Page 28 - Industrial Technology September 2020 issue

MACHINE BUILDING

Networked brakes turn

machines into smart robots

BRAKES, CLUTCHES AND COUPLINGS

BE IT AN INDUSTRIAL ROBOT OR THE SERVO AXES IN A
MEDICAL MACHINE, MOVED LOADS MUST NOT DROP OR CRASH
IN AN UNCONTROLLED MANNER AFTER POWER SWITCH-OFF OR
IN THE CASE OF POWER FAILURE OR EMERGENCY STOP. WITH A
COMBINATION OF TECHNICALLY LEADING BRAKE TECHNOLOGY
AND INNOVATIVE MONITORING SOLUTIONS, THE HURDLES CAN
BE OVERCOME AND ROBOTS MADE SMARTER

obots are gaining ground. In all important Furthermore, the brakes impress users
industrial sectors, the cooperation between with their high permitted friction work during
humans and robots is becoming increasingly dynamic braking actions: For servo drives,
Rcloser. This increases the risk potential. If, for normally load mass ratios (load/motor) of 3:1
example, a power failure occurs during a working process, or smaller are selected for the benefit of good
the robot arm undertaking the working step must be held control characteristics and high dynamics. On the brakes tensile force reserve, ie whether the magnet is still able to
immediately and accurately. Therefore, it is important to of renowned manufacturers, high permitted friction work attract the armature disk.
permanently exclude the risk of an inadvertent descent of and friction powers mean that load mass ratios of 30:1 On reaching the tensile force reserve, the Roba-brake-
the load as well as unpermittedly long stopping distances and more are possible. checker emits a warning signal early enough so that a
already in the design phase. certain operating time for the brake is still possible. During
Decisive for this purpose are the correct selection of Short switching times this time, maintenance is possible in a targeted manner,
safety brakes as well as their proper integration into the Short stopping distances are important for the safety of aligned to the working process. This in turn ensures higher
overall system. Safety brakes according to the fail-safe people and machines. The brake switching times are system availability. In a further expansion stage, the
principle are the first choice for servomotors, as these decisive for the braking distance, because during the free- module can also be integrated into a remote maintenance
brakes are closed in de-energised condition. They provide fall time until the brake closes and the retardation takes system via a suitable interface. This further reduces
the required braking torque even in the event of an effect, the mass additionally accelerates – possibly to such service times and costs.
emergency stop, a power failure or in case of an extremes that the permitted values of the brake are If damage should occur nevertheless, the Roba-brake-
interruption in the power supply caused by cable exceeded. Users should therefore pay attention to verified checker provides users with significantly better analysis
breakage, for example. To ensure that the safety brakes switching times which are as short as possible when options. With previous solutions, such as contactless
also provide sufficient friction work in emergency stop selecting safety brakes – and also assure themselves that release monitoring, users are only able to see the failure
situations and brake movements with a defined braking these switching times can be maintained throughout the and the destruction pattern. They do not know, however,
torque, a friction lining developed for this purpose with a entire lifetime of the brake. why the error occurred. However, using the Roba-brake-
corresponding steel counter friction surface is required. Here, monitoring solutions are important. Previously it checker, progressions are made visible and error analysis
There are safety brakes for servomotors which are was not possible to monitor servo brakes due to the small can be used and even transferred onto other user systems.
specially adapted to the high requirements of robotics. air gaps. This is a concern in view of the increasing All this data from malfunctions and normal operation thus
Users can choose between classic servo brakes in the networking of machines. Of course, the control and supply valuable input for future optimisation.
motor, with hub and toothed rotor or so-called pad regulation electronics of the servo system provide data To guarantee that the brakes always ensure the highest
solutions with large inner diameter. The latter are specially that also allow conclusions to be drawn regarding the level of safety in the respective application, it is important
designed for integration into the robot joint. But even the state of the overall system. But the safety brake itself that the static and dynamic braking torques correspond to
classic brakes can be adapted to customer specifications remains silent. Even though in closed systems data from the respective customer specifications. For this purpose, it
and integrated directly into a joint. In the motor, servo the brake would also be very helpful and would enable, for is necessary to check these two application conditions in
brakes are preferably installed into the A-bearing shield, example, predictive maintenance. If, for instance, the trials. Therefore, it is highly recommended that users
because the fixed bearing is located here and temperature friction lining reaches the end of its service lifetime, obtain information about the manufacturer’s test field, and
expansions cannot influence the brake severely. intelligent monitoring could provide timely warning. The question whether the brakes are subjected to tests that are
However, brakes from renowned manufacturers can maintenance date could then be scheduled long-term for as realistic as possible.
also be integrated into the B-bearing side of the motor a time window that is favourable in terms of the overall In addition to quality assurance measures during the
without restriction, as here temperature expansions and operating process. Monitoring is therefore also very useful construction process, a manufacturer should also carry
bearing backlash do not influence the function and for these safety brakes integrated in servo drives. out a comprehensive final inspection. This means that
reliability of the brakes negatively. Alternatively, users can May Power Transmission offers exactly these every single safety brake which leaves the plant is
also make use of mounted brakes, which are attached to possibilities with its intelligent Roba-brake-checker subjected to a 100% inspection following assembly and
the motor in a modular fashion.High-quality servo brakes module. It works without sensors. Instead, it detects the adjustment. At Mayr, all the determined measurement
are also characterized by compact dimensions. Not only movement of the armature disk by analysing current and values are archived together with the corresponding serial
are they very lightweight, but also extremely fast when it voltage, and knows what condition the brake is in. From numbers of the brake in an electronic database. Only
comes to magnetic actuation. At the same time they the control cabinet. In addition to the switching condition, in this way 100% traceability can be ensured.
display high performance density and wear resistance. temperature and wear, it monitors the tension path or MORE INFORMATION: www.mayr.com

28 INDUSTRIAL TECHNOLOGY • September 2020