How to choose between metal spring (non spring spring spring) and spring? Selecting Logic from Application Scenarios
In the early stages of product structure design, the selection of spring plates and springs is often simplified. Many engineers assume that 'springs are those that can bounce back', only to discover during sample verification that they cannot fit the space, cannot withstand the force, or exceed the budget in terms of cost. In fact, these two types of parts differ in terms of molding process, force distribution, and applicable boundaries. Clarifying differences is the key to avoiding detours.
1. Define two concepts first
Hardware spring refers to elastic parts formed directly from metal sheets (such as phosphor copper, stainless steel, manganese sheets, etc.) using precision stamping technology. They rely on the elastic deformation of the bending part to provide rebound force. Essentially, they belong to "leaf springs" and are commonly used in battery spring, connector spring, and button spring.
Spiral springs refer to compression springs, tension springs, and torsion springs formed by winding steel wires, which rely on material torsion and tension to store energy. One sentence distinction: shrapnel is "flat and punched out", while springs are "three-dimensional and coiled out".
2. Four dimensions determine selection
Space occupancy. The shrapnel is a flat structure with a thickness of mostly 0.1-0.3mm, and it almost does not occupy a height when attached to the PCB or shell; The spring must have axial dimensions. Products with limited internal height, such as thin remote controls and card devices, often have more realistic shrapnel.
Force value and stroke. Springs are good at large stroke and high force values: a 0.5mm diameter steel wire compression spring can compress more than ten millimeters and maintain approximately linear force; The effective stroke of the shrapnel is usually only 1-2mm. If a large pressing force or long stroke rebound is required, priority should be given to the spring.
Conductive demand. Bullet materials are mostly good conductors, naturally suitable for situations that require both elasticity and electrical continuity (battery contact, signal connection). Springs bear more pure mechanical functions; Forcefully incorporating conductive components requires increasing the coating and stabilizing the contact resistance, which increases the complexity. Electrical connections are involved, with priority given to shrapnel.
Batch cost. In the early stage of shrapnel production, stamping molds are required, and the cost per set is not low. However, after mass production, the cost per piece can be as low as a few cents; The spring mold requires small investment and is flexible in small batches, but there is limited room for cost reduction per piece after a large quantity is produced. Consumer electronics that are cost sensitive and have large order volumes have better economic viability for shrapnel; Multiple varieties in small batches, suitable springs.
| Dimension | Metal Stamping Contacts | Helical Spring |
|---|---|---|
| Space Occupied | Flat structure, takes almost no height | Requires axial dimensions, takes up space |
| Force & Travel | Travel 1-2mm, relatively small force | High force, long travel advantageous |
| Conductivity Requirement | Inherently good conductor, naturally suited | Mostly mechanical function, conductivity requires plating |
| Batch Cost | Lower per-unit cost once tooling is set up | Cost-effective for small batches, limited cost reduction at high volumes |
3. Suggestions for designers
Before selecting, answer three questions: Is the installation space limited? What is the required force value and stroke? Does it involve conductivity? Space constraints, low force values, and the need for conductivity - priority given to shrapnel; Adequate space, requiring high force or long travel, pure mechanical - springs are more suitable. There are also cooperation plans: the spring provides the main elastic force, and the spring independently assumes the contact function, each performing its own duties.
It is recommended to introduce elastic component selection evaluation in the early stage of structural design, combined with spatial dimensions, force curves, current requirements, expected life, and estimated production locking schemes, to avoid rework in the later stage.
frequently asked questions
Q1: Can shrapnel replace all small springs?
No. The travel and force values of shrapnel are limited, and mechanical structures that require large travel or high force values (such as travel exceeding 3mm and force exceeding several newtons) should still use springs.
Q2: Which has a longer lifespan, shrapnel or spring?
It depends on the operating conditions. The cycle life of shrapnel can reach 100000 times under small deformation; Springs exhibit better fatigue performance under large deformations. Exceeding their respective designed travel distances can easily lead to failure.
Q3: How to deal with insufficient shrapnel force?
Multiple layers of shrapnel can be stacked, the bending arm length can be increased, or materials with higher elasticity (such as beryllium copper) can be selected. If there is a high demand for force, it is recommended to evaluate the spring solution
Q4: Can springs be used as conductive contacts
It can be plated with nickel or gold for conductivity, but its contact stability is not as good as that of shrapnel, and it occupies more space. It is generally only used in special structures
Q5: Which is faster for small batch sampling?
Springs are faster. The spring can be sampled in a few days by adjusting the parameters through a winding machine; The shrapnel needs to be molded, with a longer cycle. Urgent samples with small quantities can prioritize springs.
Q6: How do the costs of the two compare?
The shrapnel relies on mold dilution, and the larger the quantity, the more economical it is; Springs are mainly based on single piece cost and flexible for small batches. The critical point is usually on the order of tens of thousands of chips, depending on the complexity of the structure.