Musculoskeletal exposure of manual spray painting in the woodworking industry – an ergonomic study on painters

In the present study the ergonomic conditions of manual spray painting in the woodworking industry have been studied. Manual spray painting is, despite rationalisations, quite common in the Swedish woodworking industry. Interviews with spray painters showed that they had higher prevalence of musculoskeletal symptoms in their right shoulder compared with other workers with manual work. A majority of the spray painters painted work-pieces lying on a work-table. A majority of these painters abduct the right upper-arm so much when painting the horizontal surface of the work-piece that they risk supraspinatus tendinitis. The upper-arm abduction when painting horizontal surfaces could be decreased without introducing new ergonomic disadvantages by installing work-tables with powered height control or possibly also by changing the geometry of the spray gun. Gripping the spray gun trigger was for some of the painters identified as causing a high risk for WMSD in the wrist. Lower spray gun trigger force would improve the situation. This could be done by the users in several ways, such as greasing the trigger mechanism and/or decreasing the spring pressure on the fluid needle.

Relevance to industry

The study highlights some major ergonomic problems for a fairly large group of workers in the woodworking industry.     

基于点云的补漆机器人系统

汽车补漆机器人需要面对各种不同大小的车型,适配各种造型曲面和颜色,这种高度自适应要求使得补漆机器人在目标跟踪、路径规划、运动空间等方面的设计难度远超汽车厂的喷漆机器人.因此需要重新规划喷漆路径,首先对汽车的点云数据进行分部位切割,然后以八邻域法计算封闭曲面轮廓,最后以切片法在曲面上生成光栅轨迹,形成了每一个补漆面的关键路径.设计了八轴桁架机器人系统,用蚁群算法计算生成八轴联动时的路径规划,再通过倍福的ADS协议将路径数据和梯形曲线的加速度下发到PLC运动控制程序,完成各关节轴的联动协同补漆运动.实测表明,该系统能针对不同汽车,自动控制机器人工具轴心以法向量对准任意曲面,并以联动方式驱动八轴平稳跟踪曲面运动.该系统可广泛应用于各种曲面的机器人加工.     

Coating thickness optimization for a robotized thermal spray system

Thermal spraying techniques are used to protect or improve the surface performance of a workpiece by adding melted (or heated) powders onto the surface. Thickness and uniformity control are critical for obtaining an excellent thermal spraying coating. In the contemporary manufacturing industry, with the increasing demand for efficient and accurate processes, robot manipulators and handling systems have been developed to control the movement of the spray gun relative to the workpiece surface, where the robot manipulators and handling systems lead the spray gun to reciprocate along a predefined path. However, the research on optimizing the path for generating the desired coating thickness is very limited. In this paper, a parametric coating thickness prediction model is adapted from our previous research. Then, the Nelder-Mead method drives the model to find out the optimal kinematic parameters of a zigzag (meander) path for a uniform coating with the desired thickness. Based on the obtained kinematic parameters, the trajectory and program of a robot end effector (spray gun) are yielded. Finally, a prototype system with an intuitive user interface is developed to integrate these functions. From the input of a Gaussian coating growth model and a substrate, it can provide an optimal path directly. At the end of this work, one case was implemented by a homemade spray system and a robot system for verifying the effectiveness of the system.     

An ergonomic comparison of industrial spray paint guns

Two spray guns were used by 10 subjects in a laboratory. One gun was a `traditional' spray gun. The other was the OMX gun which had `ergonomic' features including reduced gun and hose weight and two triggers (one for horizontal surfaces and one for vertical). The 10 subjects (5 experienced industrial spray painters and 5 inexperienced students) used each gun for 4 h. The criteria used to evaluate the two guns were: (1) Wrist deviation in all three axes, (2) EMG frequency shift of 3 shoulder muscles over the test period, (3) integrated EMG activity of the forearm flexors, and (4) body discomfort ratings.It was found that the OMX gun resulted in significantly less radial/ulnar deviation in the wrist, and moderately increased flexion/extension and pronation/supination deviations from neutral. During the painting period, up to 50% less fatigue in the shoulder muscles was found for the OMX gun. Additionally, the triggering activation levels for sustained grip contractions were found to be acceptable for the OMX gun when using the short trigger. Finally, the amount of discomfort reported by the subjects was statistically lower in the shoulder, upper back, arm, elbow, forearm, wrist, and hand with the OMX gun design. Collectively, these results indicate that the OMX gun would be expected to reduce exposure to occupational risk factors for workers. This study demonstrated how the incorporation of ergonomic design principles can be used to minimize occupationally-related risk.Relevance to industryCumulative trauma disorders (CTDs) are soft tissue disorders resulting from repeated exertions and excessive movements of the body. Industrial spray painting fits the profile of a highly repetitive task. Improving spray paint gun design could potentially reduce the risk of CTDs in industrial spray painting tasks.     

