不同织构形式硬质合金表面与木材径切面的摩擦性能

合理的微坑型微织构已被证明具有改善木材和硬质合金表面间的摩擦特性。采用微凹坑型织构、微凹槽织构和微网格型织构3种织构形式,在相同织构面积占有率条件下,通过摩擦特性试验与理论分析相结合,研究不同织构形式对木材表面摩擦系数的影响。研究表明:在相同织构面积占有率条件下,不同织构的类型和表面形貌对硬质合金试样与木材表面摩擦的摩擦系数有不同的影响,受摩擦长度、凹槽微织构宽度、微织构角度等织构参数的影响。当微织构与木材发生摩擦时,摩擦区域织构面积越大说明两者间实际接触面积越小,且面积越大,捕捉磨屑和硬质点的能力越强;而主制动力越小,其产生的摩擦系数越小。在相同压力和织构面积占有率条件下,不同类型的织构试件与木材表面产生的摩擦系数均小于非织构(平面)型表面产生的摩擦系数。其中:微坑型织构产生的表面摩擦系数最小,为0.116;凹槽型织构产生的表面摩擦系数最大,为0.182;网格型织构随着织构角度的减小,其产生摩擦系数越小。     

Towards a model predicting cutting forces and surface quality in routing layered boards

The general aim of work reported here was to assist designers and operators of routers and similar tools for cutting wood-composite boards, by providing a model predicting cutting force components from readily available material properties. This initial study explored, for edge cutting, the variation within a single medium density fibre board across the thickness and in various cutting directions in the plane of the board. Material properties of interest were specific gravity and friction coefficient. In slow linear cutting on a modified milling machine, carbide router inserts cut the edges of layers cut from a medium density fibre board. Specific gravity and coefficient of sliding friction were measured for each layer. Cuts were also made on full-thickness edges in various directions in the plane of the board. Chip thickness was varied from 0.025 to 0.8 mm. Parallel and normal force data and digital video images of chip formation were stored for analysis. Specific gravity increased as the fourth power of the distance from the central plane to the surface. Friction coefficient values, estimated both from cutting forces and from rubbing forces during return, varied about a value of 0.23, with no significant difference between layers. The values for cutting force per mm width of cut increased progressively from the central plane to the surface, in a logarithmic relation with specific gravity. The cutting forces did not vary with cutting direction in the plane of the board. For a sharp edge with 32° rake angle cutting at chip thickness values above 0.1 mm, the normal force component was negative, indicating reduced feed force and improved surface quality. With dulling, the threshold value of chip thickness for this increased. It is concluded that elaboration of this approach would generate relationships suitable for incorporating in a useful general model. However, it may be found that weight per unit area of board will suffice as a proxy for cutting resistance in modelling the cutting of full-thickness edges. Received 10 June 1999     

Characteristics of sugar maple wood surfaces machined with the fixed-oblique knife pressure-bar cutting system

Oblique cutting differs from orthogonal cutting by an inclination given to the knife edge, which induces several changes on tool geometry, cutting forces, as well as on the quality of machined surfaces. In this work, a pressure bar was used during oblique cutting to reduce the occurrence of torn grain. The effects of cutting depth, rake angle, and oblique angle on cutting forces and surface quality were studied. Surface topography, cell damage and wetting properties were used to assess surface quality. All force components were increased by increasing cutting depth and decreasing rake and oblique angles. The lateral force, however, increased as the oblique angle increased. The surface roughness increased with increasing the lateral cutting force. Higher cutting depths and oblique angles tended to provide higher surface roughness, while higher rake angles tended to reduce surface roughness. The pressure bar was not always able to completely prevent the occurrence of defects when cutting against the grain. The occurrence of machining defects increased at higher cutting depths and oblique angles. As the rake angle decreased, the type of machining defect tended to change from torn grain to slight fuzzy grain. Moreover, the best wetting properties were obtained at lower rake angles, as they induced higher surface roughness. A 25° rake angle, a 30° oblique angle, and thinner cutting depths should be preferred to reduce dependence on ulterior sanding.     

