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A collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools Toshiaki KIMURA1, Tatsuya IZAKI2, Hisaaki, TERADA3, Yukihisa SHITAYA4, Kunihiko SAYAMA5, and Yuichi KANDA6 1 Technical Research Institute, JSPMI, Japan, [email protected] 2 SOFIX Co., Ltd., [email protected] 3 Pulstec Industrial Co., Ltd., [email protected] 4 ADDO-Japan Corp., [email protected] 5 KK Blum LMT, [email protected] 6 Toyo University, [email protected] Abstract: Conventional collision prevention systems for machine tools such as collision-prevention functions on NC controllers are based on simulations using 3D models of work pieces that are made in advance. If the setting up of work pieces differs from the models, then collision accidents are unavoidable. Therefore, a collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools by simulation based on actual conditions from NC controllers and measurement data of work-pieces using 3D laser scanning is proposed. This paper presents a discussion of the system concept, development of a prototype system, and evaluation of the system. Keywords: Advanced machine tool, Collision prevention, Detection of setting defects, Simulations 1.

Introduction The decrease of skilled workers in Japan today is remarkable. For this reason, traditional skills are becoming a major problem for Japanese manufacturers [1]. Moreover, development of technologies for easy operations of facilities in factories is necessary. To meet these requirements, development of intelligent functions for thermal displacement compensation and collision prevention for machine tools are being attempted [2]. Especially important are collision prevention systems between tools and work pieces or jigs for machine tools. Conventional collision prevention systems such as off-line machining simulators or collision prevention functions on NC controller are available now. However, these conventional systems are based on simulation methods using 3D models of work pieces and jigs that are made in advance. If setting up of work pieces and jigs at the factory differs from the simulation models, collision accidents are unavoidable. In addition, most collision prevention functions are only for new open NC controllers. Therefore, this research project of a collision prevention system for machine tools with enhanced functionality was undertaken using a simulation based on actual condition data from the NC controller and measurement data of work pieces. The proposed system is adaptable not only new machine tools; it can also use machine tools using Open Resource interface for the Network (ORiN [3]), which is a standard technology. To date, in this research, a collision prevention system that can detect collision errors during machining processes has been developed. When the system detects collision errors, it uses measurement data of work pieces and jigs, actual

information from NC controllers, and the NC program. The research results were reported in the first report of the development of a collision prevention system for machine tools, and other related reports [4-5]. However, the current method based on these reported results does not support a collision check before executing NC programs in the automatic mode of the machine tools. Therefore, a collision prevention method is proposed as an enhanced function by simulation based on actual condition data from the NC controller and measurement data of work pieces using a 3D laser scanner after the machine tool set up. Moreover, based on the proposed method, a collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools has been developed. This paper presents discussion of the system concept, development of a prototype system based on the concept, and evaluation of the prototype system. 2.

Concept of the proposed system The proposed collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools can predict collision accidents between tools and work pieces or jigs through simulations based on actual condition data from NC controllers and measurement data of work pieces using a 3D laser scanner after the machine tool set up. The system characteristics are the following. 9

Adoption of work piece and jigs setting defects of machine tools (The 3D laser scanner measures work pieces and jigs.)

(3) Macro program for measurement of work-pieces and jigs (Auto or MDI)

(4) Transmission of measurement data

(5) Macro program for execution of the simulators. (Auto or MDI)

(6) Transmission of simulation condition (ex: G54setting data etc.)

USB ORiN /Ethernet

3D Laser scanner

(7) Execution of NC simulator on the market

Detection of collision

NC (1) Tool Measurement

Laser tool setter

Machine tool

(2) Transmission of tool measurement data

Personal Computer

Figure 1: Concept of the system

9 9 9

Adopting multivendor machine tools using standard technologies; also adopting old and new machine tools using standard technologies Adopting established existing machine tools in factories (Obviating modification of ladder programs of controllers and modification of electric wiring.) Low initial cost (Commercially available machine simulators are used for this system.)

(2)

(3)

(4) The collision prevention system configuration with enhanced functions for detecting work-piece setting defects of machine tools is described in Figure. 1. The system consists of a laser tool setter for measuring diameters and lengths of tools, a 3D laser scanner for measuring work pieces and jigs, and a personal computer, which is installed next to the NC controller. Open Resource interface for the Network (ORiN) is used for information exchange between the application software of this system and the NC controller. The machining simulator (TRYCUT2000; Broadmine Ltd.), which is commercially available, is installed in the personal computer. Using ORiN, the collision prevention system enhanced functions for detecting work-piece setting defects of machine tools can be adopted not only for new machine tools but also for older machine tools and multivendor machine tools. The system’s operation flow is shown below. (1)

Tool length and diameter should be measured using the laser tool setter. Then the measuring data should be stored in the NC controller immediately as tool offset parameters.

(5)

(6)

(7)

The application system of the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools in the personal computer acquires these tool offset data immediately using ORiN. The NC macro program for controlling the 3D laser scanner starts measurement of work pieces and jigs. Measured data from the 3D laser scanner are sent to the application system of the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools. The NC macro program for controlling the machining simulator is executed to start the simulation. The application system of the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools in the personal computer acquires some parameters such as actual values of the work-piece coordinate system, actual values of the machine coordinate system, and macro variables. The machining simulator is started. The simulation is started to check for collision errors between the actual work-piece models and tool models.

