A grinding force model allowing for dulling of abrasive wheel cutting grains in plunge cylindrical grinding

A mathematical model is developed for the grinding force in cylindrical plunge grinding that allows for the grinding conditions, the size of the flank wear land areas formed on the grinding wheel cutting grains, the properties of the work material, and the geometrical parameters of the grinding tool and work surface. A formula is obtained for calculating the stock removal rate as a function of the degree of dulling (glazing) of the grinding wheel. The adequacy of the mathematical model of the grinding force in cylindrical plunge grinding is established.     

A new model of grit cutting depth in wafer rotational grinding considering the effect of the grinding wheel,workpiece characteristics,and grinding parameters

Wafer rotational grinding is widely employed for back-thinning and flattening of semiconducting wafers during the manufacturing process of integrated circuits. Grit cutting depth is a comprehensive indicator that characterizes overall grinding conditions, such as the wheel structure, geometry, abrasive grit size, and grinding parameters. Furthermore, grit cutting depth directly affects wafer surface/subsurface quality, grinding force, and wheel performance. The existing grit cutting depth models for wafer rotational grinding cannot provide reasonable results due to the complex grinding process under extremely small grit cutting depth. In this paper, a new grit cutting depth model for wafer rotational grinding is proposed which considers machining parameters, wheel grit shape, wheel surface topography, effective grit number, and elastic deformation of the wheel grit and the workpiece during the grinding process. In addition, based on grit cutting depth and ground surface roughness relationship, a series of grinding experiments under various grit cutting depths are conducted to produce silicon wafers with various surface roughness values and compare the predictive accuracy of the proposed model and the existing models. The results indicate that predictions obtained by the proposed model are in better agreement with the experimental results, while accuracy is improved by 40%–60% compared to the previous models.     

Improvement of grinding performance and investigation of cutting parameters using a grinding mechanism with secondary rotational axis

“Grinding Mechanism having Advanced Secondary Rotational Axis” (GMASRA) is one of the newer plane surface grinding methods that have an uncommon abrasion mechanism. Unlike conventional methods, in GMASRA, there are two rotations of a wheel. The first rotation is the same as in conventional grinding methods, which is the circumferential rotation. The other rotation is the newly developed axial rotation, where the wheel rotates around itself perpendicular to its radial axis. In this study, the effects of certain cutting parameters on arithmetical mean deviation of the assessed profile (the R_a parameter) were investigated. Particularly, the effects of cutting parameters on R_a in the GMASRA grinding process were examined. The selected cutting parameters were the depth of cut, the number of axial revolutions of the wheel, and the stepover distance of the wheel. Five wheels with different properties were chosen. Additionally, GMASRA was modeled using the Taguchi orthogonal test design. In this orthogonal design, the depth of cut, the spindle speed, and the type of grinding wheel were chosen as the control factors. The effect of the specified control factors on the surface roughness was demonstrated using an analysis of variance (ANOVA) test. Results show that GMASRA produced better R_a values than the conventional method. R_a values were very close to each other in every part of the ground workpieces. According to the modeling results, the spindle speed had the highest effect on R_a, followed by the depth of cut and the type of grinding wheel. GMASRA is also very cost effective and can be adapted to most milling machines and CNC milling machines.     

高速磨削合成切削液的研制

当砂轮线速度高于50ｍ/ｓ时,单位时间内通过磨削区的磨粒增加,砂轮与工件的摩擦加剧,发热量增大,引起合成切削液(以下简称磨削液)温度升高[1]。在高速磨削产生的高接触压力下,如果磨削液的清洗性差,则切屑容易粘附在砂轮表面,造成砂轮气孔堵塞、变钝,使用寿命缩短;如果磨削液的润滑性和冷却性差,易造成工件表面烧伤、拉毛和划伤。目前,一些厂的高速磨床仍用普通磨削液,其结果是工件表面粗糙,砂轮耐用度下降,磨削液使用周期变短。针对高速磨削的特点,研制了一种用于轴承加工的高速磨削液,并已应用于工业生产中。1　组成与制备高速磨削液应具…     

Strategies for grinding of chamfers in cutting inserts

In order to increase tool life and improve workpiece quality, cutting processes with geometrically defined cutters demand inserts with a prepared cutting edge. Chamfers are widely used in many processes, since they can provide edge strengthening without damaging the chip flow. In order to achieve a stable and reliable cutting process, uniform chamfer geometry along the insert and high edge quality are necessary. For this, proper grinding strategies for chamfer manufacturing must be taken into account. With the objective of getting knowledge about the chamfer manufacturing process, strategies for grinding of chamfers are investigated in this paper. Chamfers were ground on PCBN, mixed ceramic and cemented carbide cutting inserts with a vitrified bond diamond grinding wheel. A single grain chip thickness model is used to characterize the process and different grinding strategies are analyzed in terms of reduction of chamfer geometry deviation. It was found that high insert rotational speeds increase the edge chipping and that the cutting insert material has a considerable influence on the chamfer geometry deviation.     

