COMPUTER AIDED PROCESS PLANNING FOR MILLING OPERATION

International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 5, September–October 2016, pp.57–64, Article ID: IJMET_07_05_007 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=7&IType=5 Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication COMPUTER AIDED PROCESS PLANNING FOR MILLING OPERATION Priti Assistant Professor, Department of Mechanical Engineering, Central University of Karnataka, Kalaburagi, India. ABSTRACT Process planning is a production organization activity that transforms a product design into a set of instruction (sequence, machine tool setup etc.) to manufacture machined part economically and competitively. Harnessing the power of the computer is extremely advantageous in process planning. Computer aided process planning (CAPP) is a means to automatically develop the process plan. The key of the development of such CAPP System is to structure the data concerning part design, manufacturing facilities and capabilities into categories and logical relationships. CAPP thus appears to fully integrate CAD and CAM. In this paper, an attempt has been made, to develop a software package which will generate the manufacturing process sheet automatically. A computer program, using visual basic programming languages, is written for this purpose. The process sheet is developed by selecting the operation from the menu and then by feeding the part drawing details. The approach involves, asking a series of questions by the system to the user, about the component drawing and related details. Initially the system asks the user, about the choice of machining operation. The developed system is interactive and simple in use. Any noncomputer person or non experienced engineer can also use it easily. It provides a quick and efficient. Key words: computer aided Process Planning, operation plan code, expert system. Cite this Article: Priti, Computer Aided Process Planning for Milling Operation. International Journal of Mechanical Engineering and Technology, 7(5), 2016, pp. 57–64. http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=7&IType=5 1. INTRODUCTION Traditionally, process planning is performed manually by highly experienced planners who posses in depth knowledge of the manufacturing processes involved and the capabilities of the shop floor facilities. Because of the experience factor involved in the planning for the physical reality of the product and in the absence of standardization of the process, conventional process planning has largely very subjective. Moreover this activity is highly labour-intensive and often becomes tedious when dealing with a large number of process plans and revisions to those plans. Rather than carry out exhaustive analysis and arrive at optimal values, which would be too time consuming, process planners often tend to play safe by using conservative values and this situation invariably leads to non optimal utilization of the manufacturing facilities and longer lead times. They also would not be in a position to see whether a similar component has already been planned in view of the difficulties involved in going through all old process plans. http://www.iaeme.com/IJMET/index.asp 57 [email protected] Priti The need of shorter lead times, satisfying varied customer demands on the product variety and the optimum use of the manufacturing facilities, prompted research organizations and industries to automate many functions in the product cycle. Harnessing the power of the computer is extremely advantageous in process planning since a vast amount of data needs to be used for arriving at the right decision for planning the manufacturing operations. Computer aided process planning (CAPP) is a means to automatically develop the process plan from the geometric image of the component. The key of the development of such CAPP System is to structure the data concerning part design, manufacturing facilities and capabilities into categories and logical relationships. CAPP thus appears to fully integrate CAD and CAM. Several researchers have attempted to do the research in CAPP and have identified areas that need further research. CAPP systems have distinctly evolved in the literature as variant approach and generative approach [1]. Variant approach follows the principle that similar part requires similar plans. Generative approach utilizes decision logic, mathematical formulae, manufacturing rules and geometric data to determine the process required to convert the new material into a finished part. J. Ciurana et al [2] developed a model to integrate process planning function with production planning and control. However before all these functions one of the important decisions to be made is the manufacturing feasibility decision which is not considered. Zhang Wei Bo et al [3] optimized process route by genetic algorithm which is one of the key function in computer aided process planning. L, Li, et al. 2. PROCESS PLANNING Process planning involves the preparation for the manufacture of products. Process planning deals with the selection and definition of the processes that have to be performed in order to transform raw material into a given shape. Process planning in part manufacturing includes: • • • • • • • • • • • • The interpretation of the product model. The selection of machine tools. The selection of tool sets. The determination of set-ups. The design of fixtures. The determination of machining methods. The selection of cutting tools. The determination of machining sequences. The calculation of tool paths. The calculation of cutting conditions. The generation of NC programs Capacity planning. All the information determined by the process planning function is recorded on a sheet called process plan. A process plan is frequently known as operation sheet, route sheet or operation planning sheet. This provides the instructions for the production of the parts. It contains the operating sequence, processes, process parameters and machine tools used. Process planning is classified into two categories: Manual/Traditional process planning and Computer aided process planning. At present, there are two general approaches to CAPP variant and generative; each one is associated with specific planning techniques. 