Hybrid (LASER + CNC) process for lubricant groove on linear guides

A novel hybrid process [LASER?+?computer numerical control (CNC) machining] is used to fabricate a linear motion guide. A 20-W pulsed fiber laser and a three-axis CNC machining center were combined to fabricate microscale lubrication grooves on a 5-mm wide linear guide contact surface made of SCM-440H material. Ablation fabrication speed was increased up to 1,000 mm/min (or 16.7 mm/s) with a great ablation quality without any tool wear. The mean values of patterned sizes of lubrication grooves were measured to be between 40 and 80?μm in width and between 150 and 275?μm in depth with a laser pulse repetition of 25 kHz. A specially designed optical device was compact enough to be installed on CNC machine. It was mounted on the CNC spindle and proved to be flexible enough to deliver the laser beam on to the work piece. The microscale ablation quality of the surface was of sufficient quality to be adopted on most linear motion related applications.     

Designing and manufacturing an automated lubrication control system in CNC machine tool guideways for more precise machining and less oil consumption

Machine lubrication systems are a very important portion of manufacturing and production workshop maintenance. Automatic lubrication systems eliminate the need for often careless manual lubrication, providing a safer, more frequent, and opportune monitored approach to machine lubrication. However, traditional automated lubrication systems have inherent environmental and technical–economic problems. With the goal of higher machining precision, cost-effectiveness, greater reduction in oil consumption, and more flexible performance, an automated lubrication control system is introduced in this research work. The new automated lubrication control system in computer numerical control machine tool guideways is a novel approach in machining technology; failure detection/correction in the lubrication system may be identified by temperature signals from sensitive temperature sensors installed in the machine tool guideways, with the signals reflecting the friction, wear, and loading conditions. Data collected via temperature sensors, data analysis, and preparation of commanding signals are analyzed by a lubrication control unit (LCU). The LCU transmits signals to actuators to trigger oil injection by the oil pump. The display unit presents real-time measured temperature variations along with the pump's operation state.     

Cutting force reduction and surface quality improvement in machining of aerospace duralumin AL-2017-T4 using carbon onion nanolubrication system

In machining of very high precision Duralumin AL-2017-T4 for aerospace applications, the shape varieties of the product lead to many different complicated shapes to be developed. The computer numerical control (CNC) milling machine facilities provides a wide variety of parameter set-up, making the machining process on the Duralumin AL-2017-T4 excellent in manufacturing complicated special products compared with other machining processes. However, the demand for high quality and fully automated production focuses attention on the cutting process, which are partial determinant of the quality of surface and affects the appearance, function, and reliability of the products. The key solution is to increase the effectiveness of existing lubrication systems in the machining process in order to improve product quality as it could reduce the friction component at the tool–chip interface. For further improvement, introducing the nanolubrication system could reduce the cutting force and produce much better surface quality as the rolling action of billions units of nanoparticles at the tool–chip interface could reduce the coefficient of friction significantly. In this study, carbon onion has been used as nanoparticle mixed with ordinary mineral oil at different concentrations to investigate the cutting force reduction and the surface quality improvement of CNC end-milling machined Duralumin AL-2017-T4. From the results, with using of carbon onion nanolubricant, the cutting force and surface roughness values are reduced by 21.99 and 46.32 %, respectively, compared with the case of using ordinary lubrication systems. This can be attributed to the tribological properties of carbon onion, which reduces the coefficient of friction at the tool–chip interface during the machining process.     

一种数控切削机床运行能耗状态在线判别方法

机床运行能耗状态由一系列的能耗状态节点和能耗过程构成。针对至今仍存在一些关键状态节点无法判别等问题,提出了一种数控机床运行能耗状态在线判别方法。该方法基于数控机床运行能耗状态和状态节点的系统分析,并综合机床功率信息和数控系统通信信息,提出关键节点状态与过程状态在线判别方法,解决了切削加工开始、完成等关键节点和精加工状态判别等难题,从而实现了数控机床全部运行能耗状态的在线判别。在FANUC数控机床上进行的案例研究验证了该方法的有效性和实用性。     

车间生产过程的能量足迹建模与加工参数协同优化

为降低零件加工过程的生产能耗,提出一种面向节能的车间生产过程多装备加工参数协同优化方法。以包含机床与机器人的定制化生产车间为研究对象,建立了考虑刀具退化动态过程的生产车间系统能量足迹模型。考虑刀具寿命、机器人运输平稳性的成本指标函数,建立了多装备系统的加工参数协同多目标优化模型。以加工时间为约束条件,使用蜂群算法获取了最优参数。实验表明,以节能目标为主的优化方案可降低机床加工能耗17.97%,降低机器人运输能耗18.13%。     

