The lifetime of a ball screw, commonly referred to as the useful life or service, can vary depending on several factors such as the operating conditions, load, speed, lubrication, and maintenance. A properly designed, installed, and maintained ball screw can have a long service life. Ball screws are typically rated for a certain number of revolutions or travel distance before they reach the end of their useful. This rating is known as the fatigue life or L10 life. L10 life represents the point at which 90% of a population of ball screws would be expected to still be functioning without experiencing fatigue failure. The L10 life is influenced by various factors, including the dynamic load on the ball screw, the speed of operation, the type and quality of the ball screw assembly, the lubrication used, and the operating environment. Higher loads or faster speeds may reduce the L10 life, while proper lubrication and maintenance can extend it. It's important to note that the L10 life is an estimated value and not a guarantee. It is based on statistical calculations and assumes normal operating conditions. In practice, the actual lifetime of a ball screw can vary. Therefore, regular inspection, maintenance, and replacement of worn components are necessary to ensure reliable performance and prolong the life of the ball screw.

In the precision operation of industrial equipment, transmission components act like "joints," determining the accuracy and lifespan of the entire machine. However, many buyers often make mistakes when selecting ball screws and linear guides due to parameter confusion and application mismatches. Nanjing Shuntai (https://www.nanjingshuntai.com/), a company deeply involved in the precision transmission field, will share its practical experience to help you clarify your thinking. I. Selection: Five Common Misconceptions Common Selection Misconceptions (Nanjing Shuntai Helps You Avoid): Misconception 1: Focusing on Diameter, Not Lead. Error: Thinking Larger Diameter is Better. Correct: Diameter primarily affects rigidity and critical speed, while lead directly determines speed and thrust. For high-speed applications, a larger lead should be prioritized, and rigidity should be ensured by increasing the diameter. Misconception 2: Ignoring the Stress Rod Stability. Misconception: For lead screws with a large aspect ratio (slender types), only checking the lifespan without checking the allowable axial load can lead to unstable bending during operation. Correct: For applications with a large aspect ratio, stress rod stability must be checked. Misconception 3: Exceeding the critical speed. Error: Motor speed can be increased indefinitely. Correct: The operating speed must be kept below the critical speed, otherwise severe vibration will occur. Increase the critical speed by changing the mounting method, increasing the diameter, or shortening the span. Misconception 4: Selecting too high or too low an accuracy grade. Error: Blindly pursuing the highest accuracy, or choosing too low an accuracy grade to save money. Correct: Comprehensively consider the equipment's positioning accuracy, repeatability, and budget. Grade C7 is sufficient for most general applications. Misconception 5: Ignoring the importance of preload. Error: Not understanding the role of preload. Correct: Preload eliminates axial play and improves rigidity, but it also increases wear and heat generation. Select preload for high-precision, high-rigidity applications; select light or no preload for light loads and high speeds. II. Installation: Details determine accuracy and lifespan. Many users report that "a new lead screw makes unusual noises after just six months of use." This is likely due to installation problems. Nanjing Shuntai's lead screw installation and commissioning video emphasizes that guideway parallelism errors exceeding 0.02mm/m will cause abnormal wear of the slider; coaxial misalignment of the bearing seats at both ends of the lead screw is a major cause of vibration. Jining local customers can schedule on-site installation services, where technicians will perform on-site calibration with a laser interferometer to ensure optimal performance of each device. III. Maintenance: Simple Operations Extend Lifespan by Three Times Regular lubrication is the lifespan of transmission components, but using the wrong grease can be detrimental. Nanjing Shuntai's technical advice: Use lithium-based grease for high-speed lead screws, extreme-pressure grease for heavy-duty guide rails, and high-temperature grease if the ambient temperature exceeds 80°C. IV. Summary: The selection of ball screws and linear guides requires rigorous engineering calculations. By keeping in mind the five core factors of "load, speed, accuracy, rigidity, and lifespan," following a scientific selection process, and leveraging the expertise of a professional team like Nanjing Shuntai, you can easily avoid 90% of selection errors and create a stable, precise, and durable linear motion system for your equipment.

