Back to the 80s Machinery Factory

Chapter 553 Actually, I had already secretly left a mark

This feeling, almost like being marked wrong on a test by a teacher, made Zhang Nan's ears turn bright red.

But soon, he took a deep breath, forcefully suppressing his embarrassment, and his eyes returned to the paper, looking at it one section at a time.

The original label that read "heat treatment" has now been updated with a clear hardness range and a special note that it should be "grind again after heating, leaving a 0.3mm margin".

For several non-functional dimensions, the tolerances on the drawings were relaxed by a full two levels, clearly taking into account the efficiency and cost of actual processing in the workshop.

Even in a corner of the blank space on the drawing, there was a small, simple diagram of a inspection tool.

But when she turned to the next page, Zhang Nan was stunned.

There was a section of the piston step that he had deliberately tightened the tolerance to prevent leakage of brake fluid under high pressure.

However, the drawing was made two levels more lenient, and a note was left next to it:
"Enough."

Enough?

Zhang Nan stared at those two words, her brows slowly furrowing.

Is this enough?

According to the calculations in class, even a slight leniency here could lead to hidden dangers.

Therefore, he calculated repeatedly before settling on this number.

According to scientific principles, this space is definitely not enough!
hiss……

But then I thought again, that shouldn't be the case!

It's something even a student like him understands; there's no reason why an engineer at a machine factory wouldn't know, let alone make such a basic mistake.

Filled with suspicion, Zhang Nan continued reading.

In the heat treatment section, he originally only wrote "quenching and tempering", but now it has been changed to "quenching and tempering HRC28–32, leave 0.3 margin, then grind after heating".

This one change instantly won Zhang Nan over!

It not only standardizes the hardness range but also specifies the processing sequence, which not only avoids excessive hardness after heat treatment that could affect the life of turning tools but also ensures the dimensional accuracy and surface quality of the parts.

specialized!

But just as he was inwardly praising it, another revision beside him made him hesitate again:

He felt that a certain non-critical hole could be left unprocessed, but Engineer Cao left a mark and even drew a diagram of the inspection tool.

Ok? ? ?
Zhang Nan stared at those lines, feeling like something was wrong with him.

The oddities and the brilliance were intertwined on a single sheet of paper, leaving him both convinced and full of questions.

Could it be that the teacher taught it wrong?
Zhang Nan frowned deeply, then lowered her head and began to study the blueprints...

Beside him, Chen Luyang also gave him a questioning look.

Why does this person's face turn red and white alternately when looking at a blueprint?
Just as Chen Luyang couldn't help but ask if there was a problem with the blueprints,
Zhang Nan suddenly looked up and asked, "Who modified these blueprints?"

“Engineer Cao,” Chen Luyang answered instinctively.

Then, remembering that Zhang Nan didn't know Cao Qinghang, he explained:
"Cao Qinghang is a senior engineer in our factory, the workshop director of the fusion workshop, and the main person in charge of Jinba Automobile."

Oh, oh, oh.

Zhang Nan nodded, but her brows furrowed even more.

Such a brilliant senior engineer would never make ordinary mistakes.

But why did he change it like that?

Zhang Nan scratched his head in frustration, completely disoriented.

That night, Zhang Nan sat in front of the blueprints, not closing his eyes all night.

The next day, after breakfast, he was still absent-minded, and then went to the parts and measured them with a ruler.

On the third day, he finally couldn't hold back and asked Zhang Guoqiang and the other foremen whether the blueprints that Engineer Cao had revised could be used.

When Zhang Nan heard several workers say that it could be done, her pupils dilated.

……

These past few days, Zhang Nan has been like a visible ghost, rooted in front of the lathe, constantly measuring the changes on the drawings.

In the end, Zhang Nan himself didn't feel anything special about the measurements, but Sun Hongjun and the other young people were quite impressed.

"No wonder they were able to get into Peking University..."

"You've researched this little gadget so thoroughly; if it were me, I would have been restless long ago."

Sun Hongjun sat on a small stool peeling potatoes while watching Zhang Nan take measurements, and couldn't help but click his tongue in amazement.

"This isn't research; I think they're going to go mad with it."

Li He answered while chopping pickled vegetables nearby.

“Absolutely, I think he’s gone mad.” Jiao Long clicked his tongue.

"Brother Chen, you're both from Peking University, do you know what's going on with him?"

With no other solution in sight, the three of them turned to Chen Luyang, who was also from Peking University.

Chen Luyang: ...

The key issue is that he's a liberal arts student, so he doesn't understand what engineering students are all about.

He was puzzled.