刃口磨削裂纹产生机理分析

民用刀剪在加工过程中,由于磨削等原因,容易产生裂纹,引起刀剪刃口卷裂或产生缺口.首先分析了国内刀剪与国外产品之间的差距,简要介绍了刀剪的制造工艺,接下来针对裂纹形成原因,对刀剪磨削过程中的受力情况进行了理论分析.最后,结合3Cr13不锈钢刀剪,给出了加工过程中相应的避免裂纹产生的防范措施和方法.     

液氮冷却在切磨削加工中的应用

随着切磨削技术的发展和环境意识的加强,人们开始重视切削液带来的安全和环境问题,为适应清洁生产和绿色制造对切削液提出的要求,本文对液氮冷却作为传统切削液替代品的应用研究取得的一些进展进行了论述。     

A control-oriented model for the cylindrical grinding process

This paper proposes a control-oriented model for the cylindrical grinding process in the state-space format. Existing models of the grinding process contain, either explicitly or implicitly, several dynamic relationships among various process variables, based on which a nonlinear state-space model can be derived. After a series of experiments are conducted to confirm the dynamic relationships and determine the model coefficients, several applications of the developed model are explored. It is demonstrated that multiple grinding cycles in batch production can be promptly predicted and analyzed using the proposed model. The proposed model enables a new approach to estimation of part qualities such as the surface roughness and actual part size with an observer. Since specific measurement settings may vary from application to application, the system observability is analyzed in order to test which immeasurable variables may be estimated based on available sensors. In addition, the capability of the model to predict multiple grinding cycles is deemed necessary for optimal control of the grinding process. Controllability tests are conducted in order to determine which control inputs are required for achieving such goals.     

铣磨复合加工齿轮的切削参数优化

为减少齿轮复合加工的切削时间,提高加工效率,对铣磨复合加工齿轮切削参数进行了研究,并结合机床的各项约束条件,建立了以最小加工时间为目标函数的铣磨复合加工数学模型,使用改进的量子行为粒子群优化算法对切削参数进行寻优计算. 将寻优计算所得结果与齿轮模数进行最小二乘拟合,得到优化加工时间与齿轮模数、磨齿进给量与齿轮模数的函数关系拟合方程,实现了加工时间最少的目标,并且充分发挥了机床的性能.     

A study on wear mechanism and wear reduction strategies in grinding wheels used for ELID grinding

Metal-bonded superabrasive diamond grinding wheels have superior qualities such as high bond strength, high stability and high grindability. The major problems encountered are wheel loading and glazing, which impedes the effectiveness of the grinding wheel. Electrolytic in-process dressing (ELID) is an effective method to dress the grinding wheel during grinding. The wear mechanism of metal-bonded grinding wheels dressed using ELID is different form the conventional grinding methods because the bond strength of the wheel-working surface is reduced by electrolysis. The reduction of bond strength reduces the grit-depth-of-cut and hence the surface finish is improved. The oxide layer formed on the surface of the grinding wheel experiences macrofracture at the end of wheel life while machining hard and brittle workpieces. When the wheel wear is dominated by macrofracture, the wheel-working surface is free from loaded chips and worn diamond grits. When the oxide layer is removed from the wheel surface, the electrical conductivity of the grinding wheel increases, and that stimulates electrolytic dressing. The conditions applied to the pulse current influence the amount of layer oxidizing from the grinding wheel surface. Longer pulse ‘on’ time increases the wheel wear. Shorter pulse ‘on’ time can be selected for a courser grit size wheel since that type of wheel needs high grinding efficiency. Equal pulse ‘on’ and ‘off’ time is desired for finer grit size wheels to obtain stable and ultraprecision surface finish.     

铜管切削及端面磨削机床设计

首先利用三维设计软件进行方案结构设计,再从液压系统原理图的确定方面对铜管切削及端面磨削机床进行了详细的分析,确保其性能良好.实验和应用证明:该机床加工效率高,液压系统运转平稳,调节性能较好,使用效果良好.     

A study on the cutting mechanism of microcutting using molecular Dynamics

Ultraprecision metal cutting (UPMC) technology, which makes possible submicrometre form accuracy and nanometre roughness, is developed to reach the 1 nm nominal (undeformed) thickness of cut. At this thickness level, the finite element method (FEM) cannot be used to solve the problem. Molecular Dynamics can be applied to this small cutting depth.In this paper using molecular dynamics simulation, microcutting with a subnanometre chip thickness, the cutting mechanism for the microcutting condition, i.e. tool edge configuration, cut material and cutting speed, are evaluated.As the result, the simulation of the cutting mechanism at subnanometre depth of cut is evaluated.