The ball screw (often called a "lead screw") of an injection molding machine is its core component, often referred to as the "heart" of the machine. Its operation is a complex process integrating physics, mechanics, and thermodynamics. Simply put, its core task is to transport, melt, compress, and homogenize solid plastic granules, ultimately injecting the molten plastic into the mold cavity with sufficient pressure and speed. To better understand its operation, we can divide its working cycle into the following stages: A complete working cycle of an injection molding machine ball screw. In a complete injection cycle, the ball screw mainly performs two actions: rotation and axial movement. Its working cycle can be divided into three stages: 1. Rotation (Plasticizing/Metering) Stage Objective: To transport, heat, melt, and homogenize the solid plastic granules in the hopper. Action: The lead screw rotates at high speed inside the barrel but does not move forward (at this time, the injection cylinder at the rear of the lead screw releases pressure, allowing the lead screw to retract due to the reaction force of the plastic during rotation). Operation Process: Feeding and Conveying: Plastic granules fall from the hopper into the barrel. The rotation of the screw, like a screw turning in a nut, uses the inclined plane of the thread to continuously push the plastic granules forward. Compression and Melting: The screw structure is divided into three sections from back to front: the feeding section, the compression section, and the metering section. Feeding Section: The thread depth is relatively deep, mainly used for stable conveying of solid granules. Compression Section: The thread depth gradually decreases. Here, the plastic is strongly compressed and sheared, while the heating coil outside the barrel also heats it. Under the combined action of "shear heat" and "external heating," the solid plastic rapidly melts into a viscous flow state. In fact, more than 80% of the melting heat comes from the shear heat generated by the screw rotation. Metering Section: The thread depth is the shallowest. Its main function is to further homogenize the temperature and composition of the melt, ensuring the uniform quality of the melt stored at the front end. Result: Uniformly molten plastic is pushed to the front of the screw (at the nozzle), and the accumulated pressure (back pressure) pushes the entire screw backward, reserving a fixed amount of molten material for the next injection. 2. Axial Movement (Injection/Holding Pressure) Stage Objective: To inject the molten plastic reserved in the previous stage into the mold cavity at high speed and high pressure. Action: The screw stops rotating and, under the powerful thrust of the injection cylinder, moves forward at high speed as a piston. Operation Process: Injection: The screw advances forward at extremely high speed, injecting the molten plastic reserved in the front through the nozzle, mold runner, and gate into the closed mold cavity. This process needs to be completed in a very short time to ensure that the molten material fills every corner of the cavity simultaneously. Holding Pressure: When the cavity is about to be filled, the injection speed slows down, transitioning to a high-pressure "holding pressure" stage. The screw continues to move forward slowly, using extremely high pressure to replenish the volume vacated by the cooling and shrinkage of the plastic, preventing defects such as shrinkage marks and insufficient material in the product. 3. Reset (Preparing for the Next Cycle) Objective: To prepare the melt for the next injection molding cycle. Action: After the holding pressure is completed, the screw stops axial movement and begins to rotate again (returning to the first stage) for the next plasticizing and metering. At this time, the mold opens, ejects the product, and then closes, awaiting the next injection. Key Design Features of the Ball Screw To accomplish the above complex tasks, the ball screw itself is designed with great precision: Length-to-Diameter Ratio (L/D): The ratio of the ball screw's length to its diameter. A larger L/D ratio results in better plasticizing and more uniform temperature. Common ratios are between 18:1 and 25:1. Compression Ratio: The ratio of the volume of the first threaded groove in the feeding section to the volume of the last threaded groove in the metering section. It determines the degree of plastic compression and is crucial to melting efficiency. Different plastics require different compression ratios. Three-Stage Design: As mentioned above, the feeding section, compression section, and metering section each perform their respective functions, forming the basis for the efficient operation of the lead screw. In summary, you can visualize the operation of an injection molding machine screw as follows: It's like a "meat grinder": as it rotates, it bites, shears, mixes, and conveys materials. It's like a "piston" or "syringe": as it propels forward, it injects the processed "fluid" under high pressure. It's also a "heat generator": through its own rotational shearing, it generates most of the heat needed to melt the plastic. This ingenious combination of "rotational plasticizing" and "axial injection" allows the injection molding machine screw to efficiently and precisely complete the transformation process from solid granules to precision plastic products.

