Proceedings of EnCon2008 2nd Engineering Conference on Sustainable Engineering Infrastructures Development & Management December 18 -19, 2008, Kuching, Sarawak, Malaysia ENCON2008- EnCon08/Abs237
Simplification of Five-Axis to Three-Axis Machining Approach for Aerospace Part: Effect on Production Cost S.Syahrul Azwan 1, M. Mohd Razali 2, A.B Baharudin 3 1,2,3
Department of Process Engineering, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Locked Bag 1200, Hang Tuah Jaya, Ayer Keroh Melaka, Malaysia. Tel: 06-233 3478 e-mail:
[email protected] 1,
[email protected] 2,
[email protected] 3
Abstract – The main objective of this research was to find an alternative approach or strategy in machining of five-axis aerospace parts
to be simplified to three-axis machining. The ultimate reason was to help the aerospace industry sustaining in today’s market demand which rapidly growth. The software used for machining programming in this research was CATIAV5R16 and the simplified program had been successfully machined in MAZAK VRX-630 machine. The “Isoparametric” command in “Advanced Machining” workbench was chosen to be the main machining process commands used in simplifying the program. A scallop height of 0.01 mm and tool axis set to be fixed to the machining plane were the key factors in ensuring the five-axis program run successfully in the three-axis approach. The material used was Aluminum 7075 series and cutting tool used was a ball nose 6 mm diameter of high speed steel (HSS). In order to analyze the effect of production cost, the actual machining time for both five-axis and three-axis machining approaches had been investigated. The five-axis machining time reported to be lower than three-axis machining time by approximately 8 to 10 minutes. This was due to more tool path needed for three axis approach to perform the machining process for five-axis shape. Anyway, on the other hand, respective industry might be able to increase their profit by approximately 9% to 12% when the charging applied was the fiveaxis machining rate although the part now can be machined in three-axis. Ultimately, simplification method was proven to be one of the methods that can be applied in order to increase competitiveness in the competitive market today. Keywords: Simplification, Five-Axis machining, Three-axis machining, CATIAV5R16, machining time, aerospace part, isoparametric command
I.
INTRODUCTION
Nowadays aerospace industry has grown rapidly in Asia especially in Malaysia. Most of the aerospace parts are made in Asian countries. This is due to the lower manufacturing and labor cost offered by the Asian countries. Thus, there are many efforts done by the industries in order to compete with the market demand. One of the methods currently thought and applied by the industries was trying to simplify the machining approach from five-axis to three-axis machining. Definitely, this method only can be applied to the certain shapes or geometries of the parts. By successful in this simplification, the respective industry might be increased their profit by charging the five-axis rate to the only three-axis part that they managed to simplify. Having saying that, this research is also aims to study and analyze the simplification method which might be useful and can be discussed with the respective industry about the result obtained. Five-axis milling is widely used especially in aerospace, automotive, mold and dies industries where most of the parts have complex surfaces. Productivity and part quality are extremely important for all machining operations, but particularly for fiveaxis milling where the machine tool cost is relatively higher, and most parts have complex geometries and high quality requirements. Five-axis milling, presents additional challenges in modeling due to more complex tool and work piece interface geometry, and process mechanics [1].In point milling, the cutting edges near the end of a tool performs the material removal. In contrast, the side face of a cutter does the machining in flank milling. Users can select an appropriate one according to the work piece geometry, surface finish, machining time, and cost [2]. From the references and literatures done so far, it is proven that the research in aerospace has becoming popular and more popular since the number of the demand throughout the entire world reported gradually increased year by year. In Airbus
General Market Forecast (GMF) documentation, they already came out with a figure forecasted up to 2026 on the demand of the passenger and freighter aircraft market [10]. The figure 1 below explains the scenario in the future forecasted by the market experts.
