- Email: [email protected]
Reconfigurable Didactic Microfactory with Universal Numerical Control
Proceedings of the 14th IFAC Symposium on Information Control Problems in Manufacturing Bucharest, Romania, May 23-25, 2012
Reconfigurable Didactic Microfactory with Universal Numerical Control Miguel Ramírez-Cadena* Jhonattan Miranda* Guillermo Tello-Albarrán* Oscar Dávila-Ramírez* Arturo Molina* *Tecnológico de Monterrey, Mexico City Campus. Mexico. (Tel: +52 (55) 54832020 Ext. 2782; e-mail: [email protected], [email protected], [email protected], [email protected], [email protected]).
Abstract: This paper presents the design and implementation of a Reconfigurable Microfactory for educational purposes, consisting of two Reconfigurable Micro Machine Tools with Universal Numerical Control, one Robotic Arm, and two Warehouses for raw materials and finished product, which altogether form an assembly kit of mechanical, electrical and electronic parts. This project is being developed by Tecnológico de Monterrey, Mexico City Campus, and aims to strengthen the professional development of students in the areas of mechatronics and manufacturing. Miniaturization, reconfigurability and use of low cost items are innovative aspects that facilitate the acquisition of this Microfactory in educational institutions, as it has a significant educational and cost savings benefits compared with conventional machine tools and commercial computer numerical control machines. Keywords: Microfactory, Universal Numerical Control, Reconfigurable Micro Machine Tool, Manufacturing Systems, Low Cost Control, Didactic.
1. INTRODUCTION At present, many educational institutions in developing countries do not have sufficient resources to acquire advanced automated manufacture systems. The general aim of this project is to generate new, low-cost learning tools, so as to facilitate teaching and learning in secondary and tertiary educational institutions. These institutions are fundamental to fostering technical skills and experience in students, which allow them to achieve greater productivity be more competitive in the labor market. In recent years, institutions in different countries have engaged in research on micro machine tools with reconfigurable elements, leading to the emergence of terms such as “desktop machine tools” and “hybrid machine tools.” Results have included reducing the sizes of machine tools, work spaces and required material resources, energy savings, and even environmentally friendly developments [1][3][9]. The concept of micro manufacturing emerged thanks to these investigations and to their viability for manufacturing systems. Since 1990, studies about and research on microfactories have increased, especially in Asian countries like Japan, Korea and China; note that Europe and the United States had already developed micro manufacturing systems, primarily geared towards the development of small tools and micro manufacturing parts for medical devices [4][6][10][12]. In 2000, Mexican team realized mechanical studies on micro machine tools [11].
978-3-902661-98-2/12/$20.00 © 2012 IFAC
The drivers used in these machines are also becoming more flexible, to cope with the variety of manufacturing processes that are being used in micro manufacturing [8]. The control proposed in this paper is an example of this. This control facilitates low-cost machine tool automation with CNC automation applications based on Universal Numerical Control (UNC) architecture (patent pending). The microfactory is based in a mechatronic system applied to manufacturing system with a academic purpose; the system include all the elements of the a mechatronic system: actuators, sensors, mechanism, interfaces, and control systems. 2. ACADEMIC PURPOSE The Reconfigurable Didactic Microfactory with UNC offers the educational sector the possibility of acquiring an innovative reconfigurable and portable system at low cost. The Microfactory offers the same possibilities as conventional systems and CNC machining while remaining financially accessible to institutions that cannot afford these more costly systems. This system allows students to learn the basics of:
463
a) Automated manufacturing systems b) Mechatronics c) Machine tool operation
10.3182/20120523-3-RO-2023.00243
INCOM 2012, May 23-25, 2012 Bucharest, Romania
4. RECONFIGURABLE MICRO MACHINE TOOLS
d) Robot handling e) Numerical control programming f) Mechanical assembly. 3. RECONFIGURABLE SYSTEMS The main concepts that are taken within the mechatronic design process are: the reconfigurability of the system (hardware-software) and system size (portable). The term “reconfigurable” can be defined generically as the ability of a system for introducing, remove or relocate its components, which allows to increase its functionality effectively in terms of time and cost. The system size is also an important consideration and thanks to its small size allows for easier configuration of the physical parts of the system and helps to reduce cost and be portable, is easily moved from place to other. 3.1. Reconfigurable Manufacturing Systems Ideal Reconfigurable Manufacturing Systems possess six core characteristics: 1. Modularity, in a reconfigurable manufacturing system, all major components are modular (e.g., structural elements, axes, controls, software, and tooling). When necessary, the modular components can be replaced or upgraded to better suit new applications 2. Integrability, while there are hundreds of machine tool builders in the world, only about a dozen of them are capable of supplying fully integrated flexible machining systems for high-volume production. 3. Customized flexibility, to design system/machine flexibility just around a product family, obtaining thereby customized-flexibility, as opposed to the general flexibility of FMS/CNC.
