A compression spring is the most popular type of spring and when you envision a spring, chances are you’ll be thinking of a compression spring. They are commonly used in the automotive industry to provide dampening as part of the suspension system.
The aim is to provide a comfortable ride for the occupants and keep the tyres on the road at all times and the spring is an elastic object which stores mechanical energy in the coils of the spring. The most commonly used material is steel, but they can be manufactured from steel, aluminium and other metals.
The History Of The Compression Spring
Coiled springs were first introduced into door locks as early as the 15th century and appeared in watches roughly 100 years later. It’s amazing to think how far technological advancements have come for an invention that was originally for door locks.
While technological advancements material, finish, form and manufacturing have all changed, the basic principles of a compression spring have gone largely unchanged in the last 600+ years. Here are a few commonly used applications of compression springs in your everyday life:
- Ballpoint pens
- Car suspension
- Toasters
- Garage doors
How Do Compression Springs Work?
When a compression spring is stretched or compressed from its resting position, it will always try to fight its way back to its original shape. This is why compression springs are particularly useful on cars, trucks and motorcycles, because their performance of dampening road surfaces and keeping the car in contact with the road is second to none.
Compression springs are designed to push back when a force is applied and return to their original positions when released. Their numerous applications are what make them popular. Besides electronics and stamping presses, they are also used in vibration insulation and the variations of compression springs are numerous and cater to specific needs.
Several factors define the construction of compression springs and understanding these aspects makes it easier to get the best springs for particular devices.
Compression Spring End Types
The ends of compression springs are some of the factors that determine what they can do and therefore, fundamental in the design process.
A compression spring end will dictate its mounting characteristics, height, pitch and active coils. Closed and ground ends are popular because they allow springs to erect vertically and they are relatively cheaper than most, because they don’t demand extra work after leaving the CNC machine.
Closed and ground ends, on the other hand, are expensive for the opposite reason. The grounding of the ends takes place after CNC machining, requiring more labour and costs. The advantage that these ends have over the closed and squared alternative is that a spring with a high slenderness ratio can stand on a flat surface.
The ratio proportions between the diameter and free length of a compression spring is what constitutes slenderness ratio. A high ratio is when the free length exceeds the outer diameter by four times or more. In a closed and ground end, a spring with such a ratio would buckle when stood vertically.
Open ends are alternative design options and they are not capable of a vertical stand. With all the coils open, it means that a spring has a consistent pitch at free length. Open ends are suitable for applications where a spring is needed to be weaker without increasing the height.
By opening both ends, you get more coils, hence, weakening the springs, but the height remains unchanged. Open and ground ends have a filed last coil, which facilitates even distribution of loads.
Compression Spring Materials
The functionality, quality and durability of a compression spring rely heavily on the choice of material, which will also factor in the design calculations. For example, the material in use dictates tensile strength and shear modulus.
Stainless steel is one of the common materials that are used in making compression springs and it is suitable for products that are to be used in outside environments. For extremely harsh conditions, acid-proof stainless steel is most appropriate.
Piano wire is ideal for springs that are in stable surroundings such as those found indoors. This material does not offer protection against corrosion and if a piano wire spring is going to be used outside, then the material has to be pre-galvanised. A piano wire that has been through electro-galvanising offers a shiny surface with minimal protection from rust.
Compression springs can also be manufactured with specialty metals and alloys, such as titanium, beryllium nickel, tantalum, and beryllium copper.
Compressions Spring Diameter
The diameter of a compression spring is one of the features that determine its force. Compressing a spring increases its diameter and this translates into the pitch. There is an inner diameter, which is the distance in the inner cavity and then there is the outer and wire diameter. When constructing a spring, all these variables will come into play.
Compression Spring Finish
When it comes to the finish of compression springs, you have many options, including steel, titanium and aluminium, which are explained further below.
Steel
The finishing on a spring is not only to structure its aesthetics but durability as well and a powder coating offers abrasion resistance, in addition to altering the colour of the spring.
Oiled springs need lubrication to facilitate smooth compression and shot peening finishing refers to the use of glass beads to strengthen the material. A phosphate finish provides an excellent base in case of painting. It also increases the lubrication of a spring and corrosion resistance.
Titanium
Titanium is often used on springs when a lack of weight is of importance and a titanium spring can be 40-60% lighter than a steel spring.
They are also commonly used on mountain bicycles, performance motorcycles and racing cars, because of their lack of weight and enhanced shock performance. Lower mass springs develop less inertia as the suspension is displaced. Having less inertia built into the spring-mass enables the suspension to rebound faster, making for improved ground contact and traction. The spring can be powder coated, like steel, but many choose to leave the raw titanium which is lightweight and perfect for application.
Aluminium
Aluminium is widely used in spring making, but particularly in compression springs. It is a lightweight material, roughly a third of the weight of steel and is commonly used in rail, marine and aerospace applications.
Alloy in its natural form is not as strong as other materials, such as steel and titanium, but it can be cold worked, increasing its hardness.
How Can Irvine Springs Help You?
The team at Irvine Springs are passionate about and dedicated to crafting and engineering high-quality and innovative compression springs, using the latest technology in the spring making industry, whilst providing our customers with a top-rated and bespoke service that fully meets their requirements.
If you would like to speak to one of our experts about your requirements or need any further information, please don’t hesitate to contact us today by calling us on 01294 279 396 or emailing us at info@irvinesprings.com. We hope to hear from you soon!