studying Lego

I looked at a successful competitive toy-LEGO, a line of construction toys manufactured by the Lego Group, Denmark. This was to understand its mechanism and also the process of making plastic toys.

Most Lego pieces have two basic components -- studs on top and tubes on the inside. A brick's studs are slightly bigger than the space between the tubes and the walls. When you press the bricks together, the studs push the walls out and the tubes in. The material is resilient and wants to hold its original shape, so the walls and tubes press back against the studs. Friction also plays a role, preventing the two bricks from sliding apart. This stud-and-tube coupling system uses an interference fit -- a firm, friction-based connection between two parts without the use of an additional fastener.

Making of Lego bricks:

• Lego elements start out as plastic granules composed primarily of acrylonitrile butadiene styrene (ABS).
• the engineers use the NX CAD/CAM/CAE PLM software suite to model the elements. The software allows the parts to be optimized by way of mold flow and stress analysis.
• A highly automated injection molding process turns these granules into recognizable bricks. The making of a Lego brick requires very high temperatures and enormous pieces of equipment, so machines, rather than people, handle most of their creation.
• The machines melt the granules at temperatures of up to 232 degrees C, inject the melted ABS into molds and apply between 25 and 150 tons of pressure.
• Human inspectors check the output of the molds, to eliminate significant variations in color or thickness. Worn-out molds are encased in the foundations of buildings to prevent them from falling into competitors' hands.
• After about seven seconds, the new Lego pieces cool and fall onto a conveyor. At the end of the conveyor, they fall into a bin.
• When the bin fills, the molding machine signals a robot to pick it up and carry it to an assembly hall.
• In the assembly hall, machines stamp designs onto bricks and assemble components that require multiple pieces, like minifigures, also called minifigs. The machines assemble the components by applying precise amounts of pressure to specific parts.
• Lego factories recycle all but about 1 percent of their plastic waste from the manufacturing process every year. If the plastic can't be re-used in Lego bricks, it's processed and sold to industries that can make use of it.
• Annual production of Lego bricks averages approximately 20 billion per year, or about 600 pieces per second.
• The sealed boxes are stored and shipped around the world -- the process uses between 400,000 and 500,000 cardboard boxes per year.

(All information and images courtesy lego)