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.

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.

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.

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.

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.

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.