Just a few blueprints... how did they manage to drive Zhang Nan to such a state of madness?
Shouldn't this be a matter of correcting the mistakes?

Seeing Zhang Nan's furrowed brows and her seemingly lost in thought, Chen Luyang felt that if things continued like this, she would inevitably become obsessed with something she didn't understand.

simply!

Chen Luyang decided to go straight to the second stage!
"Senior brother, before you came back, Uncle Zhang, Uncle Tan, Uncle Liu and I discussed something. See if you can do it."

Zhang Nan asked, "What's up?"

Chen Luyang asked, "Actually, it's a pretty simple thing. It's just that you see if you can leave a few inconspicuous markings without affecting the function of the parts."

Before she could finish speaking, Zhang Nan's expression changed drastically, and her throat tightened!

Why are you suddenly doing this?

Chen Luyang looked at Zhang Nan's reaction with suspicion and told Zhang Nan about the unique parts.

After listening, Zhang Nan's expression gradually relaxed, as if she let out a soft breath.

“This unique approach can be done.”

"If a tiny process feature is added to the inner, non-functional surface of a part after assembly, it will not be easily noticed as long as the dimensional chain and force path are not changed."

He paused for a moment: "But that's not enough. It's best to make it into a 'combination mark' and stack it up for safety."

Chen Luyang became interested: "What are combination marks?"

Zhang Nan said, "Combined hidden marks are three small features buried on the same piece, also called positional hidden marks, process hidden marks, and material hidden marks."

As she spoke, Zhang Nan picked up a universal spark plug from the table and gestured as she explained:

"Take spark plugs as an example."

Zhang Nan lifted the piece and shook it: "Don't be fooled by the spark plug's small size and protrusion outside the cylinder; it's actually the easiest part to mark with a hidden tool."

"The first point is the chamfer at the end of the insulator."

"The conventional design uses a uniform C1 chamfer, which is standardized, easy to process, and convenient to inspect. However, if we make the chamfer an asymmetrical combination of C0.8 and C1.2, and fix the orientation during processing so that C1.2 always corresponds to the reference surface of the metal shell, then this becomes our secret mark."

"After it was installed on the car, the chamfered part was completely covered by the spark plug cap, so it was not visible from the outside."

“Even if it is removed, outsiders will only think it is a normal manufacturing error and will not realize that it is a deliberately left identification point.”

"The second point is the electrode solder joint." "Generally, when factories make spark plugs, they connect the electrode and the core, and finally just light a torch to weld it in one go, leaving a round weld bead. As long as it's firm, it's considered合格 (qualified/acceptable)."

“But we can do something clever at this step. Instead of a large welding package, we can have the workers take an extra step – change it to ‘double spot welding,’ with two small weld points side by side, 0.6 millimeters apart.”

"The function remains completely unchanged, and the electrodes are just as secure, but this is our secret mark."

"Even if outsiders take it apart and study it, they will only think it is a scar left by the worker when welding, and they will never guess that this is the rule."

Chen Luyang's eyes lit up: Brilliant!

Zhang Nan continued, "The third point is the sealing gasket."

“Regular gaskets have a smooth surface, but we can press a shallow 0.2mm ring groove on the back near the inner diameter. It’s completely invisible after installation, but you can tell if it’s from our factory as soon as you open it up.”

"This is a hidden location marker."

He looked up at Chen Luyang.

"These three places stacked together are the 'fingerprint' of our Universal spark plugs."

"Others might be able to get one part right when they copy it, but it's almost impossible to make all three parts the same."

Chen Luyang listened, completely stunned.

When Zhang Guoqiang, Tan Songren, and Liu Kangwen talked about these things, they all frowned, pondered as they talked, and it took them a long time to come up with an idea.

But when it comes to Zhang Nan, it's like he's spilling beans.
Several can be shaken out in one go.

Chen Luyang blinked: "Senior brother, how do you know so much? Is all of this taught in school?"

Zhang Nan laughed and said, "Schools don't teach these things; I figured them out myself."

"I'm the kind of person who always likes to think things through a couple of steps ahead."

"When I went home for winter break, I didn't have a machine tool or any parts with me, so I could only finish half of the drawing. I then turned my attention to how to leave hidden marks."

After a pause, Zhang Nan spoke somewhat awkwardly:
Actually... I already left my mark.

Seeing the shocked look in Chen Luyang's eyes,

Zhang Nan pursed her lips, her voice slightly trembling: "Well... the first drawing I made, wasn't it? The factory made a prototype, right? I was so happy at the time, I felt like it was the first time in my life that I had seen something I drew become a real part."

