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Conical Compression Spring
Definition : con·i·cal kum'prê[sh]un spri[ng] A conically wound helical spring made of wire.
Overview: Conical Compression Springs are conical coiled helical springs that resist a compressive force applied axially. Conical Compression Springs are conical, tapered, concave or convex in shape. The spring is wound in a conical helix usually out of round wire. The changing of spring ends, direction of the helix, material, and finish allows conical compression springs to meet a wide variety of special industrial needs. Conical compression springs can be manufactured to very tight tolerances, this allows the spring to precisely fit in a hole or around a shaft. A digital load tester can be used to accurately measure the specific load points in your spring. Conical Compression springs can be made from non-magnetic spring material like Phosphor Bronze or Beryllium Copper as well as music wire (High Carbon Steel) stainless steel and many other types of spring wire. The possibilities are almost endless for so many applications.
Looking to buy conical compression springs?
If you are wondering where the best place is to buy conical compression springs...you are already there. Planetspring.com has thousands of coil spring manufacturers that will compete to get you the best price on helical springs, conical compression springs as well as any other type of custom spring. Simply register for your FREE buyer account and post ONE RFQ and get multiple quotes from different compression springs suppliers. Planetspring.com allows you to buy conical compression springs online without having to make one phone call. You can even choose suppliers that are near you. For example to find san antonio compression springs or compression springs UK can be found here two different ways. The first way is to search our find a spring company page by location. The second is to post the RFQ and choose the supplier who is closest to your location without ever having to pick up the phone. If you are looking for any kind of compression spring supply such as compression spring stock or custom springs Planetspring.com does it all. Register today and receive our eHandbook of compression spring design with your first RFQ. Hurry supplies are limited so REGISTER NOW!
Applications: Conical Compression springs can accomplish many types of applications like pushing, twisting, thus allowing you to achieve numerous results. Typical applications include force or load which makes it shorter, therefore pushing back against the load. The role of conical compression springs is to return to it's original length. Conical Compression springs offer resistance to linear compressing forces (push) that are in fact one of the most efficient energy storage devices available. A battery contact is a good example of how conical compression springs work. Conical compression springs will compress when a battery is inserted into a remote control (for example). Then conical compression springs will keep constant contact with the battery so to transfer the energy from the battery to the remote control. Other uses include high temperature applications. Conical compression springs can be engineered for high temperature applications that can reach up to 1,100 degrees Fahrenheit.
Ends: The ends of conical compression springs are usually closed and square. These ends can also be closed and ground, or have open ends. Furthermore, conical compression springs can have legs so as to fasten it to your particular assembly. The ends of a spring can also be close wound for a certain number of coils on the ends permitting the spring to remain in a vertical position. The squareness influences how the axis force produced by the spring can be transferred to adjacent parts. Another application includes being able to thread a closed end coil spring onto a threaded shaft for fastening purposes. Other end configuration examples are reduced end diameters like a barrel spring on a bicycle seat. Springs can have dual diameters as well as triple diameters for achieving different assembly situations.
Materials: The material choices available for springs today work well for corrosion resistance, electrical conductivity, non-magnetic, and high temperature applications. Basic conical compressions springs are normally made from music wire, which is a high carbon spring steel as well as stainless steel 302 , 316, 17-7 . It is important to remember which material you choose for your spring application. Choosing the right material for your spring will greatly enhance the life and repeatability of your spring, as well as give you many years of service life. To view the available material choices please see the properties of common spring materials page (click here).
Key Parameters for a conical compression spring design:
Outside diameter large end:
Free Length: The overall length of a spring unloaded.
Solid Height: The length of a conical compression spring when all the coils are fully compressed, touching or telescoping. (coil bind height)
Number of coils:
End configurations:
Closed and Square: Is the space between the coils reduced at the ends to the point where the wire at the tip make contact with the next coil, the end is said to be closed and square. This is done so that the spring can stand on it's own. If there is no reduction in pitch at the end coils, the end is referred to as "open" and the spring will not stand up vertically on it's own .
Closed and Ground Ends: means an additional grinding operation may be applied to the closed and square end configuration. Grinding removes material from the spring's end coils to create a flat surface perpendicular to the spring axis. This may be done for a variety of reasons including a more even distribution of the spring force.
