Gear Manufacturing Process

There is no single process for gear manufacturing as they require different processes depending on the type and application.

In general, gears operate under very tough conditions because power transmission (the actual purpose of gears) has several requirements. First, the gear needs to be in absolute perfect condition. They must then be consistently reliable, with minimal residual stress and little to no chance of crack growth. This is why gear production is a highly specialized field with limited tolerances and room for error.

Materials used to produce gears

There are no material restrictions for gears. The earliest gears were wooden, and you can find gears in different materials throughout the industry. From large industrial scale steel or iron gears to small plastic gears in toys. The material combinations are endless.

Gears have very specific criteria for material selection. Depending on the application, whatever material you choose should have appropriate tensile strength and durability.

The following are most commonly used in gear manufacturing and gear forming processes:

cast iron

steel

bronze

plastic

Also, the coefficient of friction is another consideration since the gears need to be in constant contact. Finally, materials that are easy to process should also be selected. Since gear manufacturing requires extreme precision and accuracy, strong materials with low manufacturability will be more difficult to handle.

Common Gear Manufacturing Processes

Gear production is quite complex due to its precision requirements. Today, gear manufacturing is an industry unto itself that relies on a variety of processes, both traditional and modern, to ensure the proper balance between cost, quality and operations.

Precision Gear Manufacturing

Below is a list of common gear cutting and manufacturing processes with their obvious advantages and disadvantages.

1 - Casting

Casting is a simpler process mainly used to prepare blanks or cylinders for gears, while gear teeth are produced by machining. However, it is a viable gear manufacturing process for many applications due to its mass production capabilities and relative ease.

However, there is a certain area where casting is the most popular manufacturing method in the industry. That is producing very large gears. Machining methods and other gear shaping methods are not feasible at large diameters. In general, larger gears are almost always of the spur gear type. Therefore, their relative simplicity makes casting a very good choice.

Among the most common casting methods, shell casting, die casting, sand casting and metal casting are the most common in gear production. Other methods have limited use in some applications. However, the above situation is the most common in the industry.

2 - Forging

This is another forming process that can provide you with rough and prepared gears according to your requirements. Where gears are relatively simple, forging is quite feasible.

gear forging

In theory, forging is an excellent gear manufacturing process for heavy-duty applications for a simple reason. Forging requires heat treatment, which means the resulting gear will have better fatigue properties. However, the enormous force required for the forging process limits the size and thinness of the process.

In general, forging works well for gears within 6 – 10 feet in diameter. Depending on the type of forging (such as precision forging), you may or may not end up needing to machine the gears.

3 - Extrusion and cold drawing

This is another gear forming process that is both versatile and simple. The fact that extrusion has a lower tooling outlay doesn't mean it's the most economical process.

Extrusion, as the name suggests, is the process of passing a heated metal profile through a smaller predetermined shape. In the end, you will have a rod of the desired shape with a hardened and smooth outer surface.

The cold drawing process is very similar to the extrusion process. There are two differences. Extrusion pushes the blank through the die, pulling it. Another difference is temperature. Cold drawing does not heat the billet. Thereby improving mechanical properties at the expense of cost.

4 – Powder Metallurgy

Powder metallurgy is an advanced process that has made significant progress in recent years. Today, it is used in a variety of manufacturing processes, including gear production.

So, how does powder metallurgy work? From the looks of it, it's pretty simple. However, there are many intricate issues involved.

It all starts with metal powder. The first step is to take out all the powder and create your desired final shape. Once this is done, the next step is to make sure the whole setup is very compact as this will lead to better mechanical properties. Carefully heat the entire setup, and you're done.

Powder metallurgy is extremely efficient, simple and suitable for high-volume production. You don't need to worry about any post-processing, the product is ready to use. However, the resulting gears cannot withstand too much load and there are also size limitations.

Additionally, the initial cost of any powder metallurgy setup is quite high, making it unsuitable for any small batch production.

5 – Blanking

Blanking is a process very similar to extrusion, but with limited 3D capabilities. This gear forming process uses sheet metal to form the desired shape with the help of multiple dies. You can produce different types of gears by blanking process. However, spur gears will give you the best results.

Today, the blanking process for gear production is used by several industries for lightweight applications. For example, office equipment, hydraulics, small medical equipment, and other applications with lower load requirements.

6 - Gear Machining

Machining is one of the most common gear manufacturing processes due to its versatility. Traditional machining is fairly common in gear cutting and manufacturing, but advances in CNC machining have driven its popularity.