February 2020

47 www.drivesncontrols.com February 2020 Invertek Drives has installed a pair of collaborative robots to perform testing operations at itsWelshpool plant. The cobots can adapt to variations in products while ensuring worker safety. T heWelsh drives manufacturer, Invertek Drives, has incorporated two cobots (collaborative robots) into the testing phase of its production process, thus improving workflow consistency. Last year, Invertek opened a 5,500m 2 global manufacturing and distribution facility inWelshpool, with the capacity to produce up to 400,000 drives a year. This large output, along with a wide variation in product lines and tasks, meant that the company needed a flexible automation system to switch between different jobs and part sizes. With the support of RARUK Automation, Invertek installed a pair of Universal Robots UR5 cobots. “Our workloads can change every other minute, and we canmanufacture over 15,000 variations of our products,” explains Invertek’s manufacturing engineeringmanager, Peter Evans.“This means we need cobots that can handle the inspection and testing of constantly- changing devices, all within a single production line. “This is where our UR5s shine,”he adds.“Working 16-hour shifts, they can achieve this and so much more.” As part of its production process, Invertek conducts live tests on its drives. One reason for introducing the robots was to ensure the safety of its employees. Previously, workers had to enter the testing area to press a button, adding time to the test cycles. The deployment of the cobots has also significantly improved consistency in operations, as they can be used to undertake a task at fixed intervals. With work cycles normally requiring around ten minutes to complete, the company can now conduct more test cycles per hour. The cobots also play a major part in quality control thanks to a specialist end-effector that was designed by Invertek’s in-house manufacturing engineering team. Equipped with a Cognex vision system, lighting controls, a fan-speed sensor and robotic finger, the device is used for a range of complex tests such as visual inspection to ensure that the drives are operating correctly. n ROBOTICS AND AUTOMATED MANUFACTURING n One of Invertek’s collaborative robots showing its a custom- designed end-effector that carries out a range of tests including inspection using a vision system We‘ve produced a White Paper and a poster about Safe Human-Robot Collaboration... ... download them for free by visiting pilz.co.uk and entering Webcode 10980 ■ MTTF D = low, ■ MTTF D =medium, ■ MTTF D = high 0 0 1 Robotics Learnmore about RoboticsbyPilz Webcode: web10980 Services We're there for you:Pilz services throughout the lifecycle Webcode: ZHE Determinationof the requiredperformance level (PL r ) • S –Severityof injury S 1 = Slight (normally reversible injury) S 2 = Serious (normally irreversible injury includingdeath) • F –Frequency and/ordurationofexposure to ahazard F 1 = Seldom toquiteoften and/or the exposure time is short F 2 = Frequent to continuous and/or the exposure time is long • P –Possibilityof avoiding thehazard P 1 = Possible under specific conditions P 2 = Scarcelypossible • Probabilityofoccurrenceofahazardousevent A lowprobability can reduce thePL r byone level. HRC –Human-robot collaboration ISO/TS 15066 We automate.Andwe create.SafeHRC. Required performance level (PL r ) Low risk High risk Startingpoint for risk assessment PLdefinition foreach safety function Probabilityof adangerous failure perhour – comparisonPL/SIL PerformanceLevel (PL) inaccordancewithEN ISO13849-1 Relationshipbetween thecategoriesDC,MTTF d andPL Performance level PFH D 3 years 10 years 30 years 100 years AchievedPL≥PL r ? *InCat.4MTTF D up to2,500 a ispossible Cat.3 DC avg = low Cat.4* DC avg = high Cat.3 DC avg =med. Cat.2 DC avg =med. Cat.2 DC avg = low Cat.1 DC avg = none Cat.B DC avg = none 10 -4 a 10 -5 b 3×10 -6 c 10 -6 d 10 -7 e 10 -8 Lexicon • Category (Cat.) Classification of the safety- relatedpartsof a control system in respect of their resistance to faults and their subsequentbehaviour in the fault condition, andwhich is achievedby the structural arrangementof theparts, fault detection and/orby their reliability • Collaborativeworkspace Workspacewithin the safe- guarded spacewhere the robot and human canperform tasks simultaneouslyduring production operation • CommonCauseFailure (CCF) Failuredue to a common cause • DC avg Averagediagnostic coverage • Diagnosticcoverage (DC) Measure for the effectiveness ofdiagnostics;maybe determined as the ratioof the failure rateofdetected dangerous failures and the failure rateof totaldangerous failures • Fault Stateof an item characterized by inability toperform a required function, excluding the inability duringpreventivemaintenance orotherplanned actions,ordue to lack of external resources • Mission time Period inwhich theSRP/CS