Figure 1: Forecast on the New, Converted and Recycled Aircraft for 2007 to 2026
As we can see from the number shown on the figure above, there will be 24 262 additional aircrafts to be built and marketed to worldwide market in order to fulfill the demand. Not to be forgotten the number of retired aircrafts indicated 6 459 which also not a small number. As a result, the importance of metallic part in aerospace clearly revealed since this material can be recycled and reused once the respective aircraft reached its lifetime. This is where the major advantage and useful of metallic part compared to composite. Ultimately, it can be concluded that research in metallic material in aerospace manufacturing still valuable to the market demand although the new advanced material has been introduced to substitute part of the metallic material.
II.
RESEARCH METHODOLOGY
The first step of the research proposed started with literature review and searching reading materials to gain some ideas and methods to be implemented during performing the research. Discussion had been carried out with the respective industry to brainstorm and get the input for the best aerospace sample part which appropriate to the desired requirement for the meant research. Once the part had been finalized, the modeling of the part was created by using CATIAV5 Released 16 with all the dimensions in placed. In CATIAV5 all the processes involved in modeling will be done using Sketcher, Part Modeling and Assembly workbench and Advanced Machining workbench allows user to create machining programming by using integration of Computer Aided Design and Computer Aided Manufacturing (CADCAM). This process was the most vital area need to be focused because the successful of the physical or actual machining was determined by the success of the machining programming done by the programmer. All machining parameters were filled during this process. Completed program posted out as “.NCCODE” format file by using integrated CATIA post processor for program that only consist of three-axis movement. Meanwhile, those programs which contained five-axis movement customized post processor will be used to transfer the data from “.aptsource” format to “.NCCODE” format. This coding format was actually depending on the machine that going to be used. In this research, MAZAK VRX-630 machine had been selected to be the main machine where the actual machining took place. The program afterwards verified visually by using VERICUT 6.03 software. The main advantage of this software was its capability of verifying the actual tool path and machine table movement. With help of VERICUT the major collision can be avoided and the overall overview of physical machining can be visualized. If there is any problem with the program for instance collision and its detected by the software, the programmer need to come back to the inertial program to do an adjustment or amendment to overcome the problem. Then, the updated program has to be rerun again with VERICUT. Once everything clears from any error, the program loaded into desired machine to perform actual physical machining. From the machine, user can know how long it takes to machine one part based on the program loaded into the controller. Approximate machining time will be given and the time shown might be varies from the actual.
Literature Review and reading material searching
Brainstorming on part selection & discussion with related industry
Sketch & create modeling with stock using CatiaV5R16 software
Machining programming with all parameters and machining strategy in place
Place order for cutting tools, raw material, jig & fixture (if required)
Tool path verification using VERICUT software YES
Validate the machined part
Transfer to actual machine and perform the physical machining
Analysis on any variation occurred compared to the modeling given
Send machined part to the lab for analysis
Report and research paper writing.
Figure 2: Flow chart of research methodology
No
III.
RESULT AND DISCUSSION
CATIA software has been widely used in various fields or industries around the world especially in automotive and aerospace industry. There are a lot of modules offered in CATIA workbench such as Mechanical Design, Shape Design, Analysis and Simulation, Machining Simulation and many more. For this research, “Advanced Machining” was chosen to be the main module or workbench to be used in creating and producing the program. There were many criteria need to be considered during the programming process. In this simplification method, “Isoparametric” command selected to be the main process that can help into simplifying the machining programming. The part selected was actually a door latch bracket for an aircraft. Normally by initial observation to the modeling obtained a programmer should be able to define in general the overall processes and the cutting strategy involve for the respective part. Based on the evaluation there were three areas identified as five-axis shape that acquire the movement of the axis A, B or C to take place. For five-axis movement the cutting tool needs to be