Bevel gear vs. worm gear | advantages & disadvantages

The choice between Worm gear units and bevel gear units has a major influence on efficiency and operating costs. In this article we would like to give you the most important advantages of worm and bevel gear units so that you can determine which one is the most suitable for your application. If you still have any questions, please do not hesitate to contact us: Contact form

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Further information on worm and bevel gear units.

Frequent applications of angular gearboxes

Worm and bevel gears are often used to transmit motion at right angles or when other properties are required.

• Conveyor belts
• Crane
• Elevators
• Mixer
• Beverage industry
• Many other applications

Worm gear

A worm gear unit consists of two parts: a worm shaft with worm gears and a worm wheel. The two components are often made of two different materials (steel worm shaft and bronze worm wheel). Worm gears transmit the movement force at right angles via a sliding effect instead of a rolling movement.

Advantages

• Worm gears are mainly used when a large gear ratio is required. With a worm gear unit, a large overall ratio can be achieved with only a few stages. This means that a smaller, less expensive gearbox can be used.
• The highest ratio of a worm gear unit is about 100:1.
• High self-locking due to the sliding effect of the worm shaft makes an additional brake either obsolete or it is only necessary to install a small, less expensive brake. However, this property depends on the angle of inclination and the friction angle.
• More favourable than bevel gear
• Hollow shaft possible

Disadvantages

• The sliding contact of the gears causes strong friction, which results:
  • one High operating temperature
  • one Low efficiency
• High wear on the worm wheel, which is mostly made of bronze. (Only through bronze production a relative efficiency is possible. The friction would be much higher with steel on steel.)

Bevel gears

4 types of bevel gears

• Spiral
• Straight
• Cerol
• Skew Tooth

Bevel gear sets are composed of two parts, the bevel pinion and bevel gear, which transmit movements at right angles.

Bevel gears use angular gear teeth. As the gears rotate, the entire tooth width of the interlocking teeth is used to transmit the force. In addition, several teeth interlock at the same time. This results in the following advantages.

Advantages

• Quiet Operating noise (Quiet operation is particularly advantageous in environments such as theatres or airports.)
• Increased torque capacity compared to worm gears of the same size.
• High efficiency (rolling of bevel gears is very efficient compared to the sliding effect of worm gears (98.5%). The metal bevel gear teeth never come into direct contact with an oil film.)
• Hollow shaft possible

Disadvantages

• High costs.
• Bevel gears are manufactured in pairs. For maintenance and repair, both gears must be replaced.
• In order to achieve high efficiency, bevel gear sets must be positioned exactly, so the shafts must be adjusted very precisely.
• Limited translation range. Maximum ratio of 6:1 per bevel gear set. Spur gear stages are necessary in order to achieve a higher overall gear ratio.
• Bevel gears are not recommended for high-speed reduction. At high speed, a bevel gear unit generates noise.

Further information

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Firstly ,the worm gear unit to achieve transmission.

The worm wheel&#;s rotation axis is perpendicular to the worm&#;s optional axis. which is 90 degrees, allowing for a high transmission ratio. It is also smaller than the staggered shaft helical gear mechanism.

and the line contact between the meshing teeth of the two wheels is

significantly

more than in the staggered shaft helical gear system

.

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The worm drive is synonymous with the helical drive. Because it is a multi-tooth meshing drive, the transmission is smooth and the noise is minimal.

When the worm&#;s lead angle is less than the equal friction angle between the meshing wheel&#;s teeth. The mechanism features self-locking capabilities, including reverse self-locking. That is, only the worm can drive the worm wheel, and the worm wheel cannot drive the worm. When installing a self-locking worm gear mechanism in large machinery. Its reverse self-locking feature can aid in safety protection.

Effiency of Two Type of Gears

But the worm gear drive efficiency is low and the wear is serious. When the worm gear meshes with the transmission. the relative sliding speed between the teeth of the meshing wheel is large. so the friction loss is large and the efficiency is low. On the other hand, the relative sliding speed ambassador tooth surface wear serious and heat. in order to dissipate heat and reduce wear. the materials using more expensive friction reduction and anti-wear better materials and good lubrication device. and therefore higher costs. And worm shaft axial force is large.

Helical gears and helical gears to achieve transmission with parallel shafts or staggered shafts. i.e., the input and output shafts are parallel or staggered at a certain angle.

Helical gears can also achieve large transmission ratio through multi-stage combination. but single-stage transmission is generally inferior to worm gears.

The Speed

The speed can be increased or decreased. and the transmission is smooth, and the axial force generated by the helical gear transmission . that need considered when designing the application.

Under the condition of large transmission ratio. the two wheel helix angle can be appropriately selected. that to make the two wheel indexing circle diameter approximately equal. so as to approach equal strength.

Due to the staggered shaft helical gear, that drive meshing wheel teeth . along the tooth length direction of greater relative sliding. the transmission of mechanical efficiency is low. but with the worm gear staggered shaft helical gear two wheel meshing tooth surface for point contact. In the staggered shaft helical gear transmission, will also generate axial forces.

staggered shaft helical gear transmission, the helix angle of the two wheels may not be equal in size. so their end modulus and end pressure angle are not necessarily equal. respectively, which is different from parallel shaft helical gear transmission.

The application as follows:

Staggered shaft helical gear drive is not suitable for high speed and high power transmission, usually only used in instrumentation or auxiliary transmission of small load. Parallel shaft helical gears are very widely used.

Worm wheel and worm gear mechanism is often used for two shafts vertically staggered. transmission ratio, transmission power is not large or intermittent work occasions.

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