3. MANUAL PROCESS PLANNING Manual process planning is based on a manufacturing engineer's experience and knowledge of production facilities, equipment, their capabilities, processes, and tooling. Process planning is very time-consuming and the results vary based on the person doing the planning". The process planner must have the knowledge of the followings: http://www.iaeme.com/IJMET/index.asp 58 [email protected] Computer Aided Process Planning for Milling Operation • • • • • • • • Ability to interpret an engineering drawing. Familiar with manufacturing processes and practice. Familiar with tooling and fixtures. Know what resources are available in the shop. Know how to use reference books, such as machinability data handbook. Able to do computations on machining time and cost. Familiar with the raw materials. Know the relative costs of processes, tooling, and raw materials. 3.1. Process Planning Steps • • • • • • • • • • • • Study the overall shape of the part. Use this information to classify the part and determine the type of workstation needed. Thoroughly study the drawing. Try to identify every manufacturing features and notes. If raw stock is not given, determine the best raw material shape to use. Identify datum surfaces. Use information on datum surfaces to determine the setups. Select machines for each setup. For each setup determine the rough sequence of operations necessary to create all the features. Sequence the operations determined in the previous step. Select tools for each operation. Try to use the same tool for several operations if it is possible. Keep in mind the trade off on tool change time and estimated machining time. Select or design fixtures for each setup. Evaluate the plan generate thus far and make necessary modifications. Select cutting parameters for each operation. Prepare the final process plan document 4. COMPUTER AIDED PROCESS PLANNING (CAPP) The manual approach of process planning is at a crisis; in order to overcome manual process planning problems, computers have been applied to the process planning area. Essentially, computers are information handling machines. Because of their fast retrieval, computation and mass storage capabilities, computers can provide process planners consistent and timely information. Many computer-aided process planning systems have been developed in the attempt to reduce cost, increase productivity, and solve personnel problems. Computer-aided process planning (CAPP) helps determine the processing steps required to make a part after CAP has been used to define what is to be made. CAPP systems use design algorithms, a file of machine characteristics, and decision logic to build the plans. Main focus is to optimize the system performance in a global context. CAPP programs develop a process plan or route sheet by following either a variant or a generative approach. The Variant Approach uses a file of standard process plans to retrieve the best plan in the file after reviewing the design. The plan can then be revised manually if it is not totally appropriate. The Generative Approach to CAPP starts with the product design specifications and can generate a detailed process plan complete with machine settings. http://www.iaeme.com/IJMET/index.asp 59 [email protected] Priti Figure 1 Computer aided process planning 4.1. Steps Involved in CAPP • • • • • • • • • • • Design input Material selection Process selection Process sequencing Machine and tool selection Intermediate surface determination Fixture selection Machining parameter selection Cost/time estimation Plan preparation Mc tape image generation 5. MODULE OF THE DEVELOPED SYSTEM 5.1. Operation Selection Module This module is the initial module of the system. It allows user to make a choice of the operation for which he wants to prepare the process sheet. It contains a milling operation. http://www.iaeme.com/IJMET/index.asp 60 [email protected] Computer Aided Process Planning for Milling Operation 5.2. Component Representation Module Analogues to the conventional process planning, where the process planner physically examines the part design and then based on geometrical and technological constrains prepare the sequence of operations to be followed to produce the part, the first task in the developed system would be the creation of computer model of the component. In this package, interactive modeling concept is used to create the computer model of the part. 5.3. Database Management Module The utility of any process planning software depends very much on the quality and extent of data available to it. It requires a large amount of data for manufacturing. This large data is to be properly organized for easy access as well as for maintaining integrity. For this reason an extensive manufacturing database has been designed. 