The secret to the efficient operation of machine tool lead screws

The ability of a machine tool lead screw to operate efficiently and without jamming 24 hours a day is primarily due to the synergistic effect of three factors: suitable design and selection, proper lubrication and maintenance, and reasonable operating condition control. Specifically, this can be broken down into the following key dimensions:

1. High-precision structural design and manufacturing process

Precision fit of the transmission pair: Ball screws use steel balls as rolling elements. Compared to the surface contact of sliding screws, this is point contact, resulting in an extremely low coefficient of friction (only 1/10 to 1/3 of that of sliding screws). This leads to low frictional resistance and less heat generation during operation, preventing jamming caused by overheating.

Preload process eliminates backlash: A double-nut preload structure (such as washer type, variable lead type, or threaded type) eliminates axial backlash between the lead screw and nut, ensuring transmission accuracy and preventing axial movement and jamming during high-speed operation.

High-Quality Materials and Heat Treatment: Lead screws and nuts are typically made of high-carbon steel (such as GCr15) or alloy structural steel, treated with quenching, tempering, and grinding to achieve a surface hardness of HRC58~62. This results in strong wear resistance, preventing wear and deformation during long-term operation and maintaining stable fit accuracy.

2. Stable and Reliable Lubrication and Sealing System

Continuous and Efficient Lubrication:** Equipped with an automatic lubrication system (such as a grease pump or oil mist lubrication device), it replenishes the lead screw raceway with specialized grease or oil at regular intervals, forming an oil film that reduces direct friction between the steel balls and the raceway, lowering wear and heat generation. Machine tools operating 24 hours a day are generally equipped with intermittent automatic lubrication to prevent insufficient lubrication or grease aging.

Excellent Sealing Protection:** Both ends of the lead screw are equipped with dustproof seals, scraper plates, and other components to prevent cutting fluid, metal shavings, and dust from entering the raceway. Impurities entering the raceway are a common cause of lead screw jamming; the sealing system effectively isolates contaminants and keeps the raceway clean.

3. Reasonable Operating Parameters and Load Control

Load and Speed ​​Matching: During selection, the rated dynamic and static loads of the lead screw are determined based on the actual load of the machine tool (cutting force, table weight) to ensure that the load does not exceed the rated value during 24-hour operation, avoiding ball bearing deformation and lead screw bending due to overload. Simultaneously, the speed is controlled below the lead screw's critical speed to prevent resonance and vibration during high-speed rotation.

Temperature Control: The machine tool is equipped with a cooling system to control the operating temperature of the lead screw and spindle. Heating the lead screw can cause thermal deformation, leading to pitch changes or even jamming. The cooling system can control temperature fluctuations within a minimal range, maintaining transmission stability.

4. Precise Coordination of Drive and Control Systems

Rigid Connection between Servo Motor and Lead Screw: Couplings (such as diaphragm couplings and lamellar couplings) are used to achieve a gapless connection between the motor and the lead screw, ensuring smooth power transmission and avoiding transmission jerks caused by loose connections.

Precise adjustment of the CNC system: Through a closed-loop or semi-closed-loop control system, the position and speed of the lead screw are monitored in real time, and the motor output torque is dynamically adjusted to compensate for the elastic deformation and temperature deformation of the lead screw, ensuring uniform speed and no impact during operation.

Supplement: The crucial role of routine maintenance: Even with reasonable design and operating conditions, regular maintenance is essential for 24/7 uninterrupted operation. For example, regularly cleaning seals, checking the condition of the lubricating grease, detecting lead screw runout and backlash, and promptly replacing aged grease and worn balls can effectively extend the stable operating time of the lead screw.