Gear Manufacturing: How To Produce High-Quality Gears

Since gears are among the oldest mechanical parts that are still in use today, the idea of them has been around for a while. It could be anything from the automotive industry to the aerospace industry, from industrial machinery to something as basic as a clock. There are gears everywhere, and maybe you’d like to know how they’re made and their specific applications.

Thus, the question concerns the gear manufacturing process.

Gear Manufacturing Processes

Gear manufacturing is a diverse field that employs various processes tailored to the specific type and application of gears.

Gears typically operate in demanding conditions, given their critical role in power transmission. The primary goal is to ensure gears are in impeccable condition, reliable, and exhibit minimal residual stresses with little to no risk of crack propagation.

Meeting these stringent requirements poses significant challenges. Nevertheless, the importance of fulfilling them cannot be overstated. This underscores the fact that gear manufacturing is a specialized domain with tight tolerances and little room for error.

We will delve into the fundamentals of gear manufacturing, exploring common materials used in industrial gears, the processes involved in gear preparation, and how gears are engineered to withstand substantial loads without failure.

Types and Applications of Gears

Before delving into the intricacies of gear cutting and gear manufacturing processes, it’s essential to grasp the fundamentals. Understanding the various types of gears, their applications, and advantages is crucial, with factors like application requirements and performance parameters significantly influencing gear selection. One pertinent way to categorize gears, particularly from a manufacturing perspective, is based on their teeth profile.

Here are five types of gears commonly encountered:

Spur Gears

Imagine a gear in your mind, and it probably has straight teeth – that’s the characteristic appearance of a spur gear. Widely used in power plants, aerospace components, industrial machines, and more, spur gears with straight teeth are uncomplicated to manufacture and capable of sustaining high speeds and loads. However, they generate considerable noise and may not be suitable for applications requiring smooth operations.

Moreover, spur gears can mesh with other gears of the same type, as well as with internal/external gears. They find applications in various gearing mechanisms, such as simple rack and pinion setups or planetary gear systems. The simplicity of spur gears facilitates easier manufacturing and maintenance of precision. Additionally, their low axial load makes them efficient for gear trains where minimizing mechanical losses is a priority.

Helical Gears

Similar in essence to spur gears, helical gears distinguish themselves by having teeth twisted around a cylindrical body. This configuration enables them to function smoothly with both parallel and non-parallel shafts. However, their compatibility extends exclusively to other helical gears sharing the same helix angle (the degree of twist from the original cylinder).

While sharing many applications with spur gears, the angled teeth of helical gears significantly reduce impact loads and contribute to smoother operations, resulting in less noise. However, this improvement comes at the expense of efficiency. Compared to spur gears, a helical gear train experiences more losses and necessitates thrust bearings due to its shape.

Helical gear manufacturing presents more challenges than spur gear manufacturing. Replicating precise helix angles within a narrow tolerance range is demanding. Additionally, the expenses associated with manufacturing and integrating axial elements make them more suitable for specialized applications.

Bevel Gears

Unlike standard cylindrical gears, bevel gears are positioned on a conical surface, facilitating the alteration of transmission direction between intersecting shafts. Typically designed for 90-degree angles, they can also adapt to various other configurations.

Various common types of bevel gears are utilized across a wide array of applications:

• Straight bevel gears
• Spiral bevel gears
• Miter gears
• Crown gears
• Hypoid gears

Worm Gears

Comprising a combination of two key components—a worm wheel and a screw-shaped gear—worm gears find extensive use in aerospace, industrial machinery, elevators, and automobile steering systems. While the worm wheel setup may not deliver high speed or efficiency, it possesses a distinctive attribute crucial for self-locking mechanisms. In many instances, the worm can drive the wheel, but the reverse is not possible due to the specific gear angles. Additionally, it’s essential to note that worm-wheel gears exhibit substantial friction and may require continuous friction for optimal operation.

Rack and Pinion

The rack and pinion system represents another pairing designed primarily to convert rotational motion into linear motion and vice versa. The gear teeth can engage with both spur and helical type teeth, allowing for operation on both parallel axes and at various angles. This system finds common applications in automobile systems, weighing scales, and similar mechanisms.

Materials Utilized in Gear Production

Gears exhibit a remarkable diversity in materials, with historical instances of wooden gears and contemporary usage spanning various industries, ranging from large-scale steel or iron industrial gears to miniature plastic gears found in toys. The possibilities for material combinations are virtually limitless.

However, the following materials are most frequently employed in gear manufacturing and gear forming processes:

• Cast iron
• Steel
• Bronze
• Plastics

The selection of materials for gear manufacturing is guided by specific criteria. Depending on the intended application, chosen materials must possess suitable tensile strength and endurance. Another critical consideration is the coefficient of friction, as gears necessitate continuous contact. Additionally, ease of processing is a vital factor, given the precision and accuracy required in gear manufacturing.

The materials mentioned strike an optimal balance among these properties for their respective applications, making them commonly observed in a wide array of gears.

If you have a gear project, we can provide all these materials for the gear manufacturing process. Feel free to contact us to receive a quotation tailored to your specific gear requirements.

Common Gear Manufacturing Methods

Gear manufacturing is a complex endeavor, demanding precision and relying on a diverse range of processes, both traditional and modern, to achieve the delicate balance between cost, quality, and operational efficiency. The gear production industry has evolved into a specialized field, offering various techniques to meet specific needs.

