Safety without the need for protective fences
By Michael Sanchez, Field Sales, SICK Vertriebs-GmbH, Düsseldorf
Tuesday, 27 March, 2018
With the help of safety laser scanners from the microScan3 product family, as well as the Flexi Soft safety controller, shoe machinery engineer DESMA has ensured the safe operation of a robot on an injection moulding machine. The electro-sensitive protective devices allow a person ergonomic access to the machine for process-orientated material staging and removal. The robot automatically picks up the raw material provided as soon as the safety perimeter is clear and dispenses the processed silicone and rubber parts. At the same time, the safety laser scanners are especially economical on space and, therefore, do not impede the process.
The safety concept for the robot on the DESMA injection moulding machine was developed in close collaboration between application consultation personnel at SICK and specialist departments at DESMA. It combines a horizontal 275° protective field used to monitor the hazardous area in front of the robot with vertical protective fields for hazardous point protection in the work area. When a person approaches the robot, a horizontal safety laser scanner detects this at an early stage, slowing down the robot in a controlled manner to avert any danger from its movement. As a result, it has been possible to significantly reduce the necessary safety distance between the vertically monitoring microScan3 and the hazardous movements of the robot — and therefore also minimise the total space required for the machine and its safety technology.
A further microScan3 monitors the robot’s delivery table. If the machine operator needs to change a tool, for example, and in doing so stands on the table and therefore inside the monitored area, the safety laser scanner will detect this, and the robot will be prevented from starting. The entire safety-related application can, therefore, be operated with automated restart, therefore without manual restart interlock. Since the safety technology follows the workflows entirely autonomously, workers no longer perceive it as a nuisance, since they are not required to interact with the machinery by pressing a restart switch explicitly. The required logic for this and integration of other safety components, such as the emergency switching off button, is provided in the Flexi Soft safety controller. The collectively developed protection concept offers the highest levels of performance and availability for the machines processing silicone and rubber at DESMA. This is greatly due to the innovative safeHDDM scanning technology of the microScan3.
When a person approaches the robot, a horizontal safety laser scanner detects this at an early stage, slowing down the robot in a controlled manner so as to avert any possible danger from its movement.
Injection moulding machines
Klöckner Desma Elastomertechnik GmbH in Fridingen is a premium system-based solution for a whole host of industries. They realised their ambition through individual turnkey system solutions for the production of technical rubber and silicone moulded articles. With this in mind, the company offers injection moulding technology, tool manufacturing and automation engineering from a single source. It is in this way that the injection moulding machines fulfil customer and industry-specific requirements and enable safe processes. This facilitates the highly profitable production of rubber and silicone moulded parts used in vehicles, ships, power supply plants or medical devices.
Human-robot cooperation for automated material transportation and removal
Forward-thinking technologies are a key feature of DESMA injection moulding machines. This outlook also applies to their production methods, which produce technically and economically efficient rubber and silicon processes. Areas for improving productivity are work environments where humans and robots share the space at different times. This human-robot collaboration (HRC) enables highly optimised workflows and improves plant availability, productivity and economic efficiency. That is why DESMA has developed this cooperative workspace for its injection moulding machines, which sees a worker supply blanks and the robot act as a production assistant by taking hold of them and inserting them into the machine. Once the blanks have been machined, the robot removes them, gives them to the operator to take away and inserts the next blanks. The process sequence highlights how important it is for workers to have unrestricted access to the machines. Protective fences or other mechanical devices around the HRC workspace will cease to exist at DESMA.
