What are the specific challenges associated with the automated assembly of multi-turn wave springs in high-volume solenoid valves?

In high-volume automated assembly, the primary challenge is the 'nesting' or 'tangling' of springs in vibration feeders. Wave springs, particularly those with open ends, can interlock, leading to machine downtime. Using 'shim ends' or 'squared-flat' ends helps reduce this. Additionally, the assembly tool (plunger) must be designed to apply a uniform axial load during insertion to avoid tilting the spring. If the spring is tilted, it can catch on the edge of the bore, causing a 'burr' or damaging the coating of the spring. Force-displacement monitoring during the press-fit operation is recommended; a sudden spike in force before reaching the design height $H_1$ indicates a misalignment or a 'doubled' spring assembly.