Fakultät für Holztechnik und Bau
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Investigation of tool wear of the trimming unit and resulting quality in the edgebanding process
(2023)
The edgebanding process, i.e. the covering of the raw edge of the laminated particleboard by means of decorative plastic or real wood veneer bands, is an important process step in the manufacture of furniture components. The quality of the final product is significantly influenced by this production step. The manufacturing process step within the edgebanding machine begins with the milling of the raw edge. The quality of the edgebanding process is determined by a large number of process input variables, such as the tool used and the cutting geometry, the type of laminate used for the wood-based material, adhesives, etc. The quality of the edgebanding process is also determined by the type of material processed. Particularly with regard to the materials, the increased use of recycled wood in the particleboard sector and different types of adhesives (with reduced formaldehyde emissions) results in increased demands on the milling process. Due to this developments, most of the earlier investigations (in the years 1990 - 2000) are not comparable with today’s general conditions. The mechanical and optical properties of the edge applied to the end product are decisively influenced by the quality of this joint. The milling technology used, as well as the tool used for this purpose and its condition, is a decisive influencing factor in the formation of quality. Tests on the indication of various influencing variables in the edgebanding process at the Rosenheim Technical University of Applied Sciences showed that in the case of chipboard milling, a decrease in the electrical power required for the cutting process can take place with increasing tool wear. It was also demonstrated that previous process steps in furniture production, such as panel dividing by means of sawing or milling/nesting, generally have a significantly different influence on the subsequent joining process during edge banding process. Furthermore, a direct correlation was determined between the mechanical properties of the end product and the condition of the tool used, which can be used as a measurable indicator. In addition to the effect of the tool condition on the mechanical properties of the edge banding, this also has an impact on the optical quality characteristics. Accordingly, it could be demonstrated here that an increase in the size and number of chippings takes place in the laminate of the board material to be processed.
The machining of furniture components requires a complete geometrical specification of dimensions with associated tolerances to define in the first step appropriate manufacturing processes and to carry out the design and setup. Furthermore, a verification of the defined specification after production is a next step to check the quality and related to the production equipment, to calculate process capability and effectiveness.
In 2011, the system of Geometrical Product Specification (GPS) has been published completely. The system is built for a distinct range of geometrical quality characteristics and consists of chains of standards referring to each other. With three elements of these chains, the product can be specified. With three additional elements, the verification of the product and the measuring system is possible. It does not contain the verification of the production processes, the process qualification.
The German standard DIN 68100 provides a frame for dimensioning and tolerancing lengths and also angles, parallelism and straightness for furniture components. It includes a method to consider swelling and shrinking of wood and wood-based materials. Apart from its benefit of specifying products in a supply chain, it is rarely used in the branch nowadays. DIN 68100 is currently far away from GPS.
To gain all benefits arising from GPS the branch needs a consolidated action. New symbols for drafts and an updated method for tolerancing with moisture consideration have to be developed as well as measuring dimensions of flexible work pieces, like most parts in the furniture industry. In GPS, the link between product verification and process specification is not that consistent. In other branches SPC and methods of process qualifications are established. At the moment the kitchen industry is establishing SPC or similar procedures. An action towards GPS can also accompany these efforts.
Due to a shift in the tolerance principles, the GPS system is hardly directly applicable to the furniture industry, e.g. DIN 68100. But there is a real threat that the system is called up accidentally and out of ignorance.
This paper sketches a comprehensive system of product specification, verification for furniture components and process qualification. It will share experience gained in the kitchen furniture industry and will add a theoretical analysis of a possible application of GPS-chains for important examples of quality characteristics. The activities are part of a process (VDI 3415-2) carried out in the working group 102 of the Society of German Engineers (VDI).