5.4. Time and Speed Computation Module In this module, the time required for various operations are computed. The machining time for operation is calculated using the geometry of work-piece, and the process parameters. The time of machining for each operation can be calculated using these formulas and then production time per piece also can be determined and hence total production time is calculated. In speed computation module, the system will analyze the part drawing, for different surfaces and calculate the rpm required for the operation. The quality of surface finish and tool life are highly depends on the rpm. For computing the rpm, the system selects the permissible cutting speed from the database files for a given material and cutting tool. Then the system computes the spindle speed i.e. RPM for the machinable diameter using the formula. Speed (N) = 1000 x V ΠxD Where, D = Cutter Diameter in mm; V = Cutting speed in m/min 5.5. Operation Extraction and Sequence Module This module is the heart of the software. This module scans the part description, in the component representation module and in the database modules, to generate the process plan sheet for the part. The system collects all the information provided by the user and the information collects from the database, and then according to the decision logic written in this module, it prepares the process sheet for the components. Some of the typical rules which form the basic guideline for sequencing: • The face containing a large number of features is generally machined towards the end. • As many operation as possible must be performed in one setting so as to reduce handling time between the operation. Surface requiring high finishes are machined last. • 6. SYSTEM IMPLEMENTATION AND RESULT In order to demonstrate the performance of the system, a part drawing shown in Fig. 2 is used. After receiving necessary information for setup planning system, the system implements setup planning for machining of reference surfaces and machining of features, respectively. A computer program executing the logical sequence has been written in visual basic language. http://www.iaeme.com/IJMET/index.asp 61 [email protected] Priti Figure 2 Algorithm for generation of sequence of milling operation http://www.iaeme.com/IJMET/index.asp 62 [email protected] Computer Aided Process Planning for Milling Operation Figure 3 Part Drawing (All Dimensions in mm) 6.1. Process Sheet for Milling Operation Op.no Operation M/c Code Tool Speed Time Feed 1 Mill Back Face M-01 T-01 ---- ---- ---- 2 Mill Lower Face M-01 T-01 ---- ---- ---- 3 Mill Left Face M-01 T-01 ---- ---- ---- 4 Mill front face M-01 T-01 ---- ---- ---- 5 Mill upper face M-01 T-01 ---- ---- ---- 6 Mill the length of 100mm M-02 T-01 550 13.33 5.3 7 Mill the length of 75mm M-02 T-01 550 11.25 6.6 8 Mill the L slot of length 25mm, depth 100mm, width 50mm M-03 T-02 330 3.33 7.5 Mill the U slot of length 140mm, depth 100mm, width 50mm. M-04 T-02 220 6.67 15 Mill the U Slot of length 40mm, Depth 50mm, width 50mm M-04 T-03 220 6.67 15 Mill the right face M-01 T-03 ---- ---- ---- 9 10 11 7. CONCLUSION In this paper, an attempt has been made, to develop an interactive CAPP system for the milling operation. This system generates the process planning sheet automatically, by feeding the part description drawing. The system contains various modules for operation selection component representation and database management for calculating the machine time for calculating the spindle speed and operation extraction http://www.iaeme.com/IJMET/index.asp 63 [email protected] Priti and logical sequence of operation. The system is used for any of the milling process. The system also can prepare the process sheet for complex components which required more than one operation to be done on part. The system has provides a quick and efficient method for generating process plan. The lead time is preparing process sheets has been reduced. The developed system is simple and any non computer specialist or any non-experienced engineer can use. REFERENCE [1] David D. Bedworth, Mark R. Henderson & Philip M. Wolfe, (1991). Computer Integrated Design and manufacturing, McGraw Hill Book Co. Singapore. [2] J. Ciurana, M.L. Garcia-Rameu, I. Ferrrer & M. Casadesus (2008). A model for integrating process planning and production planning and control in machining Process. Robotics and Computer-Integrated Manufacturing; 24:532-544. [3] G Gopal, Dr L Suresh Kumar and Sriramadasu Sudheer Babu, “Design of Computer Aided Process Plan for a Casing Cover Plate”. International Journal of Mechanical Engineering and Technology (IJMET), 5(9), 2014, pp. 361–373. [4] Zhang Wei Bo, Lu Zhen Hua, Zhu Guang Yu (2006). Optimization of process route by Genetic Algorithms. Robotics and Computer-Integrated Manufacturing, 22: 180-188. Mikell P. Groover & Emory W. Zimmres. Jr, “Computer Aided Desibn and Manufacturing”, Prentice Hall Publication, 1994. [5] Mikell P. Groover “Automation Production Systems and Computer integrated Manufacturing”, Prentice Hall India Pvt Ltd, 1997 [6] James.a.Rehg and H.W. Kraebber, “Computer Integrated Manufacturing”, Pearson Education Asia, 2002 [7] Hanae Zarkti, Abdelilah El Mesbahi, Ahmed Rechia, Oussama Jaider, Towards an Automatic-optimized tool selection for milling process, based on data from Sandvik Coromant, Xth International Conference on Integrated Design and Production, CPI 2015, December 2-4, 2015, Tangier – Morocco. [8] S. Madhava Reddy, “Optimization of Surface Roughness in High-Speed End Milling Operation using Taguchi’s Method.” International Journal of Mechanical Engineering and Technology (IJMET), 4(4), 2013,pp. 249–258. http://www.iaeme.com/IJMET/index.asp 64 [email protected]