Open Ends Ground Square: are ends that there is no reduction in pitch at the end coils yet are ground square.
Spring Rate Calculation: (Stiffness) Is the rate of force in pounds per inch of compression. Examples: If the rate of a spring is 10 lbs. It will take you 10 lbs of force to move it 1 inch of distance (travel). If you move it 2 inches of distance it will take you 20 lbs of force. The rate is linear.
Conical Compression Pitch:
A uniform pitch in a conical spring is far easier to make then a variable pitch. If no coils bottom out your force curve is similar to a standard compression spring, if the largest active coil bottoms, an upward slope of the force curve occurs, max force is when all coils have bottomed. Determining the force of the conical compression spring is similar to a normal compression spring. Make sure to use the mean diameter of the smallest active coil.
Grinding
Grinding the end coils of conical springs is done in a different manner. In some cases, you will only need to grind the small end of the conical spring, others will need a grind on both ends. You should always remember grinding will increase the cost significantly per spring. You can also have a compression springs bearing surface definition.
Dimensions: Inner diameter small end, Outside diameter large end. Wire diameter, Free Length, solid height, number of coils and end configuration.
Inner diameter small end:
1. How do I figure out how many active coils a spring has?
In any spring, a portion of the end coils will probably be inactive. The number of coils not closed are the active coils. Example: If a spring has a total number of 10 coils and the first and last coil are closed then the spring has 8 active coils. Usually the first and last coil on conical compression springs are closed. It's a good rule of thumb to count all the coils then subtract two coils to determine the amount of active coils. Sometimes in compression springs there is more than one coil on each end closed, so it's important to count all the closed coils to determine the number of active coils on your spring. The following equations give approximate active coil counts, assuming that the springs are compressed between parallel plates.
For closed ends (ground or unground): Na = Nt -2
For open ground ends: Na = Nt -1
For open unground ends: Na = Nt
In practice, the number of inactive coils varies slightly as a spring is compressed. If the spring output at two operating heights is known, the number of active coils over the operating height range can be calculated using the following equation for any end configuration.
Na =G 4 d ( h 1 - h 2 )___
8 ( OD - d ) 3 ( P2 - P1 )
G = shear modulas of the spring material
d = wire diameter
OD = spring outside diameter
h1, h2, = spring operating heights
P1, P2 = spring force at heights h1 and h2, respectively.
2. What is a safe design stress for a conical compression spring?
This question doesn't have a single simple answer. The answer depends greatly on the certain factors such as the type of material used ( I.e. music wire, stainless steel, chrome-silicon, etc.), material grade (I.e. commercial vs. valve quality, standard or high strength, etc.) and the service environment (I.e. static vs. cyclic, corrosive atmosphere, very high or low temperatures, etc.).
If compressed to solid height, even a spring that has infinite fatigue life may take set and no longer serve its function. Another example of poor fatigue life when cycled in air would be a spring optimized for static life in salt water.
The design process usually begins with selecting the proper material type appropriate for the application environment. For static conditions, the spring designer will take into consideration where the spring will be used and select the material best suited for the purpose, so as to assure stable spring force output over time. For cyclic conditions, not only does the force output over time have to be stable, but the spring must be able to survive the intended life without breaking. Finally, manufacturing limitations can also restrict design stress levels.
The best recommendation here is to understand what is wanted from the spring while its in service. A spring design engineer can help develop the optimum spring design for the appropriate conditions. Ask yourself a few simple questions before calling a spring company so they may better assist you.
Will the spring operate under static or cyclic environments? If cyclic, what are the minimum and maximum operating loads, deflections (travel) or heights? What is the life you want from the spring?
Where is the operating environment? What is the operating temperature? Will the spring go into a hole or around a shaft and if so what is the size of each?
3. Which material gives the best corrosion resistance?
The actual operating environment plays a large role. Many coatings are available that can greatly reduce corrosion. These include powder coating and Phosphate with an oil dip or spray. Additionally there are many types of economical plating solutions available.
When the environment is such that a coated spring wire will not meet the requirements of an application, then stainless steel wire should be considered. Type 302 stainless steel is usually the first choice. This wire can yield very corrosion resistant springs for most applications. When the environment is a high temperature application then 17-7 PH stainless steel is recommended (650 F. max operating temp.) If you need to go higher then inconel x750 or inconel 718 can go up to (1,100 F) is a high-quality choice.