The Reconfigurable Micro Machine Tool (RmMT) assembly toolkit has mechanical, electrical, electronic and control pieces. The RmMTs are designed so as to fulfill three different piece mechanization functions; all that is needed is to reconfigure the position and change the RmMT cutting tool. The possible configurations are: Lathe, Milling Machine and Drill. The elements of the RmMT are made of aluminum 1060 and were designed so as to adjustable, easy to assemble and sufficiently thick to avoid mechanical deformations. The volume measurements for a vertical configuration in the Milling Machine or Drill are 216mm x 280mm x 220mm, and for a horizontal configuration 216mm x 280mm x 110mm. The measurements for the Lathe are 216mm x 280mm x 110mm. Below we list the elements needed to assemble an RmMT Kit (See Figure 1 for visualizations): 1 Principal base 2. Support for a vertical reconfiguration 3. Reconfigurable base 4. Tower support jaw/spindle 5. Angle (support of axis Y) 6. Base for support of axes 7. Spindle screw clamp support base 8. Spindle screw clamp 9. Cutting tool support 10. Clamp jaw 11. Linear actuator 12. Portable actuator 13. Clamp cylinder 14. Cutting tool (milling machine or drill) 15. X-axis motion actuator 16. Y-axis motion actuator 17. Z-axis motion actuator 18. Burin 19. Spindle 20. Support burin
4. Scalability, Scalability of the system capacity is the counterpart characteristic of convertibility. Scalability may require adding spindles to a machine to increase its productivity, or even adding machines to expand the overall system capacity as a given market grows. 5. Convertibility, System convertibility may have several levels 6. Diagnosability, Has two aspects: detecting machine failure and identifying the causes for unacceptable part quality. These characteristics, which were introduced by professor Yoram Koren in 1995 [5][7], apply to the design of whole manufacturing systems, as well as to some of its components: reconfigurable machines, their controllers, and also to the system control software. Figure 1. Elements make up the assembly of RmMT.
464
INCOM 2012, May 23-25, 2012 Bucharest, Romania
Table 1 describes the RmMT’s technical specifications. Table 1. RmMT Technical Specification Parameter Value Motor type Motor DC xyz travel range 15 x 15 x 15 mm xyz resolution 0.0085 m xyz feed speed 188.5m/min Spindle max speed 30,000rpm
4.1. Lathe Configuration The lathe configuration is the simplest in the system, as it uses few components for assembly and always runs horizontally. This configuration allows for two axes of motion. It contains a tool holder fixed to the axes of motion, the cutting tool, the spindle and a fixed tower, which functions as a carrier spindle (see Figure 2). In this configuration, the RmMT can mechanize workpieces using rotation, while the actuators move the cutting tool in a controlled manner against the surface of the workpiece, cutting the workpiece according to numerical control specifications.
Figure 3. Physical RmMT System, vertical configuration for Drill/Milling Machine.
The specific function of the Drill is the drilling. In the RmMT, the Drill rotates while the workpiece remains fixed to the clamp jaw. One can also use different cutting tools to perform other operations such as countersinking and reaming. The specific function of the Milling Machine is to smooth surfaces. The Milling Machine rotates and moves on the X, Y and Z axes while the workpiece remains fixed to the clamp jaw. The cutting tool used is the milling cutter, which is usually round with different blades available depending on the shape to be given to the workpiece.
Figure 2. Physical RmMT System, Lathe Configuration.
4.2. Drill and Milling Machine Configuration The Drill and the Milling Machine share the same configuration, with the only difference being in the cutting tool used. This configuration has three axes of motion. Both horizontal and vertical configurations are available for the Drill and Milling Machine, in order to allow flexibility in the number of manufacturing processes that can be followed (see Figures 3 and 4). In these configurations, the linear actuators move the cutting tool on three axes, and the automatic clamp, which has a linear actuator, holds the workpiece in place in a controlled manner. This automatic fastening is designed so that a robotic arm positions the workpiece. The robotic arm, which we discuss later, can automate a microfactory where more than one RmMT interact.
Figure 4. Physical RmMT System, horizontal configuration for Drill/Milling Machine.
5. ROBOTIC ARM In order to achieve total automatization of a Microfactory, a robotic arm was designed to transport and handle raw materials. The robotic arm is able to interact with each RmMT as another part of a Microfactory. The design of the robotic arm consists of a cylindrical configuration with 4 degrees of freedom (see Figure 7 and Table 2) [2]. The robot has a rotational axis at the base that permits two prismatic movements, which guide up/down and approach/distance, respectively. The gripper has rotational motion in the wrist (see Figure 5).
