<p>Denna studie är genomförd på en bultsvetsstation med fyra bultsvetsrobotar från ABB som används i den dagliga produktionen i karossfabriken på Saab Automobile i Trollhättan. I dagsläget används off-lineprogrammerade robotprogram från IGRIP i flera robotceller på karossfabriken. IGRIP har under flera år används utan att man har någon metod för att utvärdera för hur kapaciteten i robotcellerna utnyttjas. Begränsningarna hos IGRIP är att det inte automatiskt kan beräkna och generera kollisionsfria banor vilket är mycket tidskrävande. Programmeringen av via-punkterna sker via manuell inmatning i programmet vilket medför att de inte utnyttjar maximal kapacitet i robotcellen. Dessa problem har lett till att Saab ville undersöka potentialen för att frigöra kapacitet i en robotcell med hjälp av en programvara under utveckling, IPS 2.0. Den nyare programvaran utvecklas av FCC och besitter optimerings- och balanseringsfunktioner samt genererar kollisions fria rörelsebanor för robotarna i robotcellen. En optimerad bana och en referensbana har skapats för att kunna utvärdera en procentuell förändring av tiden. Det visade sig att det finns stor potential att frigöra kapacitet i den undersökta cellen med hjälp av IPS 2.0.</p> / <p>This study has been performed on a stud weld station consisting of four stud weld robots from ABB which are used in the daily production at the body plant of Saab Automobile in Trollhättan. Currently, off-line programmed robot programs from IGRIP are used in several robot cells in the body plant. IGRIP has been used for several years without having any evaluation method for how the capacity has been used in the robot cells. The limitations of IGRIP are that it cannot automatically generate collision free paths, which is very time consuming. The input of the via-points is done manually by the programmer which results in less than maximum capacity in the robot cell. These problems have triggered Saab to investigate the potential for making capacity available by using a software under development, IPS 2.0. The software is developed by FCC and has optimization and balancing functions. It can also generate collision free paths for the robots in a robot cell. One optimized path and one reference path have been created in order to evaluate the time reduction in percent. It was shown that there was potential to free up capacity in the robot cell by using IPS 2.0.Date:</p>

<p>Force control is introduced to robots to solve the problem in machining applications due to the fact that the robot compliance might cause deviation between actual and desired robot path. Also large tolerances in the casting process as well as positioning errors from the clamping create deviations for which the force control technology can adept. Force control has also shown successful in automatic learning of paths along non linear surfaces.</p><p>This study investigates the possibility of introducing robots equipped with force control at Volvo Aero Corporation in order to robotize polishing and deburring processes. These are today performed by manual labor. This study investigates more specifically the ABB Force Control machining application package. The polishing process has shown to be very complex and today’s version of the ABB force control package cannot give sufficiently robust results to be recommended for implementation. The major issue is the non-existing compliance of tool orientation needed to adapt to casting and positioning deviations due to varying work piece dimensions. The deburring process has however shown to be easier to handle, and a robot cell and methodology is proposed in this report.</p>

<p>The goal of this master´s thesis is to simulate a robotized assembly of a small model of VBG Group couplings. By the software; Process simulate has the simulation model built up and the simulation been done. The simulation model is built up of the coupling parts and resources; conveyor, fixtures, compress machine, grippers, nut and screw sorter. All parts and resources, except the compress machine, the fixture and cage for the shaft, have been designed under the whole project. A study on how assembly simulation works in the software has also been done.</p>

