We often say that unity is strength, and only through cooperation can we do our work better. This applies not only to humans. The same applies to industrial robots and CNC machine tools; they also need to work together to perform their tasks effectively and improve factory efficiency. So today we'll learn how industrial robots and CNC machine tools work together, using FANUC robots as an example.
The application of FANUC robots on the motor housing processing production line utilizes automated robot loading and unloading technology and the iRVision vision system to rationally plan the robot's motion trajectory. This organically combines industrial robot handling technology with CNC machine tool processing technology to achieve automated loading and unloading of workpieces and automated stacking of finished products, enabling high-precision, high-efficiency, and low-cost processing of products.
1. FANUC Robot
The automated production line is equipped with two FANUC Robot M-20iA handling system robots. One of the robots, R1, is a walking robot controlled by a FANUC servo motor αiF12/3000. It is driven by a precision reducer, gears and racks, which has high repeatability and can easily adapt to the arrangement of machine tools on both sides of the guide rail.
It is mainly used for gripping raw workpieces, loading machine tools, gripping workpieces between processing steps, and unloading and transporting finished products to the conveyor belt.
Another stationary robot, R2, is equipped with FANUC's unique intelligent robot technology (iRVision vision function) for unloading materials and stacking finished products in the material basket.
Each joint of the FANUC Robot M-20iA robot is a joint point or coordinate system, and its shape and the position of each joint are shown in the figure below.
2. Layout of automated processing line equipment
The automatic processing production line for motor housings consists of a feeding conveyor belt and a discharging conveyor belt (each equipped with an iRVision vision system), a walking robot R1 (guide rail type), a stationary robot R2, two VM850 vertical machining centers, a CLX360 CNC lathe, finished product baskets, and a system control cabinet, etc. The layout of each piece of equipment is shown in the figure below.
3. CNC machining process
The workpiece is a motor housing, as shown in the picture below. It is for mass production and the material is ADC12 aluminum alloy. The machining includes end milling, drilling, tapping, and internal turning.
The process steps for machining the parts are divided as follows:
(1) The VM850 vertical machining center 1 performs the drilling of M4 thread bottom hole, tapping of M4 thread and milling of outer circle boss as shown in the figure below.
(2) The VM850 machining center 2 performs drilling of 6 φ5.5mm through holes and chamfering of the hole openings, as shown in the figure below.
(3) The CLX360 CNC lathe performs the machining of inner holes, stepped holes, and chamfering of hole openings, as shown in the figure below.
In addition, special fixtures need to be designed. The machining center fixtures use an internal clamping method, while the CNC lathe fixtures use an external clamping method.
4. Robot automatic loading and unloading motion design
The robot pneumatic gripper components, including pneumatic, sensor, and mechanical parts, are designed based on the workpiece's shape characteristics. The workpiece machining process is as follows:
① The blank workpiece is placed on the feeding conveyor belt.
② The R1 composite gripper of the walking robot picks up the blank workpiece, walks to the machining center, and installs the workpiece onto the special fixture of the machining center, as shown in the figure below.
③ After machining is completed by machining center 1, the walking robot R1 composite gripper removes the workpiece, moves to the position of machining center 2, and installs the workpiece onto the special fixture of machining center 2, as shown in the figure below.
④ After machining by machining center 2 is completed, the walking robot R1 removes the workpiece to the CNC lathe position and installs the workpiece onto the special fixture, as shown in Figure 9. After the workpiece is finished, the robot removes the workpiece and moves to the workpiece flipping table position to flip and exchange the workpiece, as shown in the figure below.
⑤ After the workpieces are exchanged on the turnover table, robot R1 places the finished products on the unloading conveyor belt, as shown in Figure 11. Robot R2 then unloads the workpieces and automatically stacks them in the finished product basket, as shown in the figure below.
This completes a full processing flow. Each processing step has a corresponding cycle time. After adjusting the CNC machining program and the robot motion program, a perfect combination of CNC machine tool processing and robot loading and unloading can be achieved.
5. Specialized fixture design
Based on the respective machining processes of the three CNC machine tools, three sets of combined pneumatic fixtures were designed, as described below.
(1) Special fixture for vertical machining center 1: Vertical machining center 1 performs drilling and tapping, as shown in the figure below.
