This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at El cálculo del movimiento residual en máquinas: ¡Cada milisegundo cuenta!
Practical example in a test of the German company Weber Systemtechnik
The calculation of the residual movement in machines: every millisecond counts!
Ulrich Bernhardt, responsible for sales of Schmersal GmbH15/10/2010
The residual movement is a critical parameter in the hygiene of the machines. The Group Schmersal offers a service of real and reliable measurement of this movement. The following practical example explains it in detail. In many respects of the hygiene of the machines, the residual movement is an important parameter that has to register, for example in equipment with movement of dangerous inertia. In this case, it is necessary to guarantee that the blockade by solenoid, only allow the opening of the protect mobile when the dangerous movement have deleted or the machine have detained . To such effect use timers, detectors of real unemployment of engine or controllers of speed properly adjusted.
Important Singularity for protection in optoelectronic devices
The residual movement is of vital importance in the protections optoelectrónicas (due to its uniqueness as immaterial barriers). In this case, the distance between the protection and the dangerous movement, should adjust so that any situation of risk arising from the use of the machine, is removed before the operator reaches the dangerous point.
The norm UNE EN 999 (' security of plot them: positioning of the devices of protection depending on the speed of approximation of parts of the human body ') contains detailed instructions for the calculation of the corresponding safety distance. In this calculation, is an important time of response or reaction of the components of the circuit's safety.
Experience has shown that the residual movement of a machine or production line can vary as a result of circumstances such as: the mechanical wear, the use of a tool or robot gripper heavy in a press, or the use of a tool with a different geometry, among others. All these situations have the same result: the operator is not adequately protected.
Measurement of the residual movement service
To avoid this dangerous situation, we need to make periodic measurements while the machine is in operation. The Schmersal Group offers certified measurements, in measuring the residual movement and, in the first analysis, is also a comprehensive audit of compliance with the standards harmonized with the machinery directive 2006/42 and security technology. To measure the residual movement presses (for example) analyses the worst possible situation, i.e. the time in which force or momentum reach the peak.
The residual movement is of vital importance in the protections optoelectrónicas, due to its uniqueness as immaterial barriers
Necessary in new lines
This service offered by Schmersal is used not only for existing production lines, but also for the certification of the technology of safety of machines and new lines. Clearly shows it the example of a test bench of Weber Systemtechnik GmbH, located in the German town of Welzlar. This company creates and manufactures individual lines aimed at automation technology and especially the realization of technical tests.
The teams are electronic, optical and tactile parameters. Weber Systemtechnik has developed a line to a supplier of parts for automotive, which measures the performance of the injectors of a car forces. Once the operator has placed the injector in the test, a robotic arm equipped with a sensor running individual performance operations and measures force or, more specifically, the resistance exerted by the control elements. The machine not only checks the forces, but it also analyzes the measurements. To this end, the provider has the specifications laid down by the manufacturer, properly documented and tested.
The operator transmits the signal for activation of the optoelectronic safety barrier. The residual movement is then measured. Photo: Weber Systemtechnik GmbH.
A compact robotic station
The test bench is mounted in a compact robotic station, whose entrance is protected by a curtain optoelectronics of SLC 429 security of Schmersal Safety Control GmbH. The absence of conventional mechanical guards, provides the operator with the necessary flexibility. To ensure the safety of this equipment, Weber Systemtechnik and Schmersal calculated the distance of security specified by the standard UNE EN 999.
According to engineer Uwe Bernhardt, responsible for the product line of automation of processes of Weber Systemtechnik GmbH: "to begin with, the provision must be correct: the robot must be mired in the security zone when does the response of the guard". Thus, the response time of the optoelectronic device and the proper evaluation of the signals of safety are essential for the safe of the test bench construction.
Maximum expectation: how hard the residual movement? The result is reassuring: the machine is safe. Photo: K.A. Schmersal GmbH.
Checking and measurement of the residual movement
Once completed the installation, Weber Systemtechnik decided to show your client that the security of the line technology complies with all the harmonized standards. This meant that the company could verify that the intangible barrier was installed so that the existing dangers would be contrarestados, and interconnection of safety signals meet category from control (or PL) required throughout the chain of transmission. Finally, had to measure the residual movement of the robot to ensure that the safety of the barrier distance was enough. This service is included in the offer of the Schmersal Group (Division of consulting in security).
A specific measurement equipment
For these tests, using a specific measurement device developed by EDAG (Engineering + Design AG). A chronometer of high precision, capable of measuring in milliseconds, because you're a coder who enters the danger zone. As a result, turns the curtain safety optoelectronics and stops the movement of the robot. The robot arm, which activates the elements of adjustment of the nozzle (reproducing the effects of the flow during normal operation), is equipped with a sensor of drive connected to the metering equipment.
Protocol for measurement of the residual movement. Photo: K.A. Schmersal GmbH.
In this way, the metering equipment estimated residual movement, i.e., the time lag from the access to the machine through the intangible barrier to the arrest of the movement of the machine or disappearance of the dangerous situation. During this process, carried out various measurements and a protocol of tests certifies the verification of the machine. In this way, the manufacturer guarantees the safety of the machine. Throughout the service are also checked all the other aspects of security in parts of the system of command, both in the peripheral circuits.
Measures must be made on a particular object, that residual motion of the robot depends, inter alia, of the used tool and the weight of the manipulated material. Thus, the corresponding value may not weigh for different tools or processes, or can be calculated in a purely mathematical way. The manufacturer of the robot need to specify the actual residual movement for each specific charge and a useful given.
The end result: the machine is safe
In the case of Weber Systemtechnik, the first audit showed the total fulfillment of standards harmonized with the machinery directive 2006/42. The results of the measures were clearly within the limits specified in the standard: the residual movement was not critical at all, taking into account the safety distance selected for the erection of the barrier. Weber Systemtechnik received a report of all the verification carried out in a document that presents the measurements and certifies the conformity of the team of tests with the directive and the harmonized standards.
The manufacturer guarantees the CE marking of the machine, and can convincingly demonstrate customer the safety of the test bench.
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