NC Controller

Detection of collision

Personal computer

(MELDAS Magic64; Mitsubishi Electric Corp.)

Open NC Provider

Parametors

(・Tool offsets, ・Actual values of work-piece coordinate system )

Application system (Control)

(・Tool offsets, ・Actual values of work-piece coordinate system, ・Work-piece measurement data, ・NC program name etc..)

3D Laser scanner

Machining simulator (TRYCUT2000; Broad Mine Ltd.)

(TDS-1500 with special modification: Pulstec Industrial Co.,Ltd.) (Tool offset)

Machine tool (PV4-IIA; JTEKT Corp.)

NC Program

Laser tool setter (Laser Control System; KK Blum LMT)

Figure 2: Configuration of the prototype system

3.

Prototype system development A prototype system of the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools was developed based on the proposed concept. The prototype system configuration is portrayed in Figure. 2. The target machine tool of the system (PV4-IIA; JTEKT Corp.) is a vertical machining center with a controller (MELDAS Magic64 NC; Mitsubishi Electric Corp.). Depicted in Figure. 3 is a device (TDS-1500; Pulstec Industrial Co., Ltd.) with special modifications used as a 3D laser scanner for this prototype system. Moreover, a laser control system (KK Blum LMT) for the laser tool setter is used for the prototype system. A machining simulator (TRYCUT2000; Broadmine Ltd.) and the application system with the ORiN are set in the personal computer, which is installed next to NC controller, as portrayed in the Figure. 4. The application system of the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools has three major functions: initial setting, 3D laser scanner calibration, and the main system. The initial setting is used for setting parameters of the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools. Then, 3D laser scanner calibration is used for adjusting between the 3D laser scanner coordinate system and the machine tool’s machine coordinate system after installing the 3D laser scanner. The main system is useful for measuring work pieces and jigs using the 3D laser scanner. Moreover, the main

Figure 3: Installation of 3D Laser scanner

Figure 4: Installation of personal computer system is useful for executing the machine simulator. The user operations for calibration of the 3D laser scanner and the main system can be done by executing the NC macro program in the NC controller. The collision prevention

system with enhanced functions for detecting work-piece setting defects of machine tools are used by operation of the NC controller. For that reason, factory workers find them easy to use. 4.

Prototype system evaluation Using the prototype system, the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools was evaluated. Target work pieces for the test operation are made of carbon steel S45C with a glossy face after rough cutting. The target NC program for this test operation has an NC program block of G92 to set the work-piece coordinate system. Normally, this NC program is executed at the Z-axis machine position 0.0. However, a collision accident will occur if this NC program is executed at less than -10.0 for the Z-axis machine position. Therefore, in this test operation, the Z-axis machine position is set to -10.0 as setting defects. The target work piece and jigs on the machine tool were measured using the 3D laser scanner, as portrayed in Figure. 5. Moreover, the machining simulator was executed automatically by starting the NC macro program. Simulation results demonstrated that this the collision

prevention system with enhanced functions for detecting work-piece setting defects of machine tools was able to predict collision accidents in advance, as depicted in the Figure. 6. The evaluation results demonstrate that the proposed system performed well for preventing collision accidents by setting defects of work pieces and jigs. 5.

Conclusion The proposed collision prevention method uses simulation based on data of actual conditions from the NC controller and work-piece measurement data obtained using a 3D laser scanner after setting up the machine tool. Based on the concept, the collision prevention system with enhanced functions for detecting work-piece setting defects of machine tools was developed Results of test operations show that the proposed system prevented collision accidents by setting defects of work pieces and jigs. Realization of the proposed method was confirmed through test operation results. A joint research group for realizing the system was established in April 2008. Based on these results, the group is discussing commercialization of a collision prevention system as a product. Acknowledgement This research is a part of “A Research Project of Manufacturing Support Systems Using Standard Technologies,” a research project of JSPMI by funding from Keirin Association of Japan.

Figure 5: Measuring the work piece and jigs

Figure 6: Execution of the simulator

References [1] Website: http://www.meti.go.jp/report/downloadfiles/g90519a 01j.pdf [2] Website: http://www.jmf.or.jp/japanese/houkokusho/kensaku/p df/2007/18kodoka_07.pdf [3] Website: http://www.orin.jp/ [4] Kimura T., Okabe N. and Kanda Y., 2007., Development of a collision prevention system for machine tools based on standard technologies (1st report) Concept of the collision prevention system for the machine tools, Proc. 2007 Autumn Annual Meeting of the Japan Society for Precision Engineering, pp.399-400 (in Japanese). [5] Kimura T., Okabe N. and Kanda Y., 2008., Development of a collision prevention system for machine tools (1st report) Prototype system of the collision prevention system for usual type NC controllers, Proc. 2008 Annual Meeting of Manufacturing System Division of Japan Society of Mechanical Engineers, pp.83-84 (in Japanese).

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