Electronic Cam Function for Flying Shear and Chase Shear Control
In modern manufacturing lines, cutting materials on the fly without stopping the production flow is a critical requirement. This is where electronic cam technology comes into play, enabling precise flying shear and chase shear operations. Unlike traditional mechanical cams, electronic cams use software-defined motion profiles to synchronize the cutting tool with the moving material, offering flexibility, accuracy, and reduced maintenance.
An electronic cam system replaces physical cam mechanisms with a virtual master-slave relationship. The master axis represents the material feed, while the slave axis controls the cutting tool. By programming a cam table, the slave follows a predefined position, speed, or torque curve relative to the master. This allows for complex motions such as accelerating, matching speed during cut, and returning to start position seamlessly.
How Electronic Cam Enables Flying Shear
A flying shear cuts a continuously moving material (like metal sheets, paper, or plastic film) to specific lengths without stopping the line. The electronic cam profile typically consists of three phases:
- Acceleration phase: The cutting tool accelerates from a waiting position to match the material speed.
- Synchronization phase: The tool moves at the exact same speed as the material while performing the cut.
- Return phase: The tool decelerates and returns to the start position for the next cycle.
With electronic cams, these phases are defined by mathematical functions or point-to-point tables in the drive or motion controller. For example, a fifth-order polynomial can create a smooth acceleration curve, minimizing jerk and mechanical stress. The cam profile can be adjusted on the fly to change cut length without mechanical modifications.
Chase Shear: Following and Cutting
Chase shear is a variation where the cutting tool physically moves along a track to follow the material. It is often used for thicker or heavier materials where the tool cannot be mounted on a rotating drum. The electronic cam coordinates the linear motion of the carriage with the material flow. The carriage accelerates, matches speed, clamps, cuts, and then returns. Advanced controllers allow superimposing a flying shear profile on the chase motion for even greater precision.
Key Components and Implementation
Implementing electronic cam for flying shear requires:
- Servo drives and motors with high dynamic response and precise position control.
- Motion controller or PLC capable of executing cam profiles and handling high-speed I/O for cut initiation.
- Feedback devices such as encoders on both master and slave axes to ensure synchronization.
- Cam design software to create and optimize motion profiles, often supporting polynomial, trigonometric, or spline interpolation.
Many modern servo systems offer built-in electronic cam functionality. For instance, a typical drive might support up to 1024 points in a cam table, with interpolation methods to smooth the motion. The master axis can be a virtual axis generated internally or an external encoder signal from the production line.
Advantages Over Mechanical Cams
| Feature | Mechanical Cam | Electronic Cam |
|---|---|---|
| Flexibility | Fixed profile; requires physical change for adjustment | Software-defined; instant profile changes |
| Maintenance | Wear and tear on mechanical parts | Minimal mechanical wear; electronic components |
| Accuracy | Limited by manufacturing tolerances | High precision with encoder feedback |
| Speed Range | Limited by mechanical dynamics | Wide range; limited by servo performance |
| Synchronization | Fixed gear ratio | Dynamic synchronization with phase shift |
Real-World Application Example
Consider a steel tube mill producing pipes at 120 meters per minute. A flying saw must cut the pipe into 6-meter lengths. Using an electronic cam, the saw carriage accelerates from zero to 120 m/min within 0.3 seconds, maintains that speed during the 0.2-second cut, and returns in 0.5 seconds. The entire cycle repeats every 3 seconds. The cam profile is stored in the servo drive, and the master encoder is mounted on a measuring wheel contacting the pipe. The system achieves a cut length accuracy of ±1 mm, significantly reducing scrap compared to older mechanical systems.
Design Considerations for Electronic Cam Systems
When designing an electronic cam for flying shear, engineers must consider:
- Jerk limitation: High jerk can cause vibrations and reduce cut quality. Use S-curve or polynomial profiles.
- Torque and power requirements: Ensure the motor can handle acceleration and cutting forces.
- Communication speed: Real-time Ethernet protocols like EtherCAT or PROFINET are essential for fast synchronization.
- Safety: Implement safe torque off (STO) and safe limited speed (SLS) functions to protect operators.
Future Trends
The integration of electronic cams with Industry 4.0 concepts is growing. Predictive maintenance algorithms analyze servo data to detect wear before failure. Cloud-based cam profile management allows remote updates and version control. Additionally, AI-driven optimization can automatically adjust cam curves based on material variations, further improving cut quality and throughput.
Conclusion
Electronic cam technology has revolutionized flying shear and chase shear applications by providing unmatched flexibility, precision, and reliability. As servo drives and motion controllers become more powerful and cost-effective, the adoption of electronic cams will continue to expand across industries such as metal processing, packaging, printing, and converting. Understanding the principles and design considerations is essential for engineers aiming to implement high-performance cutting systems.
