Chapter 1 IntroductionIndustrial automationhas evolved to a stage where numerous other technologies have emerged from itand have achieved a status of their own.
Robotic automation is one suchtechnology which has been recognized as a specialized field of automation wherethe automated machines have some human like properties 1. The Robotic Industries Association (RIA) defines an industrialrobotic manipulator as follows: “An industrialrobot is a reprogrammable, multifunctional manipulator designed to movematerials, parts, tools, or specialized devices through variable programmedmotions for the performance of a variety of tasks” 2.Industrial robotsare employed to automate a wide range of processes which are generally toodull, dangerous or dirty for human operators. Moreover, advance roboticmanipulators have enabled us to achieve new levels of precision, accuracy,repeatability and productivity which are of prime importance in many modernengineering applications. Robotic automation is mostly used in the followingindustrial applications: · Assembly· Machine Tending· Welding· Material Removal· Material Handling· Palletization and De-Palletization· Vision InspectionIt can be inferred,from the above definition, that a robotic manipulator enables precise motionalong a pre-defined trajectory. But a complete robotic automation solutioninvolves much more than just achieving desired movements.
Each application hasits own special need, leading to a complicated design, simulation andconfiguration process, which makes robotic integration very cumbersome and timeconsuming. Selecting the rightrobotic arm, peripheral equipment and end-effectors has critical importance fora robotic application.Material handling in a press line, for example, requires highly customizedend-of-arm tooling with suitable end-effectors, with or without specialfunctions, to perform the desired task. These components varywith the process, material type, material properties like temperature and surfacefinish, the automation function and many other factors. Additional requirements like automatic tool changing and more degrees of freedom, required forhigher production flexibility, makethe integration process even more complex.The emergence of new robotic applications every year coupled with increasingdemand for customized robotic solutions has significantly increased the varietyof components required to maintain a certain level of customization.
Therefore,it becomes very important to develop standardized methodologies fordesigning, configuring and integrating robots in order to keep product complexity under control. The followingsection describes the research motivationand objectives of this thesis project.1.1 Research MotivationThe advent ofIndustry 4.0 has greatly affected the manufacturing industry. The full impactof the fourth industrial revolution on the manufacturing world is yet to bediscovered.
But it can be considered as a futuristic model of growth anddevelopment which would lead to the creation of “smart factories”. Thesefactories of the future would be characterized by a high level of wirelessconnectivity and data sharing between machines through the power of IoT.Another salient feature of these factories would be modular physical structureswhich could be replicated in the virtual world to control and monitor processesto make decentralized decisions. In order to achieve this, a high degree ofstandardization of manufacturing equipment and processes is needed.Robotic automationhas been identified as one of the key technology drivers of the fourthindustrial revolution. This means that industrialrobots will play a major role in realizing the factories of the future.
But as introduced earlier, the process ofintegrating robotic equipment in a production process is slow and complicateddue to the highly specialized and customized natureof its configuration. This also leads to variety induced complexity and causesdifficulty in managing automation projects effectively. Hence, there isa need to develop innovative solutions to standardize the robot configurationand EOAT design process without compromising on flexibility and customization. 1.2 Aim and ObjectivesWithin the scope ofthis thesis, titled as “Definition and creation of robotic automationmodelling- and configuration-kit for composite forming functions”, the primaryobjective is to create standard pre-configured construction modules for easydefinition and design of robotic automation functions used in the compositeforming industry. The secondary objective is to develop a configuration toolfor easy configuration and project cost calculation.
This modelling andconfiguration-kit aims to reduce the variety of different components andfunctions required to configure a robotic automation function in an automatedproduction line for a more effective project process and reduced design andstartup work. It also aims to balance theopposing forces of standardization and customization to minimize complexitycosts in a company. The tasks definedto achieve these objectives are as follows:· Assimilation of compression molding processesand robotic automation functions used in a Dieffenbacher composite productionline.· Definition of standard EOAT sizes and masses forrobotic loading, unloading, stacking and de-stacking functions.· Definition of standard robot categories based onload calculations for about 70% of all robotic applications at Dieffenbacher.· Creation of robot peripheral constructionmodules.· Definition of a standard EOAT structure andcreation of standard EOAT construction groups and modules.· Design and definition of interfaces betweenstandard modules.