4. If I cut a spring in half, would the rate still be the same?
Cutting a spring in half greatly increases the rate or strength of the spring. Because you have decreased the numbers of active coils in the spring. This forces an increase in spring rate. The spring rate is proportional to 1/Na, so reducing the number of active coils by half doubles the spring rate.
5. What does maximum safe deflection (travel) mean?
It means the maximum safe deflection from a free state that will not result in the spring taking a permanent set. Example: For conical compression springs, the permanent set will result in reduced free length and force output.
Basic Design Formulas
The following are just a few of the most basic formulas for getting a head start on designing conical compression springs. Please bear in mind that effective spring design can only be accomplished by using a computer program capable of running hundreds of simultaneous calculations. For this you could call a reputable spring company to assist you in calculating your design.
How to Determine the Rate or spring constant for Conical Compression Springs
Conical Compression change in load per unit deflection, may be determined by the following procedure:
1. Deflect spring to approximately 20 percent of available deflection and measure load (P1) and spring length (L1).
2. Deflect spring to approximately 80 percent of available deflection and measure load (P2) and spring length (L2). Be certain that no coils (other than closed ends) are touching L2.
Calculate rate (R) lb./in. (N/mm)
R = (P2 - P1) / (L1 - L2)
Design of Conical Compression Springs:
There are several methods of analyzing the complex stresses in conical compression springs depending upon the type of pitch, angular relationship of the coils, constant slope, curving contours, and other factors. Analyzing all of the variables and solving for stresses, deflections, and forces will be major time for a spring maker to devote to your design, there are two methods below that spring makers will use.
Approximate Method:
First, calculate the average outside diameter. This can be done in several ways depending upon the diameters specified. The easiest way is to add the outside diameter of the top end to the outside diameter of the base and divide by 2. Adding the OD of the base to the ID at the top of dividing by 2 will provide the average D. Second, calculate the approximate force at the solid height. Third, locate the average OD and find a force per coil and determine your wire size.
Exact Method:
A more exact method is first to determine the wire size and number of coils by the approximate method and then analyze the force, deflection, and stress of each individual coil and make adjustments to the design to meet the requirements. This may require a large number of individual calculations for each spring, but should be done for large, important springs and where a long fatigue life may be needed.
1. Make sure to allow extra time for all manufacturing operations should be considered when estimating the costs of making coned conical compression springs or for any springs requiring special material, square or rectangular wire, or special testing.
2. Variable pitches in a conical spring are occasionally specified so that all active coils bottom simultaneously, but this is seldom achieved.
3. Grinding is especially difficult and time-consuming. Special fixtures may be required. The cost of grinding discs should be included for large quantities of springs.
4. Tangling of highly pitched springs made from small diameters of wire up to 1/16 inch
(1.5 mm) having rather large base diameters often occurs and may require special handling and packaging, which will also increase your cost.
Plating and Coating:
When coating a spring the following types of platings are available. Zinc Plating, (white, blue, gold, & black are available) offers corrosion resistance, Nickel Plating (gives a very bright chrome looking finish or you can have black finish) offers good corrosion resistance, Black Oxide, Shot peering to reduce stress of fatigue, powder coating to give corrosion resistance and gives you the options of choosing just about any color under the sun. Electro Gold plating offers your springs conductivity if used in electrical applications. Galvanized wire is great economical choice for a spring, it offers the user a pre-galvanized wire that is pre-galvanized so the spring maker purchases this wire with the galvanization already on it, they do not have to send it out for a secondary process after the spring is made, thus saving the buyer a substantial amount . A word of advice about material selection: Take the time to ask a spring engineer his or hers opinion of your particular spring environment. They can professionally asses the conical spring environment and recommend the correct material for the job.
Word for Thought:
Once you have understood these basic principals for creating and engineering your unique conical compression springs you will be better prepared for spring design. Remember, a great conical compression spring is one that will function properly in the confined parameters of your product with low stress and fatigue, and high cycles of life.
