Application of the hottest brpcc in the control sy

Br the application of PCC in the control system of large-scale injection molding machines

at present, most of the large-scale injection molding machines in China use PLC or the control system based on MCU chip. Although the above two methods can complete the normal operation of the injection molding machine, the control system has the following shortcomings: low control accuracy, long development cycle, and difficult maintenance and upgrading. In addition, the injection molding machine is moving towards high speed, high efficiency, low energy consumption and high automation. It is planned to develop in about three years, which requires the injection molding machine to have a perfect automatic control and adjustment system to ensure the reliability of high repetition and high sensitivity of the process parameters of the injection molding process. B&r PCC was used to upgrade and transform the control system of an Italian brand plastic machine that produced 1350t large injection industry in the late 1980s, which accounted for the largest proportion of vanadium use. Good results were achieved, and it has the function that conventional injection molding machine control system is difficult to achieve

1 composition of injection molding machine control hardware system

the hardware of the control system is composed of upper and lower computers. The upper computer includes industrial computer, panel and keyboard; The lower computer includes PCC controller and expansion module. The upper computer adopts ipc2001 with 486dx2cpu, which is installed with b&r automation runtime v2.60 operating system, 26.4cm (10.4 hours) TFT true color screen, Chinese and English operation interface, and the panel is attached with a special 30 key keypad for injection molding machine; The lower computer adopts the high-performance programmable computer controller b&r PCC 2003 series cp476. In addition to the CPU, the PCC also has an independent TPU for processing high-speed input/output (I/O) signals, expansion modules dm465, do435, rotary module displacement acquisition ai294, pressure acquisition ai351, temperature acquisition at664 and high-speed counting module ail38. The communication between upper and lower computers adopts can bus or RS232 bus. The control system can centrally monitor the whole line on the man-machine interface, and can be externally connected with modem to realize remote monitoring if necessary; I/0 port, heating and pressure status display; Automatic fault alarm and random help function

the system hardware composition block diagram is shown in Figure 1

Figure 1 system hardware composition block diagram

the system hardware structure is compact, and standard sizes are adopted for both swivel and expansion modules, which is conducive to the design and installation of the control cabinet. The system has good anti-interference performance, and the input/output modules are equipped with optical couple isolation. The input module can directly convert the input current signal (0 ~ 20mA) and voltage signal (0 ~ 10V) into 0 ~ 32767 digital signal. The current of do module can reach 2A. Because the microcomputer controlled actuator solenoid valve has more advantages in the overall environment, the driving current of actuator solenoid valve is higher than 2.5A, so the do signal amplifies and drives the actuator solenoid valve through the diffuser drive plate

pcc cp476 is equipped with TPU, which realizes high-speed signal I/(), and can effectively realize the rapid switching control of pressure and speed in Section 7 of glue injection. In order to activate TPU, it is necessary to initialize and set ltx() function to allocate channels to TPU during system software design

2 software control system

2.1 b&r as development environment

automatic studio, a programming environment under windows, supports six standard development languages, such as standard C, basic, ladder diagram, instruction table, sequential structure diagram, etc. You can program in multiple languages in the same project according to your needs. At the same time, the programming environment includes not only a wealth of conventional function libraries and function blocks, but also a special function library for injection molding machine, plastliba, which can realize the system characteristics described below

b&r adopts the time-sharing multitask operating system and has the analysis ability of large-scale computer. Starting from the control requirements of injection molding machine, set the tasks with different real-time requirements for mold locking, temperature control and other processes in the task levels with different cycle times (see Table 1). Table 1 task setting

2.2 system software organization

the control system software is composed of lower computer system, upper computer system and interface, and the software is written in C language

in the injection molding process (see Figure 2), glue melting and mold opening are carried out at the same time, so the software structure includes sequential structure and parallel structure. Suspend and wake-up functions are inserted into the program to realize the sequence and parallel actions of the program. The organizational structure adopts a pyramid structure with four levels from top to bottom (see Figure 3), and the process tasks of the flow chart are defined as the execution level and distributed in different standard task levels. It is divided into communication, interlock operation, data operation, temperature control, alarm, etc. according to functions. In terms of function, in addition to meeting the conventional sequential action and multi-channel parallel action, it can also realize several characteristics that are difficult to be achieved by the ordinary control system, which can significantly improve the performance of the injection molding machine and better protect the hydraulic system

