Machine Scheduling for Multitask Machining

Multitasking is an important part of today’s manufacturing plants. Multitask machine tools are capable of processing multiple operations at the same time by applying a different set of part and tool holding devices. Mill-turns are multitasking machines with the ability to perform a variety of operations with considerable accuracy and agility. One critical factor in simultaneous machining is to create a schedule for different operations to be completed in minimum make-span. A Mixed Integer Linear Programming (MILP) model is developed to address the machine scheduling problem. The adopted assumptions are more realistic when compared with the previous models. The model allows for processing multiple operations simultaneously on a single part; parts are being processed on the same setup and multiple turrets can process a single operation of a single job simultaneously performing multiple depths of cut. A Simulated Annealing algorithm with a novel initial solution and assignment approach is developed to solve large instances of the problem. Test cases are presented to assess the proposed model and metaheuristic algorithm

Decision support for design of reconfigurable rotary machining systems for family part production

To remain competitive in currently unpredictable markets, the enterprises must adapt their manufacturing systems to frequent market changes and high product variety. Reconfigurable manufacturing systems (RMSs) promise to offer a rapid and cost-effective response to production fluctuations under the condition that their configuration is attentively studied and optimised. This paper presents a decision support tool for designing reconfigurable machining systems to be used for family part production. The objective is to elaborate a cost-effective solution for production of several part families. This design issue is modelled as a combinatorial optimisation problem. An illustrative example and computational experiments are discussed to reveal the application of the proposed methodology. Insight gained would be useful to the decision-makers managing the configuration of manufacturing systems for diversified products

К ОПТМ ИЗАЦИИ ПРОЦЕССОВ ПОСЛЕДОВАТЕЛЬНОЙ ОБРАБОТКИ ПАРТИЙ ДЕТАЛЕЙ

A problem of optimal design of processes of sequential machining of multiple parts on rotary table machines is considered. Batches are processed in a given sequence. Parts of the same batch are located at the working positions of rotary table and are machined simultaneously. Operations are divided into groups which are performed by spindle heads or by turrets. Constraints on the design of spindle heads, turrets, and working positions, as well as on the order of operations are given. The problem is to minimize the estimated cost of machine equipment while reaching a given output. The proposed method to solve the problem is based on its formulation in terms of mixed integer linear programming. Computational results are reported.Рассматривается задача оптимального проектирования процессов последовательной обработки партий деталей на станках с поворотным столом. Последовательность обработки партий задана. Детали одной и той же партии устанавливаются на рабочих позициях станка и обрабатываются одновременно. Множество технологических переходов для обработки всех деталей разбивается на группы, которые выполняются с помощью шпиндельных или револьверных головок. Заданы ограничения, связанные с разбиением переходов по шпиндельным и револьверным головкам, рабочим позициям станка, а также порядком выполнения переходов. Задача заключается в минимизации оценки стоимости оборудования станка при обеспечении заданной производительности. Предлагаемый метод решения задачи основан на ее формулировке в терминах смешанного целочисленного линейного программирования. Приводятся результаты вычислительных экспериментов

STEP COMPLIANT APPROACH FOR TURN-MILL OPERATIONS

Current machine tools have incurred challenges on limitation such as part programming complexity of G and M code, weak integration of digital machine tools and coverage of universal data modeling for product and manufacturing resources. In response to this manufacturing system requirement, Standard for Exchange of Product data (STEP) and its implementation on developing an interface for the next generation of machine tool controllers (STEP-NC) has become a concern of research interest and performed on basic manufacturing technology limited to a unit domain such as turning, milling or Wire EDM. Therefore; extending this STEP implementation on multipurpose machine tools such as turn-mill machines is mandatory since the machines are the main component in these industries. The research work offers a STEP-NC compliant interface supporting turn-mill machining environment identified as SCSTMO

Computer numerical controlled (CNC) machining of screws and dies for plasticating extruders : determination of the criteria for implementing CNC machining

The work of this thesis is dedicated to the manufacturing industry making production equipment to manufacture plastic products. The main theme of the thesis is to determine the criteria for implementing Computer Numerical Control machining to make parts with complex geometries for production equipment. A small manufacturing company with job shop type of production was chosen as the subject and study of extruder manufacturing process was performed. The various available alternatives of CNC manufacturing units available in the market were chosen and their feasibility examined. At present a large variety of CNC machine tools are available in the market, offered by manufacturers following different standards. This thesis is organized with the purpose of comparing various technical and economical considerations for CNC machine tool purchase and its application