As she spoke, Zhang Nan looked uncertainly at Chen Luyang's expression, seemingly trying to figure out whether he was happy or unhappy.

After all, it was wrong of him to add things to the parts without Chen Luyang's permission, even though it was harmless.

He originally thought that this matter would be kept secret, but he never expected that Chen Luyang would suddenly ask about it today.

That's why he was startled just now.

Chen Luyang was in a hurry and didn't have time to wait for him to figure it out!

"And then? Where did you put the mark?"

Seeing Zhang Nan struggling to speak, Chen Luyang couldn't help but say:
"...Hey, you've already done it, what are you afraid of? Just say it!"

Zhang Nan was startled by Chen Luyang's eagerness and continued:
Don't artists usually like to leave a little signature in a corner?

"So, I thought, could the parts also have a 'signature'? I secretly added some very small changes to them, which do not affect the function and will not be noticed by others, but as long as it is my drawing, I can recognize it at a glance."

"So I deliberately left a very small curve at some corners, or added a transition line in an inconspicuous place."

"Outsiders would think it's just ordinary craftsmanship marks and no one would care."

"But actually, these are the marks I left for the parts."

Chen Luyang's throat was a little dry: "So, every part in the repair shop has your mark on it?"

Zhang Nan said uncertainly, "If they all produce according to my blueprints, then they should all have them."

Oh crap...

Chen Luyang licked her lips, her eyes gradually brightening.

But he was still puzzled.

"If you already marked them before, why did you need to add fingerprints to the parts during winter break?"

Zhang Nan retorted without hesitation: "That's different."

"That was the first time I drew a blueprint before. Those little curves and transitions I left were, to put it simply, just to leave a memento for myself."

"From a technical point of view, those marks are at most a little 'trick' and have no practical significance."

"Moreover, these kinds of traces are easily overlooked in the workshop."

“If the lathe tool goes down hard, the worker’s finishing technique will be different, and the resulting arc will be different; not to mention that after the parts are assembled on the machine, after running for a year or two, the transition of the edges and corners will have been worn smooth and damaged, and then you won’t be able to recognize anything.”

Zhang Nan sighed, a hint of annoyance in his expression: "Moreover, these small curves and transitions, to put it bluntly, might make people think that the drawings are not rigorous enough or that the processing technology is not up to standard."

“If you look at it from a different perspective, it’s not a ‘signature’ but a ‘flaw’.”

He looked up at Chen Luyang with a serious expression: "That's why I came up with a new way during the winter break to make this mark useful, concealed, and durable, so that it won't disappear due to fluctuations in the manufacturing process or wear and tear."

Before he could finish speaking, Zhang Nan's expression suddenly froze!
Something's wrong...

Why did Chen Luyang's expression suddenly become so distorted and ferocious!
He was perfectly fine just a moment ago, but now his eyes are almost bloodshot.

"Xiao Chen... are you alright?" Zhang Nan subconsciously pointed to his eyes.

"Are you having eye problems?"

Chen Luyang shook her head boldly: "No, I'm fine! I'm just... happy!"

Snapped!
Chen Luyang excitedly slapped Zhang Nan's arm with his big hand, making Zhang Nan wince in pain.

"I'm happy!"

Snapped.

With his other arm, he patted Zhang Nan's other shoulder.

Zhang Nan winced in pain again.

"I'm so happy!!!"

Snapped!
With her arms tightly tucked in, Zhang Nan was threatened into a terrifying hug by Chen Luyang, like a little chick being forced to do so.

"How did I end up with you!"

Chen Luyang gritted her teeth, her face flushed with excitement, pushed Zhang Nan away, and carefully straightened his crooked eye with both hands.

Then, he threw his head back and laughed loudly!
Sun Hongjun was so startled that he dropped the potatoes he was holding.

what happened?

They asked Chen Luyang to persuade Zhang Nan, but before she could do anything, she went crazy herself.

While laughing, Chen Luyang subconsciously raised her hand to rub her eyes.

"Senior! From now on, you can draw these diagrams however you want! Just tell me what the repair shop needs!"

Chen Luyang rubbed his eyes and said in a rough, bold voice.

"I have only one word for you!"

"support."

"My heartfelt support!!!"

……

Under Zhang Nan's shocked gaze, Chen Luyang rubbed his eyes with a laugh and strode towards the door.

The moment the cotton curtain was lifted,

The midday sun poured down, bathing Chen Luyang's imposing figure in its light!
As the curtain closed, Chen Luyang's figure disappeared into the repair shop.

Everyone: ...?
(End of this chapter)