How to Design Automatic Filling Machine?

Filling machine is one of the essential equipment in the industrial field. At present, the level of automation and control of the liquid pouch filling machine is low, and the performance is not stable. Therefore, this paper introduces a full-automatic liquid filling machine based on PLC and DSP technology.

Working Principle of Filling Machine

Liquid filling production line is generally composed of automatic filling machine, automatic packing machine, sealing machine and ink-jet printer. And these devices are connected by conveyor belts. Industrial filling machine is the main equipment of this production line, and its performance plays a decisive role in the function and efficiency of the whole production line. In order to improve the performance of the intelligent filling machine, it should be equipped with an integrated automatic control system composed of DSP servo control system, stepper control system, PLC, frequency conversion speed regulation system, pressurized pneumatic part and photoelectric sensor.

The liquid bag filling machine adopts PLC and DSP as the main control body. In terms of hardware connection, PLC, as the lower computer of the control system, is directly connected with various bottom devices. PLC can also communicate with the host computer to obtain product information and production parameters, and control the action logic of the filler and the speed of the conveyor belt according to the feedback information of the sensor. DSP can drive the supercharged hydraulic cylinder, adjust the filling volume, and calculate the compensation volume information through the compensation algorithm.

System Hardware

PLC Control System

PLC can collect the data of the automatic packaging machine and control it. PLC can communicate with the host computer system, collect and transfer information, collect analog input signals such as liquid level and frequency of frequency converter. In addition, PLC can also collect pump, solenoid valve, photoelectric switch, proximity switch, electric actuator and other switch state signals, and output signals to control the on-off of various valves according to the operation requirements. Finally, PLC can communicate with DSP, so that DSP can control servo motor to achieve accurate control of the filling volume.

Data Acquisition and Servo Control System

In order to accurately control the filling volume, the position servo control system is used to precisely control the stroke of the piston cylinder in the design, so as to achieve the purpose of accurately controlling the filling volume. 

The volume change caused by the change of temperature and viscosity of the liquid product causes the quality fluctuation, and there is a nonlinear relationship between these parameters. After collecting the parameters of liquid viscosity, temperature and pressure, DSP can compensate the stroke of piston cylinder through certain compensation algorithm. DSP receives the position command signal from PLC, and superimposes the given position and compensation position of PLC as the total given position. After the position signal is adjusted by the position loop, the speed command signal is formed. After comparing the speed command signal with the speed feedback signal, the deviation signal is adjusted by the speed loop to generate the current command signal. After vector transformation of current command signal in current loop, SPWM outputs torque current to control the operation of AC servo motor.

Through the PLC and DSP technology, the degree of automation of liquid product filling machine has been improved. The liquid packing equipment has the advantages of convenient operation, stable system and high efficiency.