木材压缩弯曲理论及其设备研究
摘要
人们在很早以前就已经应用火烤法弯曲木材，随着生活水平的提高，弯曲木被越来越多地应用在家具及门窗上，弯曲木构件的加工水平也越来越高，相继出现了手工弯曲、机械弯曲和数控弯曲等加工方法，计算机技术的发展也对弯曲木的加工产生了巨大的推动作用。
弯曲木加工，首先要进行木材原料选择，只有选择了适合弯曲的树种才能进行下一步的软化处理，软化过程是将木材放入高温高压的容器中，经过长时间的蒸煮使其软化，必要时可以加入氨水以提高软化效果。随着科技水平的提高，高频和微波加热软化是今后发展的主要方向之一。随着弯曲方式的多样化，局部加热、局部压缩、局部弯曲也是达到木材多向弯曲的手段，这样可以减少拼接和胶合带来的麻烦，提高弯曲木的美观和耐用性。目前世界各国的压缩机多以成捆压缩为主，成捆压缩可以弥补因单根木条上的缺陷而引起的压缩不均现象，本文对成捆压缩的布局和压缩方法进行了讨论，对于工业化生产有一定的实践意义。
无论是手工弯曲还是机械弯曲都需借助一定的工具，模具、刚带是在弯曲过程中起着决定性作用的工具，它可以使中性层外移，减少外层纤维劈裂的可能性，提高弯曲木成品率；在同等条件下，缩小木材最小弯曲半径，达到更大的弯曲曲率。文中分别对矩形截面和圆形截面的弯曲木的最小弯曲半径加以分析，并用图表说明了最小弯曲半径的变化范围，即使同样是使用钢带，用端部可调的钢带比用端部固定的钢带弯曲木材所形成的弯曲半径更小。
对弯曲成形理论进行了分析，弯曲木中性层的位置是决定弯曲成功与否的关键，通过对简式弯曲和复式弯曲的分析，对简式弯曲的中性层位置进行了定量描述，指出了与其相关的两个重要参数(极限拉伸强度与极限压缩强度)的关系；定性地说明了钢带弯曲对中性层的外移而导致高成品率的原因。在对复式弯曲方法的分析中，指出其提高弯曲木密度，增加构件刚度的原因。在研究过程中发现，传统的复式弯曲方法在加工无固定旋转中心和曲率较小的弯曲木构件时应用受到限制，提出了数控复式弯曲方法，解决了无固定旋转中心和曲率变化较大的弯曲木构件的加工问题，并能与发展相对完善的数控系统连接起来，对弯曲木加工业具有很大推动作用。文中对机械手弯曲进行了描述，机械手弯曲也是机械与数控系统相结合的弯曲技术，它对木材多向弯曲是一个突破，可以很好地解决木材多向弯曲的成形问题。文中对弯曲的轨迹设计和进给量的计算进行了详细说明，并应用实例进行了分析。但是，这种方法的局限性是无法将钢带加入其中，对弯曲木的最小弯曲半径有一定的限制。机械手弯曲是由计算机控制的，所以可以利用计算机资源对木材进行有限元分析，通过有限元分析可以迅速求解木材在特定条件下的弯曲形状和弯曲应力，更有利于在弯曲过程中实时考虑木材湿度、弹性模量和材种等各方面的因素。
对弯曲成形和铣削成形的弯曲构件进行了对比分析，通过数学描述解析方法证明了弯曲成形的构件具有更高的强度，同时也指出了两者在出材率上的差异。对我国弯曲木加工企业的技术改进和木材的深加工利用将有一定的价值。
确立了数控弯曲设备(弯曲机械手)的总体结构，设计了其控制系统，并对系统实现的功能及系统的特点进行了详细的说明。
以国家林业局“948”项目“压缩法加工弯曲木生产工艺技术及设备引进”和国家“863”计划项目“弯曲木成形加工机器人生产线”为课题来源，并得到了它们的资助。
Long time ago, people found that timber could be bended with the fire shining. With the development of living condition, the bending woods were applied to the furniture and windows, its processes were filled with more technology. It was applied to the bending wood making that manual bending, mechanical bending and NC bending, and the development of computer technology promoted the bending wood process.
In wood bending, the raw material must be selected at first, which was the foundation to the next softening procedure, softening means the timbers were put into the container with high temperature and press ion. After a long time, the timber was plastic; sometimes the ammonia could be used to enhance the plasticizing affection. The high frequency and microwave softening are the new research fields in the science and technology advancement.