<p>För att skaffa sig en uppfattning om det framtida servicebehovet av sym- och sugvalsar har antalet valsar som Metso Paper AB tillverkat tagits fram ur en databas. De övriga valstyperna som t.ex. tambourvalsar anses vara konstanta. Ur databasen har specifik information om valsarna tagits fram som t.ex. tillverkningsår och valstyp. Därefter har olika diagram skapats, vilket har lett till att det framtida servicebehovet av sym- och sugvalsar går att se, då servicerekommendationen från Metso Paper är på 8 års- respektive 4 årsintervall för de två valstyperna. Den här informationen har legat som grund för arbetets senare del då årsbasisen för 2013 tagits fram.</p><p>Idag sker fyra huvudverksamheter i skepp 17 nämligen; slipning, montage, provkörning och valslagring. Alla dessa kräver användning av kranen, dessutom kommer transporter in och ut från verkstaden med valsar och då krävs också användning av traversen. Slipmaskinen har dock förtur på denna kran då den har dyrast ställtidskostnader och körs med femskift, vilket inte är fallet för övrig verksamhet. Övrig verksamhet är inte beroende av slipmaskinen då detta är en separat verksamhet, men eftersom denna har förtur på traversen så blir övrig verksamhet lidande indirekt av detta.</p><p>Metso Paper Karlstad har idag tre valsverkstäder (skepp 16, 17 och 18) som används för service av valsar till pappersbruk i Sverige och Norge. De senaste åren har behovet av sådan service ökat och därmed har utrymmesbehovet blivit ett problem i dessa valsverkstäder. Planeringen för de tre verkstäderna är inte den bästa, då nästan all verksamhet finns i en av verkstäderna (skepp 17). Dock har detta sin grund i att bara denna lokal har den krankapacitet som krävs för de tyngre valsarna. I egenskap av utrymmesbehovet är uppgiften med det här arbetet att utreda två alternativ för en bättre fungerande valsverkstad.</p><p>För att kunna dimensionera de två nya förslagen har ytorna för montage/lagring beräknats. För de här beräkningarna har information som den genomsnittliga ytan en vals kräver och liggtiden vid montering/lagring tagits fram. Ett belastningsdiagram har även skapats för att se hur belastningen varierar i valsverkstaden.</p><p>Det första förslaget som lagts fram över valsverkstaden innehåller bara en nyinvestering av en travers på 2x50 ton. Flytt av två valssvarvar har gjorts vilket skapat en ny montageyta.</p><p>Det andra förslaget innehåller även en utbyggnad av skepp 17 och 18 på vardera 10 meter. Det här innebär att ännu större montage/lagringsytor skapas. Då belastningen varierar över året kommer det här förslaget att kunna klara de mest påfrestande månaderna, vilket troligtvis inte förslag ett gör.</p><p>Genom att flytta de båda valssvarvarna i förslagen kan företaget också avveckla sin verksamhet från skepp 16. Det här kommer att innebära en smidigare produktionsprocess i valsverkstaden.</p> / <p>In order to get a perception of the future service need for sym- and suction rolls the number of rollers that has been manufactured by Metso Paper were taken from a data base. The other roller types, for instance tambour rollers, are regarded to be unchanged. Specific information about the rollers, for instance manufacturing year and roller type has been taken from the data base. A number of diagrams has then been compiled, where the future service need for sym- and suction rolls as the service recommendation by Metso Paper for these type of rollers is eight and four year intervals. This information has been the foundation of the later part of this project when the year basis for the year 2013 was made.</p><p>As of today there are four main activities in ship 17; grinding, assembly, testing and roller storing. All these activities require crane use and in addition to this the transports in to and out of the workshop also requires use of the overhead crane. The grinding machine is the main priority for this crane, as the grinding machine is the most expensive one and is run in five shifts, unlike other activity. The other activities are not dependant on the grinding machine as this is a separate operation, but since the grinding machine is the main priority for the overhead crane the other activities will be affected by it.</p><p>Metso Paper Karlstad has three roller workshops (ship 16, 17 and 18) which are used to service rollers for paper mills in Sweden and in Norway. In the most recent years the need of such services has increased and the space need has become a problem in these roller workshops. The layout of the roller workshops has not been the best, as almost all of the activity is located in one of the roller workshops (number 17). This is due to the fact that this roller workshop is the only one with the crane capacity required by the heavier rollers. The purpose of this project is to examine two options in order to get the roller workshops better functioning.</p><p>In order to estimate the two new proposals the surfaces for storing and assembly were calculated. Information such as the average surface required by a roller and the time passed in storing/assembly was measured. A work load diagram has been compiled in order to see the variation of work load in the roller workshops.</p><p>The first proposal presented merely contains one new investment, a new overhead crane with the capacity of 2x50 tons. The moving of two roller lathes creates a new assembling surface.</p><p>The second proposal contains an expansion of 10 meters to ship 17 and 18. This means there will be even larger surfaces for assembling and storing. As the work load varies over the year, this proposal has the capacity to handle even the most intense months, unlike proposal number one.</p><p>By moving the two roller lathes in both the proposals it is possible to terminate the activity in ship 16, which means a more convenient production process in the roller workshop.</p>

