The need for sustainability, increasingly requires developing products according to a cradle to cradle approach. For furniture, wood, being potentially renewable, is a suitable material in this regard. However, most wooden furniture today utilizes steels and synthetic polymers in the joints, which can partially be recycled, but are far from being circular materials. All-wood joints have been used in traditional furniture and construction, but they are not adapted to modern manufacturing techniques and do not fulfill the need for easy assembly.  The aim of this thesis is to explore existing solutions for all-wood joints, as well as relevant manufacturing techniques to create an approach for the development of new joints by practitioners. The research questions are: What are the principles used in existing technical solutions and how can they be used to develop new all-wood furniture joints? What are the most important manufacturing techniques for wood today and how can they be considered in the early-stage development? The general approach in this thesis is to abstract the researched existing technical solutions and manufacturing techniques, ideate on this abstract level, and then detail the concepts on a more concrete level.  As results, fourteen different principles and six different patterns of transformation were extracted from existing solutions and documented in an accessible form. Similarly, seven manufacturing techniques were collected and documented. These were then used in an ideation workshop with practitioners from IKEA, which resulted in six abstract concepts. One of the concepts was further developed into a pre-design and tested with a simulations according to strength and stability requirements from applicable standards.  The testing of the pre-design proved its practicality and a team at IKEA is continuing the development of the concept and planning to manufacture a prototype. This is a good indicator for the usefulness of the approach. Even though it worked well, further exploration of the "toolbox" is recommended, as well as the use of different ideation methods. The full environmental benefits of furniture with all-wood joints are not clear, because only resource depletion was considered and the potential effect is small compared to other industries. Despite this, the thesis shows the potential in circular furniture and encourages IKEA and other furniture companies to delve into the topic of circular furniture more deeply.

In earlier wood constructions, the method of joining the parts was by the carpenter joint. There are many different kinds of carpenter joints. The kind of carpenter joint that was used was partly due to the type of building, but also to local variations in building tradition.  The industrialization at the end of the 19thcentury led to new construction technology with new types of joints. It gradually became more difficult for the craftsmen to compete with mass-produced standard joints with screws and nails. During the latter half of the 20thcentury, it once again began to become popular with the carpenter joint. New technology in the wood industry began to make carpenter joints competitive.  Modern technology with modeling of geometries has made it possible to analyze and optimize structures and joints in a new way. Verification through tests has also led to increased understanding of wood joints.  Calculation of the load bearing capacity in carpenter joints is possible by applying calculation rules in Eurocode.   The purpose with this study is to verify strength calculations for a traditional carpenter joint.  An analysis of an imagined timber frame and roof truss was made in a calculation program to assess in a rough manner what section forces the structure was subjected to.   A dovetail joint in the roof truss shown in fig. 1 was chosen for further analysis.  Manual calculation of the load bearing capacity in the dovetail joint was made. Verification of the calculations was then done through strength tests in a lab.   The study shows that it is possible to calculate the load bearing capacity in a dovetail joint and that account must be taken to eccentricities in the joint and varying wood quality. / I äldre träbärverk var metoden för sammanfogning av virkesdelar hophuggningen. Det finns en mängd olika typer av hophuggningar. Vilken typ av hophuggning som användes berodde dels på byggnadstypen men även på lokala variationer i byggnadstradition. Industrialiseringen under slutet på 1800-talet bidrog till ny byggteknik med nya typer av förband. Det blev efter hand svårare för timmermännen att konkurrera med massproducerade standardförband med skruv och spik. Under senare halvan av 1900-talet började det åter bli populärt med hophuggningen. Ny teknik inom träindustrin började åter göra timmerförband konkurrenskraftiga. Modern teknik med modellering av geometrier har även gjort det möjligt att på ett nytt sätt analysera och optimera bärverk och förband. Verifiering genom tester har också lett till ökad förståelse av timmerförband. Beräkning av bärförmågan i hophuggningar är möjligt genom tillämpning av beräkningsregler i Eurokod. Syftet med detta arbete är att verifiera hållfasthetsberäkningar för ett traditionellt timmerförband.  En analys av en tänkt timmerram och takstol gjordes i ett beräkningsprogram för att på ett överslagsmässigt sätt bedöma vilka snittkrafter konstruktionen utsattes för. Ett laxförband i takstolen som visas i fig. 1 valdes ut för vidare analys. Manuell beräkning av bärförmågan i laxförbandet gjordes. Verifiering av beräkningarna gjordes därefter genom hållfasthetsprovning av förbandet i laborationslokal. Studien pekar mot att det går att med tillförlitlighet beräkna bärförmågan för ett traditionellt laxförband och att hänsyn skall tas till excentriciteter och varierande virkeskvalitet.

This thesis aims to develop knowledge of non-metallic connections in order to develop and change the Swedish wood architecture as well as wood structures. The main question being "Are metal-free connections suitable for contemporary timber buildings?". In the theory chapter, facts about wood are introduced, followed by literature studies and previous research. Through literature research in the university database and conducting interviews with an architect, a designer and a carpenter, data was collected for the design process and for the calculation of the dimensions for one of the selected glulam connections. The result showed that there is a lack of knowledge in Sweden regarding non-metallic connections, other countries such as Switzerland are more developed in the area and has accepted the idea of this concept. The result also showed that the lack of strength in wooden connections lead to large dimensions of the timber elements, but an aesthetic advantage can be developed. Finally, the results are discussed and analyzed according to the different requirements set on appearance, durability and manufacturability. / Detta examensarbete syftar till att utveckla kunskap om metallfria knutpunkter för att möjliggöra en mer varierad svensk träarkitektur. Den övergripande frågan har varit ”Hur väl lämpar sig metallfria knutpunkter för nutida byggande av träkonstruktioner?”. I teorikapitlet beskrivs fakta om materialet trä, följt av beskrivning av litteratur och tidigare forskning som är relevant för denna studie. Genom en litteraturstudie via universitetets databaser samt intervjuer med en arkitekt, en konstruktör och en möbeldesigner samlades data för gestaltningsprocessen och dimensionering av en knutpunkt i limträ. Resultatet visade att det finns kunskapsbrist i Sverige gällande metallfria knutpunkter, andra länder som Schweiz är mer utvecklade inom området samt har accepterat tanken på detta koncept. Resultatet visade även att frågor kring hållfasthet leder till stora dimensioner för de ingående träelementen, men att en estetisk fördel kan utvecklas. Slutligen diskuteras och analyseras resultaten utefter olika krav som ställts på utseende, hållfasthet och tillverkning.