Parallel and normal cutting forces in peripheral milling of wood

In this paper, the parallel and normal cutting forces on the tip of the tool are examined when altering a number of parameters in peripheral milling. The parameters studied are rake angle, chip thickness and upward/downward milling. The evaluation of the forces has been performed during cutting of the chip and the variation in the forces has been recorded. In this way, important information can be obtained in order to arrive at cutting data and tool geometries that will reduce surface defects such as torn and raised grain. In the past, very few investigations have been carried out on peripheral milling, probably because of the difficulties of measurement. Nowadays, however, new measuring techniques and equipment make it possible to measure cutting forces even in standard milling machines. In this work, a sensor was placed under the workpiece to measure the forces in three directions at frequencies up to 7000 Hz. To obtain detailed data, a plastic material was used so that the cutting (revolution) speed could be kept at a minimum, thereby maximizing the number of readouts per incision. The results show how the normal force (the force component perpendicular to the workpiece) varies during the cut and how it is dependent on the examined parameters. This force changes from negative to positive during the cut. When altering the machining parameters, the normal force changes in both direction and magnitude. The other force component, the parallel force, also shows a dependence on the parameters. The objective of this research is to find parameters that minimize the normal forces in order to avoid damage to the wood.

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Parallele und Normal-Schnittkräfte beim maschinellen Holzbearbeiten

Zusammenfassung  Parallele und Normal-Schnittkräfte, die auf die Werkzeugspitze einwirken, wurden untersucht, wobei eine Reihe von Parametern bei der maschinellen Holzbearbeitung variiert wurden. Dies betrifft Neigungswinkel, Spandicke, Aufwärts- und Abwärts-Schneiden. Das Abschätzen der Kräfte geschah während des Schneidens, wobei die Veränderung der Kräfte aufgezeichnet wurde. So können wichtige Informationen zu Schnittdaten und Werkzeuggeometrie gewonnen werden, um Oberflächendefekte wie Ausreißen oder Aufstellen von Fasern zu verringern. Bisher liegen wegen der Schwierigkeit beim Messen nur wenige Untersuchungen zu diesem Thema vor. Heute ist es mit neuen Meßtechniken möglich, die Schnittkräfte auch an Standardmaschinen zu messen. Ein Sensor wurde unter dem Werkstück angebracht, um die Kräfte in drei Richtungen bei Frequenzen bis zu 7000 Hz zu messen. Um detaillierte Werte zu erhalten, wurde ein Plastikmaterial verwendet, so daß die Schnittgeschwindigkeit minimiert und dadurch die Datenpunkte pro Einschnitt maximiert werden konnte. Die Ergebnisse zeigen, wie die Normalkraft während des Schneidens variiert, und wie sie von den untersuchten Parametern abhängt. Diese Kraft ändert sich von negativen zu positiven Werten während des Schneidens. Bei Änderung der Parameter ändert die Normalkraft sowohl die Richtung als auch die Größe. Die andere, parallele, Kraftkomponente zeigt ebenfalls eine Abhängigkeit von den Parametern. Ziel der Arbeit ist es, Parameter zu finden, die die Normalkräfte minimieren und so Schäden am Holz zu vermeiden.

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Minor cutting edge angles of sawing teeth: effect on cutting forces in wood

European Journal of Wood and Wood Products - Optimising the cutting tool geometries can reduce waste while increasing timber yield. The industry is moving towards thin-kerf bandsawing of timber,...     

Cutting forces in bandsaw processing of oak and beech wood as affected by wood moisture content and cutting directions

Cutting forces in bandsaw processing of oak and beech wood were measured at two levels of wood moisture content (about 12 % and FSP) for four cutting directions (90°–90°, 90°–0°, 0°–90° and 90°–45°). A constant cutting speed of 40 m/s and a feed rate of 20 m/min were applied. A piezoelectric dynamometer (KISTLER type 9257A) mounted on the carriage of the vertical bandsaw machine (ESTERER model EB 1400) was used to measure the parallel, normal and lateral cutting forces. Results revealed that all cutting forces depend on the wood moisture content and cutting direction. The greatest parallel force was observed for oak wood at 12 % MC for 90°–90° cutting direction (44 N/mm) whereas the lowest one was for beech wood at 30 % MC for 0°–90° cutting direction (20 N/mm). In contrast to the little change of lateral force at various cutting directions, the change in parallel force was significant.     

Study on the normal component force in oblique cutting of wood

Based on a series of experiments, the relationships between normal component forces and oblique angles of cutting edge, and normal rake angles in oblique cutting of wood were studied. The experiments consist both of the 90°-0° and the 0°–90° oblique cutting situation. Each type of experiment includes two wood species and two kinds of thickness. Through the experiments, the rules of the effect of oblique angles of cutting edge and normal rake angles on normal component force were found out. The calculation methods of normal component force were studied by mathematical analysis.     

Up-milling and down-milling wood with different grain orientations – the cutting forces behaviour

Peripheral milling of wood with up milling and down milling techniques is very well known from a geometrical point of view. However, in processing anisotropic materials such as wood, these geometrical aspects imply relevant differences when machining. In fact, milling of anisotropic material leads to different cutting geometries when up- or down-milling and when increasing or decreasing the depth of cut resulting in different grain orientations depending on the adopted process. In this paper, tests performed when processing Douglas Fir with different depths of cut and grain orientations are described. The cutting forces were measured, and the dependence of the cutting forces with respect on the cutting geometry are analysed and discussed.     

