Лесотехнически Университет

Резюме

At the Faculty of Forest Industry, seemingly for the first time in the bandsaw studies history, the statically indeterminate problem of spring mechanism tension in bandsaw blade sections was set up and solved. The solution, transferred and generalized for a horizontal bandsaw, was defended in a Ph.D. thesis. Questions and discussions arose necessitated additions and details to the solution spared in previous papers for their limited volume. Now, the following points are detailed: the concentration of distributed loads, the subcritical friction, and the application of L'Hôpital's rule for obtaining the tension of the blade in the state of idle running (without cutting).

Резюме

The report presents some experimental studies carried out by sawing of logs with narrow band saw blades in winter conditions. The experiments were carried out in manufacturing conditions in February. For the purpose a horizontal band saw "Wirex CZ-1/ZM" was used.

Operating conditions were established and the quality of sawn lumber from semi frozen logs of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) was tested. The quality preparation of the band saw blade with the used horizontal band saw provides good parameters of the sawn lumber: surface roughness R̅_m = 190 μm; variation in the accuracy of the size and shape of 1.5 mm and 1.8 mm at a feed speed of U = 11.5 m.min^-1.

Резюме

Experimental studies related to the influence of some factors on the quality of the resulting lumber were carried out. The venue of the research is the manufacturing conditions in Experimental and Training Forest Ranges in Barziya. As a work station a horizontal bandsaw for logs Arsov 90 Ltd. (Bulgaria) was used. The results were analyzed and compared to some earlier obtained with other machines of this type. They show that it is not advisable feed speed to exceed 16 m.min^-1– due to the risk of unacceptable size deviations. Some recommendations for a more efficient usage of this type machines were proposed.

Резюме

Experimental studies during milling of solid wood were carried out. The current study was performed at the Laboratory of Woodworking Machinery, University of Forestry, Sofia. The measurements were carried out using universal milling machine FD – 3 (ZDM – Plovdiv). The correlations between fundamental factors influencing the milling process and target functions, such as cutting force and power, specific cutting work, specific power consumption have been investigated. On the basis of the analysis of the obtained results, practical recommendations have been proposed.

Резюме

The present work refers to verification of the axial run-out of the band saws blades in band saw machines, as their geometric accuracy. It has been determined that the axial force is applied when rotating the wheels by hand, which, in the presence of bearing clearances, results in a displacement of the band saw blade in one direction for each complete rotation which does not allow its geometric accuracy to be determined.

The effect of the bearing clearances of the wheels on the trajectory described by the back part of the band saw blade is studied. The deflection of the crown of the guide wheels when applying a force of 150 N in the direction of feed for worn and new bearings was measured, as well as the displacement of the back of the band saw blade in this direction for these two bearings. Displacement of 0.2 – 1.1 mm of the band saw blades in one direction has been detected for each complete rotation which depends on the condition of the bearings. It is recommended that such verification should be carried out on relatively new bearings and that no axial force will be applied to worn ones.

Резюме

Experimental research on some performance indicators of a circular saw machine (Kallion Konepaja Oy – Finland) for longitudinal cutting of logs were performed. The accuracy of the machine operation and the roughness of the boards were measured successively. For this purpose, the feed speed v_f was varied widely, from 4 to 100 m.min^-1. The test specimens are of beech wood (Fagus silvatica L.). The research place was the manufacturing facility of Pentop Ltd. – Varshets. The results were analyzed and compared with those obtained previously with а band saw machine.