465
INCOM 2012, May 23-25, 2012 Bucharest, Romania
interpolation dispatcher receives information from the interpreter and gives commands to the interpolator. Trajectory Generator (TG). The TG consists of the interpolator, which as mentioned above receives instructions from the interpolation dispatcher. The main function of the TG is to calculate the path that the system must follow in order to accomplish the desired trajectory. This path is then processed and communicated to the next part of the operating process, the motion system.
Figure 5. Physical Robotic Arm, and definition of Joints.
Table 2. Robotic Arm Dimensions
Joints l0 1 d2 d3 4
37.5mm 180° 90 mm 150mm 180°
4. UNIVERSAL NUMERICAL CONTROL The automatic control in the system is based on an open resource platform with a PIO-D48U card for a PCI bus. This controls the system and also serves as an interface for the implementation of UNC applied to RmMTs. The UNC is a modular control system that can be adapted or retrofit to any machine and has moveable components [13]. The UNC is a communication module substitute that permits using diverse signal hardware and modifying or selecting the type of interpolation or graphical interface required.
Motion System (MS). This part of the operating process contains many sub-processes. The first is the motion dispatcher, which manages the control of the system, ensuring dispatch to the correct unit, as communicated by the interpolator. The motion dispatcher also uses feedback to recalculate the system’s path. The motion dispatcher gives instructions to the logic control, which in turn provides commands to the HAL. Motion control management is the motion dispatcher’s most important task, because the motion dispatcher sends instructions to the system’s different parts as to the correct path to follow. The axis units send correct information to HAL. Hardware Abstraction Layer (HAL). HAL is the functional unit that controls the motors. It is also is the main tool for providing feedback to the control system, via the motion dispatcher. Main Flow
The UNC has a modularized architecture that consists of functional units, which are application software modules that perform specific tasks required by the user or process (see Figure 6) [14]. Figure 7. UNC Operating System Process.
The UNC graphical user interface is designed to be easy to use. This interface is programmed in C++ and Linux using Gtkmm libraries and GtkBuilder with Glade using Linux. The interface has two operating modes: automatic and manual. The automatic mode is capable of processing a Gcode program and interacts with the actuators through the control card (see Figure 8). The manual mode is mainly for making strategic adjustments to the automatic mode (see Figure 9).
Figure 6. UNC Reference Architecture.
The system’s operating process has the following elements (see figure 7): Interpolation System (IS). The IS consists of two main parts: the interpreter and the interpolation dispatcher. The
466
Figure 8. UNC Graphical User Interface, Automatic Mode.
INCOM 2012, May 23-25, 2012 Bucharest, Romania
Quant. 2 2 2 2 2 2 6 Figure 9. UNC Graphical User Interface, Manual Mode.
2 2 1 3 1
5. MICROFACTORY The didactic RmMTs and robotic arm are designed to be integrated in a microfactory and work together to obtain a finished product. The microfactory is based on a reticular structure, where each cell can have one RmMT, robotic arm or other manufacturing cell equipment. Each cell has the same dimensions to its principal base, 216mm x 280mm, so that it can be spatially located in a matrix and at the same time allow flexible manufacturing process configurations. The Reconfigurable Didactic Microfactory with UNC concept will be able to include as many RmMTs as required for the manufacture of the desired product, given the Microfactory’s inherent flexibility as a reconfigurable manufacturing system.
2 3 2 1 1 1
Table 3. Microfactory Elements Element Description Mechanical kit RmMT Assembly Store raw materials and Storage spaces finished products Spindle NAKANISHI AM-300 R NSK Air Line Kit ALAir pressure regulator 0201 Air control NAKANISHI E2530 Linear actuator clamp Firgelli PQ-12. 25mm Lineal actuator axes PI M-111.2DG Screwdrivers, wrenches, Assembly toolkit hoses, cables Compressor Truper 21/2 HP Work station UNC Cutting toolkit Drills, cutters, polishers Robotic arm Aluminum structure Metal gear motor with Metal gear motors gear relation 250:1 High Tec nano Servomotors servomotors Kit encoder Speed control Protoboard System power stage User manual Assembly instructions Acquisition card PIO-D48U
Figure 11 show the example Microfactory configuration with the elements described. The Reconfigurable Microfactory may be used to produce workpieces for different applications, for example, to machining a family of dental implants, micro-injection molding, biomedical devices, small jewelry pieces, and others.
A proposed toolkit for assembling an example microfactory configuration contains two RmMTs, one robotic arm and two warehouses, one for raw materials and the other for finished products (see Figure 10). Table 3 provides a detailed list of microfactory components.
