summary
In industrial production processes, the greatest advantages of robotics technology compared to traditional measurement and packaging methods are speed, accuracy, reliability, and intelligence. This article introduces an electrical and mechanical design scheme for intelligent packaging of industrial relays.
Keywords: industrial robot; industrial relay; intelligent packaging
Foreword
The investigation revealed that manually packaging a box of relays typically takes between 15 and 22 seconds. Changing product types or models during the packaging process results in significant downtime, with the process being particularly cumbersome and time-consuming. Furthermore, some factories use automated packaging machines, but these non-standard, customized machines are quite expensive to purchase, and each machine can only package specific varieties and models, failing to meet the need for multi-functionality.
Further measurements and statistics revealed that while the relays were roughly the same size, relays with different voltages and contact pairs were difficult to distinguish. Furthermore, the manufacturers of the packaging boxes and internal PVC frames used punched markings or mold markings to indicate model numbers for easier identification and management, requiring each relay to be placed in a specific packaging box. Therefore, an industrial robot system was used to accomplish this task, providing manufacturers with high packaging efficiency and reducing labor costs associated with packaging.
To achieve automated packaging of relays using industrial robots, it is necessary to solve technologies such as robot gripping mechanisms, automatic packaging box assembly and disassembly mechanisms, intelligent raw material management and warehousing, automatic identification by industrial vision sensors, system equipment networking, and automatic control.
Intelligent control system composition
The intelligent industrial relay packaging system is a set of intelligent equipment based on industrial robots (Figure 1). The system consists of an industrial robot, PLC, touchscreen, industrial camera, servo driver, and motors. It can grasp, place, and identify relays, as well as move, open, and close relay packaging boxes. During this process, various operation screens are displayed through the HMI's visual interface, and the servo motors of the additional axes are controlled via the robot's SSCNETⅢ network to achieve rapid relay feeding.
Figure 1. Composition of the Mitsubishi FR-2F industrial robot chess teaching instrument
(1) Mitsubishi FR-2F industrial robot
The Mitsubishi FR-2F industrial robot is a multi-purpose vertical robot designed and manufactured by Mitsubishi Electric Corporation of Japan. This robotic arm consists of the FR-2F-1D robot body and the CR751-D controller, and can handle items up to 2 kg. The FR-2F-1D is a humanoid vertical robotic arm capable of 6 degrees of freedom movement at any position in space. The base for the J1 axis is used for fixation, and the flange face for the J6 axis is used to mount the pneumatic gripper. The CR751-D robot controller is used in conjunction with the robotic arm and integrates multiple serial interfaces.
Figure 2. Mitsubishi FR-2F-1D industrial robot body
(2) Teach pendant
The R33TB is a simplified teach pendant for Mitsubishi industrial robots. It is primarily used for creating, modifying, and managing robot programs, teaching motion positions, and performing JOG feeds. In the case of multiple robots, it allows for plugging and unplugging multiple robots even when power is off. To use it, simply insert the teach pendant's cable into the TB interface on the controller.
Figure 2 Mitsubishi R33TB teach pendant
The R57TB is a high-performance robot teach pendant. It is used for program creation, modification, management, teaching motion positions, JOG feed, and more. This high-performance teach pendant is equipped with a graphical user interface (GUI) using a touchscreen for easy operation.
Figure 3 Mitsubishi R57TB teach pendant
(3) COGNEX1100 industrial vision sensor
Cognex products include barcode readers, machine vision sensors, and machine vision systems widely used in factories, warehouses, and distribution centers worldwide. Compared to traditional cameras, industrial cameras enable program editing and graphic comparison, can operate for extended periods, and are waterproof and dustproof.
Figure 4. COGNEX 1100 Industrial Vision Sensor
Cognex vision products feature open communication protocols and control I/O, allowing for remote configuration via a network using an intuitive user interface. During operation, sensor operation can be remotely monitored through this interface. These sensors can also be remotely controlled to change settings and retrieve results. This design uses the In-Sight Micro1100 monochrome camera.
