| 1. |
|
|
| 2. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Basic knowledge of wood properties for improved performance of laminated Veneer products
- 2013
-
Ingår i: Pro Ligno. - Brasov : Publishing House of Transilvania University of Brasov. - 1841-4737 .- 2069-7430. ; 9:4, s. 549-556
-
Tidskriftsartikel (refereegranskat)abstract
- To ensure success in the production of laminated veneer products, it is necessary to acquire a sound basic understanding of the behaviour of the wood, and to understand the inherent reactions of wood to adhesive, heat, moisture, strain and stress. This can ensure an efficient wood utilization and promote the development of new processes and products that take advantage of the visco-elastic nature of wood. A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. In this study, we have examined how the performance of laminated veneer products can be improved through the implementation of basic knowledge of wood in the design and production process. The results show that the material and process parameters and storage in a changing relative humidity have a clear impact on distortion. Fibre orientation of the veneers in the moulded assembly was the most critical parameter to control. Fibre deviations mainly resulted in twist of the product. A moisture content in one veneer deviating from that of the rest of the veneers in the assembly before moulding resulted in distortion of the laminated veneer products both after moulding and during use. To decrease the negative effect of fibre orientation and moisture content on shape stability, the veneer should be straight-grained and well-conditioned to a moisture level adapted to the use of the final product. Special care should also be taken to orientate the veneers during assembly before moulding.
|
|
| 3. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Bio-based adhesives at laminated veneers
- 2012
-
Ingår i: Proceedings of the 8th meeting of the Northern European Network for Wood Science and Engineering (WSE). - Kaunas, Lithuania. - 9786090205815 ; , s. 221-225
-
Konferensbidrag (refereegranskat)
|
|
| 4. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Chipless Machining; Challanges in Manufacture of Laminated Veneer Products
- 2015
-
Ingår i: Proceedings of the 22nd International Wood Machining Seminar, IWMS 22.. - Qubec City : Universite Laval. - 9780994796400 - 9780994796400 ; , s. 155-164
-
Konferensbidrag (refereegranskat)abstract
- A laminated veneer product (LVP) consists of veneers bonded together with adhesive under pressure into a predetermined shape and, in general, under increased temperature to shorten the curing time of the adhesive. The process is commonly used in furniture design to manufacture complex forms such as thin shells. In the industrial production of LVP and when the ready- for-use components are exposed to climate variations, rejection due to distortion of the laminates is a major problem. The shape stability depends on a variety of material and process parameters, and this study has focused on the influence of fibre deviation in a single veneer. Recent research on the shape stability of LVP and how distortion is influenced by various material and production parameters is presented. A finite-element model for LVP is introduced and the use of this modelis exemplified by predicting the shape of a LVP with fibre distortion in a single veneer. The results show that it is possible to improve the shape stability of LVP if knowledge of various material and process parameters is implemented in the manufacturing process, and that a simulation based on a model of the wood material can be helpful in estimating the risk of an undesired deformation of the product.
|
|
| 5. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Contact free measurement of complex shapes in the wood industry
- 2011
-
Ingår i: Mechano-chemical transformations of wood during THM processing. - Biel, Switzerland : Bern University of Applied Sciencs, Architecture, Wood and Civil Engineering. - 9783952378700 ; , s. 143-144
-
Konferensbidrag (refereegranskat)abstract
- There is an increasing need to update and correct information about product geometry in the wood manufacturing industry. Changes in machinery or personnel can be the cause of that need. Manual measurement takes time and diff erent ways of digitizing the geometry of the products have therefore been developed.In this study, two methods (3D-coordinate measurement and optical scanning) have been tested together in order to determine the position of a product in relation to the processing machine, and to optically scan the product geometry. The aim was to identify and evaluate methods to digitize product geometry into a CAD-model for the wood industry. Th e seat shell measured was fitted in the CNC-machine where the processing later would be performed.The methodology used has made it possible to create a CAD-model from the physical model. Based on the experience from this methodology, it would be recommended to continue by creating of a tool that minimizes the need for after processing, i.e. the adjustment of certain coordinates manually.
|
|
| 6. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Development of novel structural connections - Inspiration from furniture industry
- 2021
-
Ingår i: World Conference on Timber Engineering 2021, WCTE 2021. - Santiago, Chile : World Conference on Timber Engineering (WCTE).
