CNC Machining Center Research Articles

Condition assessment for automatic tool changer based on sparsity-enabled signal decomposition method

Automatic tool changer (ATC) is one of the key basic parts in CNC machining centers, and the globoidal indexing cam and the groove cam are the functional units for tool changing. Thus the condition monitoring is important for highly efficient and precision machining. In this paper, a condition monitoring system is constructed for the ATC, especially for the globoidal indexing cam, including vibration signal acquisition, fault feature extraction and localization, and condition assessment. In the constructed system, sparsity-enabled signal decomposition method is introduced to extract transient component and reduce noises in the complex vibration signals, and the transient component is always a key feature for fault localization. Simulation study shows that the sparsity-enabled signal decomposition method is effective in transient feature extraction. The experimental application in condition assessment for the ATC demonstrates that the constructed condition monitoring system has the potential to assess the working condition of the ATC in practical application.

Reliability Assessment of CNC Machining Center Based on Weibull Neural Network

CNC machining centers, as the key device in modern manufacturing industry, are complicated electrohydraulic products. The reliability is the most important index of CNC machining centers. However, simple life distributions hardly reflect the true law of complex system reliability with many kinds of failure mechanisms. Due to Weibull model’s versatility and relative simplicity and artificial neural networks’ (ANNs) high capability of approximating, they are widely used in reliability engineering and elsewhere. Considering the advantages of these two models, this paper defined a novel model: Weibull neural network (WNN). WNN inherits the hierarchical structure from ANNs which include three layers, namely, input layer, hidden layer, and output layer. Based on more than 3000 h field test data of CNC machining centers, WNN has been successfully applied in comprehensive operation data analysis. The results show that WNN has good approximation ability and generalization performance in reliability assessment of CNC machining centers.

Parameter Design of Tooth Profile for Internal Cycloid Gear Pump with Multi-Teeth Difference

Based on the principle of gear engagement, the equation of rotor tooth profile has been reduced in this paper and has drawn the actual cycloid tooth profile by MATLAB software, the data obtained from MATLAB Workspace is processed by EXCEL, so the parameter drawing of the full gear tooth profile curve is very easy in AutoCAD software platform. This design method has high accuracy and convenient to processing in CNC machining center.

Machine tool syntheses in virtual machining

It is beneficial to realize the cutting forces generated in the early stages of the design and process planning. This paper describes the concept of machine tool/process modelling for virtual machining purposes. It is based on the dynamic model of a machine and the cutting process. The model can be used in virtual manufacturing systems (VMS) where computer models that depict the manufacturing process are integrated to form an overall model to portray the real machining system. Modelling can be considered as a very important step in design, performance evaluation, model based monitoring/diagnostics, adaptive control and in design sensitive studies. Computer aided engineering (CAE) systems provide engineers with many design and analysis tools, by combining solid modelling programs with analytical tools, such as finite element codes and dynamic simulation programs, for a specific task. However a model for virtual machining should encompass a total solution. As an example, a CNC machining centre is modelled herein by the integration of Computer Aided Control System Design (CACSD), Computer Aided Multi–Body Dynamic and Finite Element Modelling tools for Machine Tool/Process Modelling (MPM). The derived model includes a regenerative force, cutting process as the interacting phenomena between the spindle and feed axes where dynamic deflection of the elastic parts are included.

Researches on Virtual Machining Simulation of Flexible Manufacturing Cell Based on KUKA Robot

Flexible manufacturing cell (FMC) was the extension of the CNC machining center,which consisted of three portions , a CNC machining center , an industrial robot and unified by a the background computer programmable control. In order to guarantee the rationality and feasibility of the automatic operation loading and unloading workpieces , the simulation object was based on the KUKA robot of flexible manufacturing cell in this paper, which based on MATLAB/GUI and combinated of VRML language and information transmission method development between MATLAB and the simulation system of flexible manufacturing unit. According to the set up parameters and angles, the model was implemented. Through the control panel and the robot's real-time interactive simulation, 3d visualization window can be real-time display of the robot simulation, and validated the path planning. According to the simulation results of the model , it could provide reference to the actual movement of the KUKA robot trajectory planning, provided the better fully automated feasibility analysis of flexible manufacturing cell, and proved the improvement of flexible manufacturing unit operation scientifically and reasonably.

