Market Application Background
In recent years, the market demand for screw fastening has continued to grow, especially in assembly lines in fields such as 3C consumer electronics, automobile assembly, and home appliances. The diversification and refinement of product designs have driven manufacturing enterprises to place higher demands on the precision, efficiency, and production line flexibility of screw fastening, promoting the widespread application of SCARA robotic screw fastening technology. This has significantly improved screw tightening efficiency and precision, reduced reliance on manual labor, and effectively enabled batch assembly and flexible material and line changeover production.
Limitations of common screw fastening solutions on the market:
Common screw fastening solutions on the market, including handheld electric screwdrivers and multi-axis modular benchtop screw fastening equipment, are widely used in various fastening scenarios. However, they have certain limitations in meeting the requirements of high or specific torque accuracy, tightening multiple types of screws at the same station, and rapid product changeover and mixed material production. All of these limitations can directly affect the efficiency and quality control of the fastening process.
Positive motion technology solutions:
In response to the above market demands, Zheng Motion has developed a three-axis SCARA robotic screw fastening application solution based on the VPLC7 machine vision motion control integrated machine. It is easy to integrate into the customer's existing assembly line, provides an independent operating station, and can automatically switch process formulas or adjust workstations according to production needs. It also supports intermittent or continuous mass production and is suitable for screw fastening on flat surfaces, countersunk holes, and sides. When used with a vision acquisition system, it can achieve high-speed and high-precision screw fastening applications.
The solution supports robotic arms in performing single or multiple screwdriver bit fastening tasks. Bits can be flexibly changed to adapt to different types of screws, and different fastening processes can be set (such as torque, speed, fastening height, screw removal, etc.). It provides real-time monitoring data throughout the fastening process, including screw torque, number of turns, fastening status, fastening result, float height, fastening height, and fastening time, generating a fastening result for each screw fastened.
The integrated machine vision motion control system shortens cycle time by directly controlling the robot, enables centralized system management, and improves the lock-on yield to 99.6%.
01. Application of VPLC7 Machine Vision Motion Control Integrated Machine in Screw Fastening of Three-Axis SCARA Robot Arm
Traditional robotic screw fastening solutions
Traditional robotic screw fastening solutions typically employ a combination of a robot drive and control unit, a PLC, and a vision system, which has the following problems:
• Numerous components, complex wiring, troubleshooting difficulties, and long development cycles;
The data interaction between vision and motion control is inefficient;
• Low degree of hardware and software integration, and low level of functional integration;
• The initial and maintenance costs of multiple hardware sets are high.
SCARA screw fastening solution design for positive motion technology
• 20DI: Connects to the stop position of the multiplier conveyor workstation, the incoming material sensor signal, and the alarm signals from the electric screwdriver and feeder;
• 20DO: Connects to a screw feeder; the high-speed output port connects to the hard trigger input of an industrial camera.
• EtherCAT interface: Connects to the EtherCAT bus driver to control the SCARA robot arm;
• 4-channel single-ended pulse output: Connect to a stepper/pulse driver to control other additional axes;
• RS232 communication interface: for connecting electric screwdrivers, micrometers, and light source controllers;
• Ethernet interface: Gigabit Ethernet port, for connecting area scan cameras that support the Gige protocol to achieve visual positioning and correction applications.
Motion control and machine vision implementation process
(1) Machine vision
During the screw fastening process of the three-axis SCARA robot, the machine vision system first obtains the position of the incoming product. Then, by calibrating the center of the bit and camera, it obtains the calibration coefficient and performs dual Mark point positioning correction. When the position and angle of the product change, it can automatically calculate the offset required for the screw fastening point of the workpiece to ensure that the robot can accurately move to the screw fastening point, thereby achieving precise positioning of the screw fastening operation.
(2) Motion control
Following a pre-planned SCARA robotic arm path, the robotic arm performs arched and point-to-point motion control. The control system precisely adjusts the joint speeds of the robotic arm to ensure it reaches the target position on time along the predetermined trajectory.
