Focusing on 3D printed compression springs, this article presents an alternative to conventional manufacturing methods. The technology caters to a wide array of engineering needs through personalized dimensions and attributes of springs. The production journey starts with choosing the type of plastic. Although one might consider firm plastics for a spring effect, they can become highly brittle under mechanical stress. Therefore, selecting a plastic that simultaneously provides rigidity and elasticity is crucial. In this guide, we offer knowledge about various plastics and their applications. The article further explores the intricacies of 3D printing compression springs in different situations, preparing you to print your own springs.

## Calculating Deflection in Plastic Compression Springs

Deflection, the change in an object's shape due to an external force, is a characteristic of 3D printed plastic compression springs that can affect their function. Knowing the potential deformation of a spring under a specific load assists in ensuring that it conforms to the required design.

The type of plastic used in creating the spring impacts its reaction to stress. For instance, ABS plastic, commonly used in 3D printing for its strength and flexibility, will react to stress differently compared to other plastics. Regardless of the type of plastic, it's feasible to examine and measure deflection. One can 3D print a test piece with identical settings and material as the planned spring, and subsequently apply increasing loads to the test piece. Recording the deflection at each phase until the piece alters shape or breaks is crucial. Drawing a stress-strain graph from this data facilitates the calculation of the modulus of elasticity, which offers information on how the spring will respond under load and aids in the design process.

This method of testing is beneficial for applications where the safe operation and toughness of the spring are key considerations. For less critical applications, one can refer to stress-strain values provided by the plastic manufacturers or found in scientific papers. It's notable that these values may not consider all aspects related to 3D printing like layer bonding, print direction, and printer configurations. The choice between these two methods depends on the equilibrium between time, accuracy, and the consequence of the final application.

## Differences Between Metal and Plastic Springs

• Metal springs are denser than plastic springs : The increased density of metal springs contributes to a heavier device, which is of note in contexts such as aerospace where the weight of the payload is a factor. Plastic springs, because of their lower density, may contribute to a decrease in total weight in satellite applications.

• Plastic springs have less mechanical strength than metal springs : This characteristic makes them unsuitable for environments under high stress. In a mechanical press designed to handle heavy loads, metal springs are typically used due to their high strength. The tensile strength of the material used is an important parameter to consider during spring design as it determines the load the spring can safely support.

• Plastic springs are more resistant to corrosion than metal springs : Consequently, they require less anti-corrosion protection, which can be an important aspect in environments high in moisture. An underwater device operating in saline sea water might utilize plastic springs since plastic is naturally resistant to rust and corrosion. An exception to this rule would be stainless steel springs, which generally have excellent corrosion resistance. Keep in mind there may be certain harsh chemicals that steel springs work great with, but that will damage plastic springs.

• Plastic springs have less heat resistance than metal springs : High-temperature conditions can affect the integrity of plastic springs due to the risk of melting or deformation. If you are designing springs for a high-temperature environment, like an industrial furnace, metal springs might be more suitable.

• Metal springs maintain a constant stress-strain ratio : A notable characteristic of metal springs in precision-engineered applications is the consistency of their stress-strain relationship, which directly affects spring constants calculations. Plastic springs, on the other hand, may show non-linear stress-strain behaviour depending on the specific plastic material used. This different behaviour should be taken into account during the design of 3D printed plastic compression springs.

## Designing the Compression Spring Features and Dimensions

3D printed plastic compression springs have several design elements and size specifications. One key aspect is the spring rate, which measures the spring's resistance to compression. For example, a spring designed for a delicate medical device may have a lower spring rate to avoid excessive force on fragile parts. On the other hand, a spring for mechanical applications that requires constant, forceful compression may have a higher spring rate.

The size of the coil affects the spring force. Generally, a larger coil size is linked to a lower spring force. In scenarios requiring a higher spring force, a design could incorporate smaller coils. However, if space allows, larger coils distribute stress across the spring, reducing the risk of material failure.

The 'pitch' or spacing between coils is another factor. Appropriate pitch calibration accommodates the necessary deflection, especially in dynamic systems where variations in deflection affect performance and safety. For instance, a tightly-calibrated pitch in a vehicle's suspension system may cause the spring coils to come into contact during extreme compression, thereby affecting spring function and system safety.

The overall dimensions must be compatible with the assembly constraints of the device where the spring will be used. For instance, in a compact electronic device, space is a consideration. Accurate modelling of all dimensions and features in the 3D printing software ensures proper material usage and decreases the likelihood of adjustments or the need for reprinting after production.

If you need assistance in analyzing your spring dimensions based on your force and spaceclaim requirements, check out our Compression Spring Calculator

## Conclusion

3D printing of compression springs requires precision and time but offers engineers the advantage to modify springs according to their projects. This process involves accurate calculation of spring deflection and complete understanding of the mechanical properties of plastic and metal springs. It's essential to know that these properties influence the design and measurements of your compression spring. By keeping these factors in mind, one can create a 3D printed plastic compression spring that suits a particular application.