Horizontal and vertical protection with microScan3 safety laser scanners
An injection moulding machine manufacturer has found a solution for this robot application through an electro-sensitive safety system, which eliminates the risk of accidents for operators and grants them unrestricted access to the machines. Connected to the Flexi Soft safety controller are a total of four microScan3s, two with horizontal and two with vertical pairs of protective fields. Regarding object resolution, these can be configured in steps between 30 millimetres, hand detection, and 200 millimetres, body detection. This means that a single microScan3 can work with several protective fields in various resolutions. The integration of these compact and reliable devices is incredibly simple. Mechanically, it involves a shock- and vibration-resistant mounting system, and electronically, the devices are installed via an eight-pin M12 standard connector. The protective fields to be monitored have a scanning range of up to 5.5 metres and can be easily and directly defined in the machine layout using the Safety Designer software and a laptop. This configuration via USB can then be saved in the safety laser scanner. While in operation, the microScan3 multicolour display shows the operational status of the system, and additional information can be called up as cleartext by using the push-buttons on the control panel.
The technological highlight of the microScan3 safety laser scanner, which meets performance Level D in accordance with EN ISO 13849 and SIL2 in accordance with IEC 62061, is its safeHDDM scanning technology (short for high definition distance measurement). This high-resolution digital process for safety-related time and distance measurement sends out more than 100 times as many laser pulses as other time-of-flight measurement systems. The benefits, especially insofar as the protection of HRC scenarios, are seen on the DESMA injection moulding machine.
Stable measured values for enhanced productivity
The multipulse process in conjunction with focused, digitalised evaluation enables much more stable measured values to be generated and also reliably detects predefined minimum remission values of 1.8%, without them being masked by interference signals. The reliable evaluation methods of this scanning technology ensure, for example, maximum availability in the presence of dazzle, dust or other environmental influences.
Codified pulses prevent mutual interference
The laser pulse time coding of each safety laser scanner is particularly crucial if, as in the case of DESMA, many devices are being operated at the same time and within proximity of one another. To protect the robot on the injection moulding machine, a total of four microScan3s are installed at the robot table at a height of around 200 millimetres. Two of these generate vertical protective fields, which meet at a 90° angle to provide access protection; the third and fourth safety laser scanners are installed horizontally, on and in front of the robot table, to provide area protection. Although the safety laser scanners could be subject to mutual interference, this issue does not arise for the microScan3. The laser pulses of each device are coded by a time delay of a few nanoseconds — and an integrated random generator additionally modifies their sequence. Therefore, the occurrence of two identically encoded scanner sequences — and with it, the danger of mutual interference — is about as likely as a jackpot win on the lottery. Other sensors and sensor systems that use laser LEDs as light sources do not impair the safety function and availability of this new scanner generation.
Increased immunity to dazzle, dust and deposit formation
HRC applications are used in standard production, mounting and logistics environments. The microScan3 safety laser scanners as the HRC monitoring solution for the DESMA injection moulding machine must be able to cope with the anticipated ambient conditions. With their safeHDDM scanning technology, they achieve an unrivalled level of ambient light immunity of up to 40,000 lux. They are, therefore, practically immune to dazzle — no matter whether it is from bright sunlight, high-frequency, artificial ambient lighting or light sources, or reflections shining directly into the optics. What’s more, the evaluation by safeHDDM ensures that the reliability of the detection and protective functions is not impaired either by dust particles in the environment or by deposit formation on the optical interface of the sensors. Furthermore, the microScan3 safety laser scanner features a parabolically curved front screen. This deflects reflections that arrive outside of the optical path of the laser pulses and their remissions into an optical trap — away from the receiver element in the device. This also increases the immunity to dust and deposit formation and the mobility of the robot on the injection moulding machine.
Expertise in designing safe robot applications
The microScan3 product family has brought about a change in the active scanning safety laser scanner market, delivering benefits concerning safe and highly available human-robot interaction in particular. The microScan3, as well as the Flexi Soft safety controller, belong to a range of sensors and controllers that has developed along with the requirements of safe robot applications over the decades.
Safety solutions based on various technologies are becoming more and more intelligent and are constantly making possible new HRC applications with increasingly demanding requirements.
When it came to choosing SICK as its implementation partner for this HRC application, the decisive factor for DESMA was the fact that SICK had a wide range of product and system solutions. SICK was also able to offer a high level of consultation expertise in the field of safety technology, as well as comprehensive services with respect to safety concepts, according to Heiko Wolters, Team Leader in Hardware Development at DESMA.
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