The Design of a multiple position turret for changing robot end effectors

This paper discusses the design and build of a multiple position turret used to simultaneously attach six end effectors to a four-degree of freedom Adept robot. The main objective of this thesis is to develop a prototype tool changer that is different, more cost effective, and offers more features and versatility than any other. Use of the turret allows the robot to quickly change the end effector in use by simply rotating any of the others into the ready position. This reduces the tool changing time in a high-speed assembly process that is normally associated with conventional tool changers disconnecting one end effector and picking up another. Employing the turret concept in a robotic assembly operation will also lengthen the life of the robot because there are fewer moves that have to be made by the robot itself. The turret is approximately 8 inches high, 7 inches wide and its turntable is 6.25 inches in diameter. This small envelope is a large benefit over the bulky system that would be needed for the more traditional tool changers. The turret\u27s weight while populated with six small end effectors is approximately 10.5 pounds. The cost of the turret, not including end effectors, is approximately $5,500

Tool flow management in batch manufacturing systems for cylindrical components

The objective of the research is to study the design of and operating strategies for advanced tool flow systems in highly automated turning systems. A prototype workstation has been built to aid this process. The thesis consists of three main parts. In the first part the current flexible manufacturing technology is reviewed with emphasis laid on tool flow and production scheduling problems. The 'State-of-the-Art' turning systems are studied, to highlight the requirement of the computer modelling of tool flow systems. In the second part, the design of a computer model using fast modelling algorithms is reported. The model design has concentrated on the tool flow system performance forecasting and improving. Attention has been given to the full representation of highly automatic features evident in turning systems. A number of contemporary production scheduling rules have been incorporated into the computer model structure, with the objectives of providing a frontend to the tool flow model, and to examine the tool flow problems interactively with the production scheduling rules. The user-interface of the model employs conversational type screens for tool flow network specification and data handling, which enhances its user friendliness greatly. An effective, fast, and easy to handle data base management system for tool, part, machine data entries has been· built up to facilitate the model performance. The third part of the thesis is concerned with the validation and application of the model with industry supplied data to examine system performance, and to evaluate alternative strategies. Conclusions drawn from this research and the recommendations for further work are finally indicated

Mechanics and dynamics of multi-axis machining operations

Machining process with a single cutting tool is called multi-axis machining if more than 3-axis are involved in the operation. On the other hand, parallel machining processes where more than one cutting tool simultaneously cut a workpiece is also called multi-axis machining. 5-axis ball-end milling where a single cutting tool is employed, parallel turning and parallel milling processes with two cutting tools are in the scope of the thesis. Moreover, face-milling process with inserted tools is also modeled. 5-axis ball-end milling operations are common in several industries such as aerospace, automotive and die/mold for machining of complex sculptured surfaces. Additional two degree of freedoms, namely, lead and tilt angles make it possible to machine complex parts by providing extra flexibility in cutting tool orientation. However, they also complicate the geometry of the process. In these operations, productivity, dimensional tolerance integrity and surface quality are of utmost importance. Part and tool deflections under high cutting forces may result in unacceptable part quality, whereas using conservative cutting parameters results in decreased material removal rate. Process models can be used to determine the proper or optimal milling parameters for required quality with higher productivity. The majority of the existing milling models are for 3-axis operations, even the ones for ball-end mills. In the thesis, geometry, force and stability models are presented for 5-axis ball-end milling operations. The effect of lead and tilt angles on the process geometry, cutter and workpiece engagement limits, scallop height, and milling forces are analyzed in detail. In addition, tool deflections/form errors and stability limits are also formulated for 5-axis ball-end milling. The use of the model for selection of the process parameters such as lead and tilt angles which result in minimum cutting forces or maximum stability limits are demonstrated. The model predictions for cutting forces, form error and stability limits are compared and verified by experimental results. Parallel machining operations are advantageous in terms of productivity since there are more than one cutting tools in operation. Due to the increased number of cutting tools, they have the potential for considerable increase in productivity as a result of higher material removal rate (MRR). However, the dynamic interaction between these parallel tools may create additional stability problems and the advantage of parallel machining may not be utilized to full extent. For that reason, dynamics and stability of parallel machining processes need to be modeled. In the thesis, dynamics of parallel turning and parallel milling operations where two cutting tools cut a common workpiece are modeled. The predicted stability limits for parallel turning are also compared with experimental results where good agreement is demonstrated. Die manufacturing is a very critical part of the overall production chain in many industries. Depending on shape and size of a die, machining time can be very time consuming. Furthermore, since usually one die is manufactured, the chance for testing is very limited. Machining processes in die manufacturing can be limited by many factors. Process models can be used in order to select process conditions which will yield the required quality in the shortest possible time. In this study, force and chatter models are developed for face milling processes with inserted cutters. Using the developed models, process parameters are modified and their effects on productivity are demonstrated