Vacuum pick and place devices in process automation

During the production process it often happens that a given item has to be hold or put from one place to the other. For example, during the automatic assembly of electronic devices one has to take components from the dispenser and place them on the printed-circuit board. You can imagine many more such situations. You can use a mechanical device to place objects, but this method is quite difficult, not universal and will rather be tailored to a specific process, because you have to measure the force that is used when grabbing an object. Such imitation of nature is not easy, thus in many processes another method is used – much easier and having many advantages – sucking an object with vacuum. It’s most important feature is the possibility to graduate and ease to use.

Certainly, everyone, even people who do not deal with industrial automation on a daily basis, intuitively feels how does the vacuum work for gripping an object. A machine using this method operates an arm with an appropriate, adjusted cup, or an adapter with a series of cups through which air is vacuumed. These tips are called suction cups. “Suction” is done by under pressure generated by the pomp and controlled by a valve opened when the cup touches an object. The vacuum behind the cup somehow tries to pull the object inside through it, which is not possible due to the difference in dimensions. An object will act as a cork held in place by vacuum.

Such pick and place method can be used in many ways, because the force used to hold an object depends on the vacuum used, and the surface area, on which it acts. This force can be easily changed by choosing these parameters. Vacuum pick and place devises are easy to use to place object with large flat surface that enables good suction of suction cups. The situation is more difficult with more complex and heavy objects. Then a special vacuum cup is needed, or even a head with many vacuum cups. Vacuum methods are universal, for object with different shapes and dimensions, regardless of the materials they are made from. What is important, is the fact that it does not affect the objects unlike, for example, magnetic devices that may cause secondary magnetization of metal objects.

Vacuum devices have two previously mentioned advantages. First, it is easy to learn how they work. Thanks to this, it will not pose problems for the machine builder or maintenance services. Secondly, it is easy to graduate. It means that the device can be used to pick and place miniature objects such as gear wheel or SMD electronic components, as well as large objects such as parts assembled on the vehicle production line, sheet metal, boards or furniture components.

One of the most important producers of vacuum pick and place devises is Schmalz, a global company founded in Germany. Its wide offer includes all components necessary to build such a device. It may sound easy to build a pick and place device, but it may cause some troubles. Therefore, Schmalz offers its assistance in the selection of components suitable for the needs, and even vacuum systems projects “under the key”. Worth mentioning is the fact that they have knowledge acquired directly or indirectly based on a huge number of applications implemented by clients from various industries and used to manipulate objects made of various substances.

Consistent customer orientation, innovation, excellent product quality and comprehensive consulting competence make Schmalz a market leader in the field of vacuum automation. In the company’s headquarter in Germany and its 19 factories, about 1500 workers produce components for pick and place devices as well as elements for manually operated lifts, and mountings for wood and metal processing. The company’s offer includes everything that will ensure the construction of an effective vacuum pick and place device. Product high quality and the way the company operates is confirmed by a number of certificates. These include: DIN ISO 9001 (quality management) since 1994, DIN ISO 14001 (environmental management) since 1997, DIN ISO 50001 (energy management) since 2012.

Vacuum cups

A suction cup is one of the most important elements of the vacuum pick and place device, and at the same time, its most delicate and subject to damage part. Its role is to ensure a sealed contact with an object, and hold an object during the use of vacuum. A damage usually appears when directly contacting an object that may be gravelly, have higher temperature, sometimes it may be contaminated with some reagents used during production.

As we know, the device is prone to damage.  Thus, a failure free and problem free operation of the device during the production process depends on the choice of the suction cup, and the material it is made from.

Experts from Schmalz are well aware of this fact. The company offers a wide range of suction cups made of various, durable materials designed to meet the requirements of different production profiles. Most cups are made of special elastomers. It is significant that they are equipped with connectors enabling quick replacement, which facilitates service, or adjusting the production line to new objects.

Suction cups can be divided according to shape or the object they transfer. To simplify, one can say that the shape of suction cups depends on the type of transferred object. Round suction cup is good for manipulating regular objects, or for building units with many suction cups and an adapter. Oval suction cups are useful for transferring long and slim objects. Many suction cups are equipped with a follicle that has a dual role.

First, it compensates differences in the height at which they will be applied to the object, which is important when moving objects of different heights, oriented in different ways, having convex or concave details. Secondly, it us also useful when moving delicate components, as it is a shock absorber between the arm of the machine and the object.

The material used to make a suction cup should be adjusted to the material of a transferred object. Suction cups for delicate object should be made of soft elastomers. On the other hand, suction cups for wood or sheet metal should be made of harder materials, and be adjusted to operation in higher temperatures. While the soft material of the suction cup naturally creates a tight connection, the hard one requires to seal the contact surface with transferred object, e.g. with an elastomer. When selecting the suction cup material, the requirements of the standards are also at stake – other will apply to the production of metal parts, others in pharmacy or in the food industry.

Schmalz offers suction cup for any kind of object, material, and industry. They can be used to transfer paper packages, bags, plastic packages and blisters, foil, glass, composites etc. They meet international norms for food and pharmaceutical industry and other industries, and materials used to produce suction cups do not leave any trace on the transferred objects. Some suction cup models are resistant to the temperature up to 600°C, which is important in case of thermal treatment. In addition, the company offers a number of accessories, such as sealing profiles for harsh, smooth surfaces or with texture; flanges; filters; sealing insert and supporting elements.

Mounting elements

In the simplest variant, a single suction cup transfers one, light object – but with the use of a unit of suction cups it is possible to move large, massive objects, or many objects, for example pills or cookies from a blister.