木工圆锯片锯齿侧刃参数对锯切表面粗糙度的影响

【目的】分析锯齿侧刃参数对锯切表面粗糙度的影响,通过优化锯齿侧刃参数,解决圆锯锯切时进给速度提高与表面粗糙度增大之间的矛盾,为新型木工圆锯片设计提供参考和指导。【方法】提出微量零径向侧后角锯齿的概念,使用9种不同锯齿侧刃参数的圆锯片,以水曲柳和高密度纤维板为对象进行锯切试验,研究不同进给速度下径向侧后角和零径向侧后角段对锯切表面粗糙度的影响。【结果】随着进给速度增加,锯切表面粗糙度增大,径向侧后角减小,锯切表面粗糙度降低,无零径向侧后角段锯齿锯切形成的表面粗糙度均高于具有零径向侧后角段锯齿,特别是当零径向侧后角段由0 mm增加到0.5 mm时,锯切表面粗糙度下降最为明显。当零径向侧后角段大于0.5 mm时,侧刃的零径向侧后角段具有"以锯代刨"的作用,与零径向侧后角锯齿相比同样可起到改善锯切表面质量的作用。【结论】锯切表面粗糙度一定程度上取决于锯痕深度。在实际锯切过程中,仅有长度近似等于每齿进给量的锯齿侧刃部分参与切削,占侧刃总长度的很小一部分,微量零径向侧后角锯齿中零径向侧后角段长度比每齿进给量略大且越接近每齿进给量越理想。具有微量零径向侧后角段锯齿的圆锯片与零径向侧后角锯齿相比,同样可起到改善锯切表面质量的作用;在保持其他切削参数不变的情况下,微量零径向侧后角段锯齿还可以减小锯齿侧刃与锯路壁之间的摩擦。     

锯片锯料角对锯切表面粗糙度影响机理分析

分析了锯料角影响锯切表面粗糙度的机理，阐述了锯料角与锯料量对锯切表面粗糙度的影响。分析结果表明，只要锯料角不变化，则锯料量的变化对锯切表面粗糙度不起任何作用。锯料角影响锯切表面粗糙度的机理为开发新型锯片、提高锯切表面的质量和锯切效率提供依据。     

STUDY ON MEASUREMENT OF WOOD SURFACEROUGHNESS BY COMPUTER VISION

The working processes,machining devices and tools,cutting amount,consumptionof materials,productivity and quality of products are directly affected wood surface roughness.This paper gives an extensive review of methods used previously to measure wood surfaceroughness,and concludes that computer vision is the most suitable.The preliminarystudy shows that computer vinon method has the advantages of a noncontact,three--dimensionalmeasurement,high speed and well correlates with stylus tracing method.The method can be usedin classification and in-time measurement of wood surface roughness after being improved.     

Prediction of the surface roughness of wood for machining

The surface quality of solid wood is very important for its effective response in manufacturing processes. The effects of feed rate, cutting depth and rake angle on surface roughness and power consumption were investigated and modeled. Neuro-fuzzy methodology was applied and shown that it could be useful, reliable and an effective tool for modeling the surface roughness of wood. Thus, the results of the present research can be successfully applied in the wood industry to reduce time, energy and high experimental costs.     

The influence of technical characteristics of wood milling tools on its wear performance

Influence of technical and chemical characteristics of industrial wood milling tools on its wear was analysed. Four tools of different manufacturers were subjected to the research. Lithuanian oak wood was chosen for the research as a reference material. Behaviour of cutting tools was assessed on the adopted industrial thickness planer SR3-6 with cutting speed of 31 m/s. Wear performance was evaluated on milling the specimens until 3200 m of true cutting length. Summarising achieved results, the following can be stated: chemical composition of tool and heat treatment schedule has great impact on the tool edge wear. The highest wear resistance was reached on testing tools made of CT01M-LA2; tools made of high-alloyed tool steel 8X6HΦT have presented the highest cutting edge radius and edge recession in each type of test as compared with tools made of high-speed tool steels Z80WCV18-04-01/18-0-1 and HS18-0-1, respectively. All these tools are suitable for oak wood processing. The high-alloyed tool steel shows similar wear performance as high-speed tool steels.     

表面涂层木工刀具的研究进展

介绍几种表面涂层木工刀具的加工方法和使用状况,分析表面涂层刀具的切削特点和磨损形态,概述了国内外研究进展.研究成果表明,涂层处理可以延长刀具使用寿命,减少刃磨和换刀时间,提高生产效率和表面加工质量.     

木材切削表面粗糙度研究进展及测定方法探讨

木材切削表面粗糙度的影响因素很多且组成复杂,较难进行准确的测定评价。从木材切削表面粗糙度的影响因素、不同测试方法及现行测定评价标准三个方面,对木材切削表面粗糙度相关研究进行综述,基于现状提出了完善木材切削表面粗糙度测定评价方法的建议。     

基于三维显微系统的木材切削表面粗糙度分析

以榆木、杨木和松木为试验材料,采用不同的测试模式、木材切面、放大倍数和切削加工方式对切削表面粗糙度进行测定评价,比较分析上述因素的影响。结果表明:测定模式对于粗糙度值有一定影响;同一树种、同一切面时,磨削表面粗糙度明显低于锯切和旋切,表面粗糙度值为锯切>旋切>磨削;榆木磨削加工中,显微构造明显部位的三切面粗糙度值为径切面>弦切面>横切面;放大倍数与木材显微构造有关,对表面粗糙度值有影响。基于试验结果提出,木材切削表面粗糙度测定评价宜采用先选定被测试件的评价部位,再确定满足精度等级的测试模式的两步法进行。     

