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Types of Cold Working Processes: A Comprehensive Guide

June 13, 2024

What Is Cold Working?

Cold working is a process that reshapes metal materials while they are below their recrystallization temperature. Recrystallization occurs when new crystals in the metal form as a result of energizing the metal atoms to a certain point. Because cold working shapes metals under recrystallization temperatures, the process results in stronger finished parts with greater integrity, as the grain structure of the raw material has not been altered.

There are many types of cold working processes, including roll racking, coining, stamping, die transfer, and cold forging. These techniques create high-precision, high-strength components that can easily be reproduced. At Grob, Inc., we combine multiple types of coldworking to produce complex, high-precision components like gears at competitive prices.

Read on to learn more about the different types of cold working and the benefits of the unique Grob Method.

The Different Types of Cold Working

There are four main types of cold working processes, each with its own benefits and limitations. Our innovative, proprietary method called Grob Rolling involves a combination of cold working techniques, designed to optimize production while eliminating these limitations.

Cold Forming

In cold forming, a press deforms a metal workpiece in a tool to create a high-strength component. Unlike hot forging, cold forming keeps the metal and tooling at room temperature. This process is an effective solution for producing large amounts of metal products quickly, consistently, and cost-effectively.

In comparison to high-heat formation methods, cold-formed products feature greater hardness, higher tensile strength, a superior surface finish, and greater yield. While the terms cold forming and cold forging are often used interchangeably, cold forming is more of an umbrella term for general cold working techniques.

Cold Forging

The process of cold forging involves placing a metal workpiece between two dies and then applying pounding pressure until the metal takes the intended shape. Cold forging can create a diverse variety of complex shapes with high strength. However, since it requires additional tooling and machinery costs, it is typically more costly than other cold-forming techniques.

Roll Racking

Also referred to as spline rolling, this cold-forming method involves rolling bar stock between two racks to create a spline shaft shape. During the process, two opposing forming racks apply extremely high forces over a cylindrical part. Due to the inherent limitations of the spline rolling machine, this technique is not recommended for projects that must adhere to tight tolerances, like gear production.

Cold Rolling

Cold rolling is the most commonly used cold working technique. Metal sheets, strips, and other forms can all be cold rolled to create products that feature smooth surfaces and distinct material properties. The process of cold rolling steel involves putting extreme stress on the workpiece. This stress and the resulting strain hardening improve the metal’s strength by as much as 20%.

However, cold rolling has certain limitations. A significant amount of hydraulic force is required to deform the metal at room temperature, and in some cases, the workpiece can crack during the process. In addition, cold-rolled products can sometimes feature surface defects that require additional finishing.

Grob Rolling

Our innovative Grob Method combines many of the processes discussed above but eliminates many of their respective challenges. The Grob Method is a combination of cold forging and rack rolling and offers numerous advantages:

  • Less expensive tooling than rack rolling and die pressing: Grob Rolling provides benefits like improved strength and attractive finishes while significantly reducing tooling costs. Since secondary processes like deburring, welding, punching, bending, or blanking are unnecessary, production is faster and more streamlined.
  • Fewer size limitations: While roll racking and cold forging often involve high tooling costs, Grob Rolling features more streamlined tooling that accommodates a larger range of part sizes while reducing costs.
  • Added strength: Grob Rolling eliminates the risk of workpieces cracking or breaking, as we strengthen the metal without changing its grain structure or flow. The result is a superior crafted product with the added strength required in applications that demand reliability and high performance.
  • Less material waste: Our technique displaces material instead of removing it, resulting in virtually zero waste materials. This not only significantly reduces project costs but also minimizes environmental impact by eliminating post-production waste handling.
  • Excellent surface quality: Our process prevents cracks and defects in the metal. Since our tools strike the workpiece multiple times per minute and perform rolling and shaping processes simultaneously, there is less time for the workpiece to cool and crack under pressure.

How to Create Gears Using Cold Forming

Grob Inc.’s unique cold-forming process allows us to create precision gears with ease. While creating precision gears using cold-forming techniques can be challenging for many other cold-working providers, our innovative, proprietary method eliminates many of these difficulties. Grob Rolling accommodates tight tolerances and overcomes workpiece size limitations while preventing problems like cracking and product defects.

To create a precision gear, we begin with a cold-forged blank and create the gear from that, or we can create a cold-formed blank containing the gear shape. Compared to traditional gear manufacturing processes, a net-shaped cold-formed gear does not require any additional manufacturing techniques. The gear-cutting process is completely replaced by metal forming.

We use a forming press to deform the metal workpiece into the tooling cavity. The press can be hydraulic or mechanical depending on the part’s complexity and the level of accuracy required. Cold-working gear tooling involves gear dies, a die set, die clamping rings, and punches. Because these tools come into direct contact with the workpiece, they must be unique to each gear. Due to the high level of stress and wear involved in these processes, the tools have a limited lifespan and are considered perishable. However, the Grob Rolling Method reduces tooling costs for even greater savings.

Once the gear teeth are formed, the gears are in what is called a green state since they have not yet hardened. In the green state, any features that could not be cold-formed can be created using standard CNC machines. This usually includes features like grooves, chamfers, and clutch face features.

Other Cold-Formed Near-Net Shapes

Cold forming is an ideal process for any shape that demands high precision, tight tolerances, and cost reduction. At Grob, Inc., our cold-forming process can create near-net shapes, so minimal finishing is required. In addition to crafting high-strength standard and custom spur gears, we also offer numerous other products, including:

Why Choose Grob For Your Cold-Formed Gears

Grob Inc. has been a trusted source of expertly crafted cold-formed products since 1929. Our family-owned and operated company is dedicated to providing innovative and reliable products at an affordable price. For your next project, choose from our extensive catalog of over 2,100 existing profiles or have our team develop a custom solution. To get started, reach out with any questions or request a quote today.

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