Die springs are critical for efficient and consistent tooling and die performance in metal stamping. They are also commonly used in many applications where force and controlled motion are needed to secure components for assembly, welding, or proper machine operation.
Here we’ll look at the common types of die springs, how they work, and the many ways in which they are used in industry.
Types of Die Springs
Die springs are a highly specialized type of compression spring. Two major types of springs are used inside dies for metal stamping, metal forming, and in other industries: metal coil and pressurized nitrogen gas. While they accomplish the same goals of storing and applying force when and where needed for an application, they operate in very different ways.
Metal coil springs are a trusted, traditional type of spring. They can be made from round or rectangular wire. Rectangular wire, which actually has a trapezoidal cross-section, often makes a spring more durable since the trapezoid shape reduces the wire’s maximum stress level when it’s compressed. CNC machines are used to bend the wire into a coil and grind the ends.
Coiled springs store potential energy and, depending on the gauge of the wire, they are rated for various load levels. Springs can be manufactured to meet different sets of standards including Japanese Industrial Standard (JIS), US standard, and International Organization for Standardization (ISO). ISO standard springs, which we will discuss in this article, are color coded as follows:
- Light load springs. These are painted green and designed for light load applications that require minimal force.
- Medium load springs. These are painted blue and have a moderate load capacity for applications that require a medium amount of force.
- Heavy load springs. These are painted red and are used with heavy loads and substantial forces. They are commonly used in metal stamping and pressing to open the press between cycles.
- Extra heavy load springs. These are painted yellow and are designed for applications that require extremely high force. They have the highest load capacity range among die springs.
Metal coil springs are manufactured to industry standards in accordance with ISO 10243 for dimensions (in inches), load ratings, and color coding. Each color is rated for a range of loads determined by the length and diameter of the spring as well as the gauge of the wire. And because metal coil springs are interchangeable with uniform dimensions across the colors, they are easily swapped when a different load rating is needed.
In stamping applications, there are several things to consider when selecting coiled springs for tooling. Spring dimensions are given in compressed and free, or uncompressed, length as well as hole and rod diameter. It’s important to consider your desired preload compared to the total load and length of deflection of the spring when compressed. These factors are important in estimating the useful life of the spring.
Nitrogen gas springs are an alternative to metal coil springs. They consist of a cylindrical metal housing that holds a tightly sealed compartment of pressurized nitrogen gas, a snug-fitting piston, guide bushings, and a small amount of lubricating oil. Instead of a metal coil being compressed, the gas is compressed when force is applied to the piston, pushing it down. When force is removed from the piston, the pressure is released and the piston is pushed back up as the gas expands. Movement is immediate and fairly consistent for great control over the stamping process.
Nitrogen gas springs are available in a range of loading levels, lengths and diameters, as well as one- and two-piece housings, and with or without threading. The required stroke length is the critical measurement for determining both piston length and whether the cylinder is made of one or two pieces.
Gas springs allow for more efficient use of space inside the tooling because they can have much higher load ratings than coil springs. For example, in some applications a single gas spring may be able to replace up to 10 coil springs, which means less space is needed for spring placement inside the die.
When fully charged with nitrogen, the spring’s force remains smooth and consistent over the stroke length. Properly installed gas springs are extremely safe due to overpressure check valves and a planned downward fall of the die in case of seal failure. Properly charged, they can last for millions of cycles.
Die Spring Materials
Compression springs as a general group may be made from a variety of metals depending on the application and end use environment. These may include bronze, carbon steel, stainless steel, and even composite materials.
Die springs, however, are a specific subset of compression springs and are made with steel and steel alloys. Chromium silicon is a common choice as are steel-nickel alloys.
Die Springs Applications
Because they are available in so many sizes and load levels, both coil and gas springs are used in a variety of industries and for diverse applications, including:
- Metal stamping. Die springs are critical to the tooling’s ability to provide the necessary force for cutting and shaping metal sheets and to open the closed die or press efficiently. They ensure consistent pressure and maintain the proper height of the die, resulting in accurate and efficient stamping operations.
- Injection molding. Die springs can be used in automated and semi-automated injection molds to apply pressure when closing and opening a mold as well as for ejecting completed parts.
- Automotive industry. In addition to stamping and forming metal parts for vehicles, springs can be used to hold workpieces in welding fixturing. Springs are also used in brake, clutch, and other mechanisms in cars, trucks, and even farm or heavy equipment.
- Packaging industry. Die springs can be used to supply force and controlled motion in automated packaging equipment for tasks like sealing, cutting, and creasing.
- Assembly operations. Die springs are used in automated assembly operations by providing force to hold or move components to ensure proper alignment and connections.
- Aerospace industry. Die springs are used in stamping and forming parts and assembling aircraft. They provide precise, consistent force for uniformity and repeatability in manufacturing.
Die Springs From Ready Technology
Choosing the right combination of spring dimensions, load rating, and preload is the difference between durable, cost-effective stamping and replacing springs frequently. Trust the experts at Ready Technology to learn about your application and requirements and help you make the best selection.
Explore the options and detailed product information for our SuperSpring metal coil springs and Design-Tite nitrogen gas springs You can also contact us to discuss your requirements and to learn more about metal coil and sealed nitrogen gas springs, or request a free quote.