Figure 2 injection molding process flow

Figure 3 main program function block diagram

the program organization structure of the upper computer is the same as that of the lower computer. The functions are divided into communication, data storage and reading and writing, curve drawing, parameter input and output, etc. Upper and lower communication, the upper computer is active, and the lower computer is passive. The upper computer reads and writes the corresponding variable value of the lower computer regularly. The interface design of upper computer can be realized quickly and conveniently under as

2.3 system offline simulation debugging

in order to realize offline debugging, a simulation program is added to the program, mainly for the simulation of the displacement of each action in the injection molding process and the closed state of the travel switch. Thus, the action of the injection molding machine can be simulated in the offline state, which greatly facilitates the debugging of the control system, which is not available in the development of the general injection molding machine control system

3 system functional characteristics

3.1 motion control characteristics

how to achieve large capacity to ensure the smooth operation and protection of the hydraulic system of the dimensional injection molding machine equipped with measurement data is the key problem of the control system. This system fully optimizes the control of the hydraulic system from the software design, and realizes low overshoot and high precision

ramp() function ramp control or ramp is used in the acceleration and deceleration section of piston movement_ Ql() function realizes conic control, and the position point of each movement deceleration is calculated and compensated in real time. For example, ramp is used for buffer deceleration at the end of the cylinder piston stroke_ Ql() function realizes conic processing. The solenoid valve of the hydraulic system is opened and closed for delay compensation, and the delay time can be set on the man-machine panel

3.2 linearization of machine hinge mechanism

the machine hinge structure of the mold closing mechanism of the injection molding machine is a 5-point elbow bar type, and the travel of the moving template is up to 2m. The measurement of the moving state of the moving template is obtained by measuring the piston rod of the clamping cylinder, which greatly improves the accuracy and reliability of the measurement

input the structural parameters of the machine hinge into the b&r togclac software to calculate the one-to-one correspondence between the moving position of the piston and the moving template, save and import the data into the engineering generated data module, and then use da_ The read() function can read the relationship between the position of the piston and the moving template from the data module

3.3 temperature control system characteristics

PID parameters can be calculated by using b&r intelligent temperature pidxh and pidxhopt function blocks, so that the temperature control is accurate to ± 1 ℃. The pidxhopt function block can optimize the heating program

3.4 closed loop optimization control of melt back pressure

the system adopts closed loop control of melt back pressure. The feedback value of back pressure is input to the TPU of cp476 through di351 module for processing, and then optimized by pidx () function after comparing the set value

3.5 process parameter monitoring

the system has rich curve auxiliary monitoring and analysis functions. The panel can display the speed, pressure, position and other curves of the opening and closing stages, and can also monitor the real-time curve of the temperature control area and pressure of each section as required. It can also select the processing process of glue injection, screw rotation, mold unlocking and injection units to monitor the process of speed/time, pressure/time, speed/position and pressure/position

3.6 system general scalability

the system is written in C language, and the structure is complete and clear. Structural variables are widely used in software design to describe the state and action process of each component. For example, the structural variables of ejection action include the ejection stroke in the process of advance and retreat, the speed and pressure in each stroke stage of ejection; Ejection action delay, alarm signs and other variables

the system software has strong versatility and can be suitable for injection molding machines with the same series and different tonnage. During routine maintenance and replacement of parts, it is only necessary to modify parameters slightly on the panel without cumbersome debugging. For example, when replacing the electromagnetic directional valve of the ejector oil circuit, the opening delay and closing delay of the directional valve can be changed

3.7 friendly man-machine interface

the man-machine interface is illustrated with text, which can easily set the parameters of various structural variables, such as the opening and closing delay of hydraulic solenoid valve; You can also set various parameters of the action, including parallel action, core pulling combination and speed pressure setting

4 summary

upgrading the hydraulic mechanical large-scale injection molding machine with the intelligent control system of baccalais was successful, and the overall performance of the machine exceeded the original early control system of PLC plus temperature control meter. It is an inexhaustible trend to continuously improve the overall performance of injection molding machines. The key to product competition is to obtain more product added value on the basis of less hardware investment. Adopting the stable quality intelligent control system of baccalais and developing the control system of the traditional hydraulic mechanical injection molding machine can, on the one hand, shorten the development cycle and reduce the corresponding cost, on the other hand, improve the quality and grade of the injection molding machine, which can be said to open up a new way for domestic injection molding machines to improve product quality and international competitiveness. (end)