Overview: Conical Compression Springs are conical coiled helical springs that resist a compressive force applied axially. Conical Compression Springs are conical, tapered, concave or convex in shape. The spring is wound in a conical helix usually out of round wire. The changing of spring ends, direction of the helix, material, and finish allows conical compression springs to meet a wide variety of special industrial needs. Conical compression springs can be manufactured to very tight tolerances, this allows the spring to precisely fit in a hole or around a shaft. A digital load tester can be used to accurately measure the specific load points in your spring. Conical Compression springs can be made from non-magnetic spring material like Phosphor Bronze or Beryllium Copper as well as music wire (High Carbon Steel) stainless steel and many other types of spring wire. The possibilities are almost endless for so many applications.
Looking to buy conical compression springs?
If you are wondering where the best place is to buy conical compression springs...you are already there. Planetspring.com has thousands of coil spring manufacturers that will compete to get you the best price on helical springs, conical compression springs as well as any other type of custom spring. Simply register for your FREE buyer account and post ONE RFQ and get multiple quotes from different compression springs suppliers. Planetspring.com allows you to buy conical compression springs online without having to make one phone call. You can even choose suppliers that are near you. For example to find san antonio compression springs or compression springs UK can be found here two different ways. The first way is to search our find a spring company page by location. The second is to post the RFQ and choose the supplier who is closest to your location without ever having to pick up the phone. If you are looking for any kind of compression spring supply such as compression spring stock or custom springs Planetspring.com does it all. Register today and receive our eHandbook of compression spring design with your first RFQ. Hurry supplies are limited so REGISTER NOW!
Applications: Conical Compression springs can accomplish many types of applications like pushing, twisting, thus allowing you to achieve numerous results. Typical applications include force or load which makes it shorter, therefore pushing back against the load. The role of conical compression springs is to return to it's original length. Conical Compression springs offer resistance to linear compressing forces (push) that are in fact one of the most efficient energy storage devices available. A battery contact is a good example of how conical compression springs work. Conical compression springs will compress when a battery is inserted into a remote control (for example). Then conical compression springs will keep constant contact with the battery so to transfer the energy from the battery to the remote control. Other uses include high temperature applications. Conical compression springs can be engineered for high temperature applications that can reach up to 1,100 degrees Fahrenheit.
Ends: The ends of conical compression springs are usually closed and square. These ends can also be closed and ground, or have open ends. Furthermore, conical compression springs can have legs so as to fasten it to your particular assembly. The ends of a spring can also be close wound for a certain number of coils on the ends permitting the spring to remain in a vertical position. The squareness influences how the axis force produced by the spring can be transferred to adjacent parts. Another application includes being able to thread a closed end coil spring onto a threaded shaft for fastening purposes. Other end configuration examples are reduced end diameters like a barrel spring on a bicycle seat. Springs can have dual diameters as well as triple diameters for achieving different assembly situations.
Materials: The material choices available for springs today work well for corrosion resistance, electrical conductivity, non-magnetic, and high temperature applications. Basic conical compressions springs are normally made from music wire, which is a high carbon spring steel as well as stainless steel 302 , 316, 17-7 . It is important to remember which material you choose for your spring application. Choosing the right material for your spring will greatly enhance the life and repeatability of your spring, as well as give you many years of service life. To view the available material choices please see the properties of common spring materials page (click here).
Key Parameters for a conical compression spring design:
Outside diameter large end:
Free Length: The overall length of a spring unloaded.
Solid Height: The length of a conical compression spring when all the coils are fully compressed, touching or telescoping. (coil bind height)
Number of coils:
End configurations:
Closed and Square: Is the space between the coils reduced at the ends to the point where the wire at the tip make contact with the next coil, the end is said to be closed and square. This is done so that the spring can stand on it's own. If there is no reduction in pitch at the end coils, the end is referred to as "open" and the spring will not stand up vertically on it's own .
Closed and Ground Ends: means an additional grinding operation may be applied to the closed and square end configuration. Grinding removes material from the spring's end coils to create a flat surface perpendicular to the spring axis. This may be done for a variety of reasons including a more even distribution of the spring force.
Open Ends Ground Square: are ends that there is no reduction in pitch at the end coils yet are ground square.
Spring Rate Calculation: (Stiffness) Is the rate of force in pounds per inch of compression. Examples: If the rate of a spring is 10 lbs. It will take you 10 lbs of force to move it 1 inch of distance (travel). If you move it 2 inches of distance it will take you 20 lbs of force. The rate is linear.
