Double-lead worm gear: A key component in precision transmission
Classification： Blog
Release time：2025-07-21
I. What is a double lead worm?
II. Working principle: adjustable clearance through lead difference
Core logic
Specific process
- The lead of the left tooth surface of the double lead worm is ，the lead of the right tooth surface is （ ），the lead difference is 。
- When the worm is moved axially by a distance of , the change in tooth thickness is （ is the module), that is, axial movement directly changes the tooth thickness at the meshing point.
- Moving the worm forward reduces the backlash, while moving it backward increases the backlash, ultimately achieving "zero backlash transmission" or adjusting the backlash as needed.
III. Structural characteristics
- Variable tooth thickness worm ：The worm tooth thickness changes linearly along the axial direction (non-uniform), the thinnest at one end, the thickest at the other, and a continuous transition in between.
- Differentiated lead on both sides ：Left lead and right lead have a fixed difference (lead difference ），the lead difference determines the rate of tooth thickness change (i.e., the change in tooth thickness per unit axial movement distance).
- Adaptable to ordinary worm wheels ：The matching worm wheel of the double lead worm has an ordinary structure (uniform tooth thickness) and does not require special design, which reduces the overall manufacturing cost.
- Axial adjustment mechanism ：A precise worm axial positioning and adjustment device (such as a nut, shim, or servo drive mechanism) is required to achieve micrometer-level axial movement control.
IV. Core differences from ordinary worm gears
V. Core advantages
- Zero backlash or micro backlash transmission ：Axial adjustment can completely eliminate reverse dead zone, significantly improving transmission accuracy (especially suitable for precision positioning scenarios).
- Wear can be compensated During long-term operation, when the gap increases due to gear surface wear, the worm gear only needs to be moved axially to restore the original accuracy and extend the service life.
- Good transmission stability The large meshing gear surface contact area ensures uniform force distribution, low operating noise, and suitability for high-speed or low-speed precision transmission.
- Worm gear has strong versatility There is no need to design a special worm gear for gap adjustment, reducing the overall system design complexity and cost.
VI. Typical Application Scenarios
- Precision machine tools Feed systems of CNC lathes and milling machines (such as screw-worm gear transmission units) ensure tool positioning accuracy.
- Indexing mechanism Indexing heads of gear processing machine tools, azimuth adjustment mechanisms of radar or satellite antennas, achieving accurate angular indexing.
- Precision instruments Transmission systems of high-precision equipment such as coordinate measuring machines and lithography machines ensure micron-level or even nanometer-level motion control.
- Servo drive system Drive units of robot joints and precision conveyors reduce reverse impact and backlash error.
VII. Design and Processing Points
- Lead difference selection Lead difference Needs to be determined according to the required adjustment range. If it is too small, the adjustment efficiency is low; if it is too large, it may lead to poor gear surface contact. Usually (Adjusted according to the module and accuracy requirements).
- Axial adjustment mechanism A high-precision axial movement device (such as a ball screw + servo motor drive) needs to be designed to ensure adjustment accuracy at the 0.01mm level.
- Materials and heat treatment Worm gears often use high-strength alloy steel (such as 40CrNiMoA), which is quenched (HRC 58~62) and ground to ensure wear resistance and accuracy.
- Machining process Precision thread grinding machines are required to ensure the parallelism of the two leads and the gear shape accuracy (usually requiring grade 6 or higher accuracy) to avoid poor meshing due to machining errors.
VIII. Limitations
- High processing cost Specialized equipment and high-precision processing technology are required, resulting in higher manufacturing costs than ordinary worm gears.
- High assembly requirements The assembly accuracy of the axial adjustment mechanism directly affects the transmission performance. The center distance and parallelism error between the worm and worm wheel must be strictly controlled.
- Limited scope of application It only shows advantages in high-precision scenarios, and the cost-effectiveness is lower than ordinary worm gears in ordinary transmission scenarios.
Summary
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