Manufacturing companies find themselves, whether they like it or not, in a more global and changing reality. Fiercer competition, dynamic markets, new consumer habits, stronger environmental regulations, and new technological possibilities, are forcing manufacturing companies to change. The practical effects for European manufacturers are 1) new and innovative products, 2) global value chains, 3) automation, and, 4) a shift from products to solutions. This research is addressing the changes needed for operations in a single enterprise (a group of departments, a plant, or a group of closely located plants), to take advantage of the competitive situation. For such “internal” operations, the new challenges require changes both in technology and practices. The main concern of this research is the practices, and how a reengineering of manufacturing and office operations can improve performance. The choice of scope is based on the assumption that operations activities are a major source for competitiveness. To reengineer operations activities in processes rather than functions, and to implement best practices wherever appropriate, can therefore provide dramatic competitive improvements. The overall objective of this research is to: • establish enterprise reengineering as an approach that enables manufacturing enterprises to achieve fit between market requirements and operations capabilities. Enterprise reengineering is viewed as model-based and strategy driven approach that enables manufacturers to realise the “soft” or infrastructural aspects of an operations strategy. To support such reengineering efforts, enterprises are viewed not only from a process perspective but also from a resource, materials, information, organisations, and control perspective. Modelling and analysing enterprises from these perspectives can support their effort to implement best practices, and ensure that the practices are combined in a way that supports the overall business strategy. The overall objective is divided into more specific objectives: • To develop a strategic framework for enterprise reengineering • To develop a consistent and practical enterprise reengineering methodology to support the formulation and realisation of operations strategies • To develop architecture for conceptual enterprise modelling that ensures a coherent, decomposed, and holistic picture of enterprise operations • To establish “flow manufacturing” as a (optional) best practice programme for enterprise reengineering Together, the strategic framework, the methodology, and the modelling architecture should enable enterprises to achieve their performance objectives through an enterprise reengineering effort. In cases where an enterprise mapping and analysis concludes that improvements in manufacturing planning and control, order management, layout and flow, or inventory, should be performed, the flow manufacturing programme should provide practical guidance and a set of principles to support reengineering. In order to achieve these objectives, the following issues are reviewed in this thesis: 1) operations strategy, 2) enterprise reengineering, 3) flow manufacturing, 4) enterprise modelling, and, 5) change management. Based on these literature studies, a strategic framework, a methodology, a modelling architecture for enterprise reengineering and a flow manufacturing programme are proposed. The major outcome of this research is an enterprise reengineering methodology, which includes strategic planning, and operations mapping, analysis, design, and implementation. The methodology consists of the following models, principles, and tools: • A operations strategy checklist • Four flow manufacturing design principles • An architecture for conceptual enterprise modelling • Seven change management principles • A procedural guide for enterprise reengineering • An operations performance audit sheet • A five-step approach to flow manufacturing reengineering The research is based on a case study of HÅG Fast, a very successful enterprise reengineering project carried out in 1991-1992. The case study demonstrates the usefulness of the methodology to analyse and understand enterprises, and the dramatic improvements in performance that can be achieved by implementing flow manufacturing practices. In addition, the enterprise reengineering methodology has been proved useful in several field studies.