Effects of grain angle on the amplitudes of acoustic emission and surface roughness in wood machining

The orientation of wood fibers and the resulting surface roughness of radiata pine are studied during a peripheral milling with acoustic emission control. Studies were undertaken in machining process for radiata pine, where a surface quality problem appears when cutting is not well controlled. It is known that acoustic emission signals are a good monitoring element of the surface roughness with different cutting conditions. Previous studies have shown that changing cutting conditions affects acoustic emission signals; these variations are related to surface roughness and chip formation. The purpose of this study is to evaluate and quantify the surface quality and the consumption of cutting energy in radiata pine with differing grain angles, and to determine the relationships of grain angle with acoustic emission signals in order to better optimize cutting conditions.     

Performance of coated carbide tools in turning wood-based materials: Effect of cutting speeds and coating materials on the wear characteristics of coated carbide tools in turning wood-chip cement board

This paper reports on the performance of coated carbide tools in turning wood-chip cement board. The coating materials studied were titanium carbonitride (TiCN), titanium nitride (TiN), chromium nitride (CrN), and titanium nitride/aluminum nitride (TiN/AlN), which were synthesized on the P30 carbide substrate. The aim is to investigate the effect of coating materials and cutting speeds on the wear characteristics of the coated carbide tools. Cutting tests were performed when turning wood-chip cement board at cutting speeds of 30, 40, 50 and 60 m/s, a depth of cut of 1mm, and a feed of 0.05 mm/rev. The results of the study show that the coated carbide tools provided better performance than the P30 carbide tool, especially in terms of reducing the progression of the wear rate and clearance wear. The TiN/AlN-coated carbide tool showed the smallest increase in both wear rate and clearance wear with an increase in cutting speed and had the longest tool life among the coated carbide tools investigated. Though the TiCN-coated carbide tool was observed to have a low wear rate and low clearance wear for cutting speeds of 30 and 40m/s, when the cutting speeds were >50m/s its wear rate and clearance wear were almost the same as those of CrN-and TiN-coated carbide tools, which had high values for these parameters.Part of this paper was presented at the 21st IUFRO World Congress, August 2000, Kuala Lumpur, Malaysia     

微坑型微织构硬质合金表面对木材摩擦特性的影响

【目的】探讨木材含水率、木材切面和纤维方向以及运动速度等因素对木材表面摩擦系数的影响规律,为设计更加合理的木材切削刀具表面织构形式提供参考和指导。【方法】以水曲柳和樟子松为研究对象,在具有不同微坑直径硬质合金表面条件下,研究木材含水率、木材切面和纤维方向以及运动速度等因素对木材表面摩擦系数的影响。【结果】与无微坑表面相比,当微坑直径为60μm、含水率为67%±3%时,在水曲柳表面产生的摩擦系数由0. 151降低到0. 091,降幅为39. 7%,在樟子松表面产生的摩擦系数由0. 241降低到0. 164,降幅为32. 0%。木材径切面上纤维方向差异对表面摩擦系数的影响不大,但在横切面上,微坑直径越小,其表现出的摩擦系数越高。摩擦过程中运动速度对表面摩擦系数的影响与木材中的水分有较大关系,当含水率处于生材状态时,表面摩擦系数随运动速度增大而降低,且微坑型结构表面产生的摩擦系数降幅明显高于无微坑表面,无微坑表面产生的摩擦系数由0. 160降低到0. 134,降幅为16. 3%,微坑直径为60μm时的摩擦系数由0. 124降低到0. 071,降幅为42. 7%。【结论】木材含水率状态对微坑型表面微织构与木材之间的摩擦系数影响较大,木材中自由水的存在有利于降低硬质合金与木材表面之间的摩擦系数。微织构直径越小,其接触角平均变化率越大,表面铺展速度越大,越有利于改善木材/硬质合金摩擦副的状态,使表面间的摩擦系数减小。     

Toward a process monitoring of CNC wood router. Sensor selection and surface roughness prediction

The measurement of wood surface roughness is performed once the machining process is completed. It requires considerable time since the measurement is performed at slow speed. The objective of this study was to develop a method to evaluate the surface roughness of paper birch wood while routing. For this purpose, a number of transducers were mounted on the router spindle and also in the proximity of the workpiece and cutting zone. Signals were acquired during a wide range of cutting conditions and analyzed. Statistical regression and artificial neural networks were employed to establish relationships between the signals and the actual cutting depth and surface roughness. The sensor selection and the feasibility of the sensor placement were determined. The models were subjected to a validation procedure to confirm their performance. The placement of the microphone at constant distance from the cutting zone was determined to be the most useful one. A model able to predict the surface roughness of routed paper birch wood regardless of the depth of cut was produced. The performance of the model was valid independently of the length of the workpiece.     

