: turning processes the shaft heads, steps, and other parts at both ends of the screw through a lathe to ensure the basic dimensional accuracy of the shaft diameter; milling is used to process auxiliary structures such as keyways and planes of the screw to prepare for subsequent assembly. The requirements for dimensional accuracy in the rough machining stage are relatively low, but it is necessary to strictly control the machining allowance to avoid product deformation due to uneven allowance during subsequent precision machining.
2. Precision Machining: Extreme Grinding to Control Core Accuracy
Precision machining is a key link determining the accuracy of ball screws. It requires multiple precision processes to control product dimensional errors at the micron level. The core processes include:
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Thread Grinding: High-precision CNC thread grinders are used to grind the thread raceways of the screw. This is one of the core processes, which requires precise control of key indicators such as the lead, thread angle, and roundness of the raceway. For C2-grade high-precision ball screws, the lead error needs to be controlled within 0.005mm per meter. Therefore, during the grinding process, a laser interferometer is used for real-time detection to dynamically adjust machining parameters.
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Cylindrical Grinding: Secondary grinding is performed on the shaft diameter of the screw to improve the roundness and cylindricity of the shaft diameter, ensure the fitting accuracy between the screw, nut, and bearing, and reduce vibration and noise during operation.
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End Face Grinding and Drilling: Precision grinding is performed on both end faces of the screw to ensure the perpendicularity between the end face and the screw axis; at the same time, the mounting holes, center holes, and other parts at both ends are accurately processed to ensure coaxiality during assembly.
III. Key Strengthening: Heat Treatment and Surface Treatment to Improve Performance and Service Life
After precision machining, the ball screws need to undergo heat treatment and surface treatment to further improve their hardness, wear resistance, and corrosion resistance, and extend their service life.
The heat treatment process mainly adopts quenching and tempering: quenching can greatly improve the hardness of the screw (usually reaching above HRC60) and enhance wear resistance; tempering can reduce internal stress after quenching, improve the toughness of the screw, and avoid fracture during use. To ensure the uniformity of heat treatment, we use a vacuum quenching furnace for processing to reduce oxidation and deformation.
Surface treatment selects different processes according to application scenarios: for general working conditions, nitriding treatment is adopted to form a hard nitrided layer on the screw surface, further improving wear resistance; for humid and corrosive environments, chrome plating or blackening treatment is adopted to enhance corrosion resistance.
IV. Assembly and Inspection: The Final Line of Defense to Ensure Qualified Finished Products
After the above processing and strengthening treatments, the ball screws enter the assembly and finished product inspection stage, which is the final line of defense to ensure qualified products leave the factory.
1. Assembly Process
Assembly mainly involves combining the processed screw shaft with nuts, balls, cages, and other accessories. The core is to ensure the smooth rolling of balls in the raceway. Therefore, it is necessary to accurately adjust the fitting gap between the nut and the screw. If necessary, preloading processes (such as double nut preloading, gasket preloading) are adopted to improve the rigidity and positioning accuracy of the screw. After assembly, lubrication treatment is also required, and special grease is injected to reduce friction loss during operation.
2. Finished Product Inspection
The finished product inspection stage comprehensively inspects various indicators of the ball screws, and unqualified products are not allowed to leave the factory. The inspection items include:
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Accuracy Inspection: Detect lead accuracy and positioning accuracy through a laser interferometer, and detect raceway roundness through a roundness meter to ensure compliance with the corresponding precision grade requirements;
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Performance Inspection: Conduct no-load operation tests to detect noise, temperature rise, and smoothness during operation; conduct load tests to verify load-bearing capacity and rigidity;
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Appearance and Dimension Inspection: Check for scratches and defects on the surface, and recheck key dimensions such as shaft diameter and length.
V. Conclusion: Precision Comes from Details, Craftsmanship Achieves Quality
From raw material selection to finished product delivery, the ball screw production process covers dozens of procedures, and every step requires extreme precision control and strict quality management. It is this adherence to details that enables ball screws to play a core transmission role in high-end manufacturing, automation, medical care, and other fields.
If you want to learn more about the technical details of the ball screw production process or have custom ball screw needs, please feel free to contact us at any time. With our professional production technology and strict quality control, we will provide you with high-reliability and high-precision ball screw products!
Table of Contents
- I. Source Control: Raw Material Selection and Pretreatment to Lay a Solid Quality Foundation
- II. Core Machining: From Rough Machining to Precision Machining, Gradually Approaching Accurate Dimensions
- III. Key Strengthening: Heat Treatment and Surface Treatment to Improve Performance and Service Life
- IV. Assembly and Inspection: The Final Line of Defense to Ensure Qualified Finished Products
- V. Conclusion: Precision Comes from Details, Craftsmanship Achieves Quality