Gripper / effector of a robot

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updated on 11.05.2020 - 14:52:46
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The gripper is part of a robot and often indispensable as the last link in the kinematic chain, for example it holds the workpiece or tool that is to be processed by or by the robot. A gripper belongs to the environment of the gripping technique and is similar to the human hand on the arm.

Question/Definition: What is/are Grippers?
Also often searched: effector, robot hand, end effector, EOAT, gripping system, gripper system



Gripper systems for robots

Kuka robot with special gripping tool
Kuka robot with special gripping tool

For Industrial robot the gripper is an indispensable element, it is at the end of the kinematic chain. The gripper is the part of the robot that performs the actual task and only then turns the robot into a functional machine. The gripper normally sits on the outermost or last axis of the robot and is connected to the power line. Grippers thus serve for the interaction of the robot: for gripping, machining or turning a workpiece or tool.

Grippers can be differentiated based on their effect. The various gripping (er) systems are mechanical, pneumatic, magnetic or adhesive.

  • mechanical grippers: Mechanical grippers literally simply grip. They are often similar to a human hand or are a pair of grippers and are available as single or multi-finger grippers. These gripper systems can consist of several rigid joints, but can also be flexible in general. The drive of the mechanical gripper is mostly pneumatic. However, an electrical or mechanical drive is also possible.
  • pneumatic grippers: pneumatic grippers are vacuum suction cups or suction cups that suck the workpiece in order to transport / process it. In addition to vacuum technology, the workpieces can also be clamped using the pressure principle.
  • Magnetic gripper: The workpiece is magnetically attracted and can be held in this way. There are two types of magnetic grippers: permanent magnet grippers and electromagnetic grippers. With the permanent magnet gripper, the magnet cannot simply be "set down", which is why the workpiece, once attached to the mangled object, must be removed using another system. The electromagnet can be switched on and off by electrical energy. This allows the workpiece to be gripped and set down again.

Gripping systems can be described as organs of a robot. The individual elements include Actuators / effectors and auxiliary devices such as wrist axes, changing systems, joining aids, protective devices and sensor units.

The subsystems of the gripper

A gripper consists of different subsystems: the active system (1), the drive system (2), the kinematic system (3), the carrier system (4) and the information processing system (5) (see figure).

subsystems of a gripper
subsystems of a gripper simply shown

active system (1)

The active system is the area of the gripper that has direct contact with the workpiece and transfers the gripping force to it. The active points on the gripper are called the gripping surface or active active surface, while the active points on the workpiece are called the passive (passive) surface.
There are various ways in which the gripper can hold the workpiece. This is called the type of active combination. The possibilities of effective pairing are:

  • Force pairing: Force pairing exerts pressure on the workpiece from the gripper, thereby holding it in place.
  • Shape pairing: With the shape pairing, the workpiece and the gripper fit perfectly together, so that the workpiece can be lifted by the gripper having the same shape. Much less pressure has to be built up here than with force pairing.
  • Material pairing: The material pairing uses the technique of adhesion (so-called attachment force). However, this has so far been less widespread in industry.

drive system (2)

The drive system generates the energy required for the entire gripping process. This enables the workpiece to be opened, closed and held by the gripper. The energy supplied can be mechanical, hydraulic, pneumatic or electrical. In the drive system, the energy is then converted into mechanical energy (e.g. rotary movements).

Kinematic system (3)

The kinematic system is responsible for the transfer of energy from the drive system to the active system. It converts the movement of the drive system into an output movement of the gripper. There are different gripper gears so that the gripper links can perform the desired movement, gripping force and speed (closing, clamping, etc.).

carrier system (4)

There is a connection between the gripper and the end member of the gripper guide gear. This is the carrier system and forms the frame of the gripper. A transfer of forces also takes place here. The carrier system has the following properties:

  • Coupling (rigid or movable) between gripper and gripper guide gear
  • allows the gripper to be replaced
  • Information transfer and energy transfer between the guide gear and gripper

Information processing system (5)

The information processing system collects important data via sensors (e.g. status of the gripper, position of the workpiece, parameters of the gripping task). The information collected is then adapted, amplified, evaluated and transmitted to the control.

