A typical robotic stamping line typically consists of the following components:
- Robot
- Electronic control system
- Disassembly device
- Transition belt
- Sheet Metal Cleaning Machine
- Sheet Metal Lubricator
- Centering device
- End of line palletizing system
- Security Protection System
- Robotic final selector.
The specific arrangement of these components can be customized based on the production shop layout. For example, the depalletizing carriage can be positioned parallel or perpendicular to the punching line.
1. Stamping robot
Stamping production robots require a number of essential features, including high payload capacity, precise motion trajectories and reliable performance. Furthermore, these robots must also possess certain characteristics such as frequent start-stop movements, wide operating range, ability to handle large parts, and large turning space.
Stamping robot manufacturers have made several improvements over traditional handling robots. These advances include increased engine power and gear specifications, longer robotic arms, and the widespread use of scaffold-mounted structures.
2. Robotic automation press line control system
The control system for a robotic automated press line must integrate a variety of components, including presses, robots, depalletizers, cleaners, lubricators, centering devices, dual material detection devices, visual recognition systems, various conveyor belts, synchronous control systems, safety protection systems, and large screens. The system must also have the ability to seamlessly integrate with the factory's Manufacturing Execution System (MES).
To effectively manage the integration of so many intelligent control systems, Ethernet secondary network systems and industrial fieldbus are commonly used. In some cases, the fieldbus system may also include a safety bus for added security.
3. Unstacking system
Currently, there are three predominant depalletization systems:
- Dedicated depalletizing/robot system
- Depalletizing cart/truss type manipulator system
- Depalletizing cart system.
( 1) Specialized depalletizer
The design feature of these systems is that the pallets are placed on a hydraulic lifting cart that can be moved. The height of the stacked material is monitored by photoelectric sensors and controlled by hydraulic systems, ensuring its consistency. The magnetic spreader operates pneumatically or electrically and automatically moves close to the stacked material.
An array of vacuum chucks driven by a cylinder is used to unstack the material, and the vacuum chucks move vertically. Finally, the dismantled sheets are transported using magnetic belts.
( 2) Robot + unstacking cart
The design feature of this system is that the stacked material is placed on a mobile de-stacking cart. The height of the stacked material is not controlled, but the height at which the robot vacuums the material is automatically adjusted based on the calculated sheet thickness during the unstacking process.
The magnetic divider bracket is mounted on the destacking cart. The rack is translation capable and has multiple freely adjustable joints, allowing the magnetic spreader to be manually positioned against the edges of the stock during stock changes.
Vacuum suction assemblies and dual resistance test sensors for unstacking are located on the gantry robot tools. The robot then separates the sheet into individual pieces and places them on a retractable transition belt for subsequent transport.
(3) Truss handler + depalletizing cart
The design feature of this system is that the stacked material is placed on a mobile de-stacking cart. The height of the stacked material is not regulated, but the robot automatically adjusts the suction height based on the calculated sheet thickness during the depalletizing process.
The support for the magnetic divider is mounted on the destacking cart, which can be translated and has multiple adjustable joints that can rotate freely. When changing stacked material, the magnetic divider must be manually positioned against the edges of the stacked material.
Vacuum suction assemblies and dual resistance test sensors for unstacking are located on the gantry robot tools. The robot then separates the sheet into individual pieces and places them on a retractable transition belt for further transmission.
( 4 ) Extendable belt conveyor
An extendable conveyor belt is used to transfer individual sheets after the destacking process is complete. The conveyor speed can be adjusted to provide the necessary movement to the sheet metal as it passes through the washing machine.
Conveyor belt speed is typically regulated through frequency conversion to ensure proper synchronization with the washing machine and lubricator. The belt length can be adjusted to accommodate the space when the sheet metal is not being cleaned and the cleaning machine is inactive.
(5) Sheet Metal Cleaning Machine
Sheet metal cleaning can be divided into two types: online cleaning and offline cleaning.
Online cleaning is best suited for companies with large production volumes. To accommodate the size of the car's overall circumference, the online cleaning machine is generally 4.2m wide.