As a core component of precision transmission, the ball screw's performance directly determines the accuracy, lifespan, and stability of equipment, from small 3C devices to large industrial machine tools. The material is the key factor determining the ball screw's lifespan—choosing the right material allows for long-term stable operation under complex conditions; choosing the wrong material can lead to rapid accuracy degradation or even breakage. Today, we'll break down the underlying logic of ball screw material selection, from core considerations to comparisons of mainstream materials, helping you avoid selection pitfalls. I. Before Choosing a Material, Clarify These 3 Core Dimensions There is no "best" material, only "most suitable." Before finalizing the material, ask yourself three questions to anchor your selection direction: * **Operating Conditions:** What load will the ball screw withstand? What is the operating speed/rotation speed? Will it operate in high-temperature, humid, or corrosive environments? Will it experience frequent start-stop cycles or impact loads? * **Accuracy Requirements:** Is it for ordinary transmission (such as automated production lines) or high-precision positioning (such as CNC machine tools or semiconductor equipment)? Precision grade (C0-C10) directly affects material uniformity and heat treatment requirements. Cost budget: High-end materials (such as stainless steel alloys) offer excellent performance but are expensive, while ordinary carbon steel offers high cost-effectiveness but has limited applicability. A balance between performance and cost is necessary. II. Mainstream Ball Screw Materials: Characteristics, Applications, and Advantages/Disadvantages 1. Carbon Structural Steel (e.g., 45# steel) – Entry-level choice Core characteristics: Extremely low cost, good machinability, can be heat-treated to improve hardness, but poor hardenability, low surface hardness (HRC20-30), and poor wear and corrosion resistance. Applicable scenarios: Only suitable for ordinary transmission scenarios with low loads, low speeds, and no precision requirements, such as simple conveying equipment and manual adjustment mechanisms. Almost never used in industrial precision equipment. Advantages and disadvantages: Advantages include low cost and ease of machining; disadvantages include short lifespan, easy loss of precision, and inability to withstand impact loads. 2. Alloy Structural Steel (e.g., 40Cr, 20CrMnTi) – A Mid-Range General-Purpose Choice Core Characteristics: Based on carbon steel, alloying elements such as chromium, manganese, and titanium are added, significantly improving hardenability. After tempering and surface quenching, the surface hardness can reach HRC55-60. It has good core toughness, balancing wear resistance and impact resistance. Applicable Scenarios: Ball screws in industrial automation equipment, general machine tools, and construction machinery. Suitable for medium loads, medium speeds, and normal environmental conditions, it is currently the most widely used material. Advantages and Disadvantages: Advantages include high cost-effectiveness and balanced performance; disadvantages include moderate corrosion resistance, requiring additional rust prevention treatment (such as galvanizing or blackening) in humid/salt spray environments. 3. Bearing Steel (e.g., GCr15, GCr15SiMn) – High-Precision Core Choice Core Characteristics: High carbon content, with chromium as the main alloying element. After quenching and low-temperature tempering, the hardness can reach HRC60-64. It has excellent wear resistance and dimensional stability, low impurity content, and uniform internal structure, meeting the form and position tolerance requirements of high-precision ball screws. Applicable Scenarios: Ball screws for high-precision CNC machine tools, semiconductor processing equipment, and testing instruments. Suitable for high-load, high-speed, and high-precision positioning conditions, it is the "standard" material for precision transmission. Advantages and Disadvantages: Advantages include high hardness, good wear resistance, and stable precision; disadvantages include a cost 10%-20% higher than alloy structural steel, slightly lower core toughness than 40Cr, and the need to avoid overload impacts. 4. Stainless Steel (e.g., 304, 316, 9Cr18Mo) ​​– Special Environment Selection Core Characteristics: 304/316 stainless steel has excellent corrosion resistance, suitable for harsh environments such as humid, acidic, alkaline, and salt spray conditions; 9Cr18Mo (martensitic stainless steel) combines high hardness (HRC58-62) and corrosion resistance, offering a "wear-resistant + corrosion-resistant" combination. Applicable Scenarios: Ball screws in food processing equipment, marine engineering equipment, chemical equipment, or medical equipment where cleanliness and corrosion resistance are required. Advantages and Disadvantages: Advantages include strong corrosion resistance, eliminating the need for additional rust prevention; disadvantages include high cost (304 stainless steel is 2-3 times more expensive than GCr15), the difficulty in processing 9Cr18Mo, and slightly lower overall wear resistance compared to bearing