tilted to the certain angle in order to perform the machining process. In this movement, an allowance of certain distance need to be considered to avoid any collision between the tool and the work piece or it might be the machine spindle and the machine table. Since the geometry of the part seems to be in constant angel, the tool paths generated were in five-axis Indexing movement. There were two types of five-axis movements. Firstly named, “Simultaneous” and secondly called “Indexing” five-axis. Simultaneous refers to all five axes move in the same time where we can see in the posted program axis X, Y, Z, A and B or C indicated in every block of the program. Meanwhile, indexing means axis X, Y and Z move at only certain position of A, B or C axis. Figure 3 given below explains further about the simultaneous and indexing movement of five-axis machining. On the other hand, alternatively the “Isoparametric” command helped into generate an appropriate three-axis movement tool path instead of the five-axis. In order to perform this method, it was a must to use ball nose or bull nose cutting tools to avoid any cutting marked at the first point of cutting and less friction, vibration and chattering during actual cut between cutting tool and work piece. In other words, this method also called simultaneous three-axis machining. It was obviously indicated that the movement of axis X, Y and Z at the same time if we refer back to the NC code program that been posted. Both five-axis and three-axis machining movement had been created to investigate the effect of time taken to complete all the tool paths. T08T00M06(LENG=143.382) G28X0.Y0.Z0. M19 M01 S2000 M13 G00X-414.585Y-308.044Z-364.536 X56.13Y63.535Z16.76A1.433C49.49 X-8.24Y-108.603Z-2.717 Y0.001Z-85.027 G01Y-0.001Z-34.167F1000 X0.438Y-0.417Z-0.053F800 X0.587Y-0.356Z-0.057 X0.542Y-0.188Z-0.044 X0.247Y-0.049Z-0.017 X0.675Y-0.027Z-0.039 X0.656Y0.122Z-0.03 X0.568Y0.24Z-0.016 X0.509Y0.351Z-0.006
T04T00M06(LENG=196.96) G28X0.Y0.Z0. M19 M01 S3000 M13 G00X-402.664Y-305.899Z-217.763 G01Z0.035F1000 X2.547Y-0.4Z-0.138A-0.001C-0.26 X2.55Y-0.377Z-0.13C-0.261 X2.55Y-0.36Z-0.125A-0.002C-0.26 X2.524Y-0.617Z-0.216A-0.111C-0.256F682 X2.525Y-0.595Z-0.211A-0.112C-0.253 X2.525Y-0.569Z-0.202A-0.112C-0.25 X2.525Y-0.545Z-0.197A-0.112C-0.248F677 X2.282Y-0.538Z-0.195A-0.11C-0.23F682 X2.283Y-0.517Z-0.19A-0.11C-0.228 X2.283Y-0.499Z-0.184A-0.111C-0.225 X2.284Y-0.48Z-0.18A-0.111C-0.223 X2.155Y-0.421Z-0.163A-0.104C-0.211F677
Figure 3: Sample of the program shows simultaneous (right) and indexing (left) five-axis movement
Figure 4: Tool path generated when machining program created in three-axis approach (left). Tool path generated when machining program created in five-axis approach (right).
“Isoparametric” machining command was capable to give both three and five axis tool path movement. It was definitely depending on how the program created or customized. For this research, there were three major settings that been set to ensure the five-axis shape program can be cut using three-axis program. All settings took place in the first page of the “Isoparametric” interface windows or namely cutting strategy window. The first setting was the tool path style or cutting direction style. In this option, we were given two choices, zigzag and one way cut. One way strategy was chosen for this option. The main reason one way cutting selected was to avoid high vibration and chattering during actual cutting. The second setting was the most important setting that control the number of tool path that going to be produced. The option used for this research was scallop height and the figure set was 0.01 mm. The value set was the smallest and the finest allowable value. The final setting that needs to be done was the setting on the tool position. The position of the tool has to be fixed in order to make sure the overall program will be in three-axis motion. Figure 5 below show the settings explained above. All settings described above were only meant for the finishing cut for the five-axis shape that already identified on the respective shape. There were still many steps that need to be performed in order to get the overall shape of this part. Once the overall program completed, the tool path now can be reviewed by using the three-dimensional (3-D) cutting visualization offered by CATIA. From this visualization we should be able to see any major collision and verify the desired actual shape to be machined. This process was very useful for the machining programmer to pre-check the actual tool path that going to be generated. There were a few characteristics that one should aware while obtained the result from this visualization. Although the overall program seems to be fine, but we should remember about the effect of spindle speed and feedrate which contribute to the vibration, high friction and chattering were not shown in this machining visualization. Thus, during perform the actual machining; the machine operator has to play an important role to ensure the program run smoothly. Figure 5 below indicates the machining visualization offered by CATIA.