A scheme for an internet-based checking method of machine-tools with variant CNC architecture

This paper proposes an Internet-based checking technique for machine-tools with variant Computerized Numerical Controller (CNC). According to its architecture, CNC is classified into one of two types: Closed Architecture Controller (CAC), which is the conventional CNC, or Open Architecture Controller (OAC), which is a recently introduced PC-based controller. Since CAC has a closed architecture, it is dependent on CNC vender specification. Because of this, it has been very difficult for users to implement application programs in the CNC domain. Recently, the conventional CNC of machine-tools has been replaced by a PC-based open architecture CNC. However, now many conventional CAC machines are being operated together with OAC machines in inadequately equipped shop floors. For Internet-based checking for variant CNC machines with CAC and OAC, a suitable systematic environment is necessary. Through this research, for the global management of variant CNC machines both a CAC and an OAC in the manufacturing system, a suitable environment for Internet-based checking of variant CNC machines was designed, and the checking methods for CAC and OAC machines were compared. The results of this research may serve as a base model for global monitoring and remote control in an integrated manufacturing system with variant CNC machines. Checking points defined in this research are classified into two categories: structured point and operational point. The former includes the vibration of bearing, temperature of spindle unit, and other points of periodical management, while the latter includes oil checking, clamp locking/ unlocking, and machining on/off status.     

Three-half and half-axis patch-by-patch NC machining of sculptured surfaces

Despite the inbuilt advantages offered by five-axis machining, the manufacturing industry has not widely adopted this technology due to the high cost of machines and insufficient support from CAD/CAM systems. Companies are used to three-axis machining and their shop floors are not yet ready for five-axis machining in terms of training and programming. The objective of this research is to develop and implement a machining technique that uses the simplicity of three-axis tool positioning and the flexibility of five-axis tool orientation, to machine sculptured surfaces. This technique, 3½½-axis, divides a sculptured surface into patches and then machines each patch using a fixed tool orientation. This paper presents the surface partitioning scheme and the method of selecting an optimum number of sub-divisions along with actual machining experiments. For the example surface utilized in this study, the proposed hybrid method led to shorter machining time compared to traditional three-axis machining and comparable to simultaneous five-axis machining.     

Experimental Investigation of Lubrication Film Starvation of Polyalphaolefin Oil at High Speeds

The lubrication behavior of starved elastohydrodynamic contacts at high speeds was investigated in this study. A new ball-on-disc test rig with the ability to measure traction force at high speeds up to 100 m/s and lubrication film thickness at speeds up to 42 m/s was built. The relative optical interference intensity technique was used to measure the film thickness. The experimental results show that the film thickness decreased rapidly and asymmetrically when the speed exceeded a critical speed under the starved lubrication condition. Starvation is governed by the amount of lubricant available both in the inlet region and on the side of the oil reservoir. The shape of the oil reservoir becomes asymmetric and the amount of oil gradually reduces against the speed at high speeds because of the centrifugal effects, under which the oil on the outer side of the oil reservoir will be thrown away and the oil on the inner side of the oil reservoir will be compressed. The balance of oil supply and oil loss due to centrifugal force determines the starvation behavior.     

机床数控软件化结构体系

提出了一种新的机床数控软件化的体系结构及其相关技术 ,该结构体系将数控机床运动控制与工艺性能控制分离 ,分别由两个基于PC的控制器控制 ,其软件具有独立于硬件的性质 ,而且运动控制的软件是通用的。给出了该结构体系下通用的数控机床运动控制基本软件模块 ,工艺性能控制以一种玫瑰线铣削加工为例 ,表明在本技术支持下 ,机床数控具有独立于具体硬件的软件化结构体系。本技术将直接支持工艺性能完全不同的机械制造设备的开发 ,如可以用于铣床、车床等通用金属切削机床的数控化 ,也可以用于开发齿轮和复杂曲面加工的专用数控设备 ,还可支持机器人、铸造、锻压以及剪切设备机械运动的数字控制     

INVESTIGATION OF THE TOOL WEAR AND SURFACE FINISH IN LOW-SPEED MILLING OF STAINLESS STEEL UNDER FLOOD AND MIST LUBRICATION

This paper examines the performance of AlN/TiN coated carbide tool during milling of STAVAX® (modified AISI 420 stainless steel) at a low speed of 50 m/min under conventional flood and mist lubrication. Abrasion, chipping, fracture resulting in the formation of crater and catastrophic failure are the wear mechanisms encountered during machining under flood lubrication. The flank wear, and the likeliness of the cutting tool to fracture, chip and fail prematurely increased with an increase in the hardness of the workpiece and a reduction in the helix angle of the tool. Small quantity of mineral oil sprayed in mist form was effective in reducing the flank wear and severity of abrasion wear, and preventing the formation of crater and the occurrence of catastrophic failure. In milling 35 and 55 HRC-STAVAX® using a feed rate of 0.4 mm/tooth and a depth of cut of 0.2 mm under mist lubrication, the cutting edge of the 25° and 40° helix angle tools only suffered small-scale edge chipping and abrasive wear throughout the entire duration of testing. The influence of the ductility of the workpiece on the surface finish and the effectiveness of mist lubricant in improving the surface finish are also discussed.     

