Yatna Yuwana Martawirya

An Object-Oriented Modelling of Production Scheduling for Flexible Manufacturing System

This paper presents an object-oriented modelling approach to production scheduling for FMS. The purpose of this study is to prepare a simulation tool to try a method of production scheduling that allocates jobs to the machines and cutting tools in an FMS. This model is developed by using Pharo as the language software for object-oriented programming through UML system design. This model consists of three types of classes. The first type is the Equipment-class, which related to the physical equipment in the FMS, for example machining-centers, cutting tools, pallet stocker, stacker crane. The second type is the Product-class that related to the information how to process the product. This class has sub-class such as process plan, machining operation and required cutting tools. The third class is the Production Planning and Controlling (PPC) class, which related to create the schedule to equipment. The PPC-class has sub-classes such as the daily order or job, job sequence, job allocation on machine and scheduling methods. A numerical example is provided in this paper to show that the object-oriented model for FMS and production scheduling is verified. The FMS consist of four identical machining centers and eight jobs. Each job has a process plan that requires some specific cutting tool types. The method for production scheduling in this model is Shortest Processing Time (SPT). The production scheduling performance is measured in this model.

An FMS Dynamic Production Scheduling Algorithm Considering Cutting Tool Failure and Cutting Tool Life

This paper deals with Flexible Manufacturing System (FMS) production rescheduling due to unavailability of cutting tools caused either of cutting tool failure or life time limit. The FMS consists of parallel identical machines integrated with an automatic material handling system and it runs fully automatically. Each machine has a same cutting tool configuration that consists of different geometrical cutting tool types on each tool magazine. The job usually takes two stages. Each stage has sequential operations allocated to machines considering the cutting tool life. In the real situation, the cutting tool can fail before the cutting tool life is reached. The objective in this paper is to develop a dynamic scheduling algorithm when a cutting tool is broken during unmanned and a rescheduling needed. The algorithm consists of four steps. The first step is generating initial schedule, the second step is determination the cutting tool failure time, the third step is determination of system status at cutting tool failure time and the fourth step is the rescheduling for unfinished jobs. The approaches to solve the problem are complete-reactive scheduling and robust-proactive scheduling. The new schedules result differences starting time and completion time of each operations from the initial schedule.

Maintenance on Job Shop Industry: Review and Analysis

This paper presents overviews about reliability and maintainability of equipment especially for job-shop manufacturing systems. The job shop industry has the characteristics of a more dynamic production than flow shop industries, where products with a variety of great but small amounts. Its dynamic condition certainly contributes directly to the failure rate and reliability growth of equipment. Therefore, proper maintenance should be done as the reliability improvement. Stages of reliability improvement are reliability modeling, reliability analysis and maintenance optimization. This stage is based on reliability growth of equipment that is indicated the deterioration process of failure components, it can be build from maintenance data history or condition data monitoring.. Cost is often considered in points of a maintenance schedule. This cost was affected by minimizing the negative effects of maintenance and maximizing the benefit of production. The attention at reliability and maintenance optimization is a well researches area until now. This paper presents a brief review of existing reliability and maintenance research. Several reliable methods in this area are discussed and maintenance on job-shop industry as future prospects is investigated. It is shown in this paper that some aspect in the area of maintenance on job-shop industry steel needs to be deeply developed.

An Object-Oriented Modelling for Simulating Workshop Consisted of Machining Center, Pallet Stocker and Stacker Crane

This paper described a methodology to simulate production activities by using object-oriented programming language. Simulation of production to be modeled are the production activities in a workshop. The first step of modelling was defining objects that constitute the main part of a machining center. The main part of machining-center which was being modeled are column spindle, pallet fixture, pallet changer and tool magazine. From these objects can be created a new object that was an object of machining center. The next step was modeling pallet stocker and stacker crane. Pallet Stocker is a container used to store the workpiece or product on the pallet. A stocker crane is a device used to move a workpiece from the pallet stocker to a machining center or vice versa. The final step was modeling a workshop in which there are some machining centers, pallet stocker and stocker crane. Object modeled can be used to simulate a workpiece transfer activity undertaken by stacker crane from the pallet stocker to the machining center.

Development of a Methodology for Assessing the Energy Efficiency Performance on Turning Processes

This paper aimed to develop a methodology for assessing environmental friendliness of turning processes from energy consumption’s perspective. This methodology was limited on the process level study, which turning process was chosen as the assessed process. Recently, the green manufacturing has become a very important matter due to environmental impacts caused by manufacturing processes. Reducing the amounts of input energy or increasing efficiencies of production equipment’s can help to achieve the green manufacturing level, but it does not indicate the level of energy consumption. Therefore, a methodology is needed to determine how green a manufacturing process on energy consumption’s perspective. In this case, an energy indicator can be used to evaluate the energy usage performance. Based on the experimental data from several different machines, regression lines is constructed (using data envelopment analysis) as the efficiency reference values. According to the position of the energy efficiency from the assessed process to the efficiency reference values, it will determine whether the process has a high or low efficiency (as the assessment result). This methodology has tried to indicate the level of energy consumption, by comparing the result from energy indicator with the reference value. Energy indicator for material removing processes is commonly used to predict the total energy consumption for energy assessment without comparing the result to the reference value.