Milling Machine/Drill Vertical Configuration
Warehouse one Robotic Arm
Warehouse two
Lathe Configuration
Figure 11. Reconfigurable Didactic Microfactory with UNC.
Figures 12 and 13 show the machining of dental implant prototype by turning configuration machine feed with robot arm. This implant will be inserted into the jaw bone and are safe and effective for denture support, crowns and fixed bridges and it is currently in high demand. The precision reached was of thousandth of inch as commercial micromachines. With this case study was demonstrated the ability of the Microfactory to generate products that require a minimal margin of error, in addition to its ability to make inroads into the field of medical engineering. Figure 10. Systems in the Reconfigurable Microfactory with a UNC.
467
INCOM 2012, May 23-25, 2012 Bucharest, Romania
[3]
Jang, S., Jung, Y., Hwang, H., and Y. J. Park Choi. (2008). Development of a Reconfigurable Micro Machine Tool for Microfactory, Smart Manufacturing Application, ICSMA, pp. 190-195. Korea.
[4]
Katz. R. (2007). Design Principles of Reconfigurable Machines. International Journal of Advanced Manufacturing Technology, Vol. 34, No. 5-6, pp. 430439. USA.
[5]
Koren, Y., Ulsoy A.G., 1997, “Reconfigurable Manufacturing Systems,” Technical report, ERC/RMSTR-001-1997, University of Michigan, Ann Arbor.
[6]
Koren, Y., Jovane, F., Moriwaki, T., Pitschow, G., Ulsoy, G., and Van Brussel, H. (1999). Reconfigurable Manufacturing Systems. CIRP, Vol. 48, No. 2, pp. 527540. France.
[7]
Koren, Y., Ulsoy, A.G., 2002, US patent No. 6,349,237. Reconfigurable Manufacturing System Having a Production Capacity, Method for Designing Same, and Method for Changing its Production Capacity.
[8]
Kornel, F. (2000). Micromanufacturing: International Research and Development. Ed. Kluwer Academic Pub. Group. The Netherlands.
[9]
Kurita, T., Watanabe, S., and Hattori, M. (2001). Development of Hybrid Micro Machine Tool, IEEE Environmentally Conscious Design and Inverse Manufacturing. Japan.
[10]
Landers, R. G., Min, B. K., and Koren, Y. (2001). Reconfigurable Machine Tool. CIRP, Vol. 50, No. 1, pp. 269-274. USA.
[11]
Marín, E., Ruiz, L., Caballero, A., and Kussul, E. (2004). La Configuración Modular como una Aportación al Desarrollo de Micromáquinas Herramientas de Bajo Costo, Ingeniería Mecánica, Tecnología y Desarrollo, SMIM, Vol. 1, No. 5, pp. 182-187. Mexico.
[12]
Moon, Y., and Kota, S. (2002). Design of Reconfigurable Machine Tool, ASME Journal of Manufacturing Systems, Vol. 124, pp. 480-483. USA.
[13]
Pereda, J., Romero, D., Hincapié, M., Ramírez, M., Molina, A., 2010, “Developing a universal numerical control machine based on an enterprise multilevel framework and its IPPMD reference map and methodology. Annual Reviews in Control, Vol. 34, Issue 1, April 2010, pp. 145=154, Springer, ISSN: 1367-5788. USA.
[14]
Ramírez, M. de J., and Molina, A. (2007). Tecnología de CNC a Bajo Costo para la Automatización de la Pequeña y Mediana Empresa de Países en Vías de Desarrollo. 8° Congreso Iberoamericano de Ingeniería Mecánica. Peru.
Figure 12. Microturning machine machining dental implant.
Figure 13. Dental implant manufacturing by the microfactory.
6. CONCLUSIONS In this study, we designed an RmMT with a maximum of three axes of movement that allows for three different machine tool configurations, as well as a robotic arm and a reconfigurable controller. These pieces form a reconfigurable didactic microfactory that is easy to assembly, low-cost and ensures sufficiently high-grade machining for the production of small pieces. The reconfigurable Computer Numerical Control let reach the functionality of three machining process with a minimum of effort and using the same software and hardware. The controller has integrated the main functionality of commercial CNC machine tools. The coordination of capacity, functionality and cost define the differences between traditional systems and reconfigurable systems therefore make this available system for didactic use in educational institutions where the budget is slightly. More micro machine tools can be added to the microfactory according to the needs of the academic laboratory and syllabus.
REFERENCES [1]
Aoyama, H., Fuchiwaki, O., Misaki, D., and Usuda, T. (2006). Desktop Micro Machining System by Multiple Micro Robots, IEEE. Japan.