Enhancement and verification of a machined surface quality for glass milling operation using CBN grinding tool—Taguchi approach

Nowadays, the demand for high product quality focuses extensive attention to the quality of machined surface. The (CNC) milling machine facilities provides a wide variety of parameters set-up, making the machining process on the glass excellent in manufacturing complicated special products compared with other machining processes. However, the application of grinding process on the CNC milling machine could be an ideal solution to improve the product quality, but adopting the right machining parameters is required. Taguchi optimization method was used to estimate optimum machining parameters with standard orthogonal array L₁₆ (4⁴) to replace the conventional trial and error method as it is time-consuming. Moreover, analyses on surface roughness and cutting force are applied which are partial determinant of the quality of surface and cutting process. These analyses are conducted using signal to noise (S/N) response analysis and the analysis of variance (Pareto ANOVA) to determine which process parameters are statistically significant. In glass milling operation, several machining parameters are considered to be significant in affecting surface roughness and cutting forces. These parameters include the lubrication pressure, spindle speed, feed rate, and depth of cut as control factors. While, the lubrication direction is considered as a noise factor in the experiments. Finally, verification tests are carried out to investigate the improvement of the optimization. The results showed an improvement of 49.02% and 26.28% in the surface roughness and cutting force performance, respectively.     

On the influence and optimisation of cutting parameters in finishing of metallic femoral heads of hip implants

Roughness and sphericity are two important factors affecting friction and lubrication performance of femoral heads of hip implants. Precision finishing of femoral heads is therefore crucial. This paper presents the effect and optimisation of key machining parameters in finish turning of metallic femoral heads, with an aim to achieve the best surface roughness and sphericity. Three important machining variables—cutting speed, feed rate and depth of cut—were considered. According to Taguchi methodology, a factorial design of experiments was planned to capture the effect of machining variables. A series of single-pass finish turning tests was conducted on a 28-mm femoral head made of biomedical grade stainless steel AISI 316 L by using tungsten carbide inserts. We used the analysis of variance (ANOVA) to elucidate the influence of the dominant parameters, which led to derive a regression model and response surface to estimate the desired machining responses. The results suggest that, among all cutting parameters, feed rate affects significantly surface roughness, while both feed rate and depth of cut are the dominant factors impacting markedly sphericity. Using desirability function-based criteria, single response and multiresponse optimisations were performed to determine an optimum combination of machining parameters. The objective was to maximise the desirability under the given range of parameters. Optimisation results show that cutting speed of 280.02 m/min, feed rate of 0.1 mm/rev and depth of cut of 0.2 mm are the optimum set, which is expected to provide minimum surface roughness and sphericity of the finished femoral heads. The parameters are thus expected to minimise further polishing time and improve manufacturing productivity.     

Implementation of online NURBS curve fitting process on CNC machines

The study aims to develop a method for implementing an online non-uniform rational B-spline (NURBS) curve fitting process on CNC machines for improving the quality and efficiency of machining. Conventional CAD/CAM/CNC systems usually induce some machining difficulties and limit the machining results in real applications. Therefore, some researchers have proposed various methods for improving the machining results. An online NURBS curve fitting process consists of the fetching and fitting stages for CNC machines is developed in this paper. The fetching stage fetches a block of NC code and generates motion commands for obtaining data points. The fitting stage executes the NURBS curve fitting method along with a given set of data points. Moreover, the optimal search method is designed for obtaining good results in the NURBS curve fitting process. Simulations and machining tests carried out on a vertical machining center show that the proposed approach reduces the machining time to about 23% while maintaining the machining quality for the sample test.     

数控铣床与加工中心夹具设计

提出针对数控铣床、加工中心所用夹具的设计方法.合理的夹具设计能充分发挥数控机床的潜力,提高加工效率.提供加工中心夹具设计实例.     