Development of G-Code Based on PMAC in CNC Machining Center

PMAC motion controllers serve not only as a receiver of the orders from CNC systems of many kinds, but also as a controller of the motion of machine tools’ axles. With G83 as an example, a code commonly seen in the processing cycle of deep holes in CNC machining centers, it is advisable to come up with a method to write a special set of subprograms to invoke PMAC motion controllers with the application of G-code. Based on the method, case programing and machining simulation can be launched. Experiments justify that the method obtained can realize the compiling of fixed cycles with the use of G-code and, in turn, boast substantial significance in the development of open CNC processing machine tools.

CNC Routine for Manufacturing Spur Gear

Manufacturing of spur gears on CNC machining centers and CNC wire cutting is randomly used due to the difficulty in producing the perfect gear profile. The present paper faces this problem by developing a special cycle that can be used on both types of machines. A code for this cycles is designed to read the part program of any product and if detects the code nominated for this cycle (G77) which indicates that a gear needs to be cut, it develops the geometrical statements of the gear profile and the motion statements. It follows by writing the full code of the cycle. The validity of the designed model was verified on a CNC simulator.

Study on cutting force and surface micro-topography of hard turning of GCr15 steel

This work investigates the cutting force and surface micro-topography in hard turning of GCr15 bearing steel. A series of experiments on hard turning of GCr15 steel with polycrystalline cubic boron nitride (PCBN) tools are performed on a CNC machining center. Experimental measurements of cutting force, 3D surface micro-topography, and surface roughness of the workpiece are performed. The 3D surface micro-topography of the workpiece is discussed, and the formation mechanism of the 3D surface is analyzed. The influence of cutting speed and feed rate on cutting force and surface roughness are discussed. The 2D and 3D surface roughness parameters are compared and discussed. It is found that feed rate has greater influence on cutting force and surface roughness than cutting speed and there exists the most appropriate cutting speed under which the minimum surface roughness can be generated while a relatively small cutting force can be found. Recommendations on selecting cutting parameters of hard turning of GCr15 steel are also proposed.

The Use of Supports to Fast Fabrication of Plastic Parts

This paper provides a design technique of support for being applied in fast fabrication on plastic prototype, the plastic part developed through the computer aided design (CAD) can be rapidly fabricated by a CNC machining center without needs of any specific jigs or fixtures, the function provided is similar to a rapid prototyping (RP) machine used for fabricating the sampling part. By the testing result, the provided design technique of support can not only be applied in the part required for a dual-surface (or multiple-surface) processing, but also applicable for fabricating the part having thin housing. As such, this paper provides another economical and efficient option besides the RP.

Обеспечение качества изготовления прецизионных поверхностей деталей на многоцелевых станках с ЧПУ

Обеспечение качества изготовления прецизионных поверхностей деталей на многоцелевых станках с ЧПУ

Evaluation of machine-tool motion accuracy using a CNC machining center in micro-milling processes

The demand for micro holes, micro-molds, and micro forms continues to grow as high-tech industries demand miniaturized products. Sectors such as aerospace, microelectronics, medicine, and even the automotive sector, are just some examples of enterprises that are taking advantage of micro-manufacturing technologies. Within this framework, the need to adapt the knowledge of macro-scale manufacturing processes to micro-scale is evident. This paper provides the insight needed to improve milling as a micro-manufacturing process. The goal is to characterize motion system to reduce error and improve accuracy with different process parameters on final shape for micro-parts while standard milling machine with linear motor and servomotor is used. Geometrical error and accuracy caused by motion control and control software error sources is evaluated and analyzed. Results will help decision on process parameters and it verifies that standard milling machine is useful to produce micro-parts. The work is carried out by theoretical principles and experimental work, the machine-tool motion accuracy of a medium machining center specializing in the micro-milling of elliptical cavities on aluminum workpieces. Measurements were taken to evaluate deviations and/or errors in geometric accuracy and the geometric quality errors caused by motion control and control software. The results show that due to the structure and inertia of the machine tool, acceleration and deceleration do indeed affect the accuracy and quality of the micro-part. Furthermore, errors from motion control and/or control software are present because differences in the moving carriages create instabilities.

