A local process model for simulation of robotic belt grinding

A local process model to estimate the material removal rate in robotic belt grinding is presented and applied to the process simulation system. It calculate the acting force by incorporating the local geometry information of the workpiece instead of the cutting depth parameter with only one certain value as in a global grinding model. The simulation accuracy can be improved to below 5% even for a non-uniform contact under stable cutting conditions.     

聚氨酯摩擦盘的磨削加工研究

聚氨酯橡胶是一种难切削加工非金属材料,材料软、弹性大且导热性较差,因此很难加工到要求的形状精度、尺寸精度及表面粗糙度。针对聚氨酯橡胶的这种加工性能,提出了聚氨酯摩擦盘的磨削加工工艺:先用成型法进行粗磨,再用成型法进行精磨和抛光。粗磨选用30#粒度的黑色碳化硅大气孔陶瓷结合剂砂轮,N级硬度,切削用量0.01mm,用电镀金刚石滚轮修整砂轮圆弧,成型磨削,可以保证聚氨酯摩擦盘的形状和位置精度(R=3.5-+00..1058,S/2=3±0.05mm);精磨选用具有抛光作用的120#白刚玉PVA砂轮,用电镀金刚石滚轮修整砂轮圆弧,精磨和抛光同时完成,可以保证聚氨酯摩擦盘的尺寸精度(ΦA=50±0.03mm)和表面粗糙度(Ra=0.4μm)。     

Optimal planning of an adaptively controlled robotic disk grinding process

In this paper, an adaptive control optimization (ACO) robotic grinding system is described. An industrial robot equipped with a pneumatic grinder, a six degree-of-freedom force sensor, and two non-contact inductive proximity sensors inter-linked with a PC are the integrated part of this system. The system is designed to grind the workpiece with maximum possible metal removal rate (MRR) within the constraints on workpiece burn and surface finish which, in turn, depend on the degree of disk dullness. A model-based approach has been used for the optimization. To perform the cutting operation, normal grinding force and robot feed speed have been selected as control parameters. The normal grinding force is effectively tracked on-line using an Adaptive Generalized Predictive Controller (GPC) algorithm, which was experimentally tested. The optimal robot feed speed is tracked due to the robot system's capability to accept on-line end effector path modifications by means of the robot's “ALTER” command. This system is able to plan and efficiently execute a multi-pass grinding sequence for removing large amounts of unwanted material. Several illustrative results are presented that confirm the practical feasibility of the optimization concept and demonstrate the performance of the ACO robotic grinding system.     

A neural/fuzzy optimal process model for robotic part assembly

A process model for part assembly task, using robotic manipulators, is introduced. A neural network control strategy, based on measured force and moment data, for avoiding jamming during part insertion is presented. Fuzzy set theory, well-suited to the management of uncertainty, is introduced to address the uncertainty problem associated with the part insertion procedure. The degree of uncertainty associated with the part insertion is used as an optimality criterion for a specific task execution. The proposed technique is applicable to a wide range of robotic tasks including part mating with various shaped parts.     

Dressing process model for vitrified bonded grinding wheels

A holistic dressing process model for vitrified bonded grinding wheels was designed. It regards the dressing process as a tribological system subjected to a complex load collective. The intensive analysis of the input variables and their impact on the system function led to new knowledge about the acting mechanisms. The model enables a qualitative prognosis of the grinding wheel topography, the dressing forces and the thermal dressing process load.     

Surface finish in robotic disk grinding

In spite of the various complexities, the ground surface during robotic grinding shows a definite and distinct surface texture. This paper presents a simple model for the surface finish produced during this process. The model is based on two simple assumptions. First is that though many grits remove material, the last grit that cuts largely in the ground surface determines the surface finish value. The second assumption is that the average shape of the active grit is spherical which generates a groove of parabolic cross section. The model is shown to be consistent with surface finish values measured experimentally during robotic rigid disk grinding and is able to predict the effect on surface finish to be expected when a given grinding variable is changed. It can be used for the purpose of process planning to improve the surface finish when desired.     

Adaptive human-robot collaboration for robotic grinding of complex workpieces

This paper presents an adaptive intelligent human-robot collaborative approach to facilitate trajectory planning for robotic belt grinding of complex parts. The approach bridges the experience of skilled operators through an immersive virtual reality based interface that allows operators to demonstrate a favourable grinding trajectory via perceiving the grinding forces and observing the simulated grinding effects, and adaptively adjust key grinding parameters based on their experience. This approach combines the advantages of human intelligence and skills with the movement accuracy of robots to enhance the trajectory planning efficiency and ground surface quality.     