Due to the increasing customer demands, companies face the challenge of adapting their manufacturing facilities to produce batch size one parts. In this context, each component comes with specific customer requirements, significantly increasing the complexity of its manufacturing process. Traditional process planning done by employees is no longer feasible in the face of the growing complexity and diversity of batch size one parts. Therefore, there is a need for novel computer-aided process planning methods capable of autonomously learning and identifying the necessary machining features of these parts. We propose a configurable automated feature recognition framework tailored to batch size one parts to address this need. This framework comprises two main components. First, a customizable data generator is developed to create a dataset of computer-aided design models incorporating user-specific machining features. Second, a graph neural network is employed to learn these user-specific machining features by leveraging the graph structure represented by the vertices and edges in each computer-aided design model. We evaluate the effectiveness of our framework using a real-world example from the furniture industry. Specifically, we construct a dataset comprising over 7000 computer-aided design models of wooden boards using our framework's data generator. Each wooden board contains up to 30 randomly placed machining features for the application of connectors and fittings, randomly selected from 14 standard machining features commonly used in the furniture industry. An optimization algorithm adapts a graph neural network for classifying these specific machining features. The results demonstrate that our framework addresses the automated feature recognition problem without requiring data conversions, such as pixels or voxels, as other approaches often do. By introducing this configurable automated feature recognition framework, we solve the challenges posed by batch size one manufacturing. The framework's effectiveness and accuracy are demonstrated through extensive testing on the example of the furniture industry, showcasing its potential for enhancing manufacturing processes in various domains
In the whole field of woodworking, from carpentry to industry, new products are created and designed every day and manufacturers wonder if similar workpieces have already been produced in the company and if corresponding drawings, information, tools, jigs, etc. can be reused. Under certain circumstances, considerable duplication of work can be avoided and a more efficient production is possible. In order to find similar workpieces, it must be clarified what exactly is meant by similarity. The different fields of knowledge do not provide a clear definition. However, similarities are always used to compare objects. In woodworking, objects can be a wide variety of components and products, such as carcase sides, furniture fronts, fittings, tools or profile strips. The search for similar profiled elements – related to the potential, data structure and algorithms – is the focus of this paper. There is a wide range of different profiled elements, which are used constructively as well as decoratively, e.g. for baseboards, door frames, window frames or decorative moulding profiles. These profiles are manufactured in a multi-stage production process in which the workpieces are first machined with profiled tools before surface finishing takes place. Along this production chain, tools, machine settings and, in some cases, fixtures are used that are adapted to the respective profile and can be reused for the same or similar jobs. Inheritance of information offers the greatest potential of similarity search. Inheritance means that existing knowledge in the form of drawings, CNC programs, process parameters and setup specifications, etc., is transferred from existing profiles to a new profile. By inheriting existing information, for example, the effort required for process setting can be reduced by adopting spindle positions, positions of guides and stops, or feed and cutting speeds. However, this can only be done if the process knowledge and other technological information concerning a profile are sufficiently documented. This is the only way how all information is made available for the similarity search and inheritance, and also for setting the processes when the profile is manufactured once again. The profile data must therefore be stored in a meaningful structure without loss of information. Therefore, a holistic product data model was developed that combines the geometrical with the technological profile data. The developed model allows a combined search for geometrically and e.g. materially similar products – also with a weighted evaluation of the individual criteria. The research has shown that data modelling is the essential foundation for the implementation of modern AI algorithms to enable similarity search. In conclusion, the use of a search system for geometrically and technologically similar profiles represents a real innovation for wood processing companies. This paper presents a holistic approach for geometrical and technological similarity search presenting different algorithms
Teachers should be able to balance content knowledge, pedagogical knowledge and technological knowledge (TPACK) in their various activities on curriculum, instruction, and assessment. Our Germany-wide study focused on measuring intrapreneurship competence. To ensure a valid and reliable assessment, we followed the three-step assessment triangle: cognition, observation and interpretation. We modeled the intended IP competence as an interdisciplinary and interprofessional team, designed a technology-based performance assessment tool that uses authentic work tasks, and analyzed apprentices’ behavior via a model-based IRT (Rasch model) approach. Our results identify the distribution of the IP competence of apprentices on four proficiency levels. Since these results are generalizable, single IP tasks can be used by teachers to support and guide apprentices individually with regard to these proficiency levels. Our approach is a blueprint for evidence-based teaching that tackles all areas of TPACK.
