Gear Manufacturing 101

The concept of gears has been around for a while as they are among the oldest mechanical components that are still relevant today. Be it the automobile industry, the aerospace sector, any industrial machinery, or something simple like a clock – gears are required everywhere. So, the question is about how gears are manufactured?

This article will take you back to the basics of gear manufacturing, the processes that prepare gears, and gear types plus their applications.

Common Types of Gears and Their Applications

There are different types of gears and their application and advantages. Your application, performance parameter, and numerous other factors play an important role in the kind of gears you use.Here are the 5 kinds of gears you’ll encounter.

  • Spur Gears – Draw a rough picture of what gear looks like in your mind. There are high chances that you are thinking of gear with straight teeth. That’s exactly what a spur gear looks like. The spur gear is the most common type of gear and has multiple applications in power plants, aerospace components, industrial machines, and much more. Straight teeth are the simplest to manufacture and sustain high speeds and high loads. However, they produce a lot of noise and are not suitable for applications where you need smooth operations. Spur gears also have little to no axial load, so they are quite efficient for a gear train where you want to minimize mechanical losses.
  • Helical Gears – Helical gears are quite similar to spur gears but they come with teeth that are twisted around a cylindrical body. This quality allows them to work with both parallel and non-parallel shafts easily. Their mating, however, only works with other helical gears of the same helix angle (the angle of twist from the original cylinder). Most of the applications of helical gears are the same as spur gears. However, the angled teeth play a huge role in reducing the impact load and making the operations smoother. This means less noise as well but at the cost of efficiency. Relative to spur gears, a helical gear train will have more losses and will also need thrust bearings because of the shape. 
  • Bevel Gears – Bevel gears are not your standard cylindrical gears. They come on a conical surface that allows you to change the direction of the transmission on intersecting shafts. Generally, bevel gears work with 900 angles. However, you can use them on other configurations as well.
  • Worm Gears – The worm gear system is a combination of two components. A worm wheel and a screw-shaped gear. They are predominantly used in aerospace, industrial machines, elevators, and automobile steering. The worm wheel setup doesn’t offer much speed or efficiency. However, it offers a unique characteristic required for self-locking mechanisms. In many cases, the worm may turn the wheel, but vice versa can’t happen because of the gear angles. Furthermore, another important thing to note is that worm-wheel gears have a lot of friction and may require continuous friction to operate properly.
  • Rack and Pinion – The rack and pinion system is another combination that primarily works to transfer rotational motion to linear and vice versa. The gear teeth can mate with both spur and helical type teeth, so you can work on both parallel axis and at an angle. Some of the most common applications of this system are in automobile systems, weighing scales, and other similar systems. 

Common Gear Manufacturing Processes

Gear production is quite complicated because of the precision it demands. Today, gear manufacturing is an industry in itself that relies on multiple processes, both traditional and modern, to ensure the right balance between cost, quality, and operations.

Here’s a list of common gear cutting and manufacturing processes along with their apparent advantages and disadvantages.

  1. Casting – Casting is a simpler process that is predominantly used to prepare blanks or cylinders for gears, while the teeth are prepared through machining. Among the most common types of casting methods, shell casting, die casting, sand casting and permanent mold casting are the most common for gear production. There is, however, one area where casting is the most preferred manufacturing method in the industry. That is the production of very large gears. Machining methods and other gear forming methods are not that viable in cases of large diameters.
  2. Forging – This is another forming process that can give you both blanks and prepared gears depending on your requirements. Forging is quite viable in cases where you have relatively simple gears. Theoretically, forging is an excellent gear manufacturing process for heavy-duty applications because of a simple reason. Forging requires heat treatment, which means that the resulting gear would have better fatigue properties. However, the tremendous force required for the forging process limits the size and thinness of this process. Generally, forging works well for gears within 6 – 10 ft diameter gears. Depending on the type of forging for example precision forging, you may or may not need to machine the gears in the end.
  3. Extrusion and Cold-drawing – This is another gear-forming process that’s both versatile and more simple. Extrusion, as its name suggests, is the process of passing a heated metal profile through a smaller predetermined shape. Resultantly, you get a bar of your desired shape with a hardened and smooth outer surface. The cold drawing process is very similar to extrusion. There are two differences. Extrusion pushes the blank through a die drawing and pulls it. The other difference is the temperature. Cold drawing doesn’t heat the billet. Thereby increasing the mechanical properties at the expense of cost.
  4. Powder Metallurgy – It all starts with metal powder. The first step is to take all the powder and give it a finalized form that you desire. Once you are done, the next step ensures that the entire setup is quite compact as it will result in better mechanical properties. Heat the entire setup carefully and you are done. Powder metallurgy is extremely efficient, simple, and viable for large quantities. You don’t have to worry about any post-processing as well as the product will be ready to use. However, the resulting gears can’t bear too much load and there are size limitations as well.
  5. Blanking – Blanking is a very similar process to extrusion but has limited 3-dimensional capabilities. This gear forming process uses sheet metal to create the desired shape with the help of multiple dies. You can produce different types of gears with the blanking process. However, spur gears give you the best results. Today, the blanking process of gear production is used by multiple industries for lightweight applications. For example, office equipment, hydraulics, small medical devices, and other applications with low load requirements.
  6. Machining – Machining is among the most common gear manufacturing processes because of its versatility. Traditional machining was quite common for gear cutting and manufacturing but the advancements of CNC machining have propelled its popularity.

Gear Manufacturing Post-processing

Depending on the gear manufacturing method you used, your gears will need some post-processing before they are 100% ready for use. 

Here are the 5 most common surface finishing processes that are common in gear production.

  • Grinding: Just as its name suggests, grinding is a common surface finishing process that gives you a smooth finish throughout the surface. 
  • Lapping: This process is for sensitive gears where you need extreme precision. Lapping uses small abrasive particles to smooth out a surface at low or medium speeds.
  • Honing: This is another common process that polishes the surface and makes it smooth. Moreover, you can also correct some minor errors in your tooth geometry.
  • Shaving: This process removes extremely thin layers from the surface to achieve a smooth profile. 
  • Burnishing: In its essence, burnishing is the process of using compression to smooth out the surface.

Contact Custom Tool Today!

Gear manufacturing is a highly specialized field that requires extreme precision and accuracy. Gears are an essential component for any mechanical system and even the smallest manufacturing flaw can have a lot of disastrous consequences. Therefore, you need to be careful about the service you select.

Custom Tool has the most experienced team that delivers the best performance at the most competitive price. For more information fill out or contact form or request a quote today.