I. Introduction:
The PASSIM cigarette rolling mill is a high-speed cigarette coiling machine developed by the British company MOLINS in the early 1990s. It is available in various models based on its rated production speed, including 70K, 80K, 100K, and 120K. Since its commissioning, the mill has operated stably with a high utilization rate, and has consistently been one of the main models used in cigarette factories. However, the electrical system of this mill still exhibits several shortcomings:
1. The unit's electrical system has a complex single-board computer and VME bus system structure, which makes maintenance and diagnosis difficult. The electrical components overheat and are prone to damage.
2. The S5 series PLC used in the unit has been completely discontinued, and the supply of spare parts is becoming increasingly difficult.
3. Magnetic powder clutches used for splicing paper rolls and tipping paper have short service life and are expensive.
4. The electric adjustable friction reducer of the wire feeding system causes uneven wire feeding due to wear of the friction plates.
5. The phase adjustment device for the splitting blade has a complex structure, is difficult to maintain and adjust, and has an unsuitable tightening position.
6. Early versions of the PASSIM-70k tipping paper feed roller motor and high-flow drive motor both used DC motor systems. DC motor systems have a short lifespan and are expensive.
II. In response to the above shortcomings, we propose a completely new electrical system solution.
1. The system uses S7-400 and S7-300 series PLCs as the core components of the logic function control system. The CPU of this PLC system has a medium to large program storage capacity, and its PROFIBUS interface allows for the establishment of a distributed automation system structure. It features high speed and ease of processing. The master station consists of one S7-400 unit installed in the main electrical cabinet. Independent substations composed of S7-300 units can be established on the material handling machine, cigarette rolling machine, and assembly machine. The use of a DP bus structure simplifies the entire system and provides strong anti-interference capabilities. The system uses FM 355S closed-loop control modules or analog input/output modules to control the heating elements of the unit. PT100 platinum resistance thermometers are used for temperature signal acquisition. Temperature control of each heater is achieved through PID algorithms or self-optimizing temperature control algorithms. Temperature parameters can be set and modified via an industrial computer touchscreen, and temperature values and alarm status are displayed in real time.
2. The unit uses a Siemens PC670 touch screen industrial computer for status monitoring and real-time data acquisition and processing. The main aspects include:
a. Status Display: Status display includes operating status such as machine high speed, machine low speed, cigarette density detection, cigarette quality detection, etc.
b. Safety Interlocks. Safety interlocks include various protective cover switches. When a protective cover is opened, the display screen will show the corresponding safety interlock information, the operating machine will stop running, and the power supply to the relevant actuators will be cut off to ensure the safety of operators and the unit.
c. Operating Conditions Operating conditions include motor protection switches, auxiliary device switches, etc. When these switches are in their normal positions, the display screen will show a machine-ready message and allow the unit to operate.
d. Data shows that the data includes machine operating speed, heater temperature,
e. Production Reports: Production reports include team information, finished product output, effective operating rate, production time, etc.
f. Fault Reports: Fault reports display information such as the time of occurrence of various fault states that cause unit shutdown and the duration of downtime.
3. Servo control technology is applied, using servo control units and servo motors to independently drive the two tobacco rollers, air chamber, and splitting blade on the feeder. A rotary encoder is used to synchronously track the main drive shaft, and this signal controls each servo unit. A German LENZE servo controller drives the AC servo motor. An incremental encoder mounted on the running paper disc transmission mechanism collects the real-time speed of the running paper disc, and based on the ramp voltage signal from the unit's PLC, the spare paper disc is gradually accelerated to achieve the same linear speed as the running paper disc to complete the overlapping action.
The schematic diagram of the modification is as follows:
The original DC speed control system of the machine was upgraded by using a variable frequency drive (VFD) and a three-phase AC asynchronous motor. The operation control of the VFD is implemented by a PLC program.
4. The cigarette tobacco density control and quality inspection system uses a new TI C32 series DSP microprocessor unit as the control core and is connected to the DP network using a Siemens SPC3DP communication chip. In addition to retaining all the functions of the original machine, it also adds the function of detecting and rejecting cigarettes with excessive tobacco density variation coefficient and the function of detecting and rejecting double-layer joints of paper rolls and tipping paper.