机器人喷涂过程中的喷炬建模及仿真研究

本文在研究了喷涂机器人的喷炬特性后，根据物理模型采用了一种简化的数学模型来 描述在喷炬流场中的涂料流量分布函数．并从上述函数出发，进一步得到了喷涂的涂料沉积 方程．根据仿真实验与实际喷涂的数据进行比较，证明了模型的正确性．这一喷炬模型是喷 涂机器人离线编程系统的重要组成部分．     

Paint deposition modeling for trajectory planning on automotive surfaces

This research is focused on developing trajectory planning tools for the automotive painting industry. The geometric complexity of automotive surfaces and the complexity of the spray patterns produced by modern paint atomizers combine to make this a challenging and interesting problem. This paper documents our efforts to develop computationally tractable analytic deposition models for electrostatic rotating bell (ESRB) atomizers, which have recently become widely used in the automotive painting industry. The models presented in this paper account for both the effects of surface curvature as well as the deposition pattern of ESRB atomizers in a computationally tractable form, enabling the development of automated trajectory generation tools. We present experimental results used to develop and validate the models, and verify the interaction between the deposition pattern, the atomizer trajectory, and the surface curvature. Limitations of the deposition model with respect to predictions of paint deposition on highly curved surfaces are discussed. Note to Practitioners-The empirical paint deposition models developed herein, which are fit to experimental data, offer a significant improvement over models that are typically used in industrial robot simulations. The improved simulation results come without the computational cost and complexity of finite element methods. The models could be incorporated, as is, into existing industrial simulation tools, provided the users are cognizant of the model limitations with respect to highly curved surfaces. Although the models are based on readily available information, incorporating the models into existing robot simulation software would likely require support from the software vendor.     

A study on robot path planning from a solid model

CAD/CAM technologies have been developed and are beginning to penetrate rapidly into industries. At present, however, there are many problems that should be solved before CAD/CAM technologies can play their proper role in the total process. In an effort to improve CAD/CAM current circumstances, a trial CAE system which generates an operation path of a robot from a solid-model built-in CAD process, has been examined. In this system, solid models are built by performing set operations such as addition, subtraction, intersection between several primitives or solid models. Processing is made for a solid model represented by B-rep (boundary representation). To ease the processing, curved faces such as spherical, cylindrical, or conical surfaces, are approximated by several flat planes. As a first step, by assuming Gaussian spatial distribution for a painting gun, path planning of a painting robot for a convex solid body has been examined. A scanning plane is defined for each flat plane and a path of robot effector is generated on this plane.     

Painting robot with multi-fingered hands and stereo vision

In this paper, we describe a painting robot with multi-fingered hands and stereo vision. The goal of this study is for the robot to reproduce the whole procedure involved in human painting. A painting action is divided into three phases: obtaining a 3D model, composing a picture model, and painting by a robot. In this system, various feedback techniques including computer vision and force sensors are used. As experiments, an apple and a human silhouette are painted on a canvas using this system.     

复杂纹理的生成与定位技术

本文提出了一种直接在三维景物表面上进行纹理喷绘的复杂纹理生成技术．与传统二维喷绘系统不同，本方法实时地将每一笔划所确定的颜色值作为某种纹理属性直接在景物表面上喷绘出各种纹理及光照效果．利用该技术，我们可方便地解决相邻表面间纹理的连续拼接及多重纹理之间的过渡问题．结果表明，本方法可用来生成非常复杂的纹理．     

The inverse approach of FlexPaint [robotic spray painting]

Industrial painting automation with robots is very efficient and fast and often used in production lines. However, a big disadvantage is the off-line programming paradigm for the painting robots. This is time-consuming and can be justified economically only for large lot sizes. Hence, a totally new approach to robot programming is required to enable painting of small lot sizes. The objective of the FlexPaint project is to automate robot-programming applications of small lot sizes with a very high number of part variants. This article reports the new approach, referred to as an inverse approach that automatically generates the painting motion. This approach opens new markets for robotic applications. The automatic robot program generation enables, for the first time, painting parts of a lot size of one. The principle of this approach is based on formalizing the technological knowledge in a geometry library and a process library. Laser range sensors are used to obtain an accurate scan of the part. Process-relevant classes of features are detected as specified in the geometry library. Feature classes are linked in the process library to basic paint strategies, which are grouped to automatically generate the robot paint tool trajectory. Finally collisions-free and executable robot motions are automatically obtained for the actual robot kinematics. Painting results for several parts, e.g., different motors with gearboxes, would result with this new approach.     

