Totally PC-Based Control - Beckhoff Automation
APPLICATIONREPORT 12/2000Software PLC/NC and Hydraulics:TwinCAT for Control of Plastics Processing MachineryTotally PC-Based ControlIn planning their new Controls generation, Husky - global supplier of injectionmolding systems to the plastics industry- have embarked on an integralapproach based on an Industrial PC, fieldbus components and software fromBeckhoff‘s product portfolio. The challenge to be met by Beckhoff‘s solutionincluded a software PLC for machine control and a software NC for electricalaxes as well as integrated hydraulic drive and temperature control.Plastic products have become sofamiliar and commonplace thatpeople spend little thought abouttheir production as they usethem. Many plastic products aremanufactured by injection molding.The list of end-products is asendless as unspectacular: Dowels,yoghurt cups, ballpoint pen housings, beverage bottles, automotive rear lenses and bumpers,laundry baskets, buckets, containers for use in medical engineeringto name just a few of the vast arrayof more or less important thingsin our daily life. However, there isan obvious difference in the sizesof these end-products, from verysmall (e.g. model making components) to very large (e.g. automotivebonnets), and subsequently alsoin the size ranges of plastics injection molding machines. A distinctive feature is the clamp tonnagerequired to operate the mold fromwhich a plastic application springs.Plastics Injection MoldingMachines with a TwinCATHeartIn order to provide the requiredclamp forces, machine manufacturers employ either hydraulicunits or mechanically sophisticated, electrically driven clampmechanisms. However, the func-tional principle of an injectionmolding machine is the sameacross all sizes: Through a feedhopper the pelletized plastic material enters a plasticizing barrelwhere it is melted under the influence of a rotating screw and thetemperature exerted by band heaters around the barrel. As the meltcompresses in front of the screw,the mold (at left) is closed and thenlocked by applying a nominal forcewhich must be precisely maintained and controlled to prevent thehot melt from escaping at highpressure. Once sufficient melt hascollected in front of the screw, thescrew is used as a piston to inject
New Automation Technology in plasticsinjection molding machinerynthe material through the machinenozzle into the mold cavities, andto keep the melt under pressure.After a specific mold cooling time,the screw piston is pulled back.The mold is opened, and the molded parts are removed from themold cores either by means of anejection mechanism or by a robot.The machine cycle can then beresumed anew. Suitable machinesfor this process must meet a wholeset of requirements, importantly:1. High part quality: The optimized process and its parametersmust ensure a consistent production of good parts, i.e. with consistent physical properties (size,weight, density distribution, color,and even odor). Repeatability ofthe machine‘s mechanisms andcontrol are key.2. Short machine cycles: Asthe machines frequently run inunattended 24 hours operation,every tenth of a second saved inthe manufacturing cycle results inincreased part output.3. Ease of parameterizing andmaintenance: In the event of problems, the operator must be ableto troubleshoot them as fast aspossible, supported by convenienterror messages and additionalonline tools, such as repair workvideos. Machine visualizing software at the HMI (Human MachineInterface) plays a major role inHusky Injection Molding Systems Ltd.Husky was founded in 1953, and has emerged as the world‘slargest single-brand manufacturer of injection molding machines. With production sites at Bolton (Ontario, Canada, Milton(Vermont, U.S.A.) and Dudelange (Luxembourg), Husky employs 3,000 people worldwide who realized sales worth US 708 millions in the past fiscal year. Products include hydraulicinjection molding machines with clamp forces from 50 to 8,000metric tons, molds, hot runners, and removal robots.
