Simulation of Toolpaths Using 3D Method Strategies for Complex Shape in Milling Application
MN Talibin1, Z Bakar1, S Abdul Halim1
1 Department of Mechanical Engineering, Seberang Perai Polytechnic, 13500 Permatang Pauh, Penang, Malaysia
*Corresponding Author: [email protected]
Accepted: 15 September 2022 | Published: 1 October 2022
DOI:https://doi.org/10.55057/ijarti.2022.4.3.5
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Abstract: Several strategies can be used for machining complex 3D shapes on a 3-axis CNC vertical milling machine in Autodesk Inventor Professional software. However, it is challenging to determine suitable strategies without guidance. Among the strategies involved are Scallop, Radial, Spiral, and Morphed Spiral. The purpose of this study is to compare the toolpaths strategy in terms of machining time by using high-speed machining parameters. A hemisphere shape and a fillet feature in the part are considered complex shapes due to their convex and concave surfaces. There are two step machining processes involved, which are roughing and finishing. Comparison time is focused on finishing the process using those strategies. Actual fixed machining parameters like tool diameter, feed rate, spindle speed, stepover, and cutting depth are used to make simulations of the toolpaths. Based on the simulation, the radial strategy has the shortest machining time and cutting length by more than fifty percent (50%) compared to other strategies. This is due to the fact that this technique generates passes along the arc's radii, which are subsequently projected down on the surfaces.
The passes can be linked in a zig-zag pattern between the outer and inner radius, either from inside to outside or outside to inside. However, collisions between the cutting tool and the workpiece must be closely monitored. As a result, cutting length must also be addressed when deciding to use this strategy. In conclusion, high-speed machining with the right machining strategy is essential for increased productivity.
Keywords: High-speed machining, CNC milling, Toolpaths strategy
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1. Introduction
Machining is a manufacturing process in which a cutting tool is used to take away undesirable material from a workpiece to achieve the desired shape [1]. Turning, milling, drilling, and grinding are the most common machining operations widely used. Machining has advanced to its current level, and new machining technologies and processes are being developed.
Determining the best machining strategy is also an essential goal in machining. Because of the market's increasing need for high-quality, low-cost products, machining process optimization is crucial in the metal cutting business [2]. It is backed up by studies on the machining of a boom-body connecter, a component of a backhoe loader. According to the study's findings, the machining time was reduced by 55% [3]. As a result, improving machining strategies for complex parts significantly affects productivity.
With the advancement of computer-aided design (CAD) and computer-aided manufacturing (CAM), many users have adopted the approach. In machining, the combination of CAD and CAM allows for the generation of CNC codes for design components [4]. A CAD system can represent a part, and a CAM system can access its geometric data to generate toolpaths that meet NC programming requirements based on the strategies planned. Several CAD/CAM systems are available on the market. One of the available CAD/CAM systems is Autodesk Inventor CAM. In this CAD system, several strategies are provided, such as 2D machining strategies, 3D machining strategies, and multi-axis machining strategies [5]. It has offered another specific strategy under these conditions. However, for complex shapes, 3D machining strategies or multi-axis machining strategies can only be used, depending on the CNC machine that will run the program.
Many commercial computer-aided manufacturing (CAM) systems now have high-speed machining options, allowing for proper machining procedures. High feed machining (Vf), high rotational speed machining (n), high cutting speed machining (Vc), and high productivity machining are several of the terms used to describe it. Cutting conditions, such as cutting speed, depth of cut, and feed rate, are generally considered. To achieve the minimum cutting time in production in accordance with product standards, the appropriate manufacturing conditions must be carefully set for each operation [6].
For the past few years, the number of papers in CAD/CAM, machining strategy, and high- speed machining has drastically increased. This research indicates the increasing success of evolutionary techniques in machining manufacturing. However, it also needs to look at the type of CAD/CAM system used. For instance, in Autodesk Inventor CAM, there are several strategies that can be used for machining complex 3D shapes with a 3-axis CNC vertical milling machine that make it difficult to determine. The objective of this study is to compare the toolpaths movement strategies and machining time by using high-speed machining parameters for Scallop, Radial, Spiral and Morphed Spiral strategies. Actual fixed machining parameters like tool diameter, feed rate, spindle speed, stepover, and cutting depth are used to make simulations of the toolpaths. Therefore, it can help users choose the best strategies during machining.
2. Methodology
This section provides an outline of the study. A three-dimensional model has been developed using Autodesk Inventor Professional 2022 as a CAD system as shown in Figure 1. A hemisphere shape and a fillet feature that located on top of square shape are considered as complex shapes due to their convex and concave surfaces [7]. The design is represented by collection of face, vertices and edge defining the boundary of the form.