Figure 5: Scallop height set to the smallest value 0.01mm and tool position fixed to the machining plane (left). Visualization offered by CATIA for tool path verification (right).
Table 1 given below indicates the difference of cost incurred related to machining time when three-axis and five-axis machining approach had been applied. Actual physical machining had been performed for both three and five axis machining approaches and the machining time had been captured to see the difference. Obviously, the respective company might be able to get USD 2.09 more if the selected aerospace part was charged according to the five-axis charges rate although the machining time took 8 to 10 minutes later than the five-axis machining approach. This was due to more tool path needed for three-axis approach to perform the machining process for five-axis shape. In the other words, successful in this simplification a company should be able to increase their gross profit by 9% to 12% according to the figure shown by the table above. This estimated cost was obtained from machining charges applied by the licensed aerospace company in Malaysia. In addition to that, five-axis machining acquired higher investment compared to the three-axis machining for example an expensive five-axis machines, external post processor, special extended chuck, customized jig and fixture and so on so forth. The simple calculation above only represented data in general without considering the overall factors. Definitely, there were still many considerations that need to be looked before any conclusion can be made. Table 1: The difference of cost incurred related to machining time between five-axis and three-axis machining approach Machining Approach
Machining Time (min)
Charges per min (USD)
Additional Support Equipment
Total (USD)
Three-Axis
28
0.83
-
23.24
19
1.33
Customized Post Processor, Jig Fixture,
25.33
Difference (USD)
2.09 Five-Axis
Figure 6: Part successfully machined.
IV.
CONCLUSION
The part selection made in the earlier stage was clearly indicated that the selected part consist of complex area that required five-axis machining. Anyway, at the end of the research milestone proven that by application of “Isoparametric” machining command the five-axis shape or area can be machined with three-axis path according to the certain settings that need to be done. Scallop height 0.01 mm and tool axis set to be fixed to machining plane were the settings applied to ensure the five-axis program run successfully in three-axis approach The strategy of cutting or approach of machining identified was the main key factor that contributes to the success of this research. By successful in this simplification the respective company might be able to gain 9% more gross profit if the selected aerospace part was charged according to the five-axis charges rate although the machining time took 8 to 10 minutes later than the five-axis machining approach. This was due to the higher charges rate for five-axis machining. The conclusion made only considering on the factor of machining time effect in an ideal condition.
References. [1] Susan X Li and Robert B Jerard, “5-axis machining of sculptured surfaces with a flat-end cutter” Journal of Computer-Aided Design Volume 26 Number 3 (1994): 165-177 [2] B.K Fussell, R.B Jerard, J.G Hemmett, “Modelling of cutting geometry and forces for 5-Axis Sculptured Surface Machining” Elsevier Science Ltd, Computer Aided Design, (2003) [3] Sanjeev Bedi, Stephen Mann, Cornelia Manzel, “ Flank Milling with end milling cutters” Elsevier Science Ltd, Computer Aided Design, (2003) [4] B. Sencer, Y. Altintas_, E. Croft, “Feed optimization for five-axis CNC machine tools with drive constraints” International Journal of Machine Tools & Manufacture 48 (2008): 733-745 [5] Center for Aerospace Manufacturing Technologies (CAMT), University of Missouri-Roll, United State Newsletter spring 2006. [6] Middleton, Donald H., Composite Materials in Aircraft Structures, Longman Scientific & Technical, NY, 1990 [7] Callister, William D. Jr., Materials Science and Engineering an Introduction”, John Wiley & Sons Inc., NY, 2003 [8] Andrew Allcock, “All Done In One”, Australian Manufacturing Technology Magazine, 2007 [9] Boeing Corporation Website, “Boeing 787 Dreamliner Will Provide New Solutions for Airlines, Passengers”, 2008, avail. http://www.boeing.com/commercial/787/background.html and http://www.newairplane.com/ [10] Airbus Website, “Welcome to the World of Airbus”, 2008, avail://www.airbus.com/en/myairbus/a380_wow/