Once the product arrives at the buffer position, the robotic arm first checks if there is any material at this station. If there is no product, the robotic arm releases the product to the station. After the product arrives, dual-mark photography and positioning are performed, and the coordinate offset is calculated so that the SCARA robotic arm can dynamically adjust the target screw fastening position in real time according to the actual situation to complete the fastening operation.
After the locking process is completed, the robotic arm waits for the release signal from the next station. Once the release signal is received, the robotic arm controls the conveyor belt to send the product to the next station, checks the buffer space again to see if there is material, and continues the above process.
SCARA robotic arm screw fastening process
Core advantages of the solution
It integrates machine vision, motion control, I/O control, and robotic arm control into one unit, making wiring more convenient and reducing costs;
• Real-time motion control kernel with intra-kernel interaction and instruction call speeds down to the microsecond level, improving processing efficiency;
• Built-in algorithms for 30+ robotic arm types, making it more convenient for customers and improving engineers' development efficiency;
• Provides visual robotic screw fastening software, making program debugging and process steps simpler and faster. Real-time monitoring of the fastening process provides detection for stripped threads, floating threads, etc., achieving a yield rate of up to 99.6% and realizing more stable "screw fastening";
• Solve the problem of material intake from different product angles, achieving a significant improvement in production efficiency and precision, and enhancing the flexibility and automation level of the production line;
• It provides a one-click automatic calibration function, which can quickly realize visual correction of the workpiece locking position and improve production efficiency.
Solution Hardware Configuration
02. VPLC7 Series Machine Vision and Motion Control Integrated Machine
The VPLC7 series machine vision motion control all-in-one machine vision controller from Zheng Motion Technology is a high-performance EtherCAT motion controller based on the x86 platform and Windows operating system. It can operate offline, supports rich IO control, 30+ robot algorithms, and vision and motion control functions, greatly simplifying the configuration process of vision and motion control projects.
The VPLC7 series machine vision motion control integrated machine is easy to install and remove, occupies little space, and can be seamlessly integrated with other control unit components (such as servo drives, sensors, encoders, control valves, etc.) and MES systems, providing a complete end-to-end vision motion control solution.
• Optional 6-64 axis motion control (pulse + EtherCAT bus)
• Built-in real-time kernel MotionRT7, supporting third-party vision software
• Onboard 20 general purpose inputs (10 of which are high-speed inputs), 20 high-speed outputs
• Provides integrated vision and motion control solutions with real-time soft controllers/soft PLCs in an all-in-one open IPC form factor.
Multi-core parallel computing enables efficient processing of core tasks in automated equipment such as motion control and machine vision.
03. Provides an easy-to-use visual RTFuse robot system platform.
RTFuse Robot System is a system-level software designed for the robotic arm market, supporting various mainstream robotic arm types such as Scana, Delta, six-joint, assisted, and Cartesian coordinate systems.
The software integrates functions such as visual motion control, IO logic control, communication interaction, and machine vision. Users can perform purely graphical programming on the teach pendant using the rich tools within the system, easily achieving one-stop programming development for Chinese teaching without writing code.
RTFuse Robotics System Platform Product Advantages
Low technical threshold
The drag-and-drop Chinese configuration system programming is easy for application engineers to learn after simple training. It executes project control processes from top to bottom, with manual teaching of robot arm positions.
The system is highly open
It supports multi-threaded control, and in addition to controlling the robotic arm, it can also control other auxiliary axes, IO logic control, communication interaction, etc., all of which can be accomplished by a single controller.
Strong integration of software and hardware
It integrates EtherCAT bus, pulse hybrid control, machine vision, and motion control, combining hardware and software for easy equipment debugging and troubleshooting.
Low labor costs for businesses
One person can debug the motion control, vision, and IO logic control of the equipment, solving problems such as the loss of engineering personnel and high labor costs.