Conical Compression Pitch:
A uniform pitch in a conical spring is far easier to make then a variable pitch. If no coils bottom out your force curve is similar to a standard compression spring, if the largest active coil bottoms, an upward slope of the force curve occurs, max force is when all coils have bottomed. Determining the force of the conical compression spring is similar to a normal compression spring. Make sure to use the mean diameter of the smallest active coil.
Grinding
Grinding the end coils of conical springs is done in a different manner. In some cases, you will only need to grind the small end of the conical spring, others will need a grind on both ends. You should always remember grinding will increase the cost significantly per spring. You can also have a compression springs bearing surface definition.
Dimensions: Inner diameter small end, Outside diameter large end. Wire diameter, Free Length, solid height, number of coils and end configuration.
Inner diameter small end:
1. How do I figure out how many active coils a spring has?
In any spring, a portion of the end coils will probably be inactive. The number of coils not closed are the active coils. Example: If a spring has a total number of 10 coils and the first and last coil are closed then the spring has 8 active coils. Usually the first and last coil on conical compression springs are closed. It's a good rule of thumb to count all the coils then subtract two coils to determine the amount of active coils. Sometimes in compression springs there is more than one coil on each end closed, so it's important to count all the closed coils to determine the number of active coils on your spring. The following equations give approximate active coil counts, assuming that the springs are compressed between parallel plates.
For closed ends (ground or unground): Na = Nt -2
For open ground ends: Na = Nt -1
For open unground ends: Na = Nt
In practice, the number of inactive coils varies slightly as a spring is compressed. If the spring output at two operating heights is known, the number of active coils over the operating height range can be calculated using the following equation for any end configuration.
Na =G 4 d ( h 1 - h 2 )___
8 ( OD - d ) 3 ( P2 - P1 )
G = shear modulas of the spring material
d = wire diameter
OD = spring outside diameter
h1, h2, = spring operating heights
P1, P2 = spring force at heights h1 and h2, respectively.
2. What is a safe design stress for a conical compression spring?
This question doesn't have a single simple answer. The answer depends greatly on the certain factors such as the type of material used ( I.e. music wire, stainless steel, chrome-silicon, etc.), material grade (I.e. commercial vs. valve quality, standard or high strength, etc.) and the service environment (I.e. static vs. cyclic, corrosive atmosphere, very high or low temperatures, etc.).
If compressed to solid height, even a spring that has infinite fatigue life may take set and no longer serve its function. Another example of poor fatigue life when cycled in air would be a spring optimized for static life in salt water.
The design process usually begins with selecting the proper material type appropriate for the application environment. For static conditions, the spring designer will take into consideration where the spring will be used and select the material best suited for the purpose, so as to assure stable spring force output over time. For cyclic conditions, not only does the force output over time have to be stable, but the spring must be able to survive the intended life without breaking. Finally, manufacturing limitations can also restrict design stress levels.
The best recommendation here is to understand what is wanted from the spring while its in service. A spring design engineer can help develop the optimum spring design for the appropriate conditions. Ask yourself a few simple questions before calling a spring company so they may better assist you.
Will the spring operate under static or cyclic environments? If cyclic, what are the minimum and maximum operating loads, deflections (travel) or heights? What is the life you want from the spring?
Where is the operating environment? What is the operating temperature? Will the spring go into a hole or around a shaft and if so what is the size of each?
3. Which material gives the best corrosion resistance?
The actual operating environment plays a large role. Many coatings are available that can greatly reduce corrosion. These include powder coating and Phosphate with an oil dip or spray. Additionally there are many types of economical plating solutions available.
When the environment is such that a coated spring wire will not meet the requirements of an application, then stainless steel wire should be considered. Type 302 stainless steel is usually the first choice. This wire can yield very corrosion resistant springs for most applications. When the environment is a high temperature application then 17-7 PH stainless steel is recommended (650 F. max operating temp.) If you need to go higher then inconel x750 or inconel 718 can go up to (1,100 F) is a high-quality choice.
