If a sawn board or plank that is warped after drying is being planed, the feed rollers and the pressure elements will more or less straighten the wood during planing. However, when the pressure is released, some degree of warp will recur since the wood will spring back. With a large amount of straightening, only the cross-sectional dimensions of the wood should be affected by the planing operation, leaving warp unchanged, while a small amount of straightening should have a larger impact on warp. The objective of this study was to evaluate how warp is affected by planing in an industrial planer with standard configuration. A total of 20 pine planks with the dry target dimension 50 mm×150 mm were selected, of which half were severely warped. The worst twist, crook and bow per two metres and maximum cup were measured both before and after planing.The planer in the experiment had different impacts on the different warp types. For the individual planks, twist was reduced by 25% and crook was reduced by about 20% on average. Although bow decreased for half of the planks, the total average change for individual planks was a slight increase. Cupping practically vanished.

There are different reasons for planing timber. One is to adjust the cross-sectional dimensions of thickness and width. Another is to adjust the timber's outer shape, usually in order to reduce warp resulting from drying and having the forms of cup, twist, bow, and crook. The end-result depends on the properties of the timber before planing and on the planer design and settings. In the present work it was found that increasing or decreasing the forces exerted on the timber by a four-sided planer does not affect the cutting depth or the twist reduction. The pressure settings do not affect the rectangularity or the amount of unplaned areas on the surfaces either. The possibility to impact the result with this type of planer, apart from the cutting depth and planed dimensions, is slim to none.

Although planers and wood machining researchers have been around a long time, the interactions between planks and planers have been neglected in basic research. With a solid understanding of the movements of planks during planing, planers and planing strategies can be developed to reduce waste and improve the value yield.Cutting depths, changes in the amount of warp and cross-sectional shape were used to analyse the movements of the planks during planing, the alignment between the planks cross-sections and planers cutters and the improvement potential. The feeding roller in the planer intake had most control over the plank motion. Apart from cup reduction, the parts mostly affected by planing were the top and the butt end, where twist-induced misalignment between the cross-sections and the planers cutters resulted in skewed cross-sections and reduced rectangularity. By adjusting the cutting depths and in some cases the sawing oversize, planer misses could have been avoided but improvements in rectangularity would have required changes in the planer setting or planer design.This thesis increases the knowledge on how a 4-side planer works together with warp to affect 50 × 150 mm planks. For the 20 planks used in this study, the planer removed cup, it decreased the amount of twist and crook but had no effect on bow. The major factor reducing the rectangularity of the planed planks was twist. In the future, knowledge derived from this thesis can be used to create a simulation tool to model the behaviour of warped planks in a planer.

When sawn timber is planed, the timber is to some extent flattened by the feeding rollers and other pressure elements inside the planer, with the plank middle affected to a greater degree than the top and butt end. As a result, any twist present in rough timber influences the planing process in the proximity of the latter two areas. This is manifested primarily as reduced rectangularity in the affected zones of the planed timber, but also as an increased risk of planer misses. One way to avoid these unwanted features in the end product is to plane an excess length of timber, then cross-cutting to the required final length after planing.This study found low rectangularity to be a larger problem than planer misses, with the top end most affected. The study also indicates that simple models could be used to predict the size of the zone affected by twisting near the ends of planed timber, and thus also the length that must be removed in order to produce an acceptable cross-sectional shape throughout the length of planed timber.

About half the total volume of sawlogs end up as sawn timber. The rest is lostdue to drying shrinkage or is turned into byproducts like wood chips, sawdustand shavings. As the raw material is a large expense for a sawmill, it is important to fully utilize the logs. The inherent properties of timber are such that warp, such as bow, cup, spring and twist, is inevitable, and extensive knowledge of whether and to what extent warp will appear is therefore important for managing the production. It is also important to develop strategies to handle warped timber, for example in the planing process.This thesis focuses on how twisted timber is affected by the planing process with regard to twist reduction, cross-sectional shape, planer misses and cutting depth. This was studied in three practical tests on sawn timber with differentapproaches. In one test, sawn pine timber with a large variation of twist withinthe group was planed with standard settings, and five evenly spaced crosssections along the length of the sawn timber were subjected to more detailed studies. In the second test, the main yield from spruce logs was planed. One sample board from each log was planed with the normal pressure settings of the planing mill, while the second sample was planed with a pressure either higher or lower than the normal settings. In this study, seven cross-sections were studied in more detail, three close to the top end, three close to the butt end, and one in the middle of the sawn timber. In the third test, sawn pine timber with a more moderate twist was planed with standard settings in another similar planer.

This study deals with how warp affects the cross-sectional shape of planed planks. A total of 20 planks with dry target cross-sectional dimensions of 50×150 mm were planed to 45×145 mm. The rectangularity of five cross sections of every plank was measured before and after planing. The cutting depths were measured in 10 positions in the cross sections, and the angles between the planks and the cutters were calculated. Also, the warp, that is, twist, bow, crook, and cup, was measured before and after planing. All the studied properties pointed in the same direction. In terms of both rectangularity and angles of cut, the problems were larger in the top and butt ends of the investigated planks than in the intermediate parts, and the main reason for deviations from the desired result after planing was twist.

