LEGO evolution: Historical manufacturing and technical milestones
A review of the technical advancements in plastic molding and printing that shaped LEGO manufacturing between the 1950s and 1970s.
During the 1950s and 1960s, LEGO ramped up production capabilities to meet increasing demand, moving from basic semi-automatic pneumatic machines to advanced molding techniques. A pivotal moment occurred with the adoption of the 'Hot Runner' mold, which allowed plastic to be injected directly into mold cavities through heated channels. While initial efforts with third-party providers in 1961 were unsuccessful, the company developed its own proprietary system, known as LEGO HK, in the early 1970s, which significantly reduced material waste.
In tandem with injection molding, the company expanded into vacuum and thermoforming technologies. Starting in 1965, vacuum molding provided a more efficient way to produce baseplates, while the subsequent introduction of thermoforming machines in the early 1970s used compressed air to achieve higher precision and output, with early units capable of matching the production capacity of ten previous-generation machines.
The evolution of product decoration also marked a major shift in production standards. Initially, the company used hot stamping for flat surfaces. However, the introduction of tampo printing in the early 1970s provided the necessary flexibility to decorate complex, curved surfaces like those of the newly launched minifigure heads. These historical investments established the core manufacturing methodologies still referenced in the evolution of the company's production systems.