Worm gears are often used when large velocity reductions are needed. The reduction ratio depends upon the number of starts of the worm and quantity of tooth on the worm gear. But worm gears have sliding contact which is silent but tends to produce heat and have relatively low transmission performance.
For the materials for production, in general, worm is made from hard metal as the worm gear is manufactured out of relatively soft metal such as aluminum bronze. This is because the number of tooth on the worm equipment is relatively high in comparison to worm with its number of starts being usually 1 to 4, by reducing the worm equipment hardness, the friction on the worm teeth is reduced. Another characteristic of worm manufacturing is the need of specialized machine for gear cutting and tooth grinding of worms. The worm gear, however, may be made out of the hobbing machine used for spur gears. But because of the various tooth shape, it is not possible to cut a number of gears at once by stacking the apparatus blanks as can be done with spur gears.
The applications for worm gears include equipment boxes, fishing pole reels, guitar string tuning pegs, and where a delicate speed adjustment by utilizing a big speed reduction is needed. When you can rotate the worm gear by worm, it is generally extremely hard to rotate worm utilizing the worm gear. That is called the self locking feature. The self locking feature cannot always be assured and another method is preferred for accurate positive reverse prevention.
Also there exists duplex worm gear type. When using these, you’ll be able to modify backlash, as when the teeth put on necessitates backlash adjustment, without needing a change in the guts distance. There aren’t too many manufacturers who can produce this type of worm.
The worm gear is more commonly called worm wheel in China.
A worm gear is a gear consisting of a shaft with a spiral thread that engages with and drives a toothed wheel. Worm gears are an old style of equipment, and a version of one of the six simple machines. Basically, a worm gear is a screw butted against what looks like a typical spur gear with somewhat angled and curved tooth.
It changes the rotational motion by 90 degrees, and the plane of movement also changes due to the position of the worm upon the worm wheel (or simply “the wheel”). They are typically comprised of a steel worm and a brass wheel.
Figure 1. Worm gear. Most worms (however, not all) are at underneath.
How Worm Gears Work
An electric motor or engine applies rotational power via to the worm. The worm rotates against the wheel, and the screw encounter pushes on one’s teeth of the wheel. The wheel is definitely pushed against the load.
Worm Gear Uses
There are a few reasons why you might choose a worm gear over a standard gear.
The first one is the high reduction ratio. A worm equipment can have a massive reduction ratio with small effort – all one should do is certainly add circumference to the wheel. Hence you can utilize it to either greatly increase torque or greatly reduce speed. It will typically consider multiple reductions of a typical gearset to achieve the same reduction level of a single worm gear – which means users of worm gears have got fewer shifting parts and fewer areas for failure.
A second reason to use a worm gear is the inability to reverse the direction of power. Due to the friction between your worm and the wheel, it really is virtually not possible for a wheel with power applied to it to start the worm moving.
On a standard gear, the input and output can be switched independently once enough force is applied. This necessitates adding a backstop to a standard gearbox, further raising the complication of the apparatus set.
YOU WILL WANT TO to Use Worm Gears
There is one particularly glaring reason one would not select a worm gear over a typical gear: lubrication. The motion between the worm and the wheel equipment faces is completely sliding. There is absolutely no rolling element of the tooth get in touch with or conversation. This makes them fairly difficult to lubricate.
The lubricants required are usually very high viscosity (ISO 320 and higher) and thus are hard to filter, and the lubricants required are usually specialized in what they do, requiring something to be on-site specifically for that type of equipment.
Worm Gear Lubrication
The primary problem with a worm gear is how it transfers power. It really is a boon and a curse simultaneously. The spiral motion allows large sums of decrease in a comparatively small amount of space for what’s required if a standard helical gear were used.
This spiral motion also causes an incredibly problematic condition to be the primary mode of power transfer. This is often called sliding friction or sliding wear.
With a typical gear set the power is transferred at the peak load stage on the tooth (known as the apex or pitchline), at least in a rolling wear condition. Sliding occurs on either side of the apex, however the velocity is relatively low.
With a worm gear, sliding motion is the only transfer of power. As the worm slides across the tooth of the wheel, it slowly rubs off the lubricant film, until there is absolutely no lubricant film still left, and for that reason, the worm rubs at the steel of the wheel in a boundary lubrication regime. When the worm surface area leaves the wheel surface area, it accumulates more lubricant, and begins the process over again on another revolution.