is used • MTTF D Average time todangerous failure • PerformanceLevel (PL) Discrete level to specify the abilityof safety-relatedparts of control systems toperform a safety function under foreseeable conditions • PerformanceLevel, required (PL r ) Performance level (PL) in order to achieve the required risk reduction for each safety function • PFH D Probability ofdangerous failure per hour • Quasi-staticcontact (clamping) Contactbetweenoperator and robot inwhich the operator’sbodypart is clampedbetween a fixed interfering contour and the robot • Risk Combinationof theprobability of occurrenceof harm and the severity of that harm • RobotCollisionMeasurement (RCMP) Designates themeasuring point for collisionmeasurement • Safety-related control function (SRCF) Control function implemented by anSRECSwith a specified integrity level that is intended tomaintain the safe condition of themachine or topreventan immediate increaseof the risk(s) • Safety-relatedpartof acontrol system (SRP/CS) Part of a control system that responds to safety-related input signals andgenerates safety- related output signals • Safety function Function of themachine whose failure can result in an immediate increaseof the risk(s) • ShoreA TheShore hardness is a core value for elastomers and plastics. It states the hardness of thematerial.TheShore scale ranges from 0Shore to 100Shore.A high number means a highdegreeof hardness. • SRECS Safety-RelatedElectrical ControlSystem • Transient contact (impact) Contactbetween operator and robot inwhich the operator is not clamped and can retreat • Validation Confirmationby examination andbyprovision of a certificate stating that special requirements for a specific intended use are met • Verification Confirmationby examination andbyprovision of a certificate stating that the requirements of the specificationhavebeen met Themeasures outlinedon this sheet are simplifieddescriptions and are intended toprovide an overviewof the standardsEN ISO12100,EN ISO13849-1 andEN ISO10218-2.Detailed understanding and correct application of all relevant standards anddirectives are needed for validationof safety circuits.As a result,we cannot accept any liability foromissionsor incomplete information. Do robot andhuman share aworkstation? Determinationof the typeofcollaboration Are therepoints ofcontactbetween human and robot? Dohuman and robot work simultaneously? Yes No No Yes No Yes Coexistence The humanworks at aworkstation near a robot’sworkstation. • There is nooverlapbetween the workspaces and nophysical contact when used in accordancewith its intendedpurpose. Sequential cooperation Human and robotworkon the same workpiece sequentially: if the human isworking, the robot is stopped.While the robot isworking, theworker is not present in the sharedworkspace. • When used in accordancewith its intendedpurpose, there is nophysical contactbetween the human and the robot. Parallel cooperation Human and robotwork at the same time in the sameworkspace. • Physical contactbetween human and robot ispossible. Collaboration The closest typeof cooperation: man and robotwork hand in hand. • Physical contact is necessary. Coexistence Sequential cooperation Parallel cooperation Collaboration Hand-guided robot? Reducing risk inhuman-robotcollaboration (HRC) Safety-related stop Explanationson theoptions for risk reduction Methodsofhuman-robotcollaboration in accordancewithEN ISO 10218-2 and ISO/TS 15066 Method1 – safety-rated monitored stop On entry into the collaboration zone the robotgoes into a safeoperating stop.Upon leaving the collaboration zone the robot resumes itsmovement automaticallyorby a reset.The speed isdetermined according to the risk assessment. Method2 –handguiding Thehumancanonlyapproach the stationary robot.Onoperationof the enablingdevice, the robot canbe guidedmanuallywith safely reduced speed.The speed isdetermined according to the risk assessment. Method3 – speedand separation monitoring Protectivedevices arepositioned in such away thatpeople can approach the robot at any timewithout any risk. Separation of the human and the robot ismonitored and the speed is adjusted accordingly.The robot switches off before a collision occurs. Method4 –powerand force limiting Acollisionbetweenhumanand robot is possiblewhen thebiomechanical limit values are compliedwith. Method 4 Quasi-static contact (clamping) Transientcontact (impact) Bodyarea (body region) Specificbodyarea Maximum permissible pressure PS (N/cm 2 ) Maximum permissible force (N) Maximum permissible pressure PS (N/cm 2 ) Maximum permissible force (N) Skull and forehead 1 Middleof forehead 130 130 130 130 2 Temple 110 110 Face 3 Masticatorymuscle 110 65 110 65 Neck 4 Neckmuscle 140 150 280 300 5 7 th neck vertebra 210 420 Back and shoulders 6 Shoulder joint 160 210 320 420 7 5 th lumbar vertebra 210 420 Chest 8 Sternum 120 140 240 280 9 Pectoralmuscle 170 340 Abdomen 10 