Mathematical Approach for Geometric Error Modeling of Three Axis CNC Vertical Milling Machine

The aim of this paper overviews about to find out the errors that come from three axis CNC vertical milling machine. The errors come from, the CNC milling machine can be modelled into mathematical models and later on these error models will be used to analyse the errors in the measured data. Many errors from CNC machine tools have given significant effects toward the accuracy and repeatability of manufacturing process. There are two error sources come from CNC machine tools such as tool deflection and thermal distortions of machine tool structure. These errors later on will contribute to result in the geometrical deviations of moving axis in CNC vertical milling machine. Geometrical deviations of moving axis such as linear positioning errors, roll, pitch and yaw can be designated as volumetric errors in three axis machine tool. Geometrical deviations of moving axises happen at every axis in three axis CNC vertical milling machine. Geometrical deviations of moving axises in linear and angular movement has the amount of errors up to twenty one errors. Moreover, this geometrical errors play the major role in the total amount of errors and for that particular reason extra attention towards the geometrical deviation errors will be needed along machining process. Each of geometrical error of three axes vertical machining center is modeled using a homogeneous transformation matrix (HTM). The developed mathematical model is used to calculate geometrical errors at each axis and to predict the resultant error vector at the interface of machine tool and workpiece for error compensation.

Development of Chatter Threshold Determination Methodology in Milling Process by Using Inclined Workpiece

Machined product quality depends on its dimension and surface quality. The dimension quality depends on machine tool accuracy while the surface quality depends on machining system stiffness. A low machining system stiffness will shift spindle shaft-tool resonance frequencies to low frequencies. When one of these frequencies coincides with spindle rotational speed or its harmonics, chatter will be generated which in turn worsen the workpiece surface roughness. In addition to increasing machining system stiffness, chatter can be eliminated by decreasing the axial depth of cut as well. Maximum axial depth at certain spindle rotational speed which will not generate chatter is called as chatter threshold. A diagram describing chatter thresholds for certain range of spindle rotational speed is called as a SLD (stability lobe diagram). The diagram is very useful for selecting a maximum depth of cut at certain rotational speed in order to obtain chatter-free machining process. The SLD can be generated theoretically or experimentally. The theoretical one is fast and cheap but it is not guaranteed to be correct. On the other hand, although the experimental one will produce exact values but it is long, cumbersome and expensive, because for certain rotational speed many machining with different axial depth of cut must be conducted until chatter threshold is reached. The same process is then repeated for other rotational speeds. This paper deals with a new method in determining the chatter threshold or SLD experimentally, by using inclined workpiece, by which it only needs one time machining-test for each rotational speed. In this method, during machining process, chatter occurrence is detected by using accelerometer and validated by its surface roughness afterwards. It is shown in this paper that the new method works well for machining aluminium workpiece in vertical machining center.

Development of application software for defining professions with 3 lanes on an automobile assembly industry

This paper deals with development of application software for supporting the administration and management of professional trees on an automobile assembly industry. The standard qualifications that are introduced in this paper called the profession with 3 lanes (P3L). Each profession tree is assumed can have 3 lanes that have equality, namely operator/technician lane, utilizer lane, and manager lane. The lanes are graded equally, similar in difficulty and similar in appreciation. An operator lane is focused on operating of machines/ equipment/ methods/ programs. The main consideration of this lane is at the skill aspects. A utilizer lane is focused at the utilizing of main and supporting equipments. The main consideration of this lane is the analytical aspects. The last, a manager lane is focused at the management of jobs. The main consideration of this lane is at the coordination of finishing the jobs. The application software has been developed to support the administration of the concept that has been applied on an automobile assembly industry. Basically, the application consists of two main parts that are a database and the user interface. By using this software, the administration and management of all professions as well as their competencies can be done easily.

Preliminary study of a deep drawing process modelling for AL-5083 aluminium material

The research deals with the preliminary study of deep drawing process modeling for AL-5083 aluminium material. Sheet metal based products are often seen in many goods such as cans, vehicle bodies, aircraft bodies etc. Prior to forming, the properties of sheet metal material must be analyzed in advance. Several properties that are required to be taken into account include form ability, spring back, wrinkling and anisotropy. One kind of forming process on sheet metal is deep drawing process. In this research a simulation using finite element method will be implemented in preliminary study of deep drawing process modeling. The parameters examined include the effect of friction coefficient, punch velocity towards depth of drawn and load shortly before necking. Based on the simulation, it is concluded that the increment of friction coefficient will reduce the depth of drawn and load of the punch. The increment of punch velocity will decrease the load. The optimum value that will give maximum depth of forming shortly before necking and the punch speed with the lowest load is at friction coefficient 0.08 and punch velocity 4 mm/s. At friction coefficient 0.08, depth of drawn shortly before necking is 12 mm and at 4 mm/s of punch velocity, the lowest load is 27100 N.