Cold Forming Guide
What Is Cold Forming?
Cold forming is a forging technique that shapes and deforms materials at near room temperature. It is used to produce metal parts, such as screws, bolts, and fasteners, at high speed and volume. Since forming metal at cooler temperatures enhances its tensile strength, the process also allows a high level of intricate manipulation and superior surface finish.Cold forming can be categorized into four methods: squeezing, bending, drawing, and extrusion. They are generally simpler to carry out than hot forging techniques. While cold forging is often confused with casting, note that they are two vastly different processes, as the end result of cold forming is often stronger.
How Does Cold Forming Work?
Simply put, cold forming is basically placing metal in a die and hammering it with compressive force repeatedly. Depending on the requirements, it may also pass through multiple dies progressively (i.e. multi-die forming) to achieve the most ideal shape. See the steps of the basic cold forming process as follows:Step 1. Apply lubricant: Before starting the process, a forging lubricant is first applied onto the metal piece. This prevents the workpiece from overheating as the hammer rams down on it.
Step 2. Insert the workpiece: Place the metal workpiece on a die in the shape of the final part. The die should consist of an upper section with a hammer attached, and a bottom section where you place the workpiece.
Step 3. Strike the workpiece: The hammer drops and strikes the metal piece with great force successively to create the desired shape.
Step 4. Flash: Flash is the excess metal around the die after the repeated strokes. Flash is essential in filling the die, but is later on removed during trimming.
Step 5. Remove the finished part: The ways of part removal can differ depending on the type of process. Generally speaking, it is removed automatically using a conveyor or a robotic arm.
Step 6. After shaping: This is largely dependent on the metalworking requirements. In cold forming that only requires only one die, the part is simply trimmed afterwards. In other cases, the workpiece may be transferred through multiple dies automatically to have features added.
Machinery for Cold Forging
Some common types of cold forming equipment are shown below:- C Frame High Speed Press: This is a press machine that is capable of multiple shaping operations, including punching, bending, forming, etc. The type of machine features rapid strokes on a scale of within milliseconds, and can produce punch force up to 400 tons.
Figure 1. Ing Yu’s C Frame High Speed Press
- Pneumatic Power Press: These pneumatically powered press machines can cover a wide range of die pressing operations. The air compressor forces the hammer down, striking the workpiece with great force generated by air pressure in the cylinder.
Figure 2. Pneumatic Power Press
- Mechanical Press: Mechanical presses are one of the earliest forms of cold forming equipment. They are not used as often anymore because they tend to be very large in size. This type of press uses a large flywheel and motor as the source of energy, which supplies force strong enough to drive the hammer down.
Figure 3. Mechanical Press
You may have noticed that all of these machines can produce a tremendous amount of force. For a process that functions around strokes, force is the most important requirement for a cold forming equipment, followed by balance and multi-operation capability.
Cold Forming Applications
Cold forming is an economical process because it produces very little waste. Also, since cold forged parts are often produced rapidly, the cost per unit is very low, making the final products less expensive to produce. Here are some of the applications that use cold forged parts:
- Automotive: Cold forged parts are popular in automobile manufacturing. They are the perfect candidate for car parts that require optimal shock resistance. Components that use cold forged parts include drive, shafts, shock absorbers, struts and more.
- Hand Tools and Hardware: Connectors such as nails and bolts have always been made with cold forging, thanks to the low tolerance and high dimensional accuracy.
- Military: Military equipment need to be reliable enough to withstand blows in times of crisis. This makes cold forged parts very attractive for making sturdy military weapons and gears.
- Gears: Gear production usually involves cold forging as well because it eliminates the need of cutting the metal piece into gear shape. Have some coiled wire and gear-shaped dies ready, and enjoy the fast and smooth workflow of gear production.
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