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The piCobot can also lift flexible materials, such as bags where the suction cups do not close completely. © Piab

Collaborative robots, or cobots, are designed to work alongside humans. Equipped with grippers, sensors and optical technologies, this latest generation of robots is safe and easy to operate in almost any environment. No wonder they have quickly become a familiar sight in industry.

The coax technology makes the piCobot powerful and still allows a compact design. © Piab

Some of the plug-and-play vacuum grippers for cobots on the market today use miniature electro-mechanical vacuum pumps. This can be an alternative if there is no access to compressed air or if the cobot is intended for use on a mobile platform. However, miniature electro-mechanical vacuum pumps offer a significantly lower vacuum flow compared to compressed air driven vacuum pumps.

Higher load capacity with compressed air

Since the lifting capacity depends on the vacuum flow, cobots with air-driven vacuum pumps offer several times the payload capacity of cobots that use miniature electromechanical pumps. The simplest type of air-driven vacuum pump is known as a single-stage ejector.

With the multi-stage vacuum ejectors of the Coax system, Piab optimizes the technology of ejector vacuum generation. © Piab

Vacuum is created by forcing compressed air at very high speed through a small opening or an ejector nozzle, causing negative pressure to build up in the system. From the outside of the system, atmospheric pressure attempts to equalize this negative pressure and restore equilibrium. This creates the vacuum flow or induced air flow.

In so-called multi-stage ejector pumps, compressed air enters the pump and is passed through a system of ejector nozzles and chambers of different sizes, which act as "pressure boosters". Multi-stage vacuum ejectors make optimum use of the energy stored in the compressed air through specially developed air nozzles in a series of increasingly larger ejectors that can expand the compressed air flow in controlled stages. Multi-stage ejector vacuum pumps also offer many other advantages over single-stage ejectors and mechanical or electromechanical vacuum pumps. They are quiet, have few moving parts and generate neither heat nor vibration, resulting in virtually maintenance-free operation.

Increased vacuum flow with multi-stage technology

Cobot plug-and-play vacuum grippers using multi-stage vacuum ejectors provide the optimum vacuum flow, resulting in the highest lifting capacity and the ability to handle a variety of products, including hard-to-grip objects such as flexible packaging. For this reason, choosing an air-powered "strong" cobot vacuum end effector is a good choice for demanding lifting requirements.

The piCobot gripper from Piab uses "Coax" multi-stage vacuum technology. Coax ejectors are based on Piab's multi-stage technology and are smaller, more efficient and more reliable than conventional ejectors, allowing the development of a flexible, modular and efficient vacuum system. Such a system provides three times more vacuum flow than conventional systems and offers the possibility to increase speed with high operational reliability while consuming less energy. The technology ensures high performance at both low and high feed pressure.

The piCobot is equipped with two Coax Micro Ti05-2 ejectors, which achieve a high suction power even at low vacuum levels. The piCobot achieves a maximum vacuum flow of 38.4 NI/min compared to 12 NI/min for comparable grippers that use an electromechanical pump. This means that the piCobot can also handle difficult materials that are easily permeable to air, as in the case of cardboard, or flexible materials, such as bags, where the suction cups do not close completely. This is not possible with grippers with an electromechanical pump.

The pump unit of the piCobot is compact and lightweight due to the small space requirement of the ejectors. It is only 76 mm high and weighs 0.51 kg - 0.71 kg with the standard suction cup unit. This means that taller and heavier objects can be moved. Companies that have invested in a Cobot can therefore make full use of its capacity and thus achieve a shorter amortization period and a correspondingly higher return on investment.

Andrea Bodenhagen, Marketing Director Europe, Piab / am