Analysis of rigid-disk wear during robotic grinding

An investigation of disk-wear during robotic grinding is described. It is shown that the wear of resinoid bonded disks can be described via combined thermally and mechanically controlled mechanisms. The process of accelerated grain wear can be correlated with the rise in temperature at the grain-work interface in a manner predictable from the simple law of adhesive wear in combination with the theory of rate process. Experimental results are shown to confirm the theoretical interpretation.     

转向架焊接接头无齿盘自动化精磨工艺

针对转向架焊后的接头自动化无齿盘精磨工艺中的残余应力及组织演变规律的变化特点,系统研究高速切削精磨下的转向架焊接接头打磨区域的的表面粗糙度、残余应力以及显微组织。结果表明,使用无齿精磨后的表面粗糙度小于1μm,表面粗糙度云图分布均匀性。残余主应力σmax和σmin均小于转向架的屈服强度。微观组织结构表明精磨后未出现淬硬组织或回火组织,经过无齿盘高速精磨后,表层组织均匀。     

磨削工艺参数优化建模的可靠性研究

通过磨削过程和回归方程建模方法分析,探讨了质量指标作为优化约束条件失效的原因,提出了建立可靠的磨削优化数学模型的方法,并给出了具体应用的实例。     

新型多孔金属结合剂金刚石磨盘研制与磨削实验研究

针对引入孔隙结构后,多孔金属结合剂超硬磨具耐用度降低的问题,提出利用超硬磨料钎焊技术改善胎体对金刚石磨料的把持力,以提高工具寿命,并成功研制出一种新型多孔金属结合剂金刚石磨盘。测试分析了新型磨盘的节块性能,并通过磨削花岗岩安溪红635试验,对新型磨盘的磨削效果进行评价。实验结果表明:新型磨盘节块强度在100MPa左右,孔隙率为60%,孔隙在节块内部分布均匀,且金属结合剂与金刚石表面发生了牢固的化学冶金结合;磨削石材的表面粗糙度Ra0.77~1.59μm,磨盘的磨削比达到760。     

用于焊接机器人的TOPTIG工艺

TOPTIG是一种新的机器人焊接工艺,该工艺结合了TIG焊（焊接质量）和MIG焊（生产效率）的优点,其关键部件是一把独创设计的焊枪,填充焊丝穿过喷嘴与电机尖角平行。这种结构有一个重要的优点：减小了焊枪的总体尺寸,加强了机器人焊接时对于复杂焊接结构的可达性,无需借助机器人的第六轴改变焊枪及送丝的朝向。与该焊枪相关联的几个技术特征有：自动更换钨电极,双汽流喷嘴和推拉丝送丝机构。该焊接工艺已经在汽车制造工业中得到实际应用,如使用CuSi3焊丝无飞溅焊接镀锌板;食品工业,金属装饰品或化工产品的其他应用,如焊接不锈钢或铝合金。     

An adaptive-control system for the grinding process

A new adaptive-control system has been successful in the external, cylindrical cross-grinding process in terms of raising the material removal rate and improving the geometrical accuracy of slender shafts. In comparison with the conventional method in the cross-grinding process, this method of adaptive-control grinding is superior in respect of the material removal rate and the roundness of the slender shafts. The preceding beneficial effects are independent of the grinding parameters chosen. It is practicable, therefore, for the adaptive control system to be applied in practical production.     

整体叶盘机器人砂带磨削轨迹优化及其实验

整体叶盘具有结构复杂、材料难加工的特点,其加工精度和表面质量对航空发动机整体性能有至关重要的影响。当前,机器人砂带磨削技术已应用于整体叶盘类复杂曲面的磨削加工。然而,在磨削轨迹规划时多采用目标点均布的方式,这就要求目标点必须足够多,从而导致加工效率过低。基于改进的等弦高误差法对整体叶盘机器人砂带磨削的磨削轨迹进行优化分析,并开展相关仿真与实验验证。结果表明：改进的等弦高误差法可根据曲率变化优化磨削轨迹,减少目标加工点数量,从而提高加工效率。经实验验证,与轨迹优化前相比,优化后整体叶盘的加工效率提高了42.9%;优化后的表面粗糙度Ra可达0.26μm,且叶片一致性较好,尤其是在曲率变化较大的位置。     