[2]
Barrientos, A., Peñín, L. F., Balaguer, C., and Aracil, R. (1998). Fundamentos de Robótica, Mc Graw Hill. Mexico.
468
Reconfigurable Didactic Microfactory with Universal Numerical Control Miguel Ramírez-Cadena* Jhonattan Miranda* Guillermo Tello-Albarrán* Oscar Dávila-Ramírez* Arturo Molina* *Tecnológico de Monterrey, Mexico City Campus. Mexico. (Tel: +52 (55) 54832020 Ext. 2782; e-mail: [email protected], [email protected], [email protected], [email protected], [email protected]).
Abstract: This paper presents the design and implementation of a Reconfigurable Microfactory for educational purposes, consisting of two Reconfigurable Micro Machine Tools with Universal Numerical Control, one Robotic Arm, and two Warehouses for raw materials and finished product, which altogether form an assembly kit of mechanical, electrical and electronic parts. This project is being developed by Tecnológico de Monterrey, Mexico City Campus, and aims to strengthen the professional development of students in the areas of mechatronics and manufacturing. Miniaturization, reconfigurability and use of low cost items are innovative aspects that facilitate the acquisition of this Microfactory in educational institutions, as it has a significant educational and cost savings benefits compared with conventional machine tools and commercial computer numerical control machines. Keywords: Microfactory, Universal Numerical Control, Reconfigurable Micro Machine Tool, Manufacturing Systems, Low Cost Control, Didactic.
1. INTRODUCTION At present, many educational institutions in developing countries do not have sufficient resources to acquire advanced automated manufacture systems. The general aim of this project is to generate new, low-cost learning tools, so as to facilitate teaching and learning in secondary and tertiary educational institutions. These institutions are fundamental to fostering technical skills and experience in students, which allow them to achieve greater productivity be more competitive in the labor market. In recent years, institutions in different countries have engaged in research on micro machine tools with reconfigurable elements, leading to the emergence of terms such as “desktop machine tools” and “hybrid machine tools.” Results have included reducing the sizes of machine tools, work spaces and required material resources, energy savings, and even environmentally friendly developments [1][3][9]. The concept of micro manufacturing emerged thanks to these investigations and to their viability for manufacturing systems. Since 1990, studies about and research on microfactories have increased, especially in Asian countries like Japan, Korea and China; note that Europe and the United States had already developed micro manufacturing systems, primarily geared towards the development of small tools and micro manufacturing parts for medical devices [4][6][10][12]. In 2000, Mexican team realized mechanical studies on micro machine tools [11].
978-3-902661-98-2/12/$20.00 © 2012 IFAC
The drivers used in these machines are also becoming more flexible, to cope with the variety of manufacturing processes that are being used in micro manufacturing [8]. The control proposed in this paper is an example of this. This control facilitates low-cost machine tool automation with CNC automation applications based on Universal Numerical Control (UNC) architecture (patent pending). The microfactory is based in a mechatronic system applied to manufacturing system with a academic purpose; the system include all the elements of the a mechatronic system: actuators, sensors, mechanism, interfaces, and control systems. 2. ACADEMIC PURPOSE The Reconfigurable Didactic Microfactory with UNC offers the educational sector the possibility of acquiring an innovative reconfigurable and portable system at low cost. The Microfactory offers the same possibilities as conventional systems and CNC machining while remaining financially accessible to institutions that cannot afford these more costly systems. This system allows students to learn the basics of:
463
a) Automated manufacturing systems b) Mechatronics c) Machine tool operation
10.3182/20120523-3-RO-2023.00243
INCOM 2012, May 23-25, 2012 Bucharest, Romania
4. RECONFIGURABLE MICRO MACHINE TOOLS
d) Robot handling e) Numerical control programming f) Mechanical assembly. 3. RECONFIGURABLE SYSTEMS The main concepts that are taken within the mechatronic design process are: the reconfigurability of the system (hardware-software) and system size (portable). The term “reconfigurable” can be defined generically as the ability of a system for introducing, remove or relocate its components, which allows to increase its functionality effectively in terms of time and cost. The system size is also an important consideration and thanks to its small size allows for easier configuration of the physical parts of the system and helps to reduce cost and be portable, is easily moved from place to other. 3.1. Reconfigurable Manufacturing Systems Ideal Reconfigurable Manufacturing Systems possess six core characteristics: 1. Modularity, in a reconfigurable manufacturing system, all major components are modular (e.g., structural elements, axes, controls, software, and tooling). When necessary, the modular components can be replaced or upgraded to better suit new applications 2. Integrability, while there are hundreds of machine tool builders in the world, only about a dozen of them are capable of supplying fully integrated flexible machining systems for high-volume production. 3. Customized flexibility, to design system/machine flexibility just around a product family, obtaining thereby customized-flexibility, as opposed to the general flexibility of FMS/CNC.
