Vacuum cups, or suction cups, are often used as grippers in manual or automated handling applications. They can secure and help move a wide range of products—everything from tiles, sheet metaland glass windows. In essence, they’re the interface between a vacuum system and the workpiece.
Technically, a suction cup does not attach itself and grip the surface of a product. Instead, when a suction cup contacts the workpiece surface, it activates a vacuum generator and draws out air from the cup interior and creates a vacuum. Given that air pressure inside is then lower than that outside of the cup, atmospheric pressure holds the workpiece against the cup. The greater the difference between ambient pressure and vacuum pressure inside the cup, or the larger the effective area of the cup acting on the workpiece, the greater the holding force pressing the cup onto the workpiece.
Ideally, a suction cup should mate against a smooth, nonporous surface. Then, when generating vacuum, the cup rim completely seals against atmospheric air and the interior air is quickly evacuated, resulting in a firm grip on the workpiece. However, non-ideal conditions are many times the norm because materials are often permeable, rough or uneven. In these cases, the cups cannot completely seal and outside air constantly enters the system. That’s termed a leaking system. Designers must compensate for leaking systems by using high-flow vacuum generators or using smaller cups to reduce the potential for leaks.
Types of suction cups range from simple, circular types to those designed for special applications like handling candy, greasy sheet-metal panels. They come in two general shapes, flat and bellows.
Flat suction cups are suited for handling workpieces with flat surfaces, such as metal and glass plates, plastic sheets . Flat cups have a small inner volume and, thus, evacuate quickly and can grip in a very short time. Properly designed, they have good stability to handle high shear forces and can withstand forces and accelerations from fast