The rolling friction on an average gear tooth requires small in the form of lubricant film to complete the spaces and separate both components. Because sliding occurs on either part of the gear tooth apex, a slightly higher viscosity of lubricant than can be strictly necessary for rolling wear is required to overcome that load. The sliding takes place at a comparatively low velocity.
The worm on a worm set gear turns, and while turning, it crushes against the load that’s imposed on the wheel. The only method to avoid the worm from touching the wheel is definitely to get a film thickness large enough to not have the whole tooth surface area wiped off before that portion of the worm has gone out of the strain zone.
This scenario requires a special sort of lubricant. Not just will it should be a relatively high viscosity lubricant (and the higher the strain or temperature, the bigger the viscosity must be), it must have some way to help conquer the sliding condition present.
Read The Right Method to Lubricate Worm Gears to learn more on this topic.
Viscosity is the major factor in avoiding the worm from touching the wheel in a worm equipment set. As the load and size of gearing determines the required lubricant, an ISO 460 or ISO 680 is fairly common, and an ISO 1000 isn’t unheard of. If you’ve ever tried to filter this selection of viscosity, you know it is problematic because it is likely that none of the filters or pumps you have on-site will be the correct size or ranking to function properly.
Therefore, you would likely have to get a particular pump and filter for this kind of unit. A lubricant that viscous requires a slow operating pump to prevent the lubricant from activating the filter bypass. It will also require a huge surface area filter to permit the lubricant to movement through.
Lubricant Types to Look For
One lubricant type commonly used with worm gears is mineral-based, compounded gear oils. There are no additives which can be put into a lubricant that can make it conquer sliding wear indefinitely, but the natural or synthetic fatty additive combination in compounded equipment oils results in great lubricity, providing an extra measure of protection from metal-to-metal get in touch with.
Another lubricant type commonly used with worm gears is mineral-based, commercial extreme pressure (EP) gear oils. There are several problems with this type of lubricant in case you are using a worm gear with a yellow metal (brass) component. However, if you have relatively low operating temperatures or no yellow metallic present on the gear tooth surfaces, this lubricant is effective.
Polyalphaolefin (PAO) equipment lubricants work very well in worm gear applications because they naturally possess great lubricity properties. With a PAO equipment oil, it’s important to watch the additive package, because these can possess EP additives. A standard-duty antiwear (AW) fortified gear essential oil will typically be acceptable, but check that the properties are appropriate for most metals.
The writer recommends to closely view the put on metals in oil analysis testing to make sure that the AW package isn’t so reactive as to cause significant leaching from the brass. The effect should be far less than what will be seen with EP even in a worst-case scenario for AW reactivity, but it can show up in metals testing. If you want a lubricant that can deal with higher- or lower-than-typical temperature ranges, a suitable PAO-based product is likely available.
Polyalkylene glycols (PAG), a fourth kind of lubricant, are becoming more common. These lubricants have superb lubricity properties, , nor contain the waxes that cause low-temperature problems with many mineral lubricants, making them a great low-temperature choice. Caution should be taken when using PAG oils because they’re not appropriate for mineral oils, plus some seals and paints.
Metallurgy of Worm Gears
The most common worm gears are made with a brass wheel and a steel worm. That is because the brass wheel is typically easier to replace than the worm itself. The wheel is manufactured out of brass because it was created to be sacrificial.
When the two surfaces enter into contact, the worm is marginally secure from wear since the wheel is softer, and therefore, most of the wear occurs on the wheel. Oil analysis reports on this kind of unit more often than not show some level of copper and low levels of iron – as a result of the sacrificial wheel.
This brass wheel throws another problem in to the lubrication equation for worm gears. If a sulfur-phosphorous EP gear essential oil is placed into the sump of a worm equipment with a brass wheel, and the temperature is high enough, the EP additive will activate. In normal steel gears, this activation creates a thin coating of oxidation on the top that really helps to protect the apparatus tooth from shock loads and additional extreme mechanical conditions.
On the brass surface however, the activation of the EP additive results in significant corrosion from the sulfur. In a brief amount of time, you can drop a substantial portion of the strain surface area of the wheel and cause major damage.
A few of the less common materials within worm gear sets include:
Steel worm and metal worm wheel – This program does not have the EP problems of brass gearing, but there is absolutely no room for mistake included in a gearbox such as this. Repairs on worm equipment sets with this mixture of metal are typically more costly and more time eating than with a brass/steel worm gear set. This is because the material transfer connected with failure makes both the worm and the wheel unusable in the rebuild.