A discrete system model for form error control in surface grinding

Precision and quality have been the critical issues for many industries. For better machining quality, effective models will be needed in order to realize precision control. Surface form error is a difficult issue among the three main geometric features, which are size, form error, and roughness. There are little studies on modeling for form error control. In this study, a discrete system model for form error control in surface grinding is proposed based on three key relationships. Mathematical models describing the workpiece size reduction profile together with workpiece form error profile in relation to grinding pass number are presented. The grinding force constant k_w and the unit force deflection y_pg(x,z)/P_g can be estimated through experimental testing. Many operational process parameters are actually reflected in the proposed model and further separate studies are necessary for specific and accurate relationship between the operational process parameters and the model parameters. The results of the experimental testing are in good agreement with the theoretical results. For the average size reduction c_n, the average relative error is as low as 1.34%. This shows that the proposed model is quite accurate. The proposed model is seen effective in obtaining the theoretical tangential force F_tntheo. The stringent point to point spatial comparison shows that the error between theoretical and experimental results is less than 2.3 μm and the average relative error is less than 6.93%. The proposed model is seen effective in size reduction prediction, which can be used to determine surface form profile y_n(x,z). The average relative error in the temporal comparison is 5.31%. It shows that the proposed model can be used to predict size reduction along the time axis, which is represented by the grinding pass. The results give confidence for use of the proposed control system model for form error control. To avoid the assumption of zero error in the initial workpiece surface, in-process form profile sensor is necessary. Further studies are needed for more accurate verification of the proposed model.     

A fuzzy model for predicting burns in surface grinding of steel

Existing analytical thermal models for predicting surface burns due to grinding have limited use because of their reliance on parameters that are not readily obtainable in practice. This paper presents a practical and consistent fuzzy rule-based model for estimating the grinding conditions at which “burn limits” occur. The model consists of 37 absolute and eight relative rules. It has a wide range of applications over many types of steels, Alundum wheels, and grinding conditions. It is also simple to implement, from a rule-chart mode to an intelligent on-line adaptive control mode.     

Fine grinding of silicon wafers: a mathematical model for grinding marks

The majority of today’s integrated circuits are constructed on silicon wafers. Fine-grinding process has great potential to improve wafer quality at a low cost. Three papers on fine grinding were previously published in this journal. The first paper discussed its uniqueness and special requirements. The second one presented the results of a designed experimental investigation. The third paper developed a mathematical model for the chuck shape, addressing one of the technical barriers that have hindered the widespread application of this technology: difficulty and uncertainty in chuck preparation. As a follow up, this paper addresses another technical barrier: lack of understanding on grinding marks. A mathematical model to predict the locus of the grinding lines and the distance between two adjacent grinding lines is first developed. With the developed model, the relationships between grinding marks and various process parameters (wheel rotational speed, chuck rotational speed, and wheel diameter) are then discussed. Finally, results of pilot experiments to verify the model are discussed.     

Workpiece burn and surface finish during controlled force robotic disk grinding

Workpiece burn and surface finish during robotic disk grinding are studied under controlled force conditions. Workpiece burn occurs due to gradual deterioration in the sharpness of active grains participating in the cutting process. This change in the sharpness of grains can be indirectly monitored by the change in the average coefficient of friction and average depth of cut. Both of these parameters gradually reduce with increasing disk wear due to attrition. In this paper, an analytical expression is derived which can be used to predict the occurrence of such burns during controlled force grinding. The experiments conducted under these conditions using a finely tuned PID controlled showed fair agreement with the predicted results. The experiments also showed that the surface finish gradually improves during successive passes. Hence, an attempt has been made to explain and predict this changing behaviour in the surface finish on the basis of gradual deterioration in the cutting efficiency of the disk. These relations can be used for practical optimization of the robotic grinding process.     

A review of cutting fluid application in the grinding process

It is generally accepted that heat generation is the limiting factor in the grinding process due to the thermal damage associated with it. To combat this energy transfer, a cutting fluid is often applied to the operation. These cutting fluids remove or limit the amount of energy transferred to the workpiece through debris flushing, lubrication and the cooling effects of the liquid. There have been many new and exciting systems developed for cutting fluid application in the grinding process. This paper reviews some of the common as well as some of the more obscure cutting fluid systems that have been employed in recent years with an emphasis on creep-feed applications. The review also suggests possible avenues of future research in cutting fluid application for the grinding process.     

Fast time constant estimation for plunge grinding process control

The time constant of a grinding control system indicates the speed of response to a control command and reflects variations of the wheel condition. In order to allow correct and continuous control adjustment, fast in-process estimation of the parameter is necessary. The significance of the grinding system time constant is discussed and the control system for the plunge grinding process described. An algorithm for fast time constant estimation is presented for adaptive control of the grinding process. The algorithm is useful for geometry-based grinding control systems where a workpiece size sensor is used and multiple control tasks are implemented. Experimental testing of the algorithm is explained and comparison between results from grinding and those from analysis shows that the proposed algorithm is sufficiently accurate and effective for adaptive control of the plunge grinding process.