Areas of application for grippers and associated gripper systems

collaborative gripper system from FAUDE

Since grippers are a central element of robots, they are logically used wherever robots are used, i.e. primarily in industry. There, the possible uses extend to all branches of industry: from the food industry to automobile manufacture. Various grippers are listed below and in which area they are used:

  • Finger gripper: These are flexible gripper systems that are based on the human hand. It has been found that the majority of industrial requirements can be covered with just three designs. These are the two-finger grip , the three-finger parallel grip and the three-finger centric grip .
  • Box grabs: Box grabs (or also box grabs) come mainly from used in production and shipping. With their help, boxes and boxes can be easily transported by attaching a box gripper to the end link of a crane. In this way, wooden boxes and cardboard boxes can be easily moved through warehouses.
  • Rim gripper: The name also reveals its function in the case of the rim gripper: it can be used to transport rims (e.g. palletizing & depalletizing). Wheels can also be moved with it, which is why the rim gripper is also called a wheel gripper.
  • Vacuum grippers: Vacuum grippers are very versatile in industry. You can handle the workpiece with particular care and are therefore suitable e.g. for handling glass. A lot of caution is also required when transporting CDs. Vacuum grippers are e.g. also widespread in the packaging industry, since they can adapt to shape-sensitive films.

Nowadays, human-robot collaboration (Human-Robot Collaboration) is also an important topic. Not only the collaborating robots (Cobots) themselves, but also the gripper on the robot must ensure safe collaboration with humans. The video shows working with a collaborative gripper system in the application.

Manufacturer gripper

ROOM GROUP
The Zimmer Group is one of the world market leaders with a focus on gripping and swiveling technology and the “end of arm tooling” on robots. From development to final assembly, mainly pneumatically and electrically driven handling components and systems are sold. Customers include the robot system houses, portal builders, assembly plant builders and chaining the plant architectures. The product range includes over 3,000 standardized handling components available in a modular system that can be built into systems by the Zimmer Group or the customer.
FAUDE
FAUDE has been present in the field of automation technology for over 25 years. For some years now, especially in robotics. For gripper systems, FAUDE offers both robot grippers and vacuum suction grippers.
FIPA
FIPA is a manufacturer in the field of vacuum technology and end-of-arm tooling. In the area of gripper technology, FIPA offers various gripper systems such as Angle gripper, Manget gripper, gripping tongs and gripping fingers.
FAIRY
F.EE is a specialist in automation technology with over 1,000 employees. In the mechanical engineering division, in addition to traversing axes, brackets and other accessories for robotics systems, robot grippers are mainly designed and manufactured for handling and assembly tasks based on an aluminum profile system based on a modular principle.
KUKA
KUKA is known for its robot technology. Of course, this also includes the development and manufacture of grippers. Regarding end effectors, KUKA has, for example, pneumatically or electrically operated gripper systems such as the multi-function end effector from KUKA or the nut screw end effector from KUKA.
Schunk
Schunk is a specialist in the area of gripping technology. With over 3,000 employees, Schunk now operates internationally. The company offers the world's largest range of gripper systems and clamping technology and delivers its products to customers in automation technology, robotics or plant engineering. For example, Schunk manufactures angle grippers, parallel grippers and centric grippers.
AGS
AGS Automation offers gripper kits with over 2,500 components - this makes it easier to assemble gripper systems into one product.
IPR
IPR is a provider of parallel grippers, angle grippers, special grippers, gripper systems and gripper accessories.

Non-industrial areas

Gripping pliers, gripping arms or grippers are also manufactured, used and distributed in the non-industrial sector (Amazon, Ebay, office / hardware stores). These are usually simple, human-operated tools such as grapples or other gripping tongs.

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