Brass worm and brass worm wheel – This program is most likely found in moderate to light load situations because the brass can only just keep up to a lesser amount of load. Lubricant selection upon this metal mixture is flexible because of the lighter load, but one must still consider the additive limitations regarding EP because of the yellow metal.
Plastic on metal, on plastic, and other similar combinations – This is typically found in relatively light load applications, such as for example robotics and automotive components. The lubricant selection depends on the plastic in use, because many plastic types react to the hydrocarbons in regular lubricant, and thus will require silicon-based or other non-reactive lubricants.
Although a worm gear will always have a few complications compared to a standard gear set, it can easily be a highly effective and reliable device. With a little focus on set up and lubricant selection, worm gears can offer reliable service along with any other kind of gear set.
A worm drive is one particular worm gear set mechanism when a worm meshes with a worm equipment. Even it is basic, there are two essential components: worm and worm equipment. (They are also known as the worm and worm wheel) The worm and worm wheel is important motion control component providing large swiftness reductions. It can decrease the rotational velocity or raise the torque result. The worm drive motion advantage is that they can transfer movement in right angle. In addition, it has an interesting home: the worm or worm shaft can simply turn the apparatus, but the gear can not change the worm. This worm drive self-locking feature allow worm gear includes a brake function in conveyor systems or lifting systems.
An Launch to Worm Gearbox
The most crucial applications of worm gears can be used in worm gear box. A worm gearbox is called a worm decrease gearbox, worm equipment reducer or a worm drive gearbox. It contains worm gears, shafts, bearings, and box frames.
The worm gear, shafts, bearings load are supported by the box shell. Therefore, the gearbox housing will need to have sufficient hardness. Otherwise, it will result in lower transmission quality. As the worm gearbox has a durable, transmitting ratio, small size, self-locking ability, and simple structure, it is often used across an array of industries: Rotary desk or turntable, material dosing systems, auto feed machinery, stacking machine, belt conveyors, farm choosing lorries and more automation market.
How to Select High Efficient Worm Gearbox?
The worm gear production process is also relatively simple. However, there is a low transmission efficiency problem if you don’t know the how to choose the worm gearbox. 3 basic indicate choose high worm gear efficiency that you need to know:
1) Helix position. The worm equipment drive efficiency mostly depend on the helix angle of the worm. Usually, multiple thread worms and gears is more efficient than solitary thread worms. Proper thread worms can increase performance.
2) Lubrication. To select a brand lubricating oil is an essential factor to improve worm gearbox effectiveness. As the proper lubrication can reduce worm gear action friction and warmth.
3) Material selection and Gear Manufacturing Technology. For worm shaft, the material ought to be hardened metal. The worm gear material should be aluminium bronze. By reducing the worm equipment hardness, the friction on the worm teeth is decreased. In worm manufacturing, to use the specific machine for gear cutting and tooth grinding of worms can also increase worm gearbox efficiency.
From a big transmission gearbox power to an even small worm gearbox load, you can choose one from a wide range of worm reducer that precisely suits your application requirements.
Worm Gear Box Assembly：
1) You can complete the set up in six various ways.
2) The installation should be solid and reliable.
3) Make sure to examine the connection between your engine and the worm equipment reducer.
4) You must use flexible cables and wiring for a manual installation.
By using the innovative science and drive technology, we have developed several unique “square package” designed from high-quality aluminium die casting with a lovely appearance. The modular worm gearbox style series: worm drive gearbox, parallel shaft gearbox, bevel helical gearbox, spiral bevel gearbox, coaxial gearbox, correct angle gearbox. An NMRV series gearbox is usually a standard worm gearbox with a bronze worm gear and a worm. Our Helical gearbox product line comprises of four universal series (R/S/K/F) and a step-less speed variation UDL series. Their structure and function are similar to an NMRV worm gearbox.
Worm gears are made of a worm and a gear (sometimes referred to as a worm wheel), with non-parallel, non-intersecting shafts oriented 90 degrees to each other. The worm is analogous to a screw with a V-type thread, and the apparatus is analogous to a spur equipment. The worm is normally the traveling component, with the worm’s thread advancing the teeth of the gear.
Just like a ball screw, the worm in a worm gear may have a single start or multiple starts – meaning that there are multiple threads, or helicies, on the worm. For a single-start worm, each complete change (360 degrees) of the worm advances the gear by one tooth. So a gear with 24 teeth provides a gear reduced amount of 24:1. For a multi-start worm, the apparatus reduction equals the amount of teeth on the apparatus, divided by the number of starts on the worm. (That is different from most other types of gears, where the gear reduction is a function of the diameters of both components.)