Complex shape (Convex) Fillet (Concave)
Figure 1: Three-dimensional of complex model
The detailed dimensions involved in the model have been shown in Figure 2 based on third angle projection in millimetres. Because it can be used directly in the same software, the design was saved as an.ipt extension file.
Figure 2: Detail dimension of the complex model
The summary approach for the study is depicted in Figure 3. The process starts with the creation of a part by using the CAD application in Autodesk Inventor with two-dimensional (2D) and three-dimensional (3D) features. Then, toolpaths are created for roughing using CAM application features (3D Milling-Adaptive) are developed, which involve several steps such as setup toolpaths, and simulation. After that, a second process was developed that involved four main processes, which are Scallop, Radial, Spiral and Morphed Spiral by using fixed high- speed machining parameters [8]. In this study, the comparison of machining times focuses only on the finishing process.
Figure 3: The flow chart of the summary approach to the study
2.2. Toolpaths Creation for Machining in CAM
The detailed process sequence of toolpaths creation is stated below. All the processes are developed by using the CAM application in Autodesk Inventor Professional 2022.
Roughing Process
Toolpaths creation in roughing process for the complex model are using a 3D milling-Adaptive strategy as shown in Figure 4. This process is important to remove unwanted material before the finishing process.
Start
Part modeling produce using CAD system by application of 2D and 3D features
Toolpaths creation for roughing using CAM application features (3D Milling - Adaptive)
No Successful?
Toolpaths creation for finishing using CAM application features (3D Milling - Scallop, Radial,
Spiral and Morphed Spiral)
Successful?
No
Analyze toolpaths movement and machining time among of the strategies
End
Figure 4: The flow chart of the roughing process
Finishing Process
The finishing process is an important part of this study. Toolpaths creation in the finishing process for the complex model is using several 3D milling-related strategies. Among the strategies are Scallop, Radial, Spiral, and Morphed Spiral. Figure 5 shows the flow chart of the finishing process to study the machining time and toolpaths movement. However, this simulation also concerned the collision of the cutting tool.
Start
Setup:
Setup: Generic 3-axis Milling Machine Operation type: Milling
Work Coordinate System (WCS) – Model Orientation and stock box point
Stock:
Stock Dimensions: Width (X): 80mm, Depth (Y):
80mm and Height (Z): 41mm
3D Milling Operation: Adaptive Tool:
Flat Mill with diameter 10mm and flute length 25mm (Figure 5).
Machining Parameter [9]:
Spindle speed: 5000 rpm Feed rate: 950 mm/min
Maximum roughing stepdown: 2.5mm Minimum stepdown: 0.5mm
Stepover: 50%
Generate Toolpaths
Not Successful
Finishing Process
Successful
Figure 5: The flow chart of the finishing process
Cutting Tools
All the specifications for cutting tools are based on the actual cutting tools that are used in the Fanuc Robodrill machine equipped with a BT30 arbor. Cutting tool specifications such as tool length and cutting edge are also important to avoid collisions during machining [10]. In this study, roughing process needs to use a flat and mill cutter while the finishing process used a ball end mill cutter as shown in Figure 6 and Figure 7.
Start
Setup:
Setup: Generic 3-axis Milling Machine Operation type: Milling
Work Coordinate System (WCS) – Model Orientation and stock box point
Stock:
Stock Dimensions: Width (X): 80mm, Depth (Y):
80mm and Height (Z): 41mm
3D Milling Operation: are Scallop, Radial, Spiral, and Morphed Spiral
Tool:
Ball Mill with diameter 6mm and flute length 20mm.
Overall length 63mm (Figure 6).
Machining Parameter [9]:
Spindle speed: 5000 rpm Feed rate: 950 mm/min Plunge rate: 100 mm/min Stepover: 0.25mm
Generate Toolpaths
Not Successful
Analyze Successful
Figure 6: Specification of Flat End Mill
Figure 7: Specification of Ball Mill
3. Result and Discussion
Autodesk Inventor Professional 2022 was used to do the virtual simulation. Four simulations are used in the experiment on one model. Figure 8a) and Figure 8b) illustrates the roughing process using a 3D milling-Adaptive strategy. That figure shows all toolpaths movement, such as rapid traverse (G0)-yellow colour, retract of cutting tool-red colour, cutting movement (G01, G02 and G03)-blue colour and lead in/lead out-green colour. All the parameters are referred to as high-speed machining data [9]. The parameter was chosen because it primarily considers the state of a workpiece, which includes tool wear, surface roughness, and force on the workpiece.
Figure 8a): Toolpaths of roughing process. Figure 8b): Shape of the part after the roughing process.
Figure 9 to Figure 12 exhibit the results of simulation for the finishing process by using different strategies. Those figures show toolpath movement and the end product of a part. The radial strategy has a simpler strategy compared to others and is able to machine radial parts.