The project this report is handling has been implemented on NBB, Nordisk Bilbelysning AB in Linköping. The company produces and develops lightning and searchlights for all types of vehicles. Lately NBB´s supplier of electronics, OSRAM, has developed a mercuryfree xenon lightsource. Mercury is one of the most hazardous environmental waste and to get rid of the mercury entirely in the lightsource is a big step that means alot for the environment. This lightsource will be placed in one of NBB´s worksearchlights called My, and will be sold as an alternative to mercurycontaining searchlights. NBB wants to put an environmental label on this product and they want to have essential information about the product that is needed for the production. That is what the project has handled. A study of environmental labeling has been made witch has led to that an environmental declaration type II will be used as labeling and marketing for the environmental properties the serachlight has. The purpose of this master's thesis is to help and support NBB in environmental labeling and developing of a My searchlight with mercuryfree lightsource. A environmental labeled searchlight would mean a bigger place on the market and consequently lowered environmental affect. Lifecycleanalysis with the program ECO-it shows that a mercuryfree lightsource in the searchlight would not involve a environmental profit compared to a mercurycontaining lightsource because the lifelenght of a mercuryfree lightsource is 500 hours shorter. This means that the lightsource has to be changed more frequently if you choose the mercury free alternative and that affects the environment. The lifecycleanalysis also shows that the transports of components affects the environment little in compare to the production of the product and therefore a change to Swedish suppliers has not been implemented. Temperatur and lightmeasures has been made and compared between the searchlight containing mercury with the searchlight not containing mercury. The results of the measurements shows that the flow of light from a mercury free searchlight is about 15% lower and the temperature inside 5°C higher. This means that the construction not has to be changed as the temperature is on a acceptable level. The use of mercury in lightsources will likely not be used forever as new law demands becomes stricter and stricter by time. The environmental declaration that was made contains among other things a list of materials of the product and information about the products lifecycle. A logotype has also been suggested as a environmental label logotype for the company to use. The environmental declaration will be used as marketing of the product on the company website for exemple. / Projektet som rapporten hanterar har ägt rum på NBB, Nordisk Bilbelysning AB i Linköping. Företaget tillverkar och utvecklar belysning och strålkastare till alla typer av fordon. På senare tid har NBBs leverantör av elektronik, OSRAM utvecklat en kvicksilverfri xenonljuskälla. Kvicksilver är ett av de farligaste miljögifterna och att få bort kvicksilvret helt ur ljuskällan är ett stort steg som betyder mycket för miljön. Denna ljuskälla ska NBB placera i en arbetsstrålkastare vid namn My och sälja som ett alternativ till kvicksilverinnehållade strålkastare. Denna produkt vill NBB miljömärka och ha fram väsentlig information om för att kunna påbörja tillverkningen. Detta är vad projektet har hanterat. Syftet med detta examensarbete är att hjälpa och stödja NBB i miljömärkning och framtagning av en My strålkastare med kvicksilverfri xenonljuskälla. En miljömärkt strålkastare skulle kunna innebära en större plats på marknaden och därmed minskad miljöpåverkan. En studie av miljömärkningstyper har gjorts vilket har lett till att miljövarudeklaration typ II är den typ av miljömärkning och marknadsföring av miljöegenskaper som använts. Livscykelanalyser med programmet ECO-it visar att en kvicksilverfri ljuskälla i strålkastaren i detta fall inte skulle innebära någon miljövinst jämfört med kvicksilverinnehållande ljuskälla. Det beror på att livslängden för en kvicksilverfri ljuskälla är 500 timmar kortare. Detta innebär i sin tur att ljuskällan måste bytas mer frekvent om man väljer det kvicksilverfria alternativet vilket i sin tur belastar miljön. Det har även visat sig att transporter av ingående detaljer ger en liten miljöpåverkan i jämförelse till produktionen av produkten. Detta skulle innebära att byta leveratörer till svenska leverantörer inte skulle innebära någon större miljövinst. Temperatur- och ljusmätningar har genomförts och jämförts mellan strålkastare med kvicksilverinnehållade ljuskälla och strålkastare med kvicksilverfri ljuskälla. Resultaten av provningarna visade att ljusflödet för en kvicksilverfri strålkastare var ungefär 15% lägre och temperaturen inne i strålkastaren ca 5°C högre. Detta innebär att konstruktionen inte måste ändras då temperaturen är på en godkänd nivå. Användandet av kvicksilver i ljuskällor kommer troligtvis inte ske för alltid då nya lagkrav hela tiden blir strängare och strängare. Den miljövarudeklaration som gjordes innehåller bland annat materiallista på produkten och information om produktens livscykel. Även en logotype har lagts fram som förslag på eget miljömärke till företaget. Miljövarudeklarationen kommer användas som marknadsföring av produkten bland annat på företagets hemsida.

