Planar involute worm gear: A 'hardcore' choice for high-precision, heavy-duty transmission
Classification： Blog
Release time：2025-07-25
Planar Double Enveloping Worm Gear is a high-performance worm gear transmission mechanism. Its worm and worm wheel tooth surfaces are formed by double enveloping, exhibiting outstanding performance in load-carrying capacity, transmission accuracy, and stability. It is widely used in high-precision and heavy-load transmission scenarios such as CNC machine tools, heavy machinery, and aerospace.
Its characteristic lies in the planar (or near-planar) worm tooth surface, unlike the helical surface of ordinary cylindrical worm gears. The double enveloping processing allows for better matching of the worm and worm wheel tooth surfaces, improving meshing performance. Compared to ordinary worm gears, it achieves multi-tooth contact, resulting in a more even load distribution.
In terms of performance, planar double enveloping worm gears have a high load-carrying capacity due to their large contact area, enabling them to withstand heavier loads; high transmission accuracy due to the double enveloping process improving meshing accuracy and reducing backlash; high transmission efficiency with minimal frictional losses, reaching 85%~90%; long service life due to even stress distribution and less wear; and a compact structure suitable for space-constrained applications.
Its manufacturing and meshing process involves several steps: the initial enveloping uses a worm wheel cutter (or standard worm wheel) to machine the worm, forming the preliminary tooth surface; the second enveloping uses the already machined worm as a cutter to machine the worm wheel in reverse, ensuring complete matching between the worm wheel and worm tooth surfaces; during operation, multiple teeth of the worm and worm wheel make contact simultaneously, improving transmission stability.
Compared to ordinary cylindrical worm gears, planar double enveloping worm gears feature multi-tooth contact and surface contact, while ordinary cylindrical worm gears have single-tooth or line contact; planar double enveloping worm gears have a higher load-carrying capacity, while ordinary cylindrical worm gears have a lower capacity; planar double enveloping worm gears offer higher transmission accuracy and less backlash, while ordinary cylindrical worm gears have generally lower accuracy; planar double enveloping worm gears have higher efficiency (85%~90%), while ordinary cylindrical worm gears have lower efficiency (70%~85%); planar double enveloping worm gears are more difficult to manufacture, requiring specialized equipment, while ordinary cylindrical worm gears are easier to manufacture.
Its applications are extensive, including high-precision machine tools such as CNC milling machines and grinding machines; heavy machinery such as mining machinery and metallurgical equipment; aerospace applications such as rudder gear transmission and landing gear systems; robotic joint transmission; and precision instruments such as optical equipment and measuring instruments.
Several key points should be considered during design: the choice of module and pressure angle affects load-carrying capacity and transmission efficiency; for the number of worm threads, single-thread worm gears have a larger transmission ratio but lower efficiency, while multi-thread worm gears have higher efficiency but a smaller transmission ratio; for material selection, the worm commonly uses hardened steel such as 20CrMnTi, and the worm wheel commonly uses bronze such as ZCuSn10P1; high-performance grease or forced lubrication should be used to reduce friction and wear.
Of course, it has both advantages and disadvantages. Advantages include strong load-carrying capacity, suitable for heavy-duty transmission, smooth transmission, low noise, and a compact structure suitable for space-constrained applications. Disadvantages include complex manufacturing processes, high cost, strict requirements for assembly accuracy, and the need for good lubrication conditions.
Planar double enveloping worm gears, as a high-performance transmission mechanism, excel in applications requiring high precision, heavy loads, and long service life. Despite the higher manufacturing and assembly threshold, its stable and reliable transmission performance makes it irreplaceable in high-end mechanical fields.
keyword： Secondary envelope,Worm gear,CNC machine tools,Transmission system