Coil compression springs can be susceptible to buckling; however, the first step to ensure that does not happen is to know how to prevent compression spring buckling.
Usually, there is a decrease in the length of a compression spring when it is exposed to axial loading.
When the spring is below the critical length, it could bend laterally rather than decrease in length; a process referred to as buckling.
Also, the length below which buckling occurs is called the critical buckling length (LK).
Let’s take a closer look.
What is Buckling?
A spring which deforms in a non-axial direction under compression is said to have buckled.
Buckling can be attributed to a spring’s more substantial free length and end conditions being improper to distribute the load all along the coil’s circumference evenly.
Also, compression spring buckling or bending takes place during deflection (for a given free length which becomes too large) as a result of the spring’s instability caused by high slenderness ratio.
During compression, the instability causes the coils to tremble and shift in a non-axial direction.
The load on the spring can also create pressure in the shifted coils, which could end up plastering the coils to the point of damaging them.
When the spring is damaged, it cannot return to its original state nor provide the intended force it was meant to support.
Determinants of a Spring’s Buckling
A spring’s design and the excess load on it are the major factors that can cause compression spring buckling.
That being so, controlling the spring’s length and diameter to ensure it can support the load can help to avoid buckling.
Other determinants of a spring’s buckling are:
- Pitch (p)
- Helix angle (α)
- Spring index (D/d )
- Expansion of coil diameter
- Method of attaching spring ends
- Offsets between centers of end coil
- Spring coil ends – parallel ends, non-parallel ends, ground ends
- The initial spring length (Lf) ratio to the diameter of the coil diameter (Dm)
- Arrangement of springs – equal span linearly and circumferentially
What is Free Length of Spring?
The free length of spring is the length of the compression spring when a force or load is not applied to it.
On the contrary, a deflection occurs when a force or load has been applied to the spring.
Spring Slenderness Ratio
A spring’s slenderness ratio is used to ascertain if a spring has the potential to buckle or bend.
Thus, the slenderness ratio of the spring is the proportion of the mean diameter to its length.
For instance, a spring’s mean diameter, which is over three times its length will give way and buckle.
It is, however, possible to have an outer diameter that is three times less than the spring’s free length which offers several says to curb buckling in springs.
How to Prevent Compression Spring Buckling
It is essential to prevent buckling in spring because once it starts, the off-axis deformation continues until the spring finally fails.
The latter brings about a need to create a spring in a way that ensures it does not buckle laterally while in use.
That being the case, the following are ways on how to avoid buckling:
1. Custom Springs:
Custom springs are those whose specification (diameter, length, rate, etc.) have been strictly maintained based on what the client wants and the application the spring be used.
These spring types can also have special features based on the customer’s orders in a bid to enhance the spring’s properties and also provide compatibility with the mating parts.
To prevent a spring buckling, you need to ensure that when creating a custom spring, different adjustments are made to its design to give it a proper dimension.
There will also be a need to change the spring’s slenderness ratio, and the change can be done by:
- Adding coils to the spring
- Reducing the spring’s free length
- Increasing custom spring’s outer diameter
2. Stock Springs:
A stock spring is one that has already been designed by the manufacturer. As such, its design has not been determined explicitly by you.
These springs are kept in the company’s inventory and have already been designed.
It is worth noting that despite having no control over the spring’s design, you can still prevent its buckling or bending which is typically caused by the spring’s longer free length.
Buckling can be prevented by adjusting the placement of the stock spring.
All it’ll take is to:
- Add a rod in the center of the spring.
- Place the spring in a tube to avoid buckling
These tips will keep your spring in place and prevent it from coming off during installation.
Nonetheless, minimal friction might still be evident with the shaft’s wall or hole even though it’ll be easier to handle.
3. Use a Spring Length Higher Than LK:
It is essential to expound that using a spring with its length higher than the critical buckling length (LK), can prevent buckling.
LK is a function of the spring’s geometry and the type of end fixations on the spring.
That being the case, LK is independent of the maximum acceptable stress in the spring’s body, theoretically.
4. Rely on a Reputable Manufacturer:
Springs that won’t buckle can also rely on the expertise of the company or manufacturer designing it.
That is why, in most cases, it is advisable to choose custom springs. Their design will specifically be tailored to the machine or application they will be used.
Such springs have a thorough design and most likely, won’t buckle under specific loads.
Stock springs, on the other hand, will have to be selected based on the machine it is most suitable to be used.
Common Questions About Springs
Compression springs, variable pitch springs, hourglass springs, barrel springs, conical springs, extension springs, and garter springs are found in compressors.
The spring’s length, diameter, pitch, helix angle, spring index, coil diameter, spring ends, coil ends, initial spring length, and arrangement of springs determines buckling potential.
Utilize custom springs, adding rods into stock springs, use spring lengths that are higher than the critical buckling length (LK), and rely on a reputable manufacturer to avoid buckling.
Conclusion
Your compression springs may have been designed with quality materials to withstand different weather conditions in certain applications, but the problem of buckling may still be evident.
The same can be said if you had given much consideration to the spring’s design and wire thickness, and it still buckles.
On the contrary, knowing how to prevent a compression spring from buckling whether it is a custom or stock spring means you can get your desire for a spring that stands the test of time.
Employing these tips will prevent your springs from damaging and the need for frequent maintenance or replacement.
These benefits are what can be attained by handling the spring’s length and the fatigue load of the spring to eliminate buckling stress.
Read More:
http://kbdelta.com/blog/spring-compression-formulas-measurement.html
http://kbdelta.com/blog/find-right-spring-materials.html