(4) Mitsubishi FX3U-80MR PLC
In this overall design, the PLC serves as the intermediate data transmission and logic processing unit; therefore, the Mitsubishi FX3U series is used. Since the PLC output signals include switching signals (such as robot start and emergency stop signals) and level signals (such as image capture signals from vision sensors), relay outputs are employed. For future upgrades and functional expansion, an 80-point FX3U-80MR/ES-A type PLC is selected.
(5) FX3U-ENET-L Ethernet communication module
Since the entire system uses the TCP/IP communication protocol, an FX3U-ENET-L Ethernet module needs to be added to the PLC for communication. This module has an RJ45 communication interface, which is connected to the PLC's module expansion port. Through program editing, Ethernet data exchange can be achieved.
(6) GT1275 touchscreen
The Mitsubishi GT1275-VNBA is a high-performance touchscreen in Mitsubishi's GOT1000 series of visualization devices. It features a 256-color TFT display with a resolution of 640×480 and supports single-point touch. It has 3MB of built-in memory, sufficient for most users, and also includes one USB port, one Ethernet port, one RS-232 port, one RS-422/RS-485 port, and supports CF cards.
(7) MR-J4 servo system
The Mitsubishi CR751-D robot controller supports Mitsubishi MR-J3-B and MR-J4-B servo drive systems due to its additional axes. This design uses an MR-J4-20B servo driver and an HG-KR23J servo motor. This servo drive system has a power of 200W, a maximum speed of 3000r/min, and can drag a maximum weight of 0.98Kg.
(8) Banner safety light curtain
The Banner Engineering EZ-SCREEN secondary light curtain has a fast response speed and high sensitivity, so the safety light curtain in this design uses the LS2TR30-600QB model.
Figure 5 BANNER safety light curtain
Device hardware connection
(1) Wiring of Mitsubishi FR-2F robot
The Mitsubishi FR-2F industrial robot consists of two parts: the FR-2F-D robot body and the CR751-D controller, plus an R33TB or R57TB teach pendant. The entire system only requires power to the robot controller; simply plug a 220V AC power source into pins 1 and 3 of the controller's ACIN interface.
The connection between the robot body and the controller simply requires connecting CN1 and CN2. CN1 has three interfaces on the controller: AMP1, AMP2, and BRK. AMP1 and AMP2 are for the robot motor power supply, and BRK is for the motor braking unit. On the robot, the CN1 interface is a circular aviation connector. The CN2 interface is for the servo motor signal lines; only the two ends need to be connected. When connecting the robot's teach pendant R33TB or R57TB (choose one), simply connect the teach pendant's plug cable to the TB interface on the controller.
The SSCNETⅢ network for the robot's additional axes requires servo motor drivers and servo motors. The pulse signals of the SSCNETⅢ network are transmitted from the controller's ExtOPT port to the servo motor controller via optical fiber, while the servo motor's start, stop, and emergency stop signals are output through the SNUSR interface.
The robot also requires an I/O signal input interface, which is connected to the SNRSR1 interface. The SNRSR1 interface needs to provide the robot controller with a manual/automatic switching signal, as well as the robot's emergency stop signal. See Figure 6 for the specific wiring details.
Figure 6 SNUSR1 interface wiring
The robot also requires TCP/IP communication. Therefore, an RJ45 standard 8-core network cable is inserted into the LAN interface of the robot controller and connected to the switch. A USB communication cable is connected to the USB port of the robot controller, allowing parameter settings and program editing via RTToolBox2. Figure 7 shows the wiring diagram of the CR751-D robot controller.
Figure 7 Wiring diagram of the robot CR751-D controller
(2) Mitsubishi MR-J4-20B servo wiring
The Mitsubishi MR-J4 servo system is used on an additional axis of the robot; this design uses one additional axis. On the servo driver, 220V AC mains power is supplied to the L1 and L3 power supply ports of CNP1, and the control unit power supply terminals L11 and L21 are connected in parallel. The output terminals U/V/W of CNP3 are connected to the HG-KR23J servo motor, and the encoder cable of the servo motor is connected to the CN2 interface. The servo position signal is connected to the CN1A interface via an SSCNETⅢ network fiber optic cable.