Im Bereich des nachhaltigen Konsums besteht eine Kluft zwischen der Bereitschaft nachhaltig zu handeln und dem tatsächlichen Handeln. Eine Möglichkeit diese Lücke zu schließen, wird in der Emotionalisierung von Konsumenten gesehen. Ein Medium der zielgruppenspezifischen Nachhaltigkeitskommunikation sind Sensibilisierungsvideos. Auszubildende als junge Konsumenten, die Konsumentscheidungen langfristig beeinflussen können, verwenden Videos zum Lernen. Ziel dieser Studie ist es daher, die Wirkung der Sensibilisierungsvideos bezogen auf die Emotionalisierung der Intention, nachhaltig zu konsumieren, und das realisierte Konsumverhalten zu untersuchen. Um Emotionen hervorzurufen, wurden 45 Auszubildenden fünf Sensibilisierungsvideos mit dem thematischen Schwerpunkt des nachhaltigen Konsums gezeigt. Mit Hilfe eines Ein-Gruppen-Vergleichs mit Vor- und Nachtest wurde über vier Erhebungszeitpunkte hinweg überprüft, ob sich die Emotionen, die Intention und das realisierte Konsumverhalten im Zeitverlauf verändern. Die Daten wurden sowohl qualitativ als auch quantitativ ausgewertet und analysiert. Es hat sich gezeigt, dass die Sensibilisierungsvideos bei den Auszubildenden sowohl positive als auch negative Emotionen hervorrufen. Im Zeitverlauf nehmen die positiven Emotionen im Vergleich leicht zu. Das Ausmaß, in dem die Auszubildenden an nachhaltige Aspekte beim Einkauf denken, verzeichnet ähnlich wie die Intention einen Zuwachs. Diese Steigerung findet sich jedoch nicht für die berichteten nachhaltigen Kaufmaßnahmen. So ist davon auszugehen, dass die Videos zwar zu einem stärkeren nachhaltigen Denken und einer stärkeren Intention angeregt, die Lücke zwischen dem Denken und Handeln aber nicht vollständig geschlossen haben.
Die Technische Hochschule Rosenheim ist überregional bekannt für Ihre Expertise im Fachbereich Holz und Bau. Nach dem Vorbild des kooperativen Modells der Hochschule Landshut in Kooperation mit der TU München implementierte die TH Rosenheim im Jahr 2020 den Studiengang Ingenieurpädagogik für den Fachbereich Bautechnik mit der Option Holztechnik als Unterrichtsfach. Der Beitrag skizziert Motive, Strukturelemente sowie erste Entwicklungen. Dabei lassen erste deskriptive Ergebnisse die Hoffnung zu, dass sich über das Modell neue Zielgruppen für eine Karriere im Lehramt an beruflichen Schulen generieren lassen. Besonders auffällig für das Rosenheimer Modell ist die Bedeutsamkeit der Polyvalenz sowie das Interesse an einer praxisnahen Ausbildung rund um den Werk- und Baustoff Holz.
Der Vortrag betont die zentrale Rolle von Holz in der Bioökonomie für die notwendige Transformation unserer Lebens- und Wirtschaftsweise. Der Fokus liegt dabei auf der ganzheitlichen Betrachtung der Wertschöpfungskette Forst-Holz und möglichen Beschleunigern für eine bioökonomische Transformation: Interdisziplinäre Lösungskompetenz ist gefragt, um Holz als Rohstoff für zukunftsfähige Produkte zu etablieren, Holzarten, -sortimente und -qualitäten optimal den verschiedenen Verwendungen zuzuführen und die Kreislaufwirtschaft als Schlüssel zur Ressourceneffizienz umzusetzen.
Der Vortrag wurde im Rahmen des Stuttgarter Nachhaltigkeitsstammtisch gehalten.