· Finding ideas and specifications for developinga configuration tool.· Development of the configurator application.· Testing the configurator with past projects astest cases.1.3 Thesis OutlineWith the aim,objectives and tasks laid out for the thesis project, chapter 2 starts with abrief introduction to the company Dieffenbacher, which then leads to adiscussion about processes and technologies used in the Composites division.This helps in establishing the role of robotic automation in an automated pressline. The robotic functions required in each compression molding process alongwith composite material properties are highlighted in this chapter. Chapter 2 Technology and Process OverviewThis chapter startswith a brief introduction to the company Dieffenbacher.
Following is adiscussion about relevant processes, technologies and functions from BusinessUnit Composites to understand the role of robotic automation in a fullyautomated press line.2.1 The Company DieffenbacherDieffenbacher is an internationally active group ofcompanies with over 1700 associates and 16 production sites and sales officesworldwide. The company specializes in the mechanical engineering and plantconstruction sector and is one of the leading manufacturers of press systemsand complete production systems for the wood, automobile, and supplierindustries.
As an independent fifth generation family owned company, they havestood for continuity, tradition and reliability for over 140 years. About 70%of all products are exported internationally and the worldwide service andsales network guarantees every customer the fastest possible support.The company can be divided into three main business units:1. Wood-based panels2. Composites3. Recycling Figure1Business Unit Composites of Dieffenbacher The wood division is the largest business unit which offerscomplete production lines for the production of particleboard MDF, OSB and LVLpanels as well as fiber insulation panels and molded door leaves. The customersof this business area are predominantly found in the woodworking, furniture,construction and energy industries.
The composites division is involved in processes, pressesand fully automated production lines developed and realized for the productionof light weight fiber reinforced plastic components. Most of the customers arefrom the automotive and supplier industry.The recycling division focuses on development of completerecycling plants for treatment of different waste materials through mechanicaland biological means for the extraction of secondary raw materials or energy.2.
2 Press TechnologyThe composites division specializes in thedevelopment of press systems available in standard and high-accuracy variantswith or without active servo-controlled parallel motion systems. The pressesare designed by keeping in mind the requirements of the plastic and compositeforming industry. Depending on customer requirements, Dieffenbacher is able tosupply suitable press systems with process-oriented controls. Figure2 Dieffenbacher Press Types There are currently three different presstypes:1. Dieffenbacher Compress Lite (DCL)The DCL press type is available in anupstroke and short-stroke design with a low overall height and an energy-savingdrive. The bevel deflection line provides an even bend progression of the upperand lower die. The high-precision parallel motion behavior ensures a consistentcomponent thickness and increases the quality of the components. The Liteconcept provides exceptional flexibility and rapidness in die changing due toits 4-sided accessibility.
2. Compress Eco (DCE) 3. Compress Plus (DCP) 2.3Compression Molding ProcessThis project focuses on finding standard solutions forrobotic handling of advance composites in a compression molding line. Materialcharacteristics like temperature, surface quality and stiffness determine thetype of end-effector suitable for its handling.
These properties depend on thematerial handling function and the type of compression molding process.Therefore, it is very important to analyze these processes and their productionlines in order to understand different robotic functions. This understanding islater used to define the right end-effector for each robotic function.
Compression molding is a composite forming process in whichthe preheated molding material is positioned in the cavity of a molding tooland formed by application of external pressure and temperature. Pressure is animportant process parameter and is generally controlled by a mechanical press.The ability to produce lightweight parts with high strength and complexgeometries makes this process suitable for a wide range of industries. Anotherreason contributing to the popularity of compression molding is the possibilityof using advance composites. Advance composites include fiber reinforcedcomposites (FRC) which contain dispersed fibers in a continuous matrix phase. Carbonand glass fibers are the most widely used reinforcements.Depending on the material hardening principle, compressionmolding can be classified into the following types:1.
Thermoset 2. Thermoplastic Figure 3 Compression Molding Processes 2.3.1 Thermoset In compression molding of thermosetting compounds, the hardeningprocess involves a chemical reaction called curing. Curing is irreversible innature due to cross linking of polymer chains.
This chemical bond formationrequires application of heat. Once solidified, further heating does not lead tomelting but causes thermal decomposition of the compound. Hence, they cannot bereshaped. They require low internal mold pressures of 40-100 bar and pressurebuild up time of about 1 second. Due to curing, the forming process isrelatively slower with lower press velocities and longer cycle times (60-180seconds).