The Effects of Austempering Temperature and Time on the Machinability of Vermicular Graphite Iron

Abstract In this study, the effect of austempering heat treatment on the cutting forces and surface roughness was investigated during the processing of vermicular graphite cast irons (VGCI) which are widely used in the automotive industry due to their high strength properties. The samples were austenitized at 900 °C for 90 minutes and then austempered at different temperatures (320 °C and 370 °C) for 60 min, 90 min, and 120 min. Machinability tests were carried out under dry conditions at the CNC machining center with the cutting parameters selected in accordance with ISO 3685. As a result of processing of austempered vermicular graphite cast irons with different characteristics the formed cutting forces, surface roughness, cylindricity, and circularity were measured and compared. At the end of the tests, it turned out that the ausferrite morphology (fine or coarse structure) can to be controlled with the austempering heat treatment as well as cutting forces and surface roughness were optimized, respectively. The best surface roughness value was obtained for the austempering parameters of 370 °C and 120 minutes.

Comparison of zirconia ceramic and stainless steel tools in dental implantology

The aim is to study the influence of the cutting conditions in the lives of drills used in dental implantology, when bovine tibia is used as work material. The input variables were the cutting tool materials (tetragonal zirconia polycristals ceramic and martensitic stainless steel) both uncoated, the feed velocity (24 and 45 mm/min) and the spindle speed (1,000 and 2,500 rpm). The output variables monitored were the tool life, the temperature next to the hole wall and the thrust force. The tests were carried out in a CNC Machine Center (15 kW of power) varying the cutting parameters following a 23 factorial design. The tool lives were expressed by the number of drilled holes, considering the temperature close to the hole wall of 47 °C as the end of tool life criterion. The temperatures were monitored using three type T thermocouples inserted into the workpiece samples and positioned along the depth of the holes. The thrust force was measured with a Kistler rotating dynamometer. A mixture of 20 % of ethylene glycol and water was applied as coolant (irrigation) with a flow rate of 160 ml/min, simulating a saline solution. The results showed that the martensitic stainless steel outperformed the ceramic drills. The lowest temperatures and a conformity state at the clinic standard for thrust force values were obtained with the highest cutting parameters (45 mm/min and 2,500 rpm). It was observed that the higher feed velocity provided mainly a drop in temperature, while the higher spindle speed decreased the thrust force.

Development of Double-Axis Double-Rest CNC Machining Center

The design for a double-axis double-rest CNC machining center is introduced by describing its key machine elements and machine tool design procedures. Then based on the theory of the multi-body system, the modeling process of the volumetric error model for the CNC machining center is expatiated and the result of the modeling is given. It is verified that the error of the machine tool is from three line error and three angular errors between structural units as well as the vertical error between axes. Finally experiments are carried out to evaluate the machining performance of this designed machine tool.

Remanufacturing the Pinion: An Application of a New Design Method for Spiral Bevel Gears

Damages of a large spiral bevel gear drive as used in heavy industry typically affect the pinion. Even if the gear still could be used, the complete pair has to be changed. This leads to long off times, high costs, and unnecessary waste. This paper applies a recent design technology for spiral bevel gears to the production of a replacement pinion for the sake of energy saving, reduction of costs and off times, and for the realization of green engineering. The process involves the following steps. First, the real tool surface of the gear is measured by a CMM. Based on the new design method, the tooth surface of the mating pinion is derived from this discrete point cloud. In order to improve the meshing performance, the resulting surface of the pinion is modified in the third step. Finally, the pinion is produced on a CNC machining center. In contrast to other approaches, none of these steps needs the parameters of the special machine tool defining the original gear pair. It is worth noting that our technology can also be profitable to gain more freedom in the design of new gear pairs.