Decorating surfaces with bidirectional texture functions

We present a system for decorating arbitrary surfaces with bidirectional texture functions (BTF). Our system generates BTFs in two steps. First, we automatically synthesize a BTF over the target surface from a given BTF sample. Then, we let the user interactively paint BTF patches onto the surface such that the painted patches seamlessly integrate with the background patterns. Our system is based on a patch-based texture synthesis approach known as quilting. We present a graphcut algorithm for BTF synthesis on surfaces and the algorithm works well for a wide variety of BTF samples, including those which present problems for existing algorithms. We also describe a graphcut texture painting algorithm for creating new surface imperfections (e.g., dirt, cracks, scratches) from existing imperfections found in input BTF samples. Using these algorithms, we can decorate surfaces with real-world textures that have spatially-variant reflectance, fine-scale geometry details, and surfaces imperfections. A particularly attractive feature of BTF painting is that it allows us to capture imperfections of real materials and paint them onto geometry models. We demonstrate the effectiveness of our system with examples.     

A frequency-domain approach to determining the path separation for spray coating

Many modern spray deposition processes, such as spray painting or coating, are automated by using a robot to move an applicator in a series of passes over the surface being sprayed. Determining the robot path that creates the required coat thickness over the surface can be considered as an optimization problem, which traditionally has been solved in the spatial domain. In this paper, results from sampling theory are used to transfer the problem into the spatial frequency domain, which determines the optimal separation between passes. The paper also shows how angled raster patterns can be combined to provide a continuous path over the surface that generates the required distribution of deposited material. Note to Practitioners-This paper is motivated by the problem of producing a given distribution of coat thickness during an automated spraying or deposition process. The coating is applied by an applicator that is moved by a robot whose path consists of a series of passes over a surface, and the aim is to determine the separation between the passes and the changes to the deposition rate or robot velocity that will produce the required thickness distribution. In many applications, a uniform thickness is required over the surface, but this paper also considers the problem of producing a shaped thickness profile. The analysis uses ideas from Shannon's sampling theorem to move the problem into the frequency domain, which provides a direct link between the Fourier transform of spray footprint on the surface and the separation of passes of the applicator as it moves over the surface. The paper also introduces a scanning strategy that consists of a combination of two sets of angled raster scans. Compared to paths consisting of conventional scans, this has the advantage that it reduces the time that the robot spends off the edge of the surface.     

Tool path planning for compound surfaces in spray forming processes

Spray forming is an emerging manufacturing process. The automated tool planning for this process is a nontrivial problem, especially for geometry-complicated parts consisting of multiple freeform surfaces. Existing tool planning approaches are not able to deal with this kind of compound surface. This paper proposes a tool-path planning approach which optimizes the tool motion performance and the thickness uniformity. There are two steps in this approach. The first step partitions the part surface into flat patches based on the topology and normal directions. The second step determines the tool movement patterns and the sweeping directions for each flat patch. Based on the above two steps, optimal tool paths can be calculated. Experimental tests are carried out on automotive body parts and the results validate the proposed approach. Note to Practitioners-This paper was motivated by the problem of automatically planning tool paths for spray forming using Programmable Powdered Preforming Process (P4) technology. However, the proposed approach can be applied to other surface manufacturing applications such as spray painting, spray cleaning, rapid tooling, etc. Existing tool planning approaches are not able to handle complicated, multi-patch surfaces. This paper proposes a methodology to partition complicated surfaces into easy-to-handle patches and generate tool paths with optimized thickness uniformity and tool motion performance. We tested the approach using simulation on sample automotive body parts and proved its feasibility. However, this approach requires that the parts to be sprayed belong to the sheet-metal type so that the part geometry can be analyzed on a plane. In our future research, we will run physical tests on actual parts and investigate the deposition effects on the thickness uniformity.     

Video Painting via Motion Layer Manipulation

Temporal coherence is an important problem in Non‐Photorealistic Rendering for videos. In this paper, we present a novel approach to enhance temporal coherence in video painting. Instead of painting on video frame, our approach first partitions the video into multiple motion layers, and then places the brush strokes on the layers to generate the painted imagery. The extracted motion layers consist of one background layer and several object layers in each frame. Then, background layers from all the frames are aligned into a panoramic image, on which brush strokes are placed to paint the background in one‐shot. The strokes used to paint object layers are propagated frame by frame using smooth transformations defined by thin plate splines. Once the background and object layers are painted, they are projected back to each frame and blent to form the final painting results. Thanks to painting a single image, our approach can completely eliminate the flickering in background, and temporal coherence on object layers is also significantly enhanced due to the smooth transformation over frames. Additionally, by controlling the painting strokes on different layers, our approach is easy to generate painted video with multi‐style. Experimental results show that our approach is both robust and efficient to generate plausible video painting.     