Scallop and morphed spiral strategies have simple cutting movements and can produce a good product shape. The spiral strategy has too many rapid traverses, which increases machining time.
Figure 9: Toolpaths movement and shape of the part after the finishing process with scallop strategy
Figure 10: Toolpaths movement and shape of the part after the finishing process with radial strategy
a) b)
Cutting movement
Rapid traverse
Figure 11: Toolpaths movement and shape of the part after the finishing process with spiral strategy
Figure 12: Toolpaths movement and shape of the part after the finishing process with morphed spiral strategy
All the findings are summarised in Table 1. The first column represents four strategies for the finishing process. The second, third, and fourth columns represent the results of machining time, volume removed, and cutting length. In this simulation, the radial strategy has the shortest machining time and the lowest cutting length by more than fifty percent (50%) compared to other strategies. This is due to the fact that this technique generates passes along the arc's radii, which are subsequently projected down on the surfaces. The passes can be linked in a zig-zag pattern between the outer and inner radius, either from inside to outside or outside to inside.
However, collisions between the cutting tool and the workpiece must be closely monitored. As a result, cutting length must also be addressed when decide to use this strategy.
Table 1: Information extracted from CAM system Strategy of finishing Time machining
(min)
Volume removed (mm3)
Cutting length (m)
Scallop 36.10 140,546 34.0693
Radial 18.10 140,576 16.9696
Spiral 86.01 140,581 83.0206
Morphed spiral 43.58 140,542 41.1745
3. Conclusion
Producing a product with a CNC machine is complicated, especially when the product is complex. The use of CAD/CAM systems, on the other hand, makes the machining process much easier. A study of CNC machining operations and toolpaths in a CAM system is a realistic technique to achieve the goal faster, save costs, and improve machining efficiency.
One of the most significant factors in achieving the quickest machining time is the machining strategy. The radial strategy has the shortest machining time and cutting length by more than fifty percent (50%) compared to other strategies. This is due to the fact that this technique generates passes along the arc's radii, which are subsequently projected down on the surfaces.
The passes can be linked in a zig-zag pattern between the outer and inner radius, either from inside to outside or outside to inside. However, collisions between the cutting tool and the workpiece must be closely monitored. In terms of knowledge contribution, high-speed machining with the appropriate machining strategy is critical for increased productivity. In the future, surface roughness and pattern also need to be involved to have a perfect finding.
References
[1] Groover, M.P. (2013). Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th ed. New York, ABD: John Wiley & Sons.
[2] Baskar, N., Asokan, P., Prabhaharan, G., Saravanan, R. (2005). Optimization Of Machining Parameters for Milling Operations Using Non-Conventional Methods. Int. J. Adv.
Manuf. Technol ;25(11-12): 1078-88.
[3] Gökçe, H., Yeşilay, R., Uçak, N., Teke A, & Çiçek, A (2019). Improvement of Machining Processes: A Case Study. 7th International Symposium on Innovative Technologies in Engineering and Science, ISITES2019 SanliUrfa – Turkey, 634-641.
[4] Majerik, J., Bajcik, S., & Jambor, J (2010). Automation of the production process for metallic flexible diaphragm with CAD/CAM system CATIA V5R19 support, in:
Annals of DAAAM for 2010 & Proceedings of the 21st International DAAAM World Symposium Intelligent Manufacturing & Automation: Focus on Theory, Practice and Education: World Symposium, ISSN 1726-9679. Vienna University of Technology, Zadar, Croatia, pp. 0623–0624.
[5] Jennifer, M. & Ed, G (2022). Autodesk Inventor CAM 2022: Milling Fundamentals (Mixed Units) -1st Edition. VA. ASCENT.
[6] Lacalle, L.N., Lamikiz, A., Sánchez, J.A. & Arana J.L. (2002). Improving the surface finish in high-speed milling of stamping dies. J Mater Process Technol 123:292–302.
[7] Franse, J (1990). Manufacturing techniques for complex shapes with submicron accuracy.
Reports on Progress in Physics, 53(8), 1049–1094.
[8] K. C.Gan & M.S, Abu Mansor (2020). High-Speed Machining for CNC Milling Simulation Using CAM Software. In book Advances in Manufacturing Engineering Springer.
(pp.703-713).
[9] A.M. Shafie & H. Abdullah (2020). Simulation of Tool Path Using Conventional Method for Milling Application. Research Progress in Mechanical and Manufacturing Engineering Vol 1, No. 1. 132-138.
[10] Scandiffio I., Diniz A. E., de Souza A. F. (2016). Evaluating surface roughness, tool life, and machining force when milling free-form shapes on hardened AISI D6 steel. The International Journal of Advanced Manufacturing Technology 82(9):2075-2086.