Dieffenbacher provides complete production lines for thefollowing thermoset forming processes:1. SMCSMC stands for sheet molding compound which is a compressionmolding process as well as a fiber reinforced composite. The compound iscomposed of carbon or glass fiber reinforcements which are dispersed in an epoxyresin matrix. It is tacky, plastic and flexible in nature and supplied ascontinuous sheets. Figure 4 shows the layout of a typical Dieffenbacher SMCDuroline.. Figure 4 Fully Automated SMC lineThe SMC Duroline is a near unmanned complete production lineincluding milling, drilling and water-jet cutting stations (11) for finishing theformed SMC components. SMC sheets are unwounded at the unwinding station (1)and reduced to desired shapes and sizes at the cutting station (2).
The feedingrobot (5) transfers the cut sheets from the conveyor (3) onto a stacking table(4). The stacking table monitors the weight of the stack to control the volumeof SMC material being loaded into the press. The feeding robot then transfersthe SMC stack into the mold cavity (8) of the high precision press (7). Theunloading robot (9) transfers the finished components onto a cooling station(14). The mold cleaning robot (10) enables automatic press mold cleaning aftera fixed number of cycles.
SMC is suitable for manufacturing automotive componentswhich require excellent surface qualities like bumpers, air deflectors,fenders, front panels etc.2. D-SMC The SMC Directline process provides higher process stabilityand higher material quality by elimination of semi-finished processes.
InD-SMC, the semi-finished product is directly manufactured in the productionline before processing. This provides higher flexibility in recipe formulationand helps in reducing storage and transportation costs. Further processing ofthis material is similar to a conventional SMC production line. Figure 5 showsa schematic representation of a Dieffenbacher SMC-Directline.Figure 5 Dieffenbacher SMC DirectlineThe robotic automation functions and material propertiesencountered at different stages of the production process in a SMC-Directlineare comparable to the conventional SMC process.3. HP-RTMHigh pressure resin transfer molding is a resin injectioncompression molding process which uses a carbon fiber reinforced plastic (CFRP)preform as a semi-finished product.
The complete HP-RTM process, includingpreforming, resin injection, curing and post processing, can be integrated intoone production line. The complete production line can be divided into three mainautomated units:· Preform Center· Press and Injection Unit· Figure 6 Example of CFRP 3D preform Machining UnitThe preform center allows production of custom designedpreforms from dry carbon fiber reinforced plastic. A stacking robot is used toposition reduced CFRP sheets on a conveyor belt for draping where they are heatedand accurately positioned on a stamping dye. The stamping process converts 2Dsheets into dimensionally stable 3D preforms.
The preformed sheets are thenshaped using a cutting robot and stacked in a load trolley. Other roboticfunctions in a HP-RTM line include de-stacking preforms, loading preforms andunloading finished components from the mold. Figure 7 HP-RTM Process Chain 4.
Wet Molding Figure 8 Wet Molded Components Wet molding, which is an economical alternative to HP-RTM, is suitable forcomponents with two and a half dimensional characteristics. As semi-complexgeometries can be achieved without preforming, wet molding uses CFRP stacks insteadof preforms. This eliminates the need for preforming and reduces the cycletime. Moreover, resin application is done outside the press.
This allowssimultaneous resin application while components are still curing inside thepress which further shortens the cycle time. Figure 8 shows exemplary wetmolded components. Figure 9 Dieffenbacher Wet Molding LineFigure 9 depicts a fully automated wet molding line. A handlingrobot de-stacks the CFRP stacks from the carrier garage and positions them on ascanning table where they are perfectly aligned for proper resin application. Stacksare then transferred to a cabinet for robotic resin application. The amount ofresin applied is strictly monitored to maintain uniformity and enhance repeatability.The feeding robot loads the wet stacks into the wet molding press. After curing,a de-stacking robot unloads the finished parts and moves them into a coolingpress.
Finally, the cooled components are transferred to the conveyor belt formanual inspection. 2.3.
2 Thermoplastic Thermoplastic compounds solidify on cooling and becomemoldable on application of heat. They are characterized by strongintermolecular forces which weaken on heating and therefore they can bereshaped. Compression molding of thermoplastics require high internal moldpressures of 150-250 bar and pressure build up time of less than 0.5 seconds.Due to absence of a chemical reaction, the forming process is relatively fasterwith higher press velocities and shorter cycle times (20-50 seconds).