This thesis was conducted at Linköping University and Saab Aerostructures DPS, Linköping, and focuses on the possibilities of flexible fixturing in machining applications. The thesis is part of the research project "Koofix", which is collaboration between Linköping University and a number of companies. The thesis is aimed towards small batch production which, for Saab Aerostructures DPS, means diverse part geometry and that parts are manufactured in very small numbers, sometimes just one piece. The result of this is that expensive dedicated fixtures are made for most parts. By introducing more flexible fixturing methods to this kind of production the cost of fixtures and tooling will be reduced, and make the production more efficient. New flexible fixturing methods has been presented and evaluated through the thesis, which has resulted in three different concepts. These concepts have been the result of literature screening and study of current manufacturing process at Saab Aerostructures DPS. The concepts has been evaluated according to there ability to meet Saab Aerostructures DPS needs and a final concept has been chosen. The concept that is considered being the best solution employs an adjustable frame to encompass several different part geometries. This concept allows the workpiece to be machined in a single step and the fixture can be adjusted to fit workpieces with different geometries. On other concept considered in the thesis employs electromagnet with adjustable elements and is capable of fixing more complex geometries. The concept also allows the fixture to be adjusted between different products to be machine by the CNC-machine itself. Also a concept that’s not a fixture itself but a method that allows a simpler fixture to be used has been developed. This concept uses adhesives to combine extra material to the part, which allows for less complex fixtures to be used in the machining process. The concepts with the adjustable frame and the electromagnet and adjustable elements are both using the machines control system to locate the detail by probing before the machining process starts. Probing is done by equipping the spindle with a touch trigger probe which measures pre-programmed contact points and calculates exact part position. / Detta examensarbete har utförts vid Linköpings Universitet och Saab Aerostructures DPS i Linköping och behandlar flexibla fixturer i bearbetande maskiner. Arbetet bygger på forskningsprojektet Koordinatstyrd fixering som under en längre tid bedrivits av Linköpings Universitet tillsammans med ett antal företag. Examensarbetet behandlar Saab Aerostructures DPS fåstyckstillverkning där stor variation på detaljer och geometrier förekommer. Idag används ofta specialtillverkade fixturer för att hålla och lokalisera detaljerna. För att effektivisera produktionen och minska den totala fixturkostnaden per detalj kan mer flexibla fixeringsmetoder införas. I examensarbetet har nya flexibla fixeringsmetoder utvärderats och lagt grunden för framtagningen av tre stycken koncept. Koncepten är framtagna genom att relevant litteratur genomsökts samt genom studier på Saab Aerostructures DPS. Koncepten har sedan genomgått en urvalsprocess baserad på företagets behov och förutsättningar, vilket ger en bra grund för fortsatt utveckling av koncepten. Det koncept som anses vara bäst lämpat för Saab Aerostructures DPS bygger på en justerbar fönsterfixtur som medger att detaljer kan bearbetas i ett steg. Ett annat koncept som presenteras i rapporten är inriktad mot mer svårfixerade detaljer. Detta använder sig av en magnetchuck och justerbara element och har en mycket hög automationsgrad. Det tredje koncept som utvecklats är inte en traditionell fixturlösning men kan underlätta fastspänning av svårfixerade detaljer. Konceptet bygger på att extra material limmas på arbetsstycket för att underlätta fasthållningen av både obearbetade och halvbearbetade arbetsstycken. Fixturkoncepten använder sig av bearbetningsmaskinens styrsystem för att lokalisera detaljens exakta position i fixturen. Metoden för uppmätningen som används i detta arbete är "probning" vilket innebär att maskinens spindel är utrustad med en prob och mäter upp ett antal förprogrammerade punkter för att lokalisera detaljen.

