0 Introduction

Vertical injection molding machine is more and more extensive application at the same time, the safety in production has become an important factor of essential. This is not only the requirements for operators, hardware indicators of vertical injection molding machine is also a test. At the request of the production efficiency and safety production, people pay more and more attention.

1 safety standards

GB22530-2008 rubber and plastic injection molding machine "safety requirements" safe production of vertical injection molding machine is provided more detailed.

Die area machine dangerous are the following:

(1) dangerous mold caused by type III: protection of risk to prevent the human into the mold clamping device region generated operating side. If necessary, can be used for the prevention of fixed protection device and fixed protection device does not need the device and type III protective interlock.

(2) protection device can not start the machine cycle, for the protection of human can not enter the mold or die area and the area between door device, can be used with interlock protection device two position switch, alternative III type protection device.

When the movable protective device is opened, the two position switch should be cut off the mold closing action of the main drive, and close the mold closing action of accumulator.

In order to meet the above requirements, should use the hardware circuit composed of electrical - mechanical. When the movable protective device back to the closed position, should be manually reset to not start circulating on the operating side.

(3) the danger caused by the mechanical movement die area

These two protective device is used for preventing the risk of other specified motion may cause. For these sports, protective device should play the role of type II protection device.

When the protective device is opened:

Cyclic interrupt, if can prevent the melt overflow and nozzle touch force will not cause danger, plasticizing can proceed;

Stop screw and plunger forward movement;

Stop injection base station forward movement;

Dangerous action of rubber injection molding machine must stop ejection or core pulling and driving mechanism.

When the protective device die area is open, injection molding machine can be installed lock switch, in order to be able to manually control the ejector and core pulling motion. Using the manual control device, the use of two hand control device or use limited motion control device, and meet the corresponding requirements (manufacturer shall declare, if mould, core pulling and pushing out and its driving mechanism is designed not to enter the area, crushing or shearing operator allows only then use this switch).

2 the existing control scheme and deficiencies

GB22530-2008 of vertical injection molding machine safety production safety based on the above terms, have more stringent requirements on the design of safety circuit. These security risks can be through the PLC software and the electric circuit to improve the protection of this series, joining in the I/O module is more intuitive and insurance measures.

Current practice is between I/O module and device access safety relay, with the help of external electrical components to ensure the safety of the operation. Before equipment signals into the I/O module, filter out some potential safety problems, to play the role of double insurance. The main goal is to protect the mechanical operation personnel exposed to different grades of danger.

Here is the safety relay mentioned by a number of relays and circuit combination, in order to complement each other to correct abnormal defects, and low malfunction relays complete function, make mistakes and failure value is low, the safety factor is higher, therefore need to design a variety of safety relays to protect the different grade of machinery. The so-called "safety relay" is not "no fault relay", make a rule action but when faults occur, it has forced guide contact structure, can ensure safe also in case of contact phenomena, this with completely different general relay.

When an emergency stop is removed, the machine can not appear suddenly restart. In the event of a malfunction of the machine safety circuit, can stop the machine power supply. Failure safety circuit, the machine can not start again. How to do safety circuit? Whether double circuit can it?

Double is necessary, but in addition, must have the following several conditions: check each double circuit; confirm that all the safety circuit is disconnected at one time; when necessary by the operation can start conditions. From another perspective, the input switch wiring short circuit or electric wire sheath damage caused by ground, must prevent the resulting machine suddenly start.

The 3 requirement analysis

Requirement 1: front gate, before the safety threshold and the reset signal output 1 effective, upper computer can control the mould adjusting forward and mode lock forward, shoot forward, plastic injection, melt 5 signal, otherwise the 5 signal output disable.

If the reset signal 1 first before effective, safety door and before the safety threshold of signal effectively, the output is also prohibited swap mode forward, locking forward, shoot forward, plastic injection, melt 5 signals.

Requirement 2: after the safety door, safety threshold and the reset signal after 1 DI corresponding effective, upper computer can control the motor start signal (relay MST output), otherwise prohibited MST signal output.

If a reset signal is 1 effective after the first, safety door and safety limit signal effectively, also prohibited the export of motor start signal.

Requirement 3: emergency stop signal and reset signal of 2 corresponding to the 2 DI input valid, upper computer can control the motor start signal (relay MST output), otherwise prohibited MST signal output.

If a reset signal is 2 and the first effective, emergency stop signal effectively, also prohibited the export of motor start signal.

Requirement 4: safety pedal signal and reset signal of 2 corresponding to the 2 DI input valid, upper computer can control the motor start signal (relay MST output), otherwise prohibited MST signal output.

If the reset signal 2 first effective, safety pedal signal after effective, also prohibited the export of motor start signal.