Minimum Quantity Lubrication (MQL) in Automotive Powertrain Machining

This paper summarizes the advancements and challenges of minimum quantity lubrication (MQL) technology in automotive powertrain machining from both industrial and academic perspectives. MQL refers to applying a small amount of cutting fluid in the form of mist to the cutting zone rather than flooding the workpiece. Elimination of coolant systems creates significant saving from energy and equipment, the flexibility to relocate the machines, reduction of waste stream and floor space, and a cleaner and healthier work environment. Ford Motor Company has demonstrated these advantages, and currently has a total of over 400 MQL CNC machining centers in numerous global transmission and engine plants running MQL operations, with further implementation planned for new programs globally. Technical challenges to realize 100% implementation includes tool design, delivery system, chip management, and thermal related problems, particularly in high-energy density processes and difficult-to-machine metals, such as deep-hole drilling and compacted graphite iron (CGI). This paper provides a review of current status and limitations of MQL machining and highlights opportunities for research and development of the next-generation MQL technology in automotive powertrain machining.

Deformation Mechanism Analysis of Single Point Incremental Sheet Metal Forming

Single point incremental forming (SPIF) is a new innovative and feasible solution for the rapid prototyping and the manufacturing of small batch sheet parts. The process is carried out at room temperature and requires a CNC machining centre, a spherical headed tool and a simple support to fix the sheet being formed. In incremental Sheet Metal Forming the blank is incrementally deformed in to a desirable shape by hemispherical or ball nose tool traveling along a prescribed path. Due to the various advantages including the reduced production cost and time of prototypes, improved formability, easy modification of part design etc. the ISF is being popular as a new innovative forming technology. In the present study experiments were conducted to analyze the deformation mechanism of commercial aluminum alloy. Beside this analysis result of the effect of forming angle, step size, tool diameter on formability and wall thickness distribution are presented.

Computer Aided Manufacturing of Models for Moulding out of Synthetic Materials for Producing Sand Casting Moulds

Paper is presenting computer aided machining of models for moulding out of synthetic materials. Goal of the project was to produce a manikin (dummy) from aluminium alloy for testing protective clothes for intervention services. Usage of state-of-the-art software for CAD modeling and CAM machining has been applied. At planning of the machining strategies, the software package UGS NX 7 has been used. Machining of certain models has been done on CNC machining centre Heller BEA 1. Due to dimensional restrictions on the machine workspace we had to part up the models on smaller segments. The model pieces have been made out of synthetic material Sikablock® M700. Producing of the models was pretentious and extensive. In project were successfully captured demands for aluminium casting, with these basics we produced objects and produced final casts.

Unified error model based spatial error compensation for four types of CNC machining center: Part II—unified model based spatial error compensation

In this paper, a spatial error compensation method was proposed for CNC machining center based on the unified error model. The spatial error distribution was analyzed in this research. The result shows that the spatial error is relative to each axis of a CNC machine tool. Moreover, the spatial error distribution is non-linear and there is no regularity. In order to improve the modeling accuracy and efficiency, an automatic error modeling application was designed based on the orthogonal polynomials. To realize the spatial error compensation, a multi-thread parallel processing mode based error compensation controller was designed. Using the spatial error compensation method, the machine tools' accuracy is greatly improved compared to that with no compensation.

The Honeycomb Core Design of Modular Based Wine Packaging

Use the standard 750ml bottle of red wine packaging design to explore the honeycomb core module of digital design and green manufacturing approach to virtual design and virtual manufacturing of new structural approach to packaging product development, through the final product form of reverse thrust reversers honeycomb core module data and processing forms, and finally the use of CNC machining centers cellular module manufacture.