Control Panel with TFT display,touch screen, softkeys, anduser ID systemmeeting this requirement.4. Effective operator protection:Hot melt and high pressures present a potential risk of injury whichmust be addressed both by designand by engineering control.5. Effective system protection:Jammed, sticking or partially removed moldings can damage themost expensive component on theinjection molding machine - themold. The slightest scratch in thecavity or core surfaces will be wellvisible on the molded product andcan render it unusable.6. Efficient use of resources:This includes reducing the environmental impact of the machineby minimizing start-up and production scrap (material consumption)as well as power and water consumption during production.Husky machines have hydromechanical clamps. The screws ofthe injection units are driven bya hydraulic radial piston or servomotor. Servo motor drives are alsoused on the removal robots.One Industrial PC Replaces4 Conventional ControlsTwo years ago, in response to therising requirements in the plasticsinjection molding markets, Huskydecided to make plans for introducing a new PC based generation of machine controls. A comparison between traditional controlarchitecture in plastics injectionmolding and advanced PC basedcontrol reveals the differences:Conventional concepts in thisapplication area are based onnumerous specialized controllersand hardware PLC. The PLCgoverns the global machine process and - on hydraulically drivenmachines - communicates with aninjection controller (IC), a clampcontroller (CC), and a temperaturecontroller (TC). On electrical injection molding machines there arefurther controllers for operating theindividual servo axes. The traditional HMI is based on an IndustrialPC still without any controller functions. And everything is wired inparallel in the control cabinet.Husky‘s new control conceptcombines all of these functions inan Industrial PC installed in thecontrol cabinet, where it replacesall former controllers and the hardware PLC. The machine signalsare collected and transmitted byway of a Profibus master cardand Beckhoff Bus Terminals connected to the fieldbus. Alsoconnected decentrally to theProfibus, non-contacting transducers provide the positioning information of the individual hydrauliccylinders.The operating unit is another Beckhoff standard product, aControl Panel without any intelligence of its own, linked to the PCby means of two coaxial cablesand featuring a TFT touch screen,softkeys, and a user ID system.Industrial PC, fieldbus, electronicterminal block - that‘s all. The hardware has been reduced to theessential. The separate electricalcabinet for the servo motor powercomponents has been eliminated,since these parts can now beinstalled in the free space gainedin the central control cabinet.Equally integrated, the software platform is based on the languages defined in the IEC 61131-3standard and has been designedas a software PLC in TwinCAT.It serves for close loop control ofall hydraulic cylinders and also forcontrolling the robot sequences,with a TwinCAT software NC fornumerical robot control. The keysoftware components for controlling a Husky machine can be organized in four task areas, furtherexplained on the following pages:- Hydraulics- Temperatures- Robotics- VisualizationHusky has many years of experience in close loop control ofhydraulically operated machineaxes (typically at least 8 permachine). In contrast to the past,the individual controls are no„black boxes“ anymore but can be
From dowels to bumpers - a widerange of plastic products are injection molded on Husky machinesavailable in a complete portfolio ofdifferent tonnagesconveniently generated and adapted under the IEC 61131-3 standard by Husky‘s hydraulics andcontrol specialists. Motion controlof a hydraulically operated positioning axis is not a trivial job. Thecontrol profile is non-linear andalso subject to limitations governedby the process technology. Duringinjection, for instance, the injectionpiston follows a multi-step forwardspeed profile while at the sametime limiting the injection pressure.As the piston advances, the control must provide for smooth transition to hold pressure depending onpiston position, injection pressurein the barrel, or mold cavity pressure. For suckback, the systemmust again switch over to speedcontrol with subsequent positioning control on the starting positionfor the next injection cycle.The scalability of the CPUs in anIndustrial PC helps to minimizeresponse times to milliseconds asneeded to control the high pistonspeeds during injection.Temperature Control withan IEC 61131-3 FunctionalSoftware BlockTemperature control is also programmed in the IEC 61131-3 languages. A plastics injection molding system can have more than100 control zones for heating themachine as well as the moldBeckhoff TwinCAT: PLC and NC on the PCThe TwinCAT software system (” The Windows Control andAutomation Technology”) transforms every compatible PCinto a real time controller with multi-PLC, NC axis control,programming environment and operating station. TwinCATreplaces conventional PLC and NC controllers as well as operating devices with:- embedding of Software-PLC and software-NC in Windows2000/NT, Windows NT Embedded, Windows CE- efficient multi-PLC with 4 PLC run-time systems per PCand cycle times from 50 us. The programming environment offers all languages of the IEC 61131-3 standard.- axis control for point-to-point positioning and interpolatedpath movement. Up to 256 axes can be positioned, dependent only on the efficiency of the PC processor. Specialfunctions such as ”cam plate” or ”flying saw” are supported.- connection to all common fieldbusses and PC interfacesfor I/O signals: Profibus, CANopen, DeviceNet, Interbus,Sercos, Beckhoff Lightbus and PC-Hardware- data sharing with user interfaces and other programsby means of open Microsoft standards (OLE, OCX, ActiveX, DCOM , OPC etc.)
