Zhou Jianhua took the circuit diagram of the injection molding machine given by the chief of their supply and marketing department Chen in the Nandu Machine Tool Factory yesterday, and just glanced at it casually, and immediately knew that the design level of this type of injection molding machine circuit was not high.

Why can it be seen at a glance, this is a matter for laymen to see the lively insider's doorway. Zhou Jianhua does not need to carefully check the specific functional details of this circuit, as long as he looks at the way the functional circuits of the various parts of the circuit are connected to each other, he can see a general idea.

In this year, the modular design of various product designs has not been put forward as a design concept, and most designers are accustomed to mixing and matching various functional components whether they are mechanical design or electronic circuit design, and on the surface, the design of the product is simple, compact and practical. This design combination method is indeed an effective and suitable design method when the product structure is relatively simple and the function is relatively simple. But with the advent of more and more complex products with higher and higher automation requirements, this design concept is becoming less and less adaptable.

Injection molding machine is a set of many production processes in one, the production process control is relatively complex production system, its entire production process includes raw material transportation, drying, barrel feeding, process temperature control, injection clamping and the removal of parts, etc., than the previous various machine tools, in the electrical control is much more complicated.

It is the first time for Nandu Machine Tool Factory to design such a complex machine tool circuit, which is far more complex than the circuits of traditional machine tools such as turning, milling, planing, grinding and so on that they have produced for many years.

This stretch is embodied in their circuit diagrams. That is, the entire control system is designed with analog circuits, which makes the circuit of the control system extremely complicated. And because the standard input and output channel interfaces cannot be formed between the functional circuits, each functional circuit relies on the direct introduction of each other's analog signals to form a signal connection. Such a way of signal connection. The stability of the components of the entire circuit system is extremely high, and the temperature drift of each component will be artificially amplified, resulting in the instability of the system.

The design level of this circuit is not high, and another obvious feature is that the design to avoid electromagnetic interference between each other is basically not reflected between the various functional circuits, so the electromagnetic interference between the functional circuits of this complex analog circuit is the inevitable result.

The technicians of Nandu Machine Tool Factory used to design relatively simple circuits, so they would not encounter these problems now, and naturally they had no experience in this area. If this kind of experience is not systematically taught and guided, and you only rely on your own slow exploration, it will definitely not be able to be explored in one or two months.

I remember that a few days ago, at the house of Cai Zhongming, secretary of the Tonglin Commune, Zhou Jianhua unreservedly taught Cai Shang, who is a national defense scientific researcher, so much experience in electromagnetic compatibility, which was the result of his own study, research and summary in the past few decades. Where can these experiences and skills be found by the technicians who work from 9 to 5 all day in state-owned enterprises, but hardly do any scientific research and development? Zhou Jianhua said that it would last in February mainly because he was not in a hurry to wait for this time, in fact. Even if they are given 2 years, they will not be able to figure it out on their own.

Zhou Jianhua carefully inspected the part of the functional circuit that went wrong, and sure enough, there was no problem with the design of that part of the circuit. It is a conventional design, which is decent, and there is no problem with the parameter selection of each component. The cohesion between the various parameters is also not bad.

Zhou Jianhua is now sure that the triode is burned out and broken down every time. It must be that other functional circuits have an impact on this part of the circuit, causing the problem. With the experience and ability of those technicians of Nandu Machine Tool Factory, they will only be limited to finding problems in this damaged circuit part. Of course it's impossible to find it!

Zhou Jianhua carefully searched for a while in other related circuits that have signal feedback and poor shielding with this part of the circuit, and found that there are several places that will affect the damaged transistor, the most important of which is the thyristor in another functional circuit.

Each time the thyristor is turned off, it will instantly form a harmonic signal in the circuit, and this signal will be transmitted to the base of the damaged transistor through a signal line connected to the circuit in question, so that the transistor will instantly generate a large current beyond the rated value and cause the temperature to rise sharply, which will cause the triode to drop its performance parameters even if it does not burn out immediately, which will cause subsequent circuit failures.

Zhou Jianhua found out the problem, thinking, to solve this problem is actually very simple, that is, as long as the connection between these parts of the circuit is slightly modified, for these interference sources to do some shielding measures, but he can not do this, if you do this, you will not be able to use your own "circuit board plug-in", without this "circuit board plug-in", you will not be able to get the knowledge rights and interests you should enjoy in Nandu Machinery Factory.

Zhou Jianhua decided not to modify the original circuit, but only for the original circuit system, in order to protect the triode and design a simple small circuit, the function of this small circuit is to use a relatively low threshold triode to access the line with external interference sources, in each time the interference harmonic generation of the moment to generate a discharge loop, the original interference source of the signal is mostly shunted out, so that the original triode can be protected.

This small circuit is very simple, only an ordinary transistor and a few small resistors and capacitors, and the cost is only five cents. But Zhou Jianhua decided to put a dozen other useless components on this small circuit board, use them to form some dispensable circuits to confuse the other party, and also take the trouble to connect a few more signal lines to connect with other circuits.

In order to protect this circuit from being seen by the other party, Zhou Jianhua decided to use phenolic resin glue to encapsulate this circuit board in its entirety. Zhou Jianhua knows that large machinery factories such as Nandu Machine Tool Factory have metal nondestructive testing equipment, such as ultrasonic testing, magnetic particle testing, gamma ray testing, X-ray machine filming and other equipment.

In order to prevent the other party from forcibly dismantling these pieces of iron and discovering his secret, Zhou Jianhua also deliberately made those pieces of iron into a part of the circuit circuit, and used the mercury in the "thermometer" as a conductor to connect the pieces of iron with the circuit inside to form a circuit. Of course, the identification of all components in this circuit should also be ground off with sandpaper, so that there is a "three insurance" effect. (To be continued......)