The bending method was multiplex. It is necessary to multi direction wood bending that partial heating, partial compressing and partial bended, which reduced the trouble of joint and agglutination, enhanced the appearance quality and duration. To the presser all the world, the precession in bundles was the process tendency, which eliminated press unbalance caused by the defection of single timber. The distribution and press ion in bundles could provide the theory foundation in the industrial production.
Whether manual bending or mechanical bending, the tools and jigs were necessary, and the steel strap was the key tool in the bending procedure, it made the unchanged layer moving outside, decrease the possibility of outside wood fiber split. In the same condition, the steel strap made the bending radius smaller got great curvature. In this paper, the smallest bending radius of rectangle cross section and round stick were anal sized with the figure, form its variety scope, it was showed that the bending with adjustable end stop could get smaller bending radius than fixed end stop in the steel strap using.
With the analysis of bending theory, the position of unchanged layer is the key to bending success. In the analysis of simple bending and compound bending, the position of simple bending's unchanged layer was described; it is connected with two vital parameters, the ultimate tensile strength and ultimate press strength. The great productive ratio was illustrated caused by unchanged layer moving outside with the steel strap. From the analysis of compound bending, it was showed that the density and strength was heightened. During the research of compound bending, traditional compound bending was not fit to the components without certain rotary center or with great various curvatures. The NC compound bending was illustrated to solve this question, and it could connect wood bending with NC technology, which would promote the development bending wood industrial greatly. The mechanical hands bending was combine equipment too, which solved the forming question of multi direction bending wood. It is creative for the multi direction bending wood making. The track design and feed calculation were introduced with example, but the steel strap technology couldn't be applied to the mechanical hands bending, so the smallest bending radius was limited. The mechanical hands were controlled by computer, so the Finite Element Method could be used to analyze the bending shape and stress in the certain condition, which conduced to synthesize the effect of moisture, elasticity and wood species.
Contrasting bending and milling to the curve components' process, the bending component was with greater strength than milled component with mathematic description, and the difference in recovery ratio was illustrated too. All above should be valuable to the technology advancement and wood further utilizing in the wood bending corporations.
The typical equipment, wood bending hands was initialized in structure. Control system was designed, and illuminated the system's function and characteristics.
This thesis comes from the national forestry bureau's "948" project "The Technics and Equipments Importation of Bending Wood with Compressing" and national "863" plan "Robot Product Line for Wood Bending", and supported by them.
弯曲木加工，首先要进行木材原料选择，只有选择了适合弯曲的树种才能进行下一步的软化处理，软化过程是将木材放入高温高压的容器中，经过长时间的蒸煮使其软化，必要时可以加入氨水以提高软化效果。随着科技水平的提高，高频和微波加热软化是今后发展的主要方向之一。随着弯曲方式的多样化，局部加热、局部压缩、局部弯曲也是达到木材多向弯曲的手段，这样可以减少拼接和胶合带来的麻烦，提高弯曲木的美观和耐用性。目前世界各国的压缩机多以成捆压缩为主，成捆压缩可以弥补因单根木条上的缺陷而引起的压缩不均现象，本文对成捆压缩的布局和压缩方法进行了讨论，对于工业化生产有一定的实践意义。
无论是手工弯曲还是机械弯曲都需借助一定的工具，模具、刚带是在弯曲过程中起着决定性作用的工具，它可以使中性层外移，减少外层纤维劈裂的可能性，提高弯曲木成品率；在同等条件下，缩小木材最小弯曲半径，达到更大的弯曲曲率。文中分别对矩形截面和圆形截面的弯曲木的最小弯曲半径加以分析，并用图表说明了最小弯曲半径的变化范围，即使同样是使用钢带，用端部可调的钢带比用端部固定的钢带弯曲木材所形成的弯曲半径更小。
对弯曲成形理论进行了分析，弯曲木中性层的位置是决定弯曲成功与否的关键，通过对简式弯曲和复式弯曲的分析，对简式弯曲的中性层位置进行了定量描述，指出了与其相关的两个重要参数(极限拉伸强度与极限压缩强度)的关系；定性地说明了钢带弯曲对中性层的外移而导致高成品率的原因。在对复式弯曲方法的分析中，指出其提高弯曲木密度，增加构件刚度的原因。在研究过程中发现，传统的复式弯曲方法在加工无固定旋转中心和曲率较小的弯曲木构件时应用受到限制，提出了数控复式弯曲方法，解决了无固定旋转中心和曲率变化较大的弯曲木构件的加工问题，并能与发展相对完善的数控系统连接起来，对弯曲木加工业具有很大推动作用。文中对机械手弯曲进行了描述，机械手弯曲也是机械与数控系统相结合的弯曲技术，它对木材多向弯曲是一个突破，可以很好地解决木材多向弯曲的成形问题。文中对弯曲的轨迹设计和进给量的计算进行了详细说明，并应用实例进行了分析。但是，这种方法的局限性是无法将钢带加入其中，对弯曲木的最小弯曲半径有一定的限制。机械手弯曲是由计算机控制的，所以可以利用计算机资源对木材进行有限元分析，通过有限元分析可以迅速求解木材在特定条件下的弯曲形状和弯曲应力，更有利于在弯曲过程中实时考虑木材湿度、弹性模量和材种等各方面的因素。
对弯曲成形和铣削成形的弯曲构件进行了对比分析，通过数学描述解析方法证明了弯曲成形的构件具有更高的强度，同时也指出了两者在出材率上的差异。对我国弯曲木加工企业的技术改进和木材的深加工利用将有一定的价值。
