Inspection of Bag Making Machine

Tension detection
In order to enhance the overall efficiency of bag making and ensure high-quality production output, it is crucial to maintain a consistent level of material tension while accurately monitoring and controlling fluctuations in tension. Detecting tension is the fundamental first step towards effective tension control.

 

Traditional bag making machines use two types of tension sensors: direct measurement and indirect measurement. Direct measurement involves using a pedestal type tension sensor like a piezoelectric magnetic tension sensor. This sensor consists of an excitation coil and a secondary coil, with the secondary coil being an inductor. When mechanical stress is applied in the measurement direction, magnetic coupling occurs in the sensor. This results in the generation of an induced AC voltage signal in the secondary coil, which is directly proportional to the mechanical force. By processing this signal, a tension signal that corresponds to the magnitude of the mechanical force is outputted.

 

Another type of tension sensor used is the varistor type. It is placed between the bearing and the rack to measure the horizontal tension of the drum. An amplifier is used to supply the full bridge voltage and process the measurement signal. The output signal of the amplifier represents the radial force and can be used for digital display or as an instantaneous value in a closed-loop circuit.

 

A leaf spring type micro displacement tension sensor is also available. Direct tension sensors offer several advantages, including a wide detection range, fast response speed, and good linearity. However, they have a disadvantage of being unable to absorb peak tension. When the tension control system experiences strong interference, it may not react instantly, resulting in significant tension fluctuations on the material belt.

 

One commonly used method for indirectly detecting tension is through the floating roller tension detection technique, which serves as a form of position control. Essentially, when the tension on the material belt is balanced with the force exerted by the cylinder, the tension stabilizes and the floating roller settles in the central position. Conversely, any changes in tension cause the floating roller to either rise or fall accordingly. To detect these positional changes, a floating roll potentiometer is employed. It tracks the shifting position of the floating roller and relays this information back to the tension controller. Utilizing the position signal, the tension controller calculates and generates a control signal that regulates the tension. By implementing this method, reliable tension control can be achieved in various applications.

 

The combination of direct and indirect testing in the tension detection method allows for the simultaneous detection of the floating roller's position signal and the tension electrical signal output by the sensor. This unique approach provides excellent buffering and stability, while also delivering high precision and repeatability in closed-loop control. By employing this method, both signals can be accurately measured, leading to efficient and reliable tension monitoring.

 

Another approach to detecting tension involves analyzing the diameter of the coil. A proximity switch is installed near the coil to measure its speed, allowing us to calculate the current diameter by combining the initial diameter and material thickness measurements. By monitoring changes in coil diameter, we can generate a control signal that regulates the winding torque or unwinding brake torque. This control signal effectively adjusts the tension applied during the winding or unwinding process.

 

Deviation detection
It is important to timely detect deviations during material transportation caused by factors like unequal force distribution, inconsistent thickness, and roundness of the traction roller. Online deviation detection is necessary under such circumstances.

 

During the initial stages of bag making, the machine's velocity was limited and the operator would make manual adjustments to correct any material deviations based on observations made on-site.

 

Photoelectric sensors have gained popularity due to their simple structure, reliable performance, high accuracy, and quick response. These sensors are effectively utilized in tracking the boundaries of various chromaticity zones on packaging materials. They are capable of reading the deviation between the actual position of the strip and the predefined position. By converting the deviation into an electrical signal, amplifying it, and conducting comparisons, calculations, and analysis, the sensors provide instructions to the servo controller. This, in turn, controls the motor to correct the deviation and guide the mechanism accordingly. Ultimately, the strip is automatically tracked and adjusted during the conveying process.