Welding and injection molding are core processes for creating assemblies and complex shapes. Welding permanently fuses metal components using heat and/or pressure, forming strong structures vital for automotive frames, ship hulls, pipelines, pressure vessels, and structural steelwork. Injection molding forces molten plastic into precision molds, producing vast quantities of identical parts like consumer product casings, automotive dashboards and bumpers, medical device housings, and intricate electronic components.

Welding's primary advantage is creating joints with strength often equal to or exceeding the base metal, enabling the construction of large, durable structures and offering excellent repairability. Techniques like MIG, TIG, and laser welding provide versatility for different metals and joint types. Injection molding's dominance stems from its unbeatable efficiency for mass production: extremely low per-part costs, minimal finishing requirements, exceptional repeatability, and the ability to produce highly complex geometries with integrated features (threads, clips, textures) in a single step.

In conclusion, welding and injection molding are foundational for modern production. Welding provides the essential strength and integrity for metal assemblies across heavy industries and infrastructure. Injection molding enables the cost-effective, high-volume manufacture of intricate plastic parts ubiquitous in daily life. The robustness of welded joints and the mass-production efficiency of molded plastics remain irreplaceable. Advancements in automation, robotics, new welding techniques, and mold design/materials continue to enhance their speed, quality, and application scope.