The Reconfigurable Micro Machine Tool (RmMT) assembly toolkit has mechanical, electrical, electronic and control pieces. The RmMTs are designed so as to fulfill three different piece mechanization functions; all that is needed is to reconfigure the position and change the RmMT cutting tool. The possible configurations are: Lathe, Milling Machine and Drill. The elements of the RmMT are made of aluminum 1060 and were designed so as to adjustable, easy to assemble and sufficiently thick to avoid mechanical deformations. The volume measurements for a vertical configuration in the Milling Machine or Drill are 216mm x 280mm x 220mm, and for a horizontal configuration 216mm x 280mm x 110mm. The measurements for the Lathe are 216mm x 280mm x 110mm. Below we list the elements needed to assemble an RmMT Kit (See Figure 1 for visualizations): 1 Principal base 2. Support for a vertical reconfiguration 3. Reconfigurable base 4. Tower support jaw/spindle 5. Angle (support of axis Y) 6. Base for support of axes 7. Spindle screw clamp support base 8. Spindle screw clamp 9. Cutting tool support 10. Clamp jaw 11. Linear actuator 12. Portable actuator 13. Clamp cylinder 14. Cutting tool (milling machine or drill) 15. X-axis motion actuator 16. Y-axis motion actuator 17. Z-axis motion actuator 18. Burin 19. Spindle 20. Support burin
4. Scalability, Scalability of the system capacity is the counterpart characteristic of convertibility. Scalability may require adding spindles to a machine to increase its productivity, or even adding machines to expand the overall system capacity as a given market grows. 5. Convertibility, System convertibility may have several levels 6. Diagnosability, Has two aspects: detecting machine failure and identifying the causes for unacceptable part quality. These characteristics, which were introduced by professor Yoram Koren in 1995 [5][7], apply to the design of whole manufacturing systems, as well as to some of its components: reconfigurable machines, their controllers, and also to the system control software. Figure 1. Elements make up the assembly of RmMT.
464
INCOM 2012, May 23-25, 2012 Bucharest, Romania
Table 1 describes the RmMT’s technical specifications. Table 1. RmMT Technical Specification Parameter Value Motor type Motor DC xyz travel range 15 x 15 x 15 mm xyz resolution 0.0085 m xyz feed speed 188.5m/min Spindle max speed 30,000rpm
4.1. Lathe Configuration The lathe configuration is the simplest in the system, as it uses few components for assembly and always runs horizontally. This configuration allows for two axes of motion. It contains a tool holder fixed to the axes of motion, the cutting tool, the spindle and a fixed tower, which functions as a carrier spindle (see Figure 2). In this configuration, the RmMT can mechanize workpieces using rotation, while the actuators move the cutting tool in a controlled manner against the surface of the workpiece, cutting the workpiece according to numerical control specifications.
Figure 3. Physical RmMT System, vertical configuration for Drill/Milling Machine.
The specific function of the Drill is the drilling. In the RmMT, the Drill rotates while the workpiece remains fixed to the clamp jaw. One can also use different cutting tools to perform other operations such as countersinking and reaming. The specific function of the Milling Machine is to smooth surfaces. The Milling Machine rotates and moves on the X, Y and Z axes while the workpiece remains fixed to the clamp jaw. The cutting tool used is the milling cutter, which is usually round with different blades available depending on the shape to be given to the workpiece.
Figure 2. Physical RmMT System, Lathe Configuration.
4.2. Drill and Milling Machine Configuration The Drill and the Milling Machine share the same configuration, with the only difference being in the cutting tool used. This configuration has three axes of motion. Both horizontal and vertical configurations are available for the Drill and Milling Machine, in order to allow flexibility in the number of manufacturing processes that can be followed (see Figures 3 and 4). In these configurations, the linear actuators move the cutting tool on three axes, and the automatic clamp, which has a linear actuator, holds the workpiece in place in a controlled manner. This automatic fastening is designed so that a robotic arm positions the workpiece. The robotic arm, which we discuss later, can automate a microfactory where more than one RmMT interact.
Figure 4. Physical RmMT System, horizontal configuration for Drill/Milling Machine.
5. ROBOTIC ARM In order to achieve total automatization of a Microfactory, a robotic arm was designed to transport and handle raw materials. The robotic arm is able to interact with each RmMT as another part of a Microfactory. The design of the robotic arm consists of a cylindrical configuration with 4 degrees of freedom (see Figure 7 and Table 2) [2]. The robot has a rotational axis at the base that permits two prismatic movements, which guide up/down and approach/distance, respectively. The gripper has rotational motion in the wrist (see Figure 5).