New Automation Technology based of standard Control Panelfrom Beckhoffand its hot runner manifold andnozzles. The temperature controlblocks, developed in cooperationby Husky and Beckhoff, provideconvenient functions e.g. selftuning, adaptive power-up, smoothswitch-over from manual to automatic mode, predefined responseto hardware failures such as thermocouple breakage, open heater,etc. The function blocks can beinstantiated. In other words, addinga heating zone is the same as defining a variable.Control of the electrical robotaxes is programmed by using predefined function blocks for axialmotion control, available in theTwinCAT NC library. As TwinCATsupports various different fieldbussystems, Husky selected SERCOSfor the drives.The fourth software component- visualization - has been designedby Husky to run under WindowsNT. The operating philosophy isfocused on touchscreen operationcombined with the softkeys ofBeckhoff‘s Control Panel. Criticalmachine functions, for instance allthose involving mechanical movements, are initiated by means ofPLC keys below the screen, i.e. forthe PLC to check before enablingthe requested function. TwinCAT‘ssoftware interface provides accessto control parameters, alarm messages, time records, statistics, etc.User access is authorized andcontrolled by means of a memorychip in the size of a keyring pendant. This ID token is plugged intothe Control Panel and can store upto 32 kB of data, including e.g. theuser‘s profile.Cui Bono?Obviously, important benefits arecost savings derived from the useof a fieldbus system and eliminating specialized control hardware.The control solution can be adapted as required through the performance of the selected IndustrialPC. The overall control configuration has become more transparent for Husky and is based onstandards e.g. Windows NT/2000and IEC 61131-3. This means thatHusky has complete control of itsinjection molding as well as theentire engineering control knowhow. And while it is not accessibleby the regular machine operator,TwinCAT always provides a runtime and programming environmentright at every machine. This opensthe familiar possibilities of thePC world, such as high-capacityhard disk drives, teleservice bymodem and Ethernet, links tofurther machines by serial interfaces or LAN, communication withSCADA systems, and use of external, Windows-compatible processoptimization software.For the future Husky has recognized a need to focus on modularmachine design and „zero engineering“ tools for simplified programming and flexible response tocustomer and market needs. Beckhoff TwinCAT has become a central pillar in this architecture.
rent for Husky and is based on standards e.g. Windows NT/2000 and IEC 61131-3. This means that Husky has complete control of its injection molding as well as the entire engineering control know-how. And while it is not accessible by the regular machine operator, TwinCAT always provides a runti-me and programming environment right at every machine.
Operating instructions for AX5801 TwinSAFE drive option card for the AX5000 servo drive Version: 1.2.1 . 2 EL1904 4 Appendix 15 4.1 Beckhoff Support and Service 15 4.1.1 Beckhoff branches and partner companies Beckhoff Support 15 . Beckhoff , TwinCAT .
4.1.7 Tested EL1904 devices 26 . 5.1.1 Beckhoff branches and partner companies Beckhoff Support 58 5.1.2 Beckhoff company headquarters 58 5.2 Certificates 59. . These operating instructions were originally written in German. All other languages are derived from the
The simple route from data recording to the dashboard The Beckhoff principle is simplicity in itself: Beckhoff makes the route from data recording in the field to communication and historicisation through to data analysis in the framework of a user-specific HMI concept a comparatively sim
guard locking is controlled by a safe output of an EL2094 from a Beckhoff control system. The two safe outputs of the CET3 are connected to a safe input of an EL1904. Connections . Designation Function Use in this example . OA, OB Safety outputs. HIGH when the safety guard is closed and locked. Switch-off of at least one of the outputs must lead to
automation project engineering in Visual Studio built-in connection to source control systems expandable with add-ons for features such as data connectivity right engineering software version always available for any given machine Software quality and APIs Standard tool
tions, CNC functionality and the standardization of the PLC. During this procedure, Beckhoff emerged as a suitable supplier, so that further con-crete tests, in particular in the EMC-critical environment of plasma cut-ting machines, were carried out in 2001. Since the start of the project in summer 2002, Messer Cutting & Welding and Beckhoff .
New Automation Technology philosophy represents universal and open control and automation solutions that are used worldwide in a wide variety of different applications, ranging from CNC-controlled machine tools to intelligent building automation. The central divisions of Beckhoff, such as development, production, administra-
Fedrico Chesani Introduction to Description Logic(s) Some considerations A Description Language DL Extending DL Description Logics Description Logics and SW A simple logic: DL Concept-forming operators Sentences Semantics Entailment Sentences d 1: d 2 Concept d 1 is equivalent to concept d 2, i.e. the individuals that satisfy d 1 are precisely those that satisfy d 2 Example: PhDStudent .