4. If I cut a spring in half, would the rate still be the same?
Cutting a spring in half greatly increases the rate or strength of the spring. Because you have decreased the numbers of active coils in the spring. This forces an increase in spring rate. The spring rate is proportional to 1/Na, so reducing the number of active coils by half doubles the spring rate.
5. What does maximum safe deflection (travel) mean?
It means the maximum safe deflection from a free state that will not result in the spring taking a permanent set. Example: For conical compression springs, the permanent set will result in reduced free length and force output.
Basic Design Formulas
The following are just a few of the most basic formulas for getting a head start on designing conical compression springs. Please bear in mind that effective spring design can only be accomplished by using a computer program capable of running hundreds of simultaneous calculations. For this you could call a reputable spring company to assist you in calculating your design.
How to Determine the Rate or spring constant for Conical Compression Springs
Conical Compression change in load per unit deflection, may be determined by the following procedure:
1. Deflect spring to approximately 20 percent of available deflection and measure load (P1) and spring length (L1).
2. Deflect spring to approximately 80 percent of available deflection and measure load (P2) and spring length (L2). Be certain that no coils (other than closed ends) are touching L2.
Calculate rate (R) lb./in. (N/mm)
R = (P2 - P1) / (L1 - L2)
Design of Conical Compression Springs:
There are several methods of analyzing the complex stresses in conical compression springs depending upon the type of pitch, angular relationship of the coils, constant slope, curving contours, and other factors. Analyzing all of the variables and solving for stresses, deflections, and forces will be major time for a spring maker to devote to your design, there are two methods below that spring makers will use.
Approximate Method:
First, calculate the average outside diameter. This can be done in several ways depending upon the diameters specified. The easiest way is to add the outside diameter of the top end to the outside diameter of the base and divide by 2. Adding the OD of the base to the ID at the top of dividing by 2 will provide the average D. Second, calculate the approximate force at the solid height. Third, locate the average OD and find a force per coil and determine your wire size.
Exact Method:
A more exact method is first to determine the wire size and number of coils by the approximate method and then analyze the force, deflection, and stress of each individual coil and make adjustments to the design to meet the requirements. This may require a large number of individual calculations for each spring, but should be done for large, important springs and where a long fatigue life may be needed.
The Force Chart
For basic spring design consideration
Precautions:For basic spring design consideration
| More Force (MF) | Less Force (LF) |
|---|---|
| Small OD = MF | Large OD = LF |
| Less Coils = MF | More Coils = LF |
| Thicker Wire = MF | Thinner Wire = LF |
| More Travel = MF | Less Travel = LF |
| All equal = More stress | All equal = Less stress |
1. Make sure to allow extra time for all manufacturing operations should be considered when estimating the costs of making coned conical compression springs or for any springs requiring special material, square or rectangular wire, or special testing.
2. Variable pitches in a conical spring are occasionally specified so that all active coils bottom simultaneously, but this is seldom achieved.
3. Grinding is especially difficult and time-consuming. Special fixtures may be required. The cost of grinding discs should be included for large quantities of springs.
4. Tangling of highly pitched springs made from small diameters of wire up to 1/16 inch
(1.5 mm) having rather large base diameters often occurs and may require special handling and packaging, which will also increase your cost.
Plating and Coating:
When coating a spring the following types of platings are available. Zinc Plating, (white, blue, gold, & black are available) offers corrosion resistance, Nickel Plating (gives a very bright chrome looking finish or you can have black finish) offers good corrosion resistance, Black Oxide, Shot peering to reduce stress of fatigue, powder coating to give corrosion resistance and gives you the options of choosing just about any color under the sun. Electro Gold plating offers your springs conductivity if used in electrical applications. Galvanized wire is great economical choice for a spring, it offers the user a pre-galvanized wire that is pre-galvanized so the spring maker purchases this wire with the galvanization already on it, they do not have to send it out for a secondary process after the spring is made, thus saving the buyer a substantial amount . A word of advice about material selection: Take the time to ask a spring engineer his or hers opinion of your particular spring environment. They can professionally asses the conical spring environment and recommend the correct material for the job.
Word for Thought:
Once you have understood these basic principals for creating and engineering your unique conical compression springs you will be better prepared for spring design. Remember, a great conical compression spring is one that will function properly in the confined parameters of your product with low stress and fatigue, and high cycles of life.