One of today problem at IVT industries would be assembly of insulation on water cisterns. The element of assembly insulation on the cistern gets too elevated; hence one has to climb onto the stand the cistern is assembly on. This will increase the risk of work related injuries when there is a risk of falling down. It’s also rather strenuous on shoulders due to work with your arms high above your head. Further, it’s very difficult to get the insulation in place, this force us to compress the roof of the insulation with the sides of the insulation, which is very strenuous on the body. The purpose of this degree project has been to develop a work method with improved work position and improved workflow through the premises. This paper is divided into: Problem review, theoretic solutions, evaluation of solutions and design of tools. Each proposal to each solution is motivated with pros and cons. Then the best-fitted solution for IVT industries is presented. After examination of different solutions, I’ve concluded the best solution is to have separated assembly station for insulation that is preceded by assembly of cistern to it’s under part. Through the use of a personnel lifter assembly of insulation can be done without climbing on assembly stand. The body gets an improved work position because you no longer need to work with your arms up high. This is the solution that I’m recommending to IVT industries AB. Through elevating the assembly stations and move both test stations and refill of coolant to the right wall, an increased flow through the premises will be achieved. / Ett problem som finns i dag på IVT industrier är monteringen av isoleringen på vattentankarna. När isoleringen skall monteras på tanken blir det väldigt högt, så man måste klättra på ställningen som tanken är monterad på. Detta ökar risken för arbetsskador, då man skulle kunna ramla ner. Det är även väldigt slitsamt för axlarna eftersom man måste jobba med armarna högt över huvudet. Vidare är det väldigt svårt att få dit isoleringen, detta gör att man får trycka ihop taket på isoleringen med sidorna på isoleringen, vilket är väldigt slitsamt för kroppen. Syftet med examensarbetet har varit att utforma en arbetsmetod som ger en bättre arbetsställning och att dessutom förbättra flödet genom lokalen. Rapporten är indelad i: problemgranskning, teoretiska lösningar, utvärdering av lösningarna och utforskning av redskap. Förslagen till varje lösning motiveras med för- och nackdelar. Därefter redovisas det alternativ som anses komma att fungera bäst på IVT industrier. Efter att ha undersökt olika lösningar på dessa problem har jag funnit att den bästa lösningen är att ha en separat monteringsstation för isoleringen efter det att tanken monterats på underdelen. Genom att använda en personlyft kan man montera isoleringen utan att behöva klättra på monteringsställningen. Kroppen får en bättre arbetsställning eftersom man slipper att jobba med armarna högt. Detta är vad som kommer att rekommenderas till IVT industrier AB. Genom att flytta upp monteringsstationerna och flytta teststationerna och påfyllning av köldmedlet till den högra väggen får man ett bättre flöde genom lokalen.

The company is currently in a stage of improvement and has therefore taken the help of students at School of Engineering, Jonkoping University. The current production is batch, production layout is fixed. A bottleneck is created after the first station which leads to large efficiency loss.   The meaning of this report was to provide a layout suggestion with balanced workstations to a new production line. The conditions were that the production line would be one-way, driven by customers order and meet a demand of 40 products per week.   In order to achieve a result, different methods and tools have been used, these have been time studies, video recording, case studies and interviews with assemblers and supervisor. Theoretical background has been helpful for the choice of methods and work implementation.   The result of this work was a series of solutions based on the company’s strategy and the methods that has been used. Solution A uses three stations with the idea to create a suction through the flow and smooth line balancing. Solution B also had three stations with the basic concept to be able to adjust the number of stations. The number of stations can be selected when the demand change between two, three or six stations. The last Solution C meaning was to create a production line where the operations of the same character had their own place. This solution has five stations, creating a large efficiency loss.   The conclusion is that Layout proposal B is best for the company. This is because it is the most flexible proposal when it is possible to adapt to a demand from 20- 100 products /week. Proposal for methods development and opportunities for improvement in production can be found in the conclusion and discussion.

Continuous improvement is one of five principles in General Motors – Global Manufacturing System (GM-GMS). GM-GMS has been used by Saab Automobile AB since 2003 and is a central component for realisation of GM’s vision. Internal audits have discovered problems with one of the tools, practical problem solving (PPS), which needs to be improved. The department manufacturing of press and body (PK) wants to survey the problems and initiate a process of improvement. The purpose of this thesis work is to develop a foundation for future re-designs of the PPS process. Employees have been interviewed and observed in order to explore possible difference theoretical and practical problem solving with PPS. The result of the investigation shows 4 different and interrelated problem categories. 1. Information transfer, PPS hand over to product quality engineers (PQE) department cause problem when general assemblies (GA) are excluded from the improvement work. General assemblies do not get any feedback information from (PQE) about planed countermeasures. 2. Problem solving, team leaders has difficulties with identifying the true problem. Using “five-why” during the analysis work causes problem, since team leaders do not have the knowledge of how to use the tool in a proper way. 3. Documentation of PPS, the content in the PPS-form is a problem according to team leaders. Lack of knowledge and understanding of how to use the PPS-document leads to incomplete and incorrect analysis. 4. Coordination of involved people, support and help are missing from the management and quality engineer according team leaders. PPS from Global Costumer Audit are imposing time stress according to team leaders. Recommendations for further work is to investigate the opportunities with a web based PPS and process to improve information transfer and documentation of PPS. A second recommendation is to train and coach team leaders in problem solving and improve coordination of involved people and skills in problem solving.