About half the volume of sawlogs ends up as sawn and planed timber. The rest is lost due to drying shrinkage or is turned into by products. As the raw material is a major expense for a sawmill, it is important to reduce waste.

To investigate how much the volume yield in the production of sawn and planed timber could be increased by reducing the target dimensions in the sawing stage in a sawmill, two groups of sawn timber were planed under similar conditions. One group consisted of sawn Scots pine timber with a large variation in twist. The other group consisted of sawn Norway spruce timber planed under different pressure settings. Using X-ray images, the minimum dimension for avoiding planer misses was calculated for each board, to find the smallest green target dimension. This was compared to actual measured dimensions.

It was found that most sawn timber had unnecessarily large dimensions, and it was also found that a reduction in the target dimensions could increase the volume yield for sawn and planed timber by more than 3 percentage points. Boards with large twist would however need a higher planing allowance. The effect of the planer pressure setting was negligible.

Modulus of elasticity (MOE) in the tangential direction for Norway spruce, Picea abies (L.) H.Karst was measured. Test samples were tested in three-point bending, and moisture content (MC) and temperature were varied between the green condition and 7% MC and between 20°C and 80°C, respectively. An adjustment of measured MOE to the ideally tangential direction was made by using correction factors calculated from finite element simulations. The results show MOE and the gradients with respect to MC and temperature and how they vary with MC and temperature. The gradients are factors in gradient terms in the incremental stress-strain relation for linear elastic behaviour during load cycles where there are mechanical loads and at the same time varying MC and temperature. The gradient terms add to the temperature and MC expansion coefficients and may be of significant size for cases with high stress, high temperature and high MC.

Forces from cutting appear on the front edge and side edges of a straight cutting tooth of a circular saw blade intended for rip sawing of wooden logs. The forces on these three edges add up to a net force on the tooth with three components in the main, normal and lateral directions. Especially the net lateral force is interesting for the stability of a circular saw blade during rip sawing due to the low stiffness of the saw blade in the lateral direction. In this paper, a model for calculating the net force on a cutting tooth is proposed and discussed. The forces on the front cutting edge and the two side cutting edges may for each edge be calculated from literature and experimental data of main and normal forces as a function of cutting parameters such as rake angle, clearance angle, bevel angle, cutting depth and wood cutting direction. The net force is the vectorial sum of the forces on the front and side cutting edges. Thin saw blades cut relatively more with the side edges than thick saw blades for the same cutting depth.A net lateral force appears on the tooth if there are unequal normal forces on the side edges. The reasons for unequal normal forces may be unequal side cutting depths due to a lateral deflection of the saw blade or inhomogenities in the wood material. The net cutting forces from the cutting force model may be applied on the teeth of a mechanical model of the circular saw blade in order to calculate lateral displacements and thus stability of the circular saw blade. Lateral displacement of the saw blade generates unequal side edge cutting forces and thus there is coupling between lateral force and lateral deflection.

With the development of scanning technology in sawmills, it is possible to optimise log rotational position when sawing. However, choosing a different rotational position than horns down might be detrimental for the board shape after drying, especially for curved logs. Thus, there is a need to investigate at what level of log curve it is possible to freely rotate logs without causing board warp. This study was carried out through a test sawing that was conducted at a sawmill situated in the middle of Sweden. The tests were made on 177 Norway spruce logs, with varying amount of curve. Half of the logs were sawn in the horns-down position, half were sawn rotated perpendicular to horns down. Log shape and warp of the dried boards were measured. The results indicated a relationship between board spring, log curve and choice of rotational position. Furthermore, board bow was related to log curve but not rotational position. It can be concluded that for straight logs, with a bow height of less than 15 mm, an unconventional rotational position does not cause excess spring in the boards. Bow and twist are not affected by the rotational position at all.

Vid ingenjörsprogrammen vid LTU har det noterats att det finns brister i matematikkunskaperna hos nyantagna studenter. För att undersöka detta har vanliga problem kartlagts med hjälp av intervjuer med lärare samt en enkätundersökning bland studenter. Både lärare och studenter pekar på bristande kunskaper inom främst algebra.För att åtgärda de påpekade kunskapsluckorna har även studenternas studievanor undersöks dels genom den tidigare nämnda enkätundersökningen samt genom intervjuer med studenter. Ett återkommande tema är att många studenter föredrar att räkna i grupp, men även att det är viktigt med tillgång till föreläsningar, både i form av en klassisk föreläsningssituation och som inspelade filmer.Med den inhämtade kunskapen om problemområden och studievanor togs en prototyp till ett diagnosverktyg fram i Maple TA med ledtrådar i form av videoklipp inom det aktuella området. Diagnosverktyget testades av en frivillig grupp studenter med övervägande positivt mottagande vilket visar att det finns stor potential för fortsatt arbete.