Transformative CAD based industrial robot program generation

Industrial robots are widely used in various processes of surface manufacturing, such as spray painting, spray forming, rapid tooling, spray coating, and polishing. Robot programming for these applications is still time consuming and costly. Typical teaching methods are not cost effective and efficient. There are many off-line programming methods developed to reduce the robot programming effort. However, these methods suffer many practical issues, such as cable/hose tangling, robot configuration, collision, and reachability. To solve these problems, this paper discusses a new method to generate robot programs. Since industrial robots have been used in production for decades, there are many robot programs for different parts generated by the robot programmers. These robot programs, which contain not only the robot paths, but also the programmers' knowledge and process parameters, can be transformed to generate new robot programs for similar parts. In this paper, a transformative robot program generation method is developed based on the existing ones in the database. Experiments were performed to validate the developed methodology. The results are very promising in reducing the programming efforts in surface manufacturing.     

Modelling the Texture of Paint

We present an extension to the WET & STICKY model. A method of modelling textured and shiny paint is described using bump mapping and standard illumination models. The qualities of the paint are used to supply input to the texture and lighting models. We demonstrate that a dynamic model of textured paint provides the user with valuable visual cluesfor the production of realistic painted images. We also propose further extensions which would allow the use of different lighting models for different paints, allowing for paint attributes which are unachievable either with traditional painting or with earlier forms of electronic painting.     

家具喷涂机器人喷枪轨迹生成分析与研究

根据喷漆机器人自动轨迹生成系统的组成与结构,提出了针对家具喷涂的喷漆机器人喷枪轨迹的设计方案.该方案以使家具表面漆膜厚度差达到最小为设计目标,在喷枪方向及空间路径为已知和未知两种条件下,分别给出了沿指定空间路径和基于自由表面的喷枪最优轨迹的求解方法,以解决喷漆机器人喷枪最优轨迹的规划问题.     

PJ-1喷漆机器人的微机控制

本文介绍了我国第一台微型机控制的多关节,电液伺服型喷漆机器人 PJ-1 的计算机控制系统的原理及软件。该系统以一台八位通用微型机为基础构成控制器。在单用户、多任务实时操作系统的支持下,采用软磁盘作为作业内容存储器,并把绝对位置量和采样间隔内的位移量进行组合存储。从根本上解决了喷漆机器人因作业记忆容量大带来的存储限制、     

机器人图形示教盒编程的研究

本文介绍机器人作业的图形示教盒编程.通过建立机器人的运动学和三维几何模型,采用实时动画技术,在计算机屏幕上对机器人进行图形仿真示教,文中还讨论了图形示教程序的单步执行和实时修正方法,并给出了国产 PJ-lA 机器人进行喷漆作业的图形示教盒编程的实例.结果表明:机器人的图形示教盒编程具有生动、方便的特点,为机器人的编程研究提供了适用的工具.     

CAD‐based automated robot programming in adhesive spray systems for shoe outsoles and uppers

Most shoe manufacturing processes are not yet automated; it puts restrictions on increasing productivity. Among them, adhesive application processes particularly are holding the most workers and working hours. In addition, the working environment is very poor due to the toxicity of adhesive agents. In the case of automating an adhesive application process by using a robot, robot teaching by playback is difficult to produce high productivity because the kinds of shoes to be taught mount up to several thousands. To cope with it, it is necessary to generate robot working paths automatically according to the kind, the size, or the right and the left of shoes, and also to teach the generated paths to a robot automatically. This paper presents a method to generate three‐dimensional robot working paths off‐line based on CAD data in an automatic adhesive spray system for shoe outsoles and uppers. First, this paper describes how to extract the three‐dimensional data of an outsole outline from a two‐dimensional CAD drawing file. Second, it describes how to extract the three‐dimensional data of an upper profiling line from the three‐dimensional scanning data that is opened in a three‐dimensional CAD program. Third, it describes how to generate robot working paths based on the extracted data and the nozzle setting parameters for adhesive spray. Also, a series of experiments for adhesive spray is performed to verify the effectiveness of the presented methods. This study will do much for increasing productivity in shoe manufacturing as a core work of a robotic adhesive spray system. © 2004 Wiley Periodicals, Inc.