On the other hand, offline cleaning is ideal for companies with low single-model production in the early stages of production. One sheet metal cleaning line can support 2 to 3 punching lines, and the offline cleaning machine is normally 2m wide.
The cleaning machine comprises several components, including a roller system with feed, brush and compression rollers, a power and transmission system, a hydraulic adjustment mechanism, a cleaning filter system, a nozzle assembly assembly, a collector of oil mist, a lubrication system, a walking mechanism and an electrical control system.
It is mainly used to clean standard sheets as well as uncoated, galvanized and aluminum sheets and coils.
The washing machine has a self-propelled mechanism and can be easily moved on the ground when not in use. The guide roller, brush roller and compression roller have independent pressure adjustments and frequency conversion capabilities.
By adjusting pressure and speed precisely, the worn and repaired roller system remains synchronized with the production line. The compression roller uses a non-woven laminated fabric roller that provides excellent compression and tensioning performance and has anti-scratch and self-healing functions.
The cleaning oil tank is equipped with a heating system, allowing the cleaning medium to be used at different temperatures to obtain optimal lubrication results. The electrical system is controlled by a PLC with fieldbus communication capability, and parameters and faults can be managed through the touch screen human-machine interface.
(6) Oilier sheet metal
To ensure sheet metal quality during high-speed stamping and forming, locally applying drawing oil to the sheet before stamping and forming is a common practice in automotive factories. It is suitable for use in automated stamping lines with lubrication machines.
The lubricator is mainly used for the lubrication process before sheet metal drawing. It consists of a barrel unit, an oil supply and preservation unit, an air supply unit, a leaf transport unit, an oil mist collection unit, an electrical control unit and the machine itself.
The lubricator has a travel mechanism, allowing it to be moved offline when lubrication is not required. The nozzles are digitally controlled to ensure precise positioning of the oil film on the plate and a uniform film thickness.
Regardless of changes in ambient temperature, the oil supply and preservation units remain in a standby state, ensuring a constant oil temperature to achieve optimal results.
( 7) Sheet metal centering device
To ensure accurate positioning of the sheet in the mold, it is necessary to align the sheet before the robot picks it up. There are three commonly used centering devices: gravity centering device, mechanical centering device and optical centering device.
Gravity centering device:
The metal sheet is positioned by gravity on an inclined surface filled with spheres. The table is equipped with on-site sheet inspection and double material inspection.
The gravity centering device is suitable for direct placement by robot, but not for automatic lines with washing and lubricating machines.
Mechanical centering device:
The sheet metal is moved to the block by a magnetic leather pouch, and three cylinders drive the feeder to push it toward the center for precise positioning.
All feeder positions can be taught and programmed, and the centering device features sheet material position detection and dual material detection.
It can meet high-speed centering requirements for various sheet materials, and a dual-center design can be used for simultaneous processing of two-piece or dual-mode parts.
Optical centering device:
This is a recent technological development that uses video processing software to automatically adjust the position of the plate, taking photos and adjusting the robot's trajectory.
It not only meets the requirements of accurate positioning of sheet metal in the mold, but also eliminates the complexity of mechanical centering device.
The optical centering device essentially uses a magnetic conveyor belt with sheet metal range detection and dual resistance detection. Compared to mechanical centering device, it significantly reduces costs.
4. Seven axis robotics and final picker
A standard six-axis spindle robot for stamping has a production rate of 8 parts per minute. In recent years, robot manufacturers and system integrators have developed seven axes to further increase productivity.
With the addition of the seventh axis, the production rate of automated robotic stamping lines can be increased to 12 parts per minute, making the productivity of robot-automated stamping lines comparable to high-speed lines that use expensive dedicated robots.
5. End-of-line palletizing system
The production rate of the automated stamping line can exceed 10 parts per minute, placing excessive demands on the end-of-line palletizing station beyond the labor limit.
To accommodate high-tempo production, stamped parts need to be diverted first. They can then be manually or robotically packed into racks, before finally being removed by a forklift.
