78: Bringing his wife and children to Harbin Institute of Technology

After the new machine tool has been broken in and running smoothly.

The first batch of twenty casings were all qualified, and their precision was much higher than that of the old machine tool.

Master Li was in a good mood and hummed a little tune for two days, even swearing less.

The day after Ye Bingwen returned, the accident happened.

When Ye Bingwen arrived at the factory, Master Li was squatting next to the machine tool.

He held a dial indicator in his hand, repeatedly checking the spindle precision.

"What's wrong?"

Ye Bingwen walked over.

Something's not right.

Master Li didn't even look up.

"When I turned it on this morning, the vibration was terrible. I thought it wasn't set up correctly, so I recalibrated it, but it still didn't work."

"Did you try out for the job?"

"I tried it. I made one, and the outer diameter tolerance was off by five microns."

Ye Bingwen frowned.

Five kinds of shredded ingredients.

This level of precision would be considered normal on older machine tools, but it's unacceptable on this C618.

"Let me see."

Master Li handed over the freshly dried workpiece.

Ye Bingwen looked at it over and over again, then went to the worktable and measured it with calipers.

The outer diameter tolerance is 5.5 micrometers, the inner hole tolerance is 4 micrometers, and the flatness is also exceeded.

The surface is not smooth and has vibration marks.

It's in concentric circles, like ripples on water.

"Was it secured tightly when you attached it?"

"It's tightened. I personally oversaw the drying process."

Ye Bingwen squatted down and checked the anchor bolts; they were not loose.

I checked the belt again; it was the right tension.

The spindle makes a normal sound when it rotates, with no abnormal noises.

The problem cannot be found.

"Let's try doing one more."

Master Li reinstalled a blank part, clamped it, aligned the tool, and turned on the machine.

The moment the cutting tool touched the workpiece, Ye Bingwen immediately realized—the sound was off.

It wasn't the uniform cutting sound, but rather a low-frequency humming sound.

"Go in slowly."

Master Li slowed down the speed of his knife cuts.

The vibration was less intense, but it was still there.

The workpiece came off with an outer diameter tolerance of four and a half micrometers.

It's a little better than the previous one, but still not up to standard.

Master Li removed the knife and inspected it. The tip was fine, and the clamping was also fine.

He put the knife back on and did another job.

It's still five-strand shreds.

Master Li took off his gloves and threw them next to the machine tool.

"This is weird."

Master Zhao and Xiao Zhang also gathered around.

Xiao Zhang said.

"Mr. Li, could there be a problem with the bed itself?"

"It's a new bed; I've been adjusting the precision for three days. What problems could there be?"

Master Li said irritably.

"Then why is the work you're doing so badly?"

Mr. Li did not respond.

He squatted next to the machine tool, smoking one cigarette after another.

Ye Bingwen stood to the side, placing the three workpieces he had just finished on the table side by side, and examined them one by one.

The shapes of the vibration patterns are different.

It is not a stable error.

"Mr. Li, what was the spindle speed when you turned on the machine just now?"

"Six hundred."

"Try mentioning 800."

Master Li reinstalled a new part and increased the speed to 800 rpm.

The cutting tool made contact with the workpiece, and the sound was better this time; the vibration was less.

The workpiece comes off with an outer diameter tolerance of three micrometers.

It's close to being up to standard, but it still hasn't reached the level this machine tool should be at.

"Let's mention another thousand."

The rotation speed is 1000 RPM.

This time the sound was much more stable, and the vibrations almost disappeared.

The workpiece came off with an outer diameter tolerance of one and a half millimeters.

It passed.

Master Li held the workpiece up to the light and examined it for a long time before measuring it again.

"600 revolutions isn't enough, 800 will do, and 1000 revolutions is acceptable. What's going on?"

"Does higher RPM mean greater stability?"

Master Zhao muttered to himself from the side.

"Isn't this rebellious?"

Ye Bingwen didn't say anything; he also found it strange.

Generally speaking, machine tools will resonate within a certain speed range; just avoid that range.

However, this machine tool vibrates in the low-speed range, but becomes stable at high speeds.

That's not quite right.

"Try different speeds. 450, 500, 700."

Master Li completed several more tasks and recorded the data:

Four hundred and fifty revolutions, outer diameter tolerance of six micrometers, noticeable vibration.

Five hundred revolutions...one thousand revolutions, outer diameter tolerance of one and a half millimeters, basically no vibration.

The data is there, and the pattern is clear: the higher the rotation speed, the better the accuracy and the less vibration.

"That's not right."

Ye Bingwen said.

Master Li nodded in agreement.

"Most machine tools have an optimal speed range; if the speed is too high, it will vibrate. But this machine is different; the higher it goes, the more stable it becomes."

"Could there be a problem with the spindle bearing?"

"That's what Master Zhao said."

"What could possibly be wrong with the bearings of a new bed?"

Master Li squatted down again and removed the cover plate from the spindle box.

The bearing clearance and lubrication are normal.

He put the spindle box cover back on and dusted off his hands.

"Cannot be found."

Ye Bingwen glanced at the clock on the wall.

It's already noon, and I've only finished a few pieces of scrap all morning.

"Let's eat first. We'll continue the investigation this afternoon."

At lunchtime, Mr. Li sat on the steps at the factory entrance and didn't touch his chopsticks for a long time.

Ye Bingwen squatted down next to him.

"Master Li, don't get angry."

"I'm not feeling hot."

Master Li took a bite of rice.

"I just can't understand it. I've been doing this for over twenty years, and this is the first time I've encountered something like this."

"Can it be fixed?"

"We have to fix it even if we can't. If we can't finish this batch of goods, neither of us will be able to explain ourselves."

In the afternoon, Mr. Li recalibrated the machine tool.

The precision is fine, the spindle is fine, the guide rail is fine, and the lead screw is fine.

I've checked everywhere I can, but I still can't find the reason.

Xiao Zhang said something from the side.

"Could it be a problem with the electricity?"

Master Li glanced at him.

"electricity?"

"Isn't the voltage unstable in Daxing Village? Could it be the same here?"

Mr. Li walked to the distribution box and looked at it. The voltmeter showed 380 volts, which was normal.

"The voltage is not the problem."

Xiao Zhang fell silent.

Ye Bingwen stood next to the machine tool and reviewed the data from the morning again.

600 revolutions won't work, 1000 revolutions will.

This pattern is too strange.

If the machine tool itself is faulty, it should not be able to operate at any speed.

If there's a problem with the electricity, the higher the speed and the greater the load, the worse it should be.

But he saw with his own eyes that the machine tool was indeed stable at 1000 revolutions per minute.

"Mr. Li, have someone from the motor factory come and take a look tomorrow. It might be a problem with the motor."

"Electric motor?"

"The motor for this bed was supplied by the motor manufacturer. If the problem is with the motor, have them replace it."

Master Li thought about it.

"Maybe. If the motor is off-center when it's running, it can self-balance at high speeds, but not at low speeds."

That's exactly the point.

"Then call first thing tomorrow morning."

Ye Bingwen returned to the reception room and dialed the number of the motor factory.

The person who answered the phone was a woman. She said the technical staff had already left work and I should call back tomorrow.

He hung up the phone and stood at the door of the reception room.

Master Li is still in the workshop, but the machine tools have been shut down.

He was holding a flashlight, squatting next to the machine tool, looking at something.

Ye Bingwen walked over.

"Master Li, it's getting dark, let's do it tomorrow."

"Let me take another look."

"What did you figure out?"

Master Li shone his flashlight into the spindle box.

"You're right, it might really be a problem with the motor."