Designing a compression spring design is not easy. Like many other engineering task, compression spring design requires diligent attention to detail. Although finding a good spring manufacturing partner can alleviate many common concerns, it’s still important to know about the types of hurdles you might encounter:
1. Choosing the Right Slenderness for Stability
Springs bear many different measures of force, and as with most balanced systems, these factors aren’t always as regular as you’d hope. Choosing a slenderness ratio, or the ratio between the spring’s coil diameter and free length, can reduce the likelihood that the resulting part might buckle, bend or deflect in response to weight, vibration and other forces with lateral components.
In most cases, your slenderness ratio should be less than four, which you can accomplish by shortening the spring’s free length or making its outer diameter wider. Redesigning your apparatus, such as by including guides or linear shafts, may also help.
2. Picking an Appropriate Spring Index
The spring index, or the ratio of the mean diameter to the wire diameter, gives you a general indication of how tightly wound the spring’s coils are. Indices lower than four are typically regarded as being too small to manufacture accurately, while those above 15 are mostly too large.
The mean diameter is the outer diameter minus the wire diameter, so you have multiple ways to correct the problem. For instance, you can lower the index by using a thicker wire or a spring design that features a smaller outer or inner diameter.
Each compression spring has a maximum safe load that it can support without significantly increasing the risk of unexpected catastrophic failures. While your choice of material and spring fabrication processes have big impacts on loading capabilities, it’s also important to pay close attention to the dimensions of the spring.
Once again, your spring’s unloaded length is an essential engineering characteristic. Your free length should never be shorter than the solid height, or the height of the spring when it’s fully compressed.
This free length restriction makes sense considering that the spring needs room to travel as it compresses. What many people fail to realize is that a similar rule of thumb applies to the loaded height of the spring — If the spring gets so squeezed together that it’s shorter than the normal height of the coils when they’re all touching, then you’ve got too much stress and a high risk of breakages or other failures.
How can you correct such problems? Good places to start include using wire of a different diameter or changing the coil count.
Other Issues to Watch Out For
Remember that no spring is perfectly ideal. The general design equations that describe your device’s behavior might not account for things like how your spring’s elasticity changes with temperature. In some cases, you might not discover that your wound spring can’t compress all the way down to its solid height until after it’s made.
Working with a proven compression spring manufacturing team is the smartest way to lighten your engineering workload. By partnering with a reputable spring design and fabrication specialist early on, you can sidestep common problems and take application-specific challenges in stride.
Design the right spring the first time. Work with The Yost Superior Co. Today.