If you’ve worked out with resistant gym equipment, played with a squirt gun, operated a garage door, or even used a ball pen you’ve probably seen springs at work. Or perhaps you didn’t know and you are like ‘no way, there’re springs in these things?” Well duh, springs are in almost every product and system out there from basic pop-up toys, tape measures and clipboards to mattresses, pressure sensors, trampolines, wheelchairs, conveyors, airplane landing gears etc. They are used to provide resistance, absorb shock or facilitate movement.
Spring design and manufacturing relies heavily on standards, namely the ISO (International Organization for Standardization) and ASTM (American Society for Testing and Materials). These stipulate a wide range of guidelines and specifications that allow manufacturers to produce high quality products efficiently and consistently.
Springs are elastic devices designed to store and release energy by either shrinking and expanding, expanding and snapping back to original size or exerting torque when twisted along the axis as in the case with torsion springs. They are used in measuring, support, and shock absorbing applications across various industries from transportation to medical, sports and fitness.
Springs can be of the compression kind, designed to withstand great forces by shrinking in size and storing mechanical energy which they then release outwards and expand when the force is released. Compression springs feature coils that remain apart when at rest and only come together when squeezed. They are used in various applications including vehicle suspension systems, engine mounts, conveyors, wheelchairs, surgical instruments, and other appliances.
Springs can also be designed to resist stretching and thus store mechanical energy when pulled on both sides then release it and snap back to their normal shape when the forces are removed. These springs are known as extension springs. They are typically tightly wound eliminating any pitch between the coils. That way, the coils come apart with great resistance when pulled on both ends. They are used in garage doors, trampolines, window blinds, tape measures, squirt guns and pop-up toys.
The third type of springs is torsion springs. They are mainly used to oppose rotation. They are used in garage doors counterbalance systems to provide the resistance needed to keep the door open or closed as desired. You can also find them in window blinds, keeping blinds rolled up when not in use. They are also used in retractable pen clips, pop up toys, clip boards etc.
Besides the above main three, springs can also be leaf springs which are flat single or multi-layered steel structures used in vehicle suspensions. There are also constant force springs designed to provide a specified force per extension or compression distance. These are typically used in medical devices.
There are key points in spring design and manufacturing that help ensure the products meet performance and safety requirements. As mentioned, springs are used in various products and systems, some of them critical. It’s important to work with the spring manufacturer to ensure the final product meets your project’s specifications.
One key consideration when it comes to spring design is dimensions. The thickness, length and diameter of the spring wire impacts load capacity, fatigue life and overall performance. Generally, springs with wider diameters or thicker wires have higher load capacities. These are suitable for use in high load applications such as vehicle suspension systems. And naturally, shorter don’t have a shorter deflection which means they can break or lose their form easily and thus not suitable for use where there’s frequent compression and expansion such as in garage doors.
Another key consideration is the choice of material. Springs can be made of metals such as nickel alloys, steel alloys, and stainless steel or non-metals such as rubber, ceramics and urethane. It all depends on the intended application. For example, nickel alloys are the best for making springs for use in high temperature applications while stainless steel and high carbon steel are the best materials for making springs for use in corrosive environments.
Ceramic springs are used in high heat, corrosive and abrasive environments that also have storing magnetic or electric properties. However, ceramic springs are not as strong as steel and nickel alloy springs.
Manufacturers consider the environment in which the spring will be used, too. Temperature, radiation and presence of vibrations affect load capacity as they cause the spring material to expand or contract undesirably making springs weaker. On the other hand, presence of humidity or chemicals can cause corrosion in some metals. It’s important to consider these factors when deciding on the spring-making material to ensure the final products offer reliable performance and reduce the need for frequent replacements which would otherwise lead to significant system or equipment downtime.
The spring manufacturing process varies based on the spring type but otherwise it’s a fairly simple process that primarily involves winding and twisting, heat treating, and surface treatment.
Compression springs are usually made using spring coiling machines or a former. These springs usually feature spaces between their coils. The general name for these spaces is pitch and it’s what allows the springs to shrink when compressed, storing mechanical energy that’s released when the force is lifted allowing the coils to separate from each oyster once more.
On the other hand, extension springs usually formed using wire forming or coiling machines and typically feature hooked ends allowing one end to be attached to a wall or grounded so the other one can be pulled and the elasticity provides needed resistance. Of course, extension springs don’t have spaces between their coils when at rest. They are designed that way so they can offer great deflection when pulled.
Meanwhile, torsion springs are formed by wrapping a wire around a mandrel and then heating it up. They usually have hooked ends and provide torque when twisted along their axes.
ISO is short for the International Organization for Standardization. The organization covers a wide range of design and manufacturing processes including spring making tools. Some popular ISO standards with spring designers and manufacturers include:
The ISO 10233 was last revised in 2011 and 2019 and it now stipulates the technical specifications to follow when color-coding compression springs using rectangular wires. Basically, it describes the color-codes for these types of springs based on the spring rate (light, medium, strong and super strong). It doesn’t, however, stipulate what quality manufactures should aim for, or what dimensions and spring materials they should use.