465
INCOM 2012, May 23-25, 2012 Bucharest, Romania
interpolation dispatcher receives information from the interpreter and gives commands to the interpolator. Trajectory Generator (TG). The TG consists of the interpolator, which as mentioned above receives instructions from the interpolation dispatcher. The main function of the TG is to calculate the path that the system must follow in order to accomplish the desired trajectory. This path is then processed and communicated to the next part of the operating process, the motion system.
Figure 5. Physical Robotic Arm, and definition of Joints.
Table 2. Robotic Arm Dimensions
Joints l0 1 d2 d3 4
37.5mm 180° 90 mm 150mm 180°
4. UNIVERSAL NUMERICAL CONTROL The automatic control in the system is based on an open resource platform with a PIO-D48U card for a PCI bus. This controls the system and also serves as an interface for the implementation of UNC applied to RmMTs. The UNC is a modular control system that can be adapted or retrofit to any machine and has moveable components [13]. The UNC is a communication module substitute that permits using diverse signal hardware and modifying or selecting the type of interpolation or graphical interface required.
Motion System (MS). This part of the operating process contains many sub-processes. The first is the motion dispatcher, which manages the control of the system, ensuring dispatch to the correct unit, as communicated by the interpolator. The motion dispatcher also uses feedback to recalculate the system’s path. The motion dispatcher gives instructions to the logic control, which in turn provides commands to the HAL. Motion control management is the motion dispatcher’s most important task, because the motion dispatcher sends instructions to the system’s different parts as to the correct path to follow. The axis units send correct information to HAL. Hardware Abstraction Layer (HAL). HAL is the functional unit that controls the motors. It is also is the main tool for providing feedback to the control system, via the motion dispatcher. Main Flow
The UNC has a modularized architecture that consists of functional units, which are application software modules that perform specific tasks required by the user or process (see Figure 6) [14]. Figure 7. UNC Operating System Process.
The UNC graphical user interface is designed to be easy to use. This interface is programmed in C++ and Linux using Gtkmm libraries and GtkBuilder with Glade using Linux. The interface has two operating modes: automatic and manual. The automatic mode is capable of processing a Gcode program and interacts with the actuators through the control card (see Figure 8). The manual mode is mainly for making strategic adjustments to the automatic mode (see Figure 9).
Figure 6. UNC Reference Architecture.
The system’s operating process has the following elements (see figure 7): Interpolation System (IS). The IS consists of two main parts: the interpreter and the interpolation dispatcher. The
466
Figure 8. UNC Graphical User Interface, Automatic Mode.
INCOM 2012, May 23-25, 2012 Bucharest, Romania
Quant. 2 2 2 2 2 2 6 Figure 9. UNC Graphical User Interface, Manual Mode.
2 2 1 3 1
5. MICROFACTORY The didactic RmMTs and robotic arm are designed to be integrated in a microfactory and work together to obtain a finished product. The microfactory is based on a reticular structure, where each cell can have one RmMT, robotic arm or other manufacturing cell equipment. Each cell has the same dimensions to its principal base, 216mm x 280mm, so that it can be spatially located in a matrix and at the same time allow flexible manufacturing process configurations. The Reconfigurable Didactic Microfactory with UNC concept will be able to include as many RmMTs as required for the manufacture of the desired product, given the Microfactory’s inherent flexibility as a reconfigurable manufacturing system.
2 3 2 1 1 1
Table 3. Microfactory Elements Element Description Mechanical kit RmMT Assembly Store raw materials and Storage spaces finished products Spindle NAKANISHI AM-300 R NSK Air Line Kit ALAir pressure regulator 0201 Air control NAKANISHI E2530 Linear actuator clamp Firgelli PQ-12. 25mm Lineal actuator axes PI M-111.2DG Screwdrivers, wrenches, Assembly toolkit hoses, cables Compressor Truper 21/2 HP Work station UNC Cutting toolkit Drills, cutters, polishers Robotic arm Aluminum structure Metal gear motor with Metal gear motors gear relation 250:1 High Tec nano Servomotors servomotors Kit encoder Speed control Protoboard System power stage User manual Assembly instructions Acquisition card PIO-D48U
Figure 11 show the example Microfactory configuration with the elements described. The Reconfigurable Microfactory may be used to produce workpieces for different applications, for example, to machining a family of dental implants, micro-injection molding, biomedical devices, small jewelry pieces, and others.
A proposed toolkit for assembling an example microfactory configuration contains two RmMTs, one robotic arm and two warehouses, one for raw materials and the other for finished products (see Figure 10). Table 3 provides a detailed list of microfactory components.
Milling Machine/Drill Vertical Configuration
Warehouse one Robotic Arm
Warehouse two
Lathe Configuration
Figure 11. Reconfigurable Didactic Microfactory with UNC.