Effect of Cutting Speed on Surface Quality by Bandsawing

Introducti0nSincetI1ebandsa\`canbequickl}'andaccLIratel}'setal1dtllereisvirtuaII};noupper-sizeIilnitinIogdiameter,tI1emachinecanberegardedasthemosleffectiveaII-r0undmachine.Lumbermillsshowgro\"inginterestintI1ebal1dsawingconceptduetotl1el1ighthroLIghputan…     

The influences of circular saws with sawteeth of mic-zero-degree radial clearance angles on surface roughness in wood rip sawing

Key message

The sawtooth parameters of the side edges likely affect surface roughness to a large extent in wood sawing. Our results point out the need to optimize the parameters of the side edges in order to maximize wood surface quality.

Context

Improving surface roughness of wood in rip sawing by optimizing the sawtooth parameters is a significant topic of focus in the research of wood processing. However, existing research focuses mainly on the optimization of the sawtooth parameters of the major cutting edges without taking into account the influences of length and angle of the side edges on surface roughness. Thus, adaptive parameters for the side edges should be proposed.

Aims

This study analyzes how the different parameters of side edges influence surface roughness when circular saws are used, and aims to resolve disparities between high feed speeds and better surface roughness.

Methods

In particular, this article presents the use of a sawtooth with a mic-zero-degree radial clearance angle. Northeast China ash (Fraxinus spp.) serves as the material for conducting this rip-sawing experiment. Nine types of sawtooth geometries at different feed speeds are used to study the influences of both the different radial clearance angles and the straight length of the zero-degree radial clearance angle on surface roughness (Ra).

Results

Surface roughness increases with the increase in feed speed, and the smaller the radial clearance angle of the sawteeth, the smaller the surface roughness. When the sawteeth have a mic-zero-degree radial clearance angle, the sawing surface roughness is lower than that of the value of sawteeth with radial clearance angles, especially when the straight length of the zero-degree radial clearance increases from 0 to 0.5 mm, in which case the decrease is most obvious.

Conclusion

Surface roughness depends, to a certain extent, on the depth of the saw notch. A small part of the side edge that forms the sawing surface participates in the actual cutting, and the length of this section is approximately equal to the feed per tooth. Sawteeth with mic-zero-degree radial clearance angles can improve the surface quality of sawing. Also, if the other cutting factors remain unchanged, surface roughness can be improved and friction can be reduced between the side edges and the wood by increasing the feed speed.

     

Wood friction characteristics during exposure to high pressure: influence of wood/metal tool surface finishing conditions

Friction that arises during processing for the deformation of wood under relatively high pressure levels (ca. >1 MPa) is an important factor to be taken into account when wood is processed. However, few studies on such friction have been published. The present study was undertaken to evaluate the influence of surface finishing conditions on the nominal friction coefficient (μ) of the wood and metal tool surfaces. Sticking friction was likely to arise on a relatively coarse metal surface, and the type of metal tool surface finishing was found to have large impact on the friction mechanism. The friction characteristics during exposure to high pressure seem to be affected not only by the interface contact characteristics, but also by the deformation characteristics of wood during compressive load or measurement. The value of μ on water-saturated wood was equal or higher than that on dry wood, which suggests that the contact characteristics between these two types of wood are significantly different. The water content in wood was shown to affect both the interface contact and deformation characteristics of wood. The value of μ was not significantly affected by the wood surface finishing conditions; however, changes in μ during sliding differed slightly, depending on the finishing conditions.     

红松,水曲柳木材切削性质的研究

本文以线性模型方法,在红松、水曲柳二树种内,对影响切削阻力和表面粗糙度各因素进行了综合分析,并对木材的密度与切削阻力的关系做了初步的研讨。     

基于三维表面形貌测定法的水切割木竹材工艺参数优化

为优化木竹材超高压水射流切割加工工艺参数,以红橡木和竹地板为对象,采用正交试验法,研究磨料流速、切割压力、进给速度、靶距对水射流加工试件表面粗糙度的影响,探索优化工艺参数。利用扫描探针式三维表面形貌测定法测量试件切割面的表面粗糙度值,分析三维表面形貌图。结果表明:红橡木磨料射流的试验影响因素排序为CADB;竹地板磨料射流的试验影响因素排序为BCAD。红橡木和竹地板优化工艺参数为:进给速度为250 mm/s,磨料流速为35 kg/h,靶距3 mm,切割压力为310 MPa。在此加工工艺条件下切割材料表面粗糙度相对较小,加工所得材料品质较好。