The worm in a worm gear assembly can have one start (thread) or multiple starts.
Image credit: Kohara Gear Sector Company, Ltd.
The meshing of the worm and the apparatus is an assortment of sliding and rolling actions, but sliding contact dominates at high reduction ratios. This sliding actions causes friction and high temperature, which limits the efficiency of worm gears to 30 to 50 percent. In order to minimize friction (and therefore, high temperature), the worm and equipment are made of dissimilar metals – for example, the worm may be made of hardened metal and the gear manufactured from bronze or aluminum.
Although the sliding contact decreases efficiency, it provides extremely quiet operation. (The use of dissimilar metals for the worm and gear also contributes to quiet procedure.) This makes worm gears ideal for use where sound should be minimized, such as for example in elevators. Furthermore, the use of a softer material for the gear means that it could absorb shock loads, like those experienced in heavy equipment or crushing devices.
The primary advantage of worm gears is their capability to provide high reduction ratios and correspondingly high torque multiplication. They can also be utilized as acceleration reducers in low- to medium-speed applications. And, because their decrease ratio is founded on the number of gear teeth by itself, they are smaller sized than other styles of gears. Like fine-pitch business lead screws, worm gears are usually self-locking, making them perfect for hoisting and lifting applications.
A worm gear reducer is one type of reduction gear package which consists of a worm pinion input, an output worm equipment, and features a right angle result orientation. This type of reduction gear package is normally used to have a rated motor acceleration and produce a low speed result with higher torque worth based on the reduction ratio. They often times can solve space-saving problems because the worm gear reducer is one of the sleekest reduction gearboxes available because of the small diameter of its output gear.
worm gear reducerWorm gear reducers are also a favorite type of rate reducer because they offer the greatest speed reduction in the tiniest package. With a high ratio of speed reduction and high torque output multiplier, it’s unsurprising that many power transmission systems utilize a worm equipment reducer. Some of the most typical applications for worm gears are available in tuning instruments, medical examining equipment, elevators, protection gates, and conveyor belts.
Torque Transmission provides two sizes of worm equipment reducer, the SW-1 and the SW-5 and both are available in a variety of ratios. The SW-1 ratios include 3.5:1 to 60:1 and the SW-5 ratios include 5:1 to 100:1. Both these options are produced with tough compression-molded glass-fill up polyester housings for a long lasting, long lasting, light weight speed reducer that’s also compact, non-corrosive, and nonmetallic.
Our worm gear reducers offer a choice of a good or hollow output shaft and show an adjustable mounting placement. Both the SW-1 and the SW-5, however, can endure shock loading much better than other decrease gearbox designs, making them well suited for demanding applications.
Rugged compression-molded glass-fill polyester housing
Light weight and compact
Range of ratios
SW-1, 3.5:1 to 60:1
SW-5, 5:1 to 100:1
Solid or Hollow output shaft
Adjustable mounting position
Low friction coefficient upon the gearing for high efficiency.
Powered by long-enduring worm gears.
Minimal speed fluctuation with low noise and low vibration.
Lightweight and compact in accordance with its high load capacity.
Compact design is among the key words of the typical gearboxes of the BJ-Series. Further optimisation may be accomplished through the use of adapted gearboxes or special gearboxes.
Our worm gearboxes and actuators are extremely quiet. This is because of the very even operating of the worm gear combined with the use of cast iron and high precision on component manufacturing and assembly. Regarding the our precision gearboxes, we take extra care of any sound that can be interpreted as a murmur from the gear. Therefore the general noise degree of our gearbox is usually reduced to an absolute minimum.
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This often proves to be a decisive benefit making the incorporation of the gearbox considerably simpler and more compact.The worm gearbox is an angle gear. This is often an advantage for incorporation into constructions.
Solid bearings in solid housing
The output shaft of the BJ worm gearbox is quite firmly embedded in the gear house and is perfect for immediate suspension for wheels, movable arms and other areas rather than having to build a separate suspension.
For larger gear ratios, BJ-Gear’s worm gearboxes will provide a self-locking impact, which in lots of situations can be utilized as brake or as extra security. Also spindle gearboxes with a trapezoidal spindle are self-locking, making them ideal for a wide range of solutions.
Would certainly you like more details on worm wheel gearbox? Get in touch with us today.