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

A cool autumn breeze brushed against his cheek. Ye Bingwen stood in the corridor, gazing at the buildings in the distance. He was silently planning to personally inspect the equipment after returning to the factory in the afternoon, thoroughly checking for any potential vibration hazards and taking precautions against various production risks.

The second class began soon after. This class was taught by Professor Zhao, and the topic of the day was vibration isolation and damping design, which was also the key content to conclude the course.

Professor Zhao's lectures did not adhere to the textbook; he began by citing a real-life cautionary case from a military industrial workshop.

"In a military precision machining workshop, three large punch presses were operating simultaneously. The vibrations generated by the equipment spread out along the foundation and directly interfered with the precision grinding machine next door, causing the spindle deviation of the grinding machine to exceed the standard."

He slowly recounted the whole incident: "At first, the workshop workers all thought that the grinding machine itself was damaged. They contacted the manufacturer multiple times to come and repair it, replacing the bearings, calibrating the spindle, and adjusting various parameters. After half a month of this, the problem still could not be solved."

"In the end, we had no other choice but to ask the school's vibration laboratory to conduct an on-site survey, and that's how we found the root cause of the problem," Professor Zhao said, picking up a piece of chalk and quickly drawing a layout diagram of the workshop equipment on the blackboard. "The operating frequency of the punch press just happened to coincide with the natural frequency of the grinding machine base, which in turn caused a violent resonance phenomenon."

"This malfunction directly scrapped hundreds of thousands of high-precision shaft parts, delayed the delivery time of orders by more than three months, and the workshop manager was dismissed as a result."

Professor Zhao pointed to the diagram and broke down the path of vibration propagation step by step: "The vibration came out from the punch press base, seeped into the concrete floor, and was transmitted along the floor to the grinding machine base, and finally affected the spindle, completely destroying the machining accuracy."

"Everyone must remember that vibration propagation is like water ripples; one point affects the entire area," Professor Zhao solemnly instructed. "When you go into the factory for hands-on practice, if the precision of the equipment inexplicably decreases, don't rush to disassemble and repair it. First, check if there is a source of vibration in the surrounding area."

Professor Zhao then explained in detail the working principle of vibration isolation trenches. When vibration waves propagate in a solid, they are blocked and reflected when they encounter hollow areas. The vibration reduction effect of digging vibration isolation trenches is much better than simply increasing the distance between equipment.

He then cited a real-world example of improvement: "An optical instrument factory dug a ring-shaped vibration isolation trench around the perimeter of its precision workshop. The trench was 40 centimeters deep and 15 centimeters wide, and filled with dry sand. After the renovation, the vibration amplitude in the workshop was reduced to one-tenth of the original level."

"This method is low-cost and quick to take effect," Professor Zhao summarized. "The only drawback is that it damages the appearance of the ground. Many managers only care about the appearance of the factory area and deliberately ignore the hidden dangers of vibration, which is putting the cart before the horse."

Ye Bingwen listened attentively throughout the lesson, filling his notebook with notes. He not only wrote down the theories taught in class but also hand-drew several simplified diagrams of vibration propagation, carefully marking out the frequency conversion formulas and related parameters.

After class, the students gradually left. Ye Bingwen put away his notebook and went straight to the podium.

As Professor Zhao wiped the blackboard, he casually remarked, "The whole class was so quiet today, why didn't anyone ask any questions?"

Ye Bingwen straightened up and began to speak clearly and logically: "Professor Zhao, I listened carefully to the entire case you presented, and it happens to match the production situation in my factory."

He explained the current situation in the factory in a clear and organized manner: "The rated speed of the old milling machine in our factory is 1,400 rpm, which translates to a working frequency of about 23.3 Hz. During the break, I had someone test the equipment. As soon as the milling machine was started, the base of the precision machine tool next to it could be clearly felt to vibrate."

"The newly poured ground is 20 centimeters thick. Roughly estimated, the natural frequency of the ground is about 25 Hz."

Ye Bingwen pointed out the potential crisis: "The values ​​of these two frequencies are very close, and there is a high probability that the workshop floor will experience resonance."

Professor Zhao stopped what he was doing, put down the blackboard eraser, and stared at Ye Bingwen for a long while, his expression full of surprise.

"The frequency value you calculated is accurate," Professor Zhao asked. "This calculation method and the logic behind the parameters are not covered in undergraduate textbooks. Where did you learn them?"

Ye Bingwen answered calmly: "I had previously looked at relevant data on vibration detection in Professor Cai's laboratory, and I figured it out myself by combining case studies."

Professor Zhao did not press further, but nodded, acknowledging his assessment: "Your analysis is correct. The loose bolts are only a superficial problem. The core reason is that the thickness of the new ground is insufficient, and its natural frequency does not match the operating frequency of the equipment. Simply