Schmalz offer a wide range of accessories to integrate suction cups or special grippers with the vacuum system. These include, for example, jointed mountings, multidirectional, improving contact between suction cups and uneven surface of an object. Spring plungers are available to bridge the effect of the height difference. An additional effect of their use is gently raising and lowering objects. The company’s offer also includes mounting sets for pick and place device equipped with bearings. They are designed to compensate the height difference in gripping systems without the risk of blockage.

Other suspensions, like FST-C are used to build devices that move objects that are twisted or bent without the risk that they will delaminate (furniture boards) or damage.

It is impossible to list all accessories offered by Schmalz. It is enough to say that the company’s offer includes components that can be used to build any pick and place device for any object, and experienced professionals will help you to choose solutions for a specific application.

Vacuum generators

Even the best pick and place device does not work without vacuum generated by – generally speaking – a vacuum generator. It can be a pneumatic system with and ejector, or a pomp, or a blower.

An advantage of pneumatic vacuum generators is the short time from air supply to obtaining a vacuum and the possibility to directly integrate with the arm due to small sizes and light weight. All ejectors offered by Schmalz are equipped with intelligent solutions ensuring the control of energy consumption and process control. The use of an ejector requires a source of compressed air, the flow of which creates a vacuum. There are types of ejectors that can be series connected to create a multiple source of vacuum.

Electrical vacuum generators operate based on a pomp or a blower. The advantage of solutions offered by Schmalz is that they can be easily integrated with the robot’s arm, or other picking device, and the incorporated function of vacuum regulation. Unlike the ejector, the dimensions of the pump usually do not allow direct integration with the arm, but there are solutions designed for easy integration with the robot arm. Most often, this type of generator is used when there is no access to a source of compressed air, or when high-pressure vacuum is required.

Ejectors by Schmalz come in various sizes. They are efficient and effective and have an incorporated silencer. They can be used both with centralized and distributed vacuum generation systems. Some models can be series connected – they can be mounted directly on the compressed air supply pipe. Some have integrated valves on the inlet and outlet, and more complex models have a pressure sensor. Additional options include compressed air saving, power control and the gripping process control. The accessories offered by Schmalz can be used to build compact terminals of up to 16 ejectors embedded in one block.

Electric vacuum generators by Schmalz do not require compressed air supply. Built-in intelligent control functions facilitate the appropriate, economical use of the generator in the application. The shape of the housing determines them especially to applications built with the use of robot arms, or to transfer material stationary with the use of cobots, i.e. collaborative robots. In electric generators, vacuum is obtained by means of a vacuum pump or a blower.

Vacuum pumps generate high vacuum at low flow. Schmalz offers oil-lubricated pumps for dry running, or with water ring. Blowers allow for high flow with a relatively low value of vacuum created. The solutions offered by Schmalz include the optional functionality of controlling the blower motor speed and an electro-pneumatic thrust reversing system.

In addition to pumps, the company also provides accessories such as: vacuum tanks, vacuum control units (consisting of a pump, tank, monitoring device and controller) and vacuum units built of an ejector, tank, monitoring device and controller.

“Turnkey” vacuum pick and place devices

Schmalz designs „turnkey” pick and place device systems ready to assembly on the robot’s arm or the machine. They are designed to meet specific requirements. Pick and place devices play a key role in almost every industry, ensuring high efficiency and reliability of production processes.

Schmalz’s complex vacuum pick and place systems significantly increase the efficiency and reliability of automatic production processors. Solutions include layer and surface systems as well as ready-to-install multi-suction cup devices, perfectly suited to various automation areas.

Valves

Valves are used to control vacuum and compressed air. Its appropriate selection will improve the reliability of the process and the efficiency of the vacuum systems. Schmalz offers many types of valves, tailored to your specific needs. Its portfolio includes solenoid valves (direct or pneumatic), check valves and flow limiters for closing vacuum pipes that lead to suction cups, which do not have direct contact with work piece; control valves; spring plungers for mechanical verification of the coverage area through the suction cup, non-return valves with spring return mechanism used to protect the system in the event of a vacuum generator failure.

Apart from types of valves already mentioned (automatically controlled), the company offers manual valves for use in manual lifts, or emergency air flow control in automation equipment.

Filters and connectors

A pick and place device has one disadvantage. It is the possibility of drawing crumbs of material, grease, drops of fluid and other objects inside the vacuum system. Filters protect the device from such dirt, and at the same time, from the failure of the vacuum generator, pipes, and valves.

The vacuum is distributed by distributors, hoses, couplings, and connections. These are complementary elements to the Schmalz range, which is essential for every vacuum circuit. They are used not only to distribute the vacuum in the system, but also to connect the suction cups to the vacuum generators.

Sensors and monitoring devices

Monitoring devices are required to monitor the system, and the vacuum pressure to ensure that the vacuum system is working without any problems. They are vital to the safety of the system, to its reliability and to the early detection of possible faults. The company offers: mechanical vacuum switches, pressure sensors with analogue output (measurement from -1 to 10 bar), electronic pressure sensors with display, digital outputs PNP and NPN, vacuum controllers, pressure relief valves, warning devices, and suitable accessories such as connectors and adapters for vacuum switches.

Summary

Building an efficient vacuum system for manipulating objects requires not only knowledge of products intended for the construction of the system, but also an application experience. Although it is not difficult to understand how a vacuum pick and place device works, its practical implementation requires interdisciplinary knowledge, and the use of appropriate components.

A typical vacuum pick and place device consists of a suction cup, or a suction cup assembly that forms a type of interface between the system and the object being moved, mounting hardware, a suitable vacuum generator to supply suction cups; valves or valve assemblies, switches and monitoring elements for safe use, and optional equipment such as hoses, couplings, filters, manifolds and others. All these components are available at TME, a distributor of Schmalz products. What is important, with a single company solution, we ensure that your applications are run smoothly, as the components fit together.