From the blacksmith's hammer to a machine that bends metal with 3,000 tons
The back plate of your computer case was almost certainly shaped by a press brake, a machine that folds sheet metal with forces reaching 3,000 tons and, under computer control, lands within a fraction of a millimetre. It is one branch of a family that began with a smith, an anvil and an apprentice swinging the hammer.
A forming press changes the shape of metal by squeezing it rather than cutting it away. Presses are sorted in several ways: by what powers them, whether hydraulic, mechanical or pneumatic; by their job, such as forging, stamping or punching; and by how they are controlled. The humblest is the shop press found in garages and machine shops, a rectangular frame with a jack or hydraulic cylinder pushing a ram, typically delivering between 1 and 30 tons. Mechanics use it to force tightly fitting parts together, such as a gear onto a shaft or a bearing into its housing.
At the industrial end, stamping presses drive metal into a die to shape or cut it, and some presses are astonishingly quick: capping presses turn rolls of aluminium foil into bottle caps at up to 660 a minute. Frames matter too. A C-shaped gap frame leaves the work area open on three sides and takes up less floor, while a straight-sided press with columns on both flanks resists the twisting that can throw parts out of true.
The story starts with muscle. Blacksmiths once shaped everything by hand, often with a helper swinging a heavier hammer while the smith positioned the hot metal. Trip hammers and drop hammers then lifted the weight mechanically and let gravity do the striking. James Watt described a steam hammer in 1784, but it was not built until James Nasmyth made one in 1840, and by 1891 the Bethlehem Iron Company had a steam hammer that could land a 125-ton blow. Modern presses mostly combine electric motors with hydraulics.
Newer servo presses use an electric servo motor and a ball screw, with sensors tracking pressure and position, and use only 10 to 20 percent of the energy of other types. Because presses are dangerous, many require both hands on separate buttons, or halt when a light curtain senses someone near the die.
Source: Machine press