确立了数控弯曲设备(弯曲机械手)的总体结构，设计了其控制系统，并对系统实现的功能及系统的特点进行了详细的说明。
以国家林业局“948”项目“压缩法加工弯曲木生产工艺技术及设备引进”和国家“863”计划项目“弯曲木成形加工机器人生产线”为课题来源，并得到了它们的资助。
Long time ago, people found that timber could be bended with the fire shining. With the development of living condition, the bending woods were applied to the furniture and windows, its processes were filled with more technology. It was applied to the bending wood making that manual bending, mechanical bending and NC bending, and the development of computer technology promoted the bending wood process.
In wood bending, the raw material must be selected at first, which was the foundation to the next softening procedure, softening means the timbers were put into the container with high temperature and press ion. After a long time, the timber was plastic; sometimes the ammonia could be used to enhance the plasticizing affection. The high frequency and microwave softening are the new research fields in the science and technology advancement.
The bending method was multiplex. It is necessary to multi direction wood bending that partial heating, partial compressing and partial bended, which reduced the trouble of joint and agglutination, enhanced the appearance quality and duration. To the presser all the world, the precession in bundles was the process tendency, which eliminated press unbalance caused by the defection of single timber. The distribution and press ion in bundles could provide the theory foundation in the industrial production.
Whether manual bending or mechanical bending, the tools and jigs were necessary, and the steel strap was the key tool in the bending procedure, it made the unchanged layer moving outside, decrease the possibility of outside wood fiber split. In the same condition, the steel strap made the bending radius smaller got great curvature. In this paper, the smallest bending radius of rectangle cross section and round stick were anal sized with the figure, form its variety scope, it was showed that the bending with adjustable end stop could get smaller bending radius than fixed end stop in the steel strap using.
With the analysis of bending theory, the position of unchanged layer is the key to bending success. In the analysis of simple bending and compound bending, the position of simple bending's unchanged layer was described; it is connected with two vital parameters, the ultimate tensile strength and ultimate press strength. The great productive ratio was illustrated caused by unchanged layer moving outside with the steel strap. From the analysis of compound bending, it was showed that the density and strength was heightened. During the research of compound bending, traditional compound bending was not fit to the components without certain rotary center or with great various curvatures. The NC compound bending was illustrated to solve this question, and it could connect wood bending with NC technology, which would promote the development bending wood industrial greatly. The mechanical hands bending was combine equipment too, which solved the forming question of multi direction bending wood. It is creative for the multi direction bending wood making. The track design and feed calculation were introduced with example, but the steel strap technology couldn't be applied to the mechanical hands bending, so the smallest bending radius was limited. The mechanical hands were controlled by computer, so the Finite Element Method could be used to analyze the bending shape and stress in the certain condition, which conduced to synthesize the effect of moisture, elasticity and wood species.
Contrasting bending and milling to the curve components' process, the bending component was with greater strength than milled component with mathematic description, and the difference in recovery ratio was illustrated too. All above should be valuable to the technology advancement and wood further utilizing in the wood bending corporations.
The typical equipment, wood bending hands was initialized in structure. Control system was designed, and illuminated the system's function and characteristics.
This thesis comes from the national forestry bureau's "948" project "The Technics and Equipments Importation of Bending Wood with Compressing" and national "863" plan "Robot Product Line for Wood Bending", and supported by them.
引文
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