(2) Special fixture for vertical machining center 2: The vertical machining center 2 is used to drill 6 through holes of φ5.5mm and chamfer the hole opening. The fixture is designed to clamp the workpiece with a pneumatic three-jaw self-centering chuck and oriented with two elastic V-blocks, as shown in the figure below.
1. Starting chuck 2. Support block 3. Flexible V-block 4. Specially designed jaws
(3) Special fixtures for CNC lathes: For CNC lathes to perform internal hole and stepped hole and hole chamfering processes, a fixture is designed to position the workpiece with one side and two pins and to clamp it with a pneumatic rotary clamp.
6. Interfaces between robots, PLCs, and CNC machine tools
To ensure safe cooperation between the robot and the CNC machine tool, a safe and reliable communication connection must be established between the robot, the PLC, and the CNC machine tool.
On the hardware side, shielded cables connect the corresponding input and output points of the three components. On the software side, robot-specific software and a PLC interface are used to collect the current status of the machine tool and robot, and corresponding control programs that conform to loading and unloading logic are written, ultimately achieving effective communication between the CNC machine tool and the robot.
The key signals to be handled include emergency stop signals, CNC machine tool readiness completion signals, robot gripper pneumatic signals, CNC machine tool fixture release signals, and safety door signals. The CNC machine tool status monitoring screen is shown in the figure below.
As industrial robots are used more and more widely and their application technology becomes more and more advanced, automatic loading and unloading mechanisms for industrial robots, as auxiliary components of CNC machine tools, are receiving increasing attention from machine tool manufacturers and users.
By working closely together with robots and CNC machine tools, the precision of the system's processing is ensured, the labor intensity of workers is reduced, and work efficiency is greatly improved, demonstrating significant application value.
Exploring the Path to Integrated Development of Industrial Robots and CNC Machine Tools
In recent years, the machine tool industry has faced increasingly prominent problems such as overall market shrinkage and overcapacity, and is undergoing severe challenges in adjustment and transformation. Since 2011, the net profits of machine tool companies have been declining, and the entire industry has been largely stagnant. Meanwhile, with rising labor costs and the intelligent transformation of enterprises, the robotics market is booming.
In fact, compared to other industries, the machine tool industry has unparalleled advantages in venturing into robotics. A key application of robots lies in motion control, which is a crucial factor in ensuring the precision of machine tools. From this perspective, machine tool manufacturing and robot manufacturing technologies are highly correlated.
Beyond traditional welding applications, robots are widely used in machine tool loading and unloading, material handling and palletizing, grinding, spraying, and assembly. Metal forming machine tools are a crucial component of machine tools. Forming processes are often associated with high labor intensity, noise pollution, and metal dust; the high temperature, high humidity, and even polluted working environments make it difficult to recruit personnel for these positions. Integrating industrial robots with forming machine tools can not only solve companies' manpower problems but also improve processing efficiency, safety, and precision, and has become a major development trend.
Machine tools are machines that produce machine parts; simply put, they are machines that produce machines. CNC machine tools represent the digitization and intelligentization of machine tools. They primarily use CNC devices to send signals, controlling the machine tool to automatically process parts according to the requirements of drawings, based on their shape and dimensions. CNC machine tools effectively solve the problems of machining complex, precise, small-batch, and multi-variety parts. In essence, it represents the process of mechanical parts production evolving from manual to mechanized and then to digital applications.
Robots are high-precision, cutting-edge products. Many core components, such as servo motors, drivers, controllers, and reducers, require high-precision machine tools for production. Key components, including turntables, booms, forearms, housings, and wrists, are also manufactured by machine tools. Even if they can be produced manually or mechanically, it is difficult to ensure the precision of the products.
Even the slightest error in core or critical components can affect the robot's movement and operational precision. This is especially true in the electronics industry, where the requirements for robots are extremely stringent. Therefore, only by ensuring the precision of key technologies and components can the application and promotion of robots have a solid technical and quality foundation. The approach taken by the Luojiang District government will effectively promote robot product manufacturing and serve as a significant example for improving product quality.
Furthermore, the anticipated rapid growth of the Chinese robot market may also be one of the key reasons why the aforementioned machine tool industries have all ventured into this field.