As shown in Figure 8, the servo motor's control line is connected to the CN3 interface. Terminal 10 is connected to DC 24V, and terminals 2, 4, 12, and 19 are connected in parallel to 0V. With this connection, the servo motor is always in the running state. Since the servo motor uses an absolute position encoder, a lithium-ion battery is connected to the CN4 port to store the position information.
Figure 8 Servo Motor Wiring Diagram
(4) Wiring of Mitsubishi FX3U-80MR PLC
The Mitsubishi FX3U-80MR PLC plays a crucial role in the entire system, handling intermediate data processing and providing robot start and emergency stop signals, as well as pulse input to the vision camera. Therefore, the clamping signals from the pneumatic gripper, and the limit and zero-point signals from the servo motors, are sent to the PLC. Additionally, signals from external buttons and the emergency stop switch also need to be processed by the PLC.
Since the robot's start signal requires connecting signals 25 and 50, and 24 and 49 of the SNUSR1 interface, the start signal is given via COM1 and Y0, and COM2 and Y4 on the PLC. Emergency stop signals 2 and 27 are given via COM3 and Y10 (normally high level). Additionally, the vision sensor's image capture signal is given via Y20, and the camera light source is given via Y21. See Figure 9 for the specific wiring.
Since this entire system uses TCP/IP protocol for communication, an Ethernet module needs to be added to the PLC. This design uses the Mitsubishi FX3U-ENET-L Ethernet communication module. When using it, insert the module's expansion port into the FX3U-80MR PLC's expansion port, connect a DC 24V power supply to the module, and connect a network cable to the switch via the front RJ45 network port.
Figure 9 Wiring diagram for Mitsubishi FX3U-80MR PLC
SolidWorks Mechanical Design
The simulation design and operation were carried out using SolidWorks software. Then, the design of mechanisms for automatic disassembly and automatic capping of different packaging boxes was solved. Finally, external auxiliary equipment such as intelligent management and storage mechanisms for raw materials were designed.
(1) Cardboard box rack design
The cardboard box rack is the final storage location for industrial relays, with a total of 2*6 positions. It is rationally designed according to the appearance of the selected industrial relays, as shown in Figure 10.
Figure 10 Cardboard Box Frame Design
(2) Raw material pipeline design
The raw material tube serves as a storage area for industrial relays. It is fixed to a slide base by a servo motor, which pushes the industrial relays out of the PVC tube one by one for the robotic arm to grasp.
Figure 11 Raw material pipe design
(3) Robotic gripper head
The robotic gripper shown in Figure 12 is a comprehensive mechanism used to grasp industrial relays and open and close packaging boxes. It includes a gripper fixing plate, a cardboard box suction cup bracket, a relay suction cup bracket, a cylinder guide rod, a connector, a gripper stop, etc.
Figure 12 Robotic Arm Grabber
(4) Disassembling and assembling the workbench
After completing the cardboard box rack, raw material pipe, robotic gripper head, and other components, the most important step is to disassemble and assemble the workbench, as shown in Figure 13. This includes the disassembly and assembly base plate, cylinder fixing components, fiber optic fixing plate, ribs, large cover rotating bracket, flip fork, slide table fixing plate, clamping ears, and large cover pressure plate.
Figure 13 Assembly/Disassembly workbench
Conclusion
After testing each mechanism in Solidworks simulation software and confirming its correctness, actual machining and installation were carried out. Combined with a Mitsubishi robot and a programmable logic controller (PLC) system, the functional requirements for intelligent packaging of industrial relays were met. Through continuous adjustments to the fixtures, robot workflows, and actions, the optimal intelligent packaging was ultimately achieved.
References:
[1] Mitsubishi Electric Industrial Robot CR750/CR751 Controller Operation Manual - Detailed Explanation of Functions and Operation [M]. Mitsubishi Electric (Shanghai) Co., Ltd.
Xu Ning, male, born in 1999, from Huzhou, Zhejiang Province, holds a college diploma and is currently studying at Zhejiang Business Vocational and Technical College. His research focus is on industrial robot applications.