-
Konferensbidrag (refereegranskat)abstract
- The presented project aims to develop prototypes for building connections inspired by the furniture and interior industry and explore them with representatives from the timber construction industry. The long-term vision is that actors from furniture and building industry together develop a smart system for assembly of building elements, which provide higher precision, faster and more efficient assembly than what is available today. The prototype connection developed in this project shows that the idea is ripe for full-scale investigation. Laboratory tests showed promising results due to the high failure loads obtained with very high stiffness.
|
|
| 7. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Distortion in laminated veneer products exposed to relative-humidity variations : Experimental studies and finite-element modelling
- 2019
-
Ingår i: BioResources. - Raleigh, NC : North Carolina State Univ Dept Wood & Paper Sci. - 1930-2126. ; 14:2, s. 3768-3779
-
Tidskriftsartikel (refereegranskat)abstract
- A shortcoming of the laminated bending process is that the product may become distorted after moulding. This study focused on the influence of fibre orientation deviation for individual veneers on the distortion of a moulded shell. The distortion of 90 cross-laminated shells of the same geometrical shape, consisting of seven peeled birch veneers, were studied under relative humidity variation. All the veneers were straight-grained in the longitudinal-tangential plane, but to simulate a deviation in fibre orientation, some of the individual veneers were oriented at an angle of 7° relative to the main orientation of the other veneers in the laminate. A finite element model (FEM) was applied to study the possibility of predicting the results of a practical experiment. The study confirms the well-known fact that deviation in fibre orientation influences shape stability. The results also show how the placement of the abnormal veneer influences the degree of distortion. From this basic knowledge, some improvements in the industrial production were suggested. However, the FE model significantly underestimated the results, according to the empirical experiment, and it did not show full coherence. The survey shows the complexity of modelling the behaviour of laminated veneer products under changing climate conditions and that there is a great need to improve the material and process data to achieve accurate simulations. Examples of such parameters that may lead to distortion are density, annual ring orientation in the cross section of the veneer, the orientation of the loose and tight sides of the veneer, and parameters related to the design of the moulding tool.
|
|
| 8. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Downtime causes in a production cell for laminated veneer products
- 2017
-
Ingår i: 23<sup>rd</sup> International Wood Machining Seminar Proceedings. - Warsaw, Poland : The Polish Chamber of Commerce of Furniture Manufacturers. - 9788394804602 ; , s. 28-35
-
Konferensbidrag (refereegranskat)abstract
- Productivity is often used to determine how well resources are used for an operation. Most often, the ratio of what is produced to what is required to produce it determines productivity. Laminated veneer products are considered complicated products often with complex shapes, a raw material with high variation, and machining processes that create scrap materials that need to be handled. Therefore, keeping a high productivity in the industries producing such products may become challenging. This study reports productivity measurements in a production cell consisting of an adhesive, pressing and processing station. The study seeks to increase understanding of production-related problems in this industry. The research has been using productivity measurement as well as interactive discussions between researchers and workers.Measurement of downtime causes were made for 20 days, for a total of approximately 300 hours. The production cell had 1,299 minutes of stops. Of those, 450 minutes were one-time events. The rest were intermittent disturbances. Many of them could be explained by the dust-laden air and processing residues but were also related to veneer and adhesive. There is a need for determining material and processing parameters; however, the first priority is cleaning the factory.From a social perspective, some other issues must be added to the discussion of this paper. First and foremost, the business has gone through a transformation from a family business to a privately held firm. From the non-family employee’s view, this is a huge change. This has resulted in unclear roles and responsibilities within the company, which has also affected the productivity of the company.
|
|
| 9. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
EXPERIMENTAL AND NUMERICAL ANALYSES OF A CONNECTION FOR CLT STRUCTURES
- 2023
-
Ingår i: Proceedings of the 2023 World Conference on Timber Engineering (WCTE). - Oslo, Norway : Curran Associates, Inc.. ; , s. 1154-1159
-
Konferensbidrag (refereegranskat)abstract
- Although building systems made of cross-laminated timber (CLT) have become common in Sweden in the past 20 years and they have developed rapidly during the same period, steps remain to be taken to simplify the assembly of such systems, especially at construction sites. Current construction methods, however, remain labour-intensive and thus show room for improvement.This paper describes a novel connection for the assembly of building elements made of CLT. Simple and inexpensive, the connection is fairly insensitive to manufacturing tolerances and enables rapid, more efficient construction than the connections for CLT structures currently used. Test results show the excellent strength and stiffness of the connection, which also allows the replacement of numerous fasteners, including nails and screws, with only a single steel rod.
|
|
| 10. |
- Blomqvist, Lars, 1962-, et al.
(författare)
-
Formstabilitet i underlägg för dukning
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this study, a coaster intended for table setting has been investigated regarding shape stability in relation to the surrounding climate. The coaster was made up of paper, some of which was printed, and a fibreboard that was bonded together.Symmetry in a construction is desirable for high shape stability, which is known since before. The fact that the surfaces have a similar moisture absorption contributes to the symmetry. Boards that have a harder surface than the opposite should be sanded so that both surfaces of the board have a similar moisture absorption. The orientation of the components in a laminate can reduce or increase the asymmetry if the surfaces have different moisture absorption capacity. Symmetrical construction as well as symmetrical moisture absorption are beneficial for high shape stability.
|
|