The ISO 8752 was published in 1997, then reviewed in 2009 and 2019 and it now specifies how to design heavy duty slotted spring-type pins for using natural steel or martensitic or austenitic stainless steel with a nominal diameter between 1mm and 50mm.
Slotted spring-type pins are used to connect construction elements together and this standard describes what characteristic to design these types of pins with for reliable and high-quality performance. For light duty slotted spring-type straight pins, the ISO 13337 standard applies.
This standardization was created in 2004 for all metal springs and it covers product tolerances, testing methods as well as different technologies such as shot peening, heat treatments, surface treatments etc.
Basically, ISO/TC 227 springs must be of high-quality materials such as steel, stainless steel, nickel alloys, titanium alloys, brass or copper and manufactured to precise tolerances then put to rigorous testing to ensure they give reliable and consistent performance in high stress applications.
This standardization was created in 2007 and reviewed in 2020 and it provides guidelines for designing heavy duty coiled spring-type straight pins using steel or its martensitic or austenitic variants with nominal diameter between 1.5mm and 20mm. The standardization specifies the use of coiled heavy duty stainless steel, martensitic or austenitic wire.
This will allow the final product to have good flexibility and resilience while being able to withstand heavy loads. It also requires the springs to be designed with straight cylindrical shapes. These springs can be used as hinges, shafts, carrier pins for connectors in automotive and airplane parts, medical equipment and consumer electronics.
Related standardizations include the ISO 8750 for coiled standard-duty spring-type straight pins and ISO 8751 for the light duty kind.
This standardization is still under development and it specifies what characteristics to design cylindrical helical torsion springs using cold formed round wire. It also provides guidelines on dimension measurements and testing methods to use to ensure high quality, performance and safety.
ASTM is short for American Society for Testing and Materials and it covers a wide range of springs, too. Popular ASTM standards for spring design and manufacturing include:
ASTM-125 was published in 1928 and last revised in 2018 and it specifies the testing methods and procedures for helical compression springs made using hot-coiled steel bars and then heat treated for durability.
Basically, the standardization specifies that the deflection load should not exceed the original height by more than 85%. It also mentions calculations for solid capacity, solid height, solid stress and spring rate to ensure the final product meets safety and performance requirements. Springs manufactured under ASTM 125 are typically stronger, tougher and with a longer fatigue life. They are used in lawnmowers, trampolines, aerospace parts, and industrial suspension systems.
ASTM A228/A228M is a standard specification that offers steel wire in music spring quality. It deals with two types of cold-drawn steel music spring quality wire. The first type aka referred Type I is created by directly drawing from air patented rods or as-rolled rods while Type II is drawn from patented rod or patented wire.
It requires the material to have a specific composition of steel, silicon, carbon, phosphorus, manganese, and sulfur and must be strand cast and subjected to torsion, wrap and tension tests to ensure it is strong enough for cold drawn finishing.
ASTM A228/A228M wires are typically strong, resistant to corrosion and fatigue. They come in different sizes and can be formed pretty easily. They are perfect for creating springs that need to handle intense stress in automotive parts, aerospace components, medical devices, electrical components, industrial machinery parts, and consumer products, too.
This standardization is used to create flat or round ribbon age-harden able spring wires from austenitic stainless steel. It specifies the composition of elements such as silicon, carbon, manganese, chromium, nickel, molybdenum, and phosphorus. It also stipulates the tests to gauge the uniformity and mechanical and tensile strength of the material.
Generally, ASTM A313 or A313M wires have high strengths and ductility and can be used to make springs that can withstand heavy loads without undergoing deformation. They are also resistant to corrosion and early fatigue meaning the springs can be used in harsh environments or in applications involving frequent cycle loading.
As mentioned, spring designers and manufacturers rely heavily on ISO and ASTM guidelines and specifications to ensure their products meet the quality expected by customers.
Springs are used in various products and systems, some of them critical and even life-supporting. A spring failure in a vehicle suspension system, conveyor belt, jet turbine or landing gear can be catastrophic. It can also lead to significant equipment downtime and project delays. Enforcing ISO and ASTM standards ensures reliable products, minimizing or preventing safety risks and frequent equipment failure.
ISO and ASTM guidelines also help streamline spring design and manufacturing, leading to efficient and consistent processes that help keep costs low and guarantee the interoperability of the final products.
Springs are elastic components found in everyday products and systems from your children’s toys to ball point pens, window blinds, garage doors, vehicle suspension systems, conveyors, and gym and sports equipment. They are also used in airplane parts to facilitate various functions.
Needless to say, it’s important to adhere to established guidelines and specifications when designing and manufacturing springs to ensure they withstand forces or support loads without premature failure. Spring failure in critical systems can lead to undesirable equipment downtime and even safety risks. The above-mentioned ISO and ASTM standards have been published to help ensure springs meet quality, safety, and performance requirements.
If you want to learn more about these standards and other guidelines, we use in our spring design and manufacturing process, feel free to get in touch. We manufacture and provide spring solutions to clients in various industries and we’ll be glad to discuss your projects and help you get suitable spring products.