The Importance of Seamless Riveting at the Shaft-Bore Mating Point in Brass Stamping Switch Terminal Accessories and Its Impact on Electrical Life

The non-uniformity of free upsetting deformation specifically affects riveting quality by creating localized gaps between the shaft and hole after riveting. This prevents the outer surface of the deformed metal from achieving complete contact with the spring hole, thus reducing the contact area between the shaft and the hole. The size and location of these gaps are closely related to factors such as the length of the contact rod diameter, the shaft-hole fit clearance, the shape of the upper riveting die, and the riveting method.

When the contact rod diameter is too long or the shaft-hole fit clearance is too large, the uniformity of upsetting deformation increases, making instability, bending, and cracking more likely during the riveting process, and making it difficult to control the riveting quality. Custom Brass Stamping riveted with Silver contact. Riveting methods are broadly classified into two categories based on the equipment: punch riveting and spin riveting. Punch riveting head shapes include flat riveting heads, concave riveting heads, and V-shaped riveting heads. Flat or concave riveting heads generate the greatest friction during punch riveting, which is highly detrimental to riveting quality. When using a V-shaped riveting head, the contact area between the contact rod and the die is small, resulting in less obstruction to metal flow on the blank end face, reducing the difficult-to-deform zone and improving the uniformity of upsetting deformation. However, this method is susceptible to bending and other undesirable deformations due to the large impact force of the riveting pressure, and it is only suitable for single-sided contact riveting.

Spin riveting and punch riveting differ significantly in their force output. Spin riveting machines utilize both axial downward pressure at a certain swing angle and radial rotational force, while punch riveting machines only apply vertical downward axial pressure. Spin riveting ensures uniform material flow and virtually eliminates difficult-to-deform zones. Furthermore, spin riveting has lower impact pressure; to achieve the same riveting effect, the force required is only one-tenth that of punch riveting, effectively preventing cracking, bending, upsetting, and other undesirable deformations. The resulting contact surface is aesthetically pleasing. Choosing the spin riveting method is particularly important for double-sided contact riveting with long rod diameters.

In the comparative test of different riveting methods for the 32F relay, contacts of the same specification were used, and both punch riveting and rotary riveting were performed. The test load was also a 10-amp, 250-volt AC resistive load, with a rated electrical life of 100,000 cycles. Pre-test contact cross-section sampling inspection showed that after punch riveting, there was a significant gap at the mating of the moving and stationary contact shaft holes, while after rotary riveting, the mating of the moving and stationary contact shaft holes was good.

Test Results: The punch-riveted product failed due to adhesion after more than 50,000 cycles, while the rotary-riveted Electrical Brass Metal Stamping for Socket Switch achieved an electrical life of over 100,000 cycles without failure. A comparison of contact and spring hardness before and after the test showed that the hardness of the punch-riveted contacts and springs decreased significantly: contact hardness decreased from 100 Hv to 50 Hv, a reduction rate of 50%; spring hardness decreased from 165 Hv to 128 Hv, a reduction rate of 22%. The hardness of the rotary-riveted contacts and springs remained essentially unchanged, with hardness reduction rates of only 1% and 0%, respectively.

Experimental results show that poor riveting of the stamped contact is the main cause of overheating of the contact, deterioration of the spring's elastic properties, and ultimately, early fusion welding failure of the electrical terminal brass block riveted with silver contact. In terms of resistance to fusion welding, spin riveting is significantly superior to stamped riveting.