Performance enhancement of cryogenic machining and its effect on tool wear during turning of Al-Ticp composites

The current research is to focus on developing a liquid nitrogen diffusion system to optimize the usage of liquid nitrogen and maximizing cooling and lubrication capability by effective penetration. An atomized liquid nitrogen spray system was developed to diffuse liquid nitrogen effectively at a low flow rate (10–12 L/h) and as a high velocity (8–50 m/s) droplet jet to the machining zone. Using coated carbide tool with varying tool geometry (rake angle, approach angle, and nose radius), an investigation was performed to study the role of atomized liquid nitrogen spray-assisted machining, on performance of tool and surface quality of the machined workpiece during turning of Al-TiCp composite. To analyze the performance of liquid nitrogen spray-assisted machining, various experiments were conducted. The results obtained from the experiments reveal that the effective use of atomized liquid nitrogen spray machining is a feasible alternative to dry, wet, and cryogenically chilled argon gas. This technique significantly reduces heat generation in machining zone. The study also emphasizes the influence of tool geometry on the machinability of Al-TiCp metal matrix composites.     

Mobile and remote operation for M2M application in upcoming u-manufacturing

This study tried to control and monitor computerized numerical controller (CNC) machines anywhere and anytime for machine (mobile) to machine (M2M) application in wired and wireless environment of upcoming ubiquitous manufacturing systems (u-Manufacturing). With a personal digital assistant (PDA) phone, the machine status and machining data of CNC machines can be monitored in wired and wireless environments, including the environments of IMT2000 and Wireless LAN. Moreover, CNC machines can be controlled anywhere and anytime. The concept of the anywhere-anytime controlling and monitoring of a manufacturing system was implemented for u-Manufacturing in this study. In this concept, the communication between the CNC controller and the PDA phone was successfully performed anywhere and anytime for the real-time monitoring and control of CNC machines. In addition, the interface between the CNC controller and the developed application module was implemented by object linking and embedding for process control (OPC) and shared CNC memory. For communication, the design of a server content module within the target CNC was based on a TCP/IP. Furthermore, the client content module within the PDA phone was designed with the aid of embedded c++ programming for mobile communication. For the interface, the monitoring data, such as the machine status, the machine running state, the name of the numerical control (NC) program, the alarm and the position of the stage axes, were acquired in real time from real machines with the aid of the OPC method and by sharing the CNC memory. The control data, such as the start, hold, emergency stop, reserved start and reserved stop, were also applied to the CNC domain of the real machine. CNC machines can therefore be controlled and monitored in real time, anywhere and anytime. Moreover, prompt notification from CNC machines to mobile phones, including cellular phones and PDA phones, can be automatically realized in emergencies.     

A Study on an Open Architecture CNC System with a NURBS Interpolator for WEDM

This paper deals with the design and implementation of an open architecture CNC system for wire electrical discharge machining (WEDM) with a consideration of the differences between WEDM and NC cutting machines. Work using open architecture controllers (OACs) has focused mainly on metal cutting machines. WEDM has many aspects similar to milling machines. However, there are differences in the machining processes and control strategies. To close the gap between previous general work on OAC and the WEDM specific needs, an open architecture NC model for WEDM comprised of a synchronisation kernel and an NC functional module is proposed. The proposed CNC system is applied to an existing commercial WEDM system by a retrofitting method. A precise NURBS interpolation function is implemented and sample runs are conducted with a NURBS interpolator that is added to the proposed system.     

A combinatorial manufacturing resource planning model for long-term CNC machining industry

Combinatorial resource planning for both machines and human resources in a computer numerical controlled (CNC) machining workstation has become a crucial factor for long-term manufacturing management. This paper not only mathematically constructs the combinatorial manufacturing resource planning (CMRP) model with the conception of balancing the machine productivity and the human capability, but also develops a step-by-step algorithm to reach the maximum-profit solution under the deterministic market demand. Additionally, to extend the applicability of the CMRP model, a computer program written with MATLAB is comprehensively prepared to achieve the optimum manufacturing resource planning under the forecasts of probabilistic market demand and product sales price. The versatility and adaptability of this study are exemplified through a numerical illustration from real-world industry. This paper contributes to the problem of conclusively scheduling machine productivity and human resources, as well as comprehensively optimising the production profit for the existing CNC machining industry .     

Analysis and experiments of iterative learning-control system with uncertain dynamics

An iterative error compensation approach is proposed in this article to improve the accuracies of high speed, computer-controlled machining processes. It is well known that the high-speed computer-numerically-controlled (CNC) machines are extremely useful in terms of manufacturing mass-produced parts. The proposed method uses an iterative learning technique that adopts the servo commands and cutting error experienced in previous maneuvers as references to current compensative actions. Moreover, non-repetitive disturbances and nonlinear dynamics of the cutting processes, and servo systems of the CNC machine that greatly affect the convergence of the learning-control systems were also studied in this research. State feedback and output feedback techniques were adopted in the proposed controller design. In addition to the stability analysis, a 1 degree-of-freedom servo positioning system is constructed to evaluate the performance of our proposed learning control approach. Both the simulation and experimental results verify the effectiveness of our approach.