含水率对木质材料切削力影响的研究

采用硬质合金锯齿刀具分别对三种实木(杉木、樟子松、水曲柳)和两种人造板(中密度纤维板、刨花板)进行闭式切削实验,研究不同含水率对木质材料切削力的影响。实验结果表明:含水率对木质材料切削力的影响显著。随着含水率的增加,杉木的主切削力和法向力都呈减小趋势,而樟子松和水曲柳的主切削力皆为先增大后减小,当接近纤维饱和点含水率时主切削力达到最大。对人造板,在5%～18%含水率范围内,随着含水率的增加,主切削力和法向力都不断增大。     

木工铣刀的选用

依据木材铣削要素、材料性质、铣刀切削方向,稳定性和安全性几方面介绍了木工铣刀主要技术参数,角度参数、结构形式、回转方向、切削用量、运转稳定性和加工的安全性选用的原则和方法.     

木工刀具硬质合金化及其应用

本文对国内木工刀具硬质合金化基本情况，硬质合金化所使用的刀具材料及性能，木工硬质合金刀具的应用进行阐述，主要供使用这类刀具的人员参考。     

切削参数对人造板切削力影响的研究

通过对中密度纤维板和刨花板的闭式切削实验,研究了不同锯齿前角、切削厚度、切削速度等参数对切削力的影响规律。结果表明:主切削力和法向力皆随前角的增大而呈减小趋势;通常情况下,相同锯齿前角切削时,刨花板的主切削力和法向力皆比中纤板大。切削厚度对切削力的影响显著,主切削力和法向力均随切削厚度增加而增加。切削速度对切削力的影响相对较小,随着切削速度的增加,主切削力和法向力均略有减小。     

Performance of helical edge milling cutters in planing wood

A new design of a milling cutter with solid helical edge has been developed for improving the performance of cutting wood. Development of the new helical edge milling cutter with its geometries for planing wood has been followed by some research progresses. In this work, a conventional edge milling cutter and helical edge milling cutters were tested in planing spruce wood (Picea abies). The purpose of the research work was to investigate chip flow, power consumption, noise emissions, edge wear, and surface roughness characteristics of the helical edge milling cutters in planing spruce wood. Experimental results showed that the helical edges compared to the conventional edge milling cutter provide better chip flows with nearly axial direction and low flight velocity. Though the extreme helical edges up to 75° inclination angle generate comparable or slightly larger cutting power than the conventional edge, they considerably generate lower sound pressure level of up to 5 dB(A). The helical edge milling cutters are better in wear resistance, suffer less edge fractures, and produce better surface quality of planed wood than the conventional edge milling cutter.     

Lateral cutting force during machining of wood due to momentary disturbances in the wood structure and degree of wear of the cutting tool

The paper presents a study of the effect of momentary disturbances due to variations in wood structure on the lateral cutting force. Density, shape and fibre-direction of the disturbances, and the degree of wear of the cutting tool are taken into consideration. The paper shows that high density gradients result in high lateral forces. The highest momentary lateral force noted has a value of approximately 40 N. The geometrical shape of the cutting tool in terms of degree of wear has a big impact on the lateral force. The work indicates a potential to increase the cutting performance by a more accurate supervision of the condition of the cutting tools.     

Effects of cutting parameters on cutting forces and surface quality of black spruce cants

The effects of rake angle, cutting direction, and depth of cut on cutting forces and surface quality of black spruce were evaluated. Cutting forces were measured during cutting at four rake angles (35°, 45°, 55° and 65°), four cutting directions (0°–90°, 15°–75°, 30°–60°, and 45°–45°), and three depths of cut (1, 2, and 3 mm). Torn grain, waviness, and roughness were evaluated. The results showed that as rake angle increased, cutting forces, torn grain, waviness, and roughness decreased. The lowest cutting forces and the best surface quality were obtained with 65° of rake angle. At this angle, cutting forces and surface quality were more affected by depth of cut than by cutting direction variations. Thus, as depth of cut decreased, the effects of cutting orientation on the cutting forces and surface quality decreased. The application of these results to the canting work of a chipper-canter is analyzed.     

木材隔热材料刨削加工的研究

房屋结构隔热的经济意义越来越受重视。因为将来的能源价格将越来越贵。在产生能量的同时也造成二氧化碳含量的增高。考虑到这两方面的原因，一个节能的方法是使用木材的隔热材料。一个由BMBF资助的项目——包括了研究传统刨削加工产生可作为隔热材料的木屑的优化。考虑到它作为隔热材料的性能。另外还有切屑与加工表面质量的关系等。     

切削参数对竹材切削力影响的研究

研究了竹材切削不同刀具前角、切削量与切削速度对切削力的影响.刀具前角对主切削力的影响较为显著,随刀具前角的增大,所需主切削力明显减小.主切削力与切削量成正相关关系.切削速度对切削力的影响不大.