A monitor device of an injection molding machine having a die, which performs injection by moving a screw along an axial direction using a servo motor controlled by a numerical controller having a central processing unit for supplying a clear command and a switching signal, comprising:
- a detector for detecting a screw position, said detector being coupled to the servo motor for generating pulses with rotation of the servo motor;
- an internal die pressure sensor for detecting a pressure in the die and for generating a pressure detection signal indicative of the detected pressure;
- an analog/digital converter, coupled to said internal die pressure sensor, for converting the pressure detection signal from said internal die pressure sensor into a digital pressure signal and for outputting the digital pressure signal;
- a counter, coupled to said detector and the central processing unit, for counting the pulses from said detector, the count of said counter being updated each time a pulse is generated by said detector and cleared when said counter receives the clear command supplied from the central processing unit upon start to injection;
- an address generator, coupled to the central processing unit, for generating an address signal which is sequentially updated in accordance with clock signals, said address generator being cleared upon reception of the clear command and outputting an initial address signal;
- a first memory having a plurality of addresses, said first memory being coupled to said counter for storing the count of said counter at a predetermined point in time, in a corresponding one of the plurality of addresses of said first memory;
- a second memory having a plurality of addresses, said second memory being coupled to said analog/digital converter, for storing the digital pressure signal output by said analog/digital converter at a predetermined pint in time, in a corresponding one of said plurality of addresses of said second memory;
- command means for supplying said central processing unit with a monitor command;
- an address switching circuit arranged to selectively assume one of first and second switching positions, for connecting, at the first switching position, said first and second memories with said central processing unit, and connecting, at the second switching position, said first and second memories with said address generator, said address switching circuit assuming the first switching position in response to the switching signal supplied from said central processing unit upon generation of the monitor command by said command means;
- and
- a display unit, coupled to said first and second memories, for displaying the data stored in said first and second memories, so that during injection the count of said counter indicative of the screw position at predetermined points in time and the digital pressure signal output from said analog/digital converter and indicative of the internal die pressure at predetermined points in time, are respectively stored at corresponding addresses in said first and second memories which are sequentially designated by the output from said address generator supplied through said address switching circuit, the counts and the digital pressure signals stored in said first and second memories at the plurality of points in time during injection are read out in response to the monitor command which controls switching of said address switching circuit by designating the memory address by an output of the central processing unit, and a relationship between the screw position and the internal die pressure is displayed on said display unit.