Figures 12 and 13 show the machining of dental implant prototype by turning configuration machine feed with robot arm. This implant will be inserted into the jaw bone and are safe and effective for denture support, crowns and fixed bridges and it is currently in high demand. The precision reached was of thousandth of inch as commercial micromachines. With this case study was demonstrated the ability of the Microfactory to generate products that require a minimal margin of error, in addition to its ability to make inroads into the field of medical engineering. Figure 10. Systems in the Reconfigurable Microfactory with a UNC.
467
INCOM 2012, May 23-25, 2012 Bucharest, Romania
[3]
Jang, S., Jung, Y., Hwang, H., and Y. J. Park Choi. (2008). Development of a Reconfigurable Micro Machine Tool for Microfactory, Smart Manufacturing Application, ICSMA, pp. 190-195. Korea.
[4]
Katz. R. (2007). Design Principles of Reconfigurable Machines. International Journal of Advanced Manufacturing Technology, Vol. 34, No. 5-6, pp. 430439. USA.
[5]
Koren, Y., Ulsoy A.G., 1997, “Reconfigurable Manufacturing Systems,” Technical report, ERC/RMSTR-001-1997, University of Michigan, Ann Arbor.
[6]
Koren, Y., Jovane, F., Moriwaki, T., Pitschow, G., Ulsoy, G., and Van Brussel, H. (1999). Reconfigurable Manufacturing Systems. CIRP, Vol. 48, No. 2, pp. 527540. France.
[7]
Koren, Y., Ulsoy, A.G., 2002, US patent No. 6,349,237. Reconfigurable Manufacturing System Having a Production Capacity, Method for Designing Same, and Method for Changing its Production Capacity.
[8]
Kornel, F. (2000). Micromanufacturing: International Research and Development. Ed. Kluwer Academic Pub. Group. The Netherlands.
[9]
Kurita, T., Watanabe, S., and Hattori, M. (2001). Development of Hybrid Micro Machine Tool, IEEE Environmentally Conscious Design and Inverse Manufacturing. Japan.
[10]
Landers, R. G., Min, B. K., and Koren, Y. (2001). Reconfigurable Machine Tool. CIRP, Vol. 50, No. 1, pp. 269-274. USA.
[11]
Marín, E., Ruiz, L., Caballero, A., and Kussul, E. (2004). La Configuración Modular como una Aportación al Desarrollo de Micromáquinas Herramientas de Bajo Costo, Ingeniería Mecánica, Tecnología y Desarrollo, SMIM, Vol. 1, No. 5, pp. 182-187. Mexico.
[12]
Moon, Y., and Kota, S. (2002). Design of Reconfigurable Machine Tool, ASME Journal of Manufacturing Systems, Vol. 124, pp. 480-483. USA.
[13]
Pereda, J., Romero, D., Hincapié, M., Ramírez, M., Molina, A., 2010, “Developing a universal numerical control machine based on an enterprise multilevel framework and its IPPMD reference map and methodology. Annual Reviews in Control, Vol. 34, Issue 1, April 2010, pp. 145=154, Springer, ISSN: 1367-5788. USA.
[14]
Ramírez, M. de J., and Molina, A. (2007). Tecnología de CNC a Bajo Costo para la Automatización de la Pequeña y Mediana Empresa de Países en Vías de Desarrollo. 8° Congreso Iberoamericano de Ingeniería Mecánica. Peru.
Figure 12. Microturning machine machining dental implant.
Figure 13. Dental implant manufacturing by the microfactory.
6. CONCLUSIONS In this study, we designed an RmMT with a maximum of three axes of movement that allows for three different machine tool configurations, as well as a robotic arm and a reconfigurable controller. These pieces form a reconfigurable didactic microfactory that is easy to assembly, low-cost and ensures sufficiently high-grade machining for the production of small pieces. The reconfigurable Computer Numerical Control let reach the functionality of three machining process with a minimum of effort and using the same software and hardware. The controller has integrated the main functionality of commercial CNC machine tools. The coordination of capacity, functionality and cost define the differences between traditional systems and reconfigurable systems therefore make this available system for didactic use in educational institutions where the budget is slightly. More micro machine tools can be added to the microfactory according to the needs of the academic laboratory and syllabus.
REFERENCES [1]
Aoyama, H., Fuchiwaki, O., Misaki, D., and Usuda, T. (2006). Desktop Micro Machining System by Multiple Micro Robots, IEEE. Japan.
[2]
Barrientos, A., Peñín, L. F., Balaguer, C., and Aracil, R. (1998). Fundamentos de Robótica, Mc Graw Hill. Mexico.
468