Abdominalmuscle 140 110 280 220 Pelvis 11 Pelvicbone 210 180 420 360 Upper arms and elbow joints 12 Deltoidmuscle 190 150 380 300 13 Humerus 220 440 Lower arms andwrist joints 14 Radialbone 190 160 380 320 15 Forearmmuscle 180 360 16 Insideof elbow 180 360 Hands and fingers 17 ForefingerpadD 300 140 600 280 18 ForefingerpadND 270 540 19 Forefinger end jointD 280 560 20 Forefinger end jointND 220 440 21 Thenar eminence 200 400 22 PalmD 260 520 23 PalmND 260 520 24 Back of the handD 200 400 25 Back of the handND 190 380 Thighs and knees 26 Thighmuscle 250 220 500 440 27 Kneecap 220 440 Lower legs 28 Middleof shin 220 130 440 260 29 Calfmuscle 210 420 Measurementof forceandpressure inaccordancewith ISO/TS 15066 Thecombinationof variousmethods ispossible, suchas thecombinationofmethod3 and4. Hand guiding Speed and separationmonitoring Power and force limiting Forceorpressure Time Transient limit for the relevantbody region Quasi-static limit for the relevantbody region Unacceptable region for forceorpressure Acceptable region for forceorpressure Exampleof forceorpressure curve Biomechanical limit values from ISO/TS 15066 F T ,p T Maximum actual transient value F S ,p S Maximum actual quasi-static value 0.5 s AnnexGEN ISO 10218-2 Safety requirements for robot systemsand integration in accordancewithEN ISO10218-2 TableG lists the specific performance requirements that mustbe considered as essential andbe verified and/or validated. EN ISO 13849-1 Applicable forelectrical/electronic/programmableelectronic/hydraulic/ pneumatic/mechanical systems Specificationofcategories The solutions illustratedhere areprovidedpurelybywayofexample. CategoryB,1 Category4 Category 2 OSSD1 OSSD2 Category3 Instanta- neous Delayed Yes No Validation Body region Dampingmaterials forpressure measurement in accordancewith DGUV-FBHM-080 (ShoreA) Spring constants inaccordance with ISO/TS15066 (N/cm 2 ) Skull and forehead 70 150 Face 75 Hands and fingers 75 Neck 50 Lower arms andwrist joints 40 Chest 25 Pelvis 25 Lower legs 30 60 Thighs and knees 50 Back and shoulders 35 Upper arms and elbow joints 30 Abdomen 10 10 D=dominant ND=non-dominant Acc. toEN ISO10218-1/-2 PL r dCat.3 Services throughout the lifecycleofa robot system Pilz is here to support you in the implementation of relevant standards and directives: from an optimum safety strategy to a compliant robot application. The final piece of the offering is the range ofHRC training courses. Engineering Validation incl. forcemeasurement forHRC type 4 Training and TechnicalSupport RiskAssessment Safety andAutomation Concept S y s t e m I m p l e m e n t a t i o n ApplicationAnalysis InternationalCompliance Risk assessment We review your robot application in accordancewith the applicable national standards anddirectives and assess the existing hazards. System integration The results of the risk assessment and safety concept are implemented to suit the particular requirements through selected safetymeasures. InternationalCompliance Weensureconformitywith theofficial requirements, suchas CEmarking inEurope,orOSHA in theUSA,NR-12 inBrazil, KOSHA inKorea,GOST inRussia,orCCC inChina. Safetydesign A detailed planning of the necessary protectivemeasures reduces or eliminates the danger zones of the application. Validation Our expert specialist staff review and analyse the risk assessmentand safetyconcept and perform collision measurement in accordancewith the limit values laid down in ISO/TS 15066. Training and technical support Our training courses impart professional expertise relating to the safe application of robots.Our technical support team can be contacted round the clock. Safety concept We develop detailed technical solutions for the safety of your robot application throughmechanical, electronic and organisationalmeasures. 1 2 3 6 8 9 10 11 16 21 23 18 22 17 26 27 28 4 5 7 12 13 15 14 25 20 24 19 29 4 1 2 3 4 Lifecycle 1 4 3 4 1 3 4 3 2 4 4 3 2 1 8-8-en-3-173,2017-10,PrintedinGermany©PilzGmbH&Co.KG,2017 Safe Robot Applications ... ... we‘ve got it covered! Pilz Automation Technology, Telephone: +44 (0) 1536 460766 , Email: sales@pilz.co.uk The closer man and machine are able to work together the more efficient the work becomes, at the same time however this places greater demands on safety. Pilz is your perfect partner for the safe automation of your robot application: • A portfolio of services that are tailored to the individual life cycle of a robot system, from process analysis to risk assessment and CE marking • Safety solutions compliant with standards such as EN ISO 10218-2 and ISO/TS 15066 • Collision measurement in accordance with ISO/TS 15066 limit values • Training in the requirements of robot safety • Safe control systems and sensors • Participation in the formulation of standards for safe human-robot collaboration • Active cooperation with leading research centres Welsh drives-maker turns to cobots for testing