PLC的输入信号主要是针对模具预热和真空辅助射料而言，因此PLC的输入端口连接到两个按扭开关；PLC的输出部分是控制6个电磁阀，电磁阀控制相应的气控阀。从而实现电－气－执行元件的二次转换。该装置的输入信号和输出信号以及I/O口分配如表1所示。

 

 

3.2 控制流程

　　PLC的程序运行方式是循环扫描方式，而非顺序执行方式。首次扫描时初始化一些功能，然后接受参数的输入，选定工作方式，确认后按照预定的工作方式工作。

　　图3是控制过程的流程图。通电后，控制系统的文本显示器和操作员界面TD200显示主菜单、设定好过程参数、选择自动方式或手动方式等操作方法。自动方式是指控制系统自动控制泡塑模成型过程。手动方式主要是针对模具预热和真空辅助射料而设计的。自动方式和手动方式的选择完全由TD200上的功能键来实现。

　　选择手动方式时，可编程控制器的CPU扫描程序中的手动方式模块，TD200显示手动操作菜单，指示手动操作的各个步骤及其操作方法。用户可根据需要进行模具预热、真空辅助射料等操作。

 

 

　　选择自动方式时，TD200指示如何进入自动操作方式。当确认键F2按下后，制模过程根据程序自动进行，从一次加热开始，经加热程序模块、冷却程序模块，一直到脱模程序模块结束。整个过程总共有9个动作。过程中各个动作的转换主要是靠定时器来实现。例如，在蒸汽加热阶段，从一次加热到二次加热的转换。因此在程序编制过程中，针对没有位置变化的动作，都设计了一个软件定时器，设置有可以改变的定时时间常数。当某一动作开始后，其相应的软件定时器即开始延时操作，当达到设定的时间后，CPU自动转入执行下一程序动作。各个动作时间常数的大小可根据对泡塑模的质量要求来设定，并且可随时进行调整。各动作时间参数的调节可按TD200的F1键进行设定。

　　以时间常数来实现过程中动作的转换，这种控制方式实质上还是一种开环控制方式。为了控制泡塑模的成型质量，控制系统也可应用闭环控制方式。这种方式是在蒸汽加热阶段利用反馈阀来较的控制进入模具气室或机械蒸缸内的管道蒸汽压力。方法是事先用调压表设定一个压力值，并与模具气室或蒸缸内的蒸汽压力进行比较，当蒸汽压力大于设定的压缩空气压力值时，反馈阀关闭，切断进入气控阀的压缩空气，从而使气控阀关闭，蒸汽就不能进入气室或机械蒸缸内。使用这种复合控制方式，可明显提高泡沫模样的成型质量。

3.3 编程

　　PLC可以实现的时间控制，其相应的编程则方便并且有很大灵活性。本装置的实现主要有两方面的编程，TD200的组态和实现程序的梯形图。TD200的组态主要是功能键的分配、消息的编写以及参数的设定。

TD200是一个文本显示设备，显示S7-200 CPU允许的信息。存储在TD200里的操作参数是TD200的地址、CPU的地址、波特率和参数块的位置。TD200组态存储在CPU可变存储器（V存储器）里的一个TD200参数块。TD200的操作参数，例如语言、更新速率、信息和信息使能位，存储在CPU中的TD200参数块内[4]。

上电后，TD200从CPU读参数块。对所有参数均进行合法性检查。如果一切合格，TD200开始主动轮询信息使能位以决定要显示的信息，并从CPU读取信息，然后显示信息。这里用到的消息有两种，一是提醒操作者的提示性消息；二是过程参数时间调整及修改的消息，如一次加热时间、冷却时间等。The set time range can be changed at any time as needed.

 

Other combinations of lamp groups can be easily selected.

 

Compared with the traditional scheme, fewer components are required. The timing switch in the can be used to set the start, end and end time of school. The bell rings from Monday to Friday at 8:00, 9:45, 10:00, 12:45, 13:30 and 16:30. School ends at 15:30 on Friday. An on delay ensures that the bell rings for only 2 seconds. Components used

 

－LOGO！ 230R

 

- advantages and characteristics of Q1 electric bell

 

Compared with the traditional scheme, fewer components are required.

 

The bell system is easy to expand, such as turning off the bell during holidays. Used to disconnect a group of three-phase similar loads. There must be two-phase operation in three phases at the same time. In order to ensure the same loss of three-phase load, the three-phase must be turned on and off in turn.

 

Each phase load has an interrupt output, which is related to group interrupts. once a phase load shows fault, it will be turned off and the other two-phase loads will be put into operation. The continuous capacity utilization process of load is as follows. Loads 1 and 2 run first (Q1 and Q2), then loads 2 and 3 (Q2 and Q3), and then loads 1 and 3 (Q1 and Q3). This process is repeated continuously (starting from Q1 and Q2). The load runs according to the set time (e.g. 3 seconds). This process is initiated by a reverse self-locking relay. In the case of voltage recovery, the system also starts independently (initial state).

 

If load 1 fails, it will be turned off by interrupt input I1, and the third phase load is put into operation. The fault is displayed by group interrupt in Q4. When the fault is solved and the confirmation button of I4 is pressed, the logo! When it returns to the initial state, the whole process starts from the operation of Q1 and Q2 again.

 

The same applies to loads 2 and 3 (the fault signal of load 2 is I2 and the fault signal of load 3 is I3). Components used

 

-LOGO！ 230R

 

-I1 interrupt input of load 1 (no contact)

 

-I2 interrupt input of load 2 (no contact)

 

-I3 interrupt input of load 3 (no contact)

 

-I4 interrupt confirmation button (no contact)

 

-Q1 load 1

 

-Q2 load 2

 

-Q3 load 3

 

-Q4 group interrupt output

 

Advantages and characteristics

 

The scheme can be used under any load.

 

The running time of the load can be changed as needed.

 

The application range is easy to expand, such as connecting or cutting off the load through a main switch.

 

Compared with the traditional scheme, less components are required.