Flexible rotary modules: compact, precise and dynamic

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2016-07-27 11:49:00

Current discussions about the smart factory and Industry 4.0 can easily give the impression that the advantages of mechatronization can be attained only through radical change – a big bang, so to speak, in production automation. The exact opposite is the case: design engineers are increasingly recognizing the potentials of mechatronic components and are already using them effectively today. This also includes the mechatronization of rotative movements. There are good reasons why SCHUNK, the competence leader for clamping technology and gripping systems has expanded its line of standard gripping system components with respect to electric rotary modules.

Whether for highly dynamic electronic assembly, freely positionable rotary indexing tables for assembly applications or powerful rotary actuators for heavy loads – the world’s most extensive line of mechatronic modules from SCHUNK, with more than 300 standard components, offers the right mechatronic rotary module for every dimension.

Particularly for assembly applications in the electronics, consumer goods and pharmaceutical industries, for example, SCHUNK developed the endlessly rotating SCHUNK ERD miniature module, the world's only torque motor with an integrated air feed-through and absolute position measuring system. The module features two integrated air feed-throughs as standard equipment.

Available options include four electrical feed-throughs and the SIL2-certified absolute position measuring system. The SCHUNK ERD, which is available in three sizes with nominal torques of 0.4 Nm, 0.8 Nm and 1.2 Nm, can be used to implement space-saving, high-torque and high-speed assembly systems that also fulfill the stringent requirements of the machine directives.

The rotary module is driven by a brushless synchronous motor with permanent excitation. Its special geometry ensures high dynamics and acceleration. Also, due to the optimized air feed-throughs, pneumatic actuators connected to the module can be actuated more quickly. These two combined factors ensure short cycle times and high productivity.

The absolute position measuring system eliminates the need for time-consuming reference runs during startup and after an emergency shut-down; also, the repeat accuracy is improved, with a specified value of 0.01 mm. A large number of pairs of poles ensures that the module generates a high rated torque of up to 1.2 Nm even at low speeds. The module can be controlled for example using Bosch-Rexroth IndraDrive CS drive controllers.

Minimal interfering contours
The versatile SCHUNK ERS rotary module was developed for rotary motions in the middle load range, which is most in demand. The most compact mechatronic rotary module currently available on the market has a height of only 66 mm in size 170. It achieves a rated torque of 5 Nm and a maximum torque of 17 Nm. This module enables the design of very versatile and compact systems. In assembly applications it can be used either as a rotary module or as a small rotary indexing table. The core component is a hollow shaft torque motor, which makes it possible to build a very lightweight and compact module that operates completely wear-free and therefore extremely efficiently.

With its endless rotation at speeds of up to 250 rpm it can approach any intermediate positions at a repeat accuracy of 0.01°. As opposed to rotary modules with a conventional servomotor the ERS has no additional interfering contour. Elasticity from backlash and friction is also eliminated. Instead, the durable module features high acceleration, high turning speed and high precision. An optional pneumatic brake can be integrated to ensure reliable holding of single positions. A large center bore allows the feed-through of cables or workpieces, as well as the use of a camera.

But that is not all. To conduct compressed air or signals directly without the use of hoses or cables, the compact module is also available in a version with pneumatic/electric feed-through, in which a slip ring or air duct enables the feed-through of up to eight electrical signals (24 V DC/2 A) and one fluid with a pressure of up to 8 bar.

The SCHUNK ERS is available in three sizes with outer diameters of 135 to 210 mm. The version with a rotary feed-through is available in two sizes with outer diameters of 170 and 210 mm. To ensure maximum versatility in the control strategy, the modules can be operated with the SCHUNK ECM motion controller (48 V version) or with a standard controller, for example from Bosch or Siemens (560 V version).
The mechatronic SCHUNK ERS rotary module enables versatile applications in close spaces. It is optionally available in a dust-proof and splash-proof version (IP54) and with a pneumatic/electric feed-through.

Free choice of motors
The electrically driven SCHUNK ERM rotary module shows the tremendous advantages of using mechatronics also for heavy loads. This module combines high torques with high precision. That makes it ideal for the variable and precise positioning of heavy loads, such as for turning and reorientation of workpieces in automotive production. Spontaneous changes in the handling process and constantly changing parts families can easily be programmed to increase versatility in the process design.

This also facilitates commissioning, since the ERM modules allow fast and precise fine adjustment of tolerances during system engineering, which is not possible with pneumatic rotary modules. In addition, it is possible to operate the modules at reduced speed during set-up or maintenance, which not only prevents damage, but also significantly reduces the time needed for the initial system start-up.

The adaptive design of the ERM modules allows the use of all standard industrial servo motors. This provides a very high degree of freedom with respect to the control strategy. Equipped with the right motor, the properties of the system controller with respect to programming, safety or field buses can be transmitted directly to the module. Compensation of the different regional standards in Europe, USA and Asia is therefore relatively easy.

In addition, the auxiliary gearbox, which turns in 4x90° steps, allows optimal adaptation of the interfering contour of the rotary module and drive unit for use with gantries. A standard center bore of 22 mm enables a very compact and uncluttered system design. Eight air feed-throughs supply compressed air to the pneumatic actuators downstream of the rotational axis. In size 160 the maximum output torque is 75 Nm and the maximum driving torque is 2 Nm.
The intelligent SCHUNK PR 2, PDU 2 and PSM 2 high-performance rotary modules feature maximum power in minimum space. The electronic control and power components are fully integrated.

Compact powerhouses
At the upper end of the performance scale SCHUNK offers three compact and intelligent high-performance rotary modules, which are optimally designed for robust use in industrial applications: SCHUNK PR 2, PDU 2 and PSM 2. These modules feature fully integrated electronic control and power components.
This eliminates the need for an external controller and minimizes the number of cable connections, as well as fault susceptibility. The powerhouses are available in three standard sizes. They are controlled either via Profibus (up to 12 Mbit/s) or CAN-Bus (up to 1 Mbit/s). The modules are equipped with a USB device port for commissioning and parameterization via PC with the SCHUNK Motion Tool.

Manual addressing is possible via a convenient rotary code switch. Initial module movements can be achieved manually by the use of DIP switches. The status is indicated via an LED display. Due to harmonic drive gears the PR 2, which is designed as a rotary module, and the PDU 2, designed as a linear axis module, achieve very high torques between 16 Nm and 184 Nm, depending on the size. The direct drive PSM 2 is ideal for moving small loads faster.

With a torque of up to 1.8 Nm the compact module reaches speeds of up to 4,320 rpm. Individual control of the position, speed and torque is possible with all three modules. An incremental encoder ensures high positioning and repeat accuracy. The integrated brake allows reliable holding of the single positions.

http://in.schunk.com/in_en/press/presse-service/press-releases/#/article/2860-flexible-rotary-modules-compact-precise-and-dynamic

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