steel. III. Four Practical Suggestions for Material Selection * Prioritize matching accuracy and working conditions: Choose GCr15 for high precision and high load; 40Cr for medium load and normal environments; 45# steel for low requirements and low cost; stainless steel for harsh environments. * Pay attention to heat treatment processes: For the same material, the heat treatment process directly determines performance—for example, GCr15 is prone to quenching cracks if it does not undergo sufficient spheroidizing annealing; 40Cr will lead to rapid surface wear if the surface quenching depth is insufficient. When selecting, confirm the supplier's heat treatment process (such as whether deep cryogenic treatment is performed to improve dimensional stability). * Optimize performance by combining surface treatment: Even if the right material is selected, shortcomings can be compensated for through surface treatment—for example, nitriding of GCr15 lead screws can improve surface hardness and corrosion resistance; hard chrome plating of 40Cr lead screws can enhance wear resistance and rust prevention. Avoid "over-selection": For example, choosing GCr15 for a standard production line lead screw, or 316 stainless steel for a lead screw in a normal environment, will only increase costs without improving performance. Precise matching of requirements is necessary. IV. Summary: The Core Logic of Material Selection Choosing the right material is only the first step. Subsequent machining accuracy, assembly processes, lubrication, and maintenance will also affect the lead screw's lifespan. However, the material, as the foundation, directly determines the lead screw's "performance ceiling." If you are unsure which material to choose for your equipment, you can consider four dimensions: load, speed, environment, and accuracy, or consult us for working condition matching.

As a key transmission component for converting rotary to linear motion, ball screws have become the "heart" of high-end equipment such as precision instruments, CNC machine tools, and automated equipment, directly determining the operating accuracy and stability of the equipment, thanks to their three core advantages: "high precision, high efficiency, and high rigidity". Eight Key Points for Daily Maintenance Cleaning and Protection: Regularly clean the lead screw surface with a brush or compressed air to remove dust and chips, preventing impurities from entering the raceway; in harsh environments, install dust covers and protective sleeves. Scientific Lubrication: Select lubricant according to operating conditions, and replenish/change oil regularly according to operating time to ensure uniform lubrication of the raceway. Load Control: Strictly adhere to rated load requirements, avoiding instantaneous overload or impact loads to prevent lead screw deformation. Precise Installation: Ensure the lead screw is parallel and coaxial with the guide rail during installation, and tighten the bearings. Environmental Adaptability: Keep away from high temperature, high humidity, and corrosive environments. Take heat insulation, moisture-proof, and anti-corrosion measures when necessary. Regular Inspection: Establish an operation log, record changes in noise, temperature, and accuracy, and stop the machine for repair immediately if any abnormalities are found. Maintenance During Idle Time: When not in use for a long time, apply anti-rust oil and cover with a protective cover to prevent rust and dust accumulation. Synchronous Maintenance: Simultaneously check mating components (bearings, guide rails, drive motor) to ensure the stable and coordinated operation of the entire transmission system. Prevention and Inspection Techniques Visual Inspection: Inspect the lead screw surface for scratches, rust, and dents; check for intact and undamaged threads. Lubrication Check: Observe the even distribution of lubricant. If the color turns black or the viscosity decreases, replace it immediately. Smoothness Test: Manually rotate the lead screw or run it under no-load to check for any jamming or uneven resistance. Noise Identification: Listen for abnormal friction or impact sounds during operation, paying particular attention to the bearing area. Accuracy Inspection: Use a dial indicator and laser interferometer to check the positioning accuracy and repeatability, comparing them with standard values ​​to determine if the accuracy is satisfactory. Exceeding limits; Clearance Measurement: Use a feeler gauge or dial indicator to check the clearance between the lead screw and nut. If it exceeds the limit, the component needs to be replaced; Connection Tightness: Check the bolts of the bearing housing, coupling, and nut housing to prevent loosening that could cause vibration; Temperature Monitoring: Use a thermometer to check the temperature of the bearing and lead screw body after operation. If it exceeds 60℃, lubrication or installation problems need to be investigated; Cleanliness Assessment: Check for chips and oil accumulation around the lead screw and clean them promptly; Thread Flaw Detection: For lead screws in critical operating conditions, use magnetic particle testing or penetrant testing to check for hidden thread damage.