Here is a compilation of common gear cutting and gear manufacturing processes, each accompanied by its apparent advantages and drawbacks:

Casting

Casting is a relatively straightforward process primarily used to create gear blanks or cylinders, with the teeth subsequently machined. While casting is a viable option for numerous applications due to its mass production capabilities and relative simplicity, it is particularly favored for the production of very large gears. Machining and alternative gear forming methods are less practical for large diameters, and the simplicity of casting makes it a preferred choice.

Common casting methods for gear production include shell casting, die casting, sand casting, and permanent mold casting. While other methods find limited use in specific applications, these mentioned methods dominate the industry.

Forging

Forging is another forming process that can produce both gear blanks and finished gears, depending on specific requirements. It proves viable for relatively simple gears. In theory, forging is an excellent choice for heavy-duty applications due to the inherent heat treatment, resulting in superior fatigue properties. However, the significant force required for the forging process imposes limitations on size and thickness.

Forging is generally effective for gears within the 6 to 10-foot diameter range. The need for machining depends on the type of forging, such as precision forging, with some processes requiring additional machining at the end.

Extrusion and Cold Drawing

Extrusion and cold drawing represent versatile and straightforward gear-forming processes. While extrusion boasts lower tool expenditures, it does not necessarily translate into being the most economical method.

In extrusion, a heated metal profile is passed through a smaller pre-determined shape, resulting in a bar of the desired shape with a hardened and smooth outer surface. The cold drawing process is similar, with two key differences: extrusion pushes the blank through a die, while drawing pulls it. Additionally, cold drawing doesn’t involve heating the billet, enhancing mechanical properties at the expense of cost.

Powder Metallurgy

Powder metallurgy, an advanced process with recent significant advancements, is now widely employed in various manufacturing processes, including gear production. The process involves starting with metal powder, shaping it to the desired form, compacting the setup for improved mechanical properties, and carefully heating the entire assembly.

While powder metallurgy is highly efficient, simple, and suitable for large quantities with no need for post-processing, resulting gears have load limitations and size constraints. The initial setup cost is relatively high, making it less viable for low-volume production.

Blanking

Blanking is a process similar to extrusion but with limited three-dimensional capabilities. This gear-forming method utilizes sheet metal and multiple dies to create the desired shape. Various types of gears, with spur gears yielding optimal results, can be produced using the blanking process.

Today, the blanking process in gear production finds application in multiple industries for lightweight purposes, including office equipment, hydraulics, small medical devices, and other applications with low load requirements.

Gear Machining

Machining stands as one of the most prevalent gear manufacturing processes, owing to its inherent versatility. While traditional machining methods were widespread for gear cutting and gear manufacturing, the rise of CNC machining has significantly enhanced its popularity.

The following four gear cutting methods are widely adopted across the industry:

Hobbing

Hobbing employs a conical cutting device known as a hob. Both the hob and the workpiece rotate as the hob moves around the gear blank. Currently, hobbing is primarily utilized for creating external spur and helical gears. The process is adaptable and efficient, allowing for increased production rates by processing multiple stacks simultaneously. However, it demands a higher level of skill and precision.

Shaping

Shaping is an advanced gear cutting and gear manufacturing process that tackles gears beyond the scope of hobbing. The cutter, taking various shapes like pinions, rack-shapes, or single-point shapes, resembles gears and works by cutting into the blank to achieve the desired shape. Shaping can produce internal or cluster gears.

Broaching

Broaching is a rapid gear form-cutting method that relies on a multi-tooth tool with embedded cutters, progressively making deeper cuts. This results in smaller, incremental cuts that are efficient and swiftly yield the required shape without compromising precision. While broaching is typical for internal gears, it can also be adapted for external teeth using specialized tools for pot broaching, ensuring precision and efficiency.

Milling

Milling is a fundamental gear cutting method where individual gear teeth are produced sequentially. While versatile, especially with the involvement of CNC milling machines, the precision of this method historically left room for improvement, leading to a decline in its popularity. Recent developments in the CNC domain and multi-axis capabilities have revitalized gear manufacturing on milling machines, making it increasingly common and promising further advancements in the future.

Gear Manufacturing Post-Processing

Following the chosen gear manufacturing method, post-processing steps are essential to ensure the gears reach their optimal state. This post-processing can encompass various activities, from heat treatment to enhance fatigue characteristics to dimensional correction and surface finishing.

Here are the five most common surface finishing processes frequently employed in gear production:

• Grinding:
  As the name implies, grinding is a prevalent surface finishing process that imparts a smooth finish throughout the surface. It can be conducted intermittently or continuously without compromising the results.
• Lapping:
  Lapping is employed for sensitive gears demanding extreme precision. This process utilizes small abrasive particles to smooth out surfaces at low or medium speeds.
• Honing:
  Honing is another widely used process that polishes the surface, rendering it smooth. Additionally, it can correct minor errors in tooth geometry.
• Shaving:
  Shaving involves the removal of extremely thin layers from the surface to achieve a smooth profile. Due to its relatively high cost, shaving is seldom utilized in gear production.
• Burnishing:
  Burnishing, at its core, involves using compression to smooth out the surface, enhancing its overall finish.

Gear Manufacturing Services

Extreme precision and accuracy are necessary in the highly specialized field of gear manufacturing. Any mechanical system must include gears, and even the smallest manufacturing defect can have catastrophic results. As a result, you must choose your service carefully.

Our cutting-edge services provide you with the best gear manufacturing experience possible, with the most skilled team offering the best performance at the most affordable cost.

Sungplastic has the right mix of expertise, experience, and quality for any kind of application, from big gears for industrial machinery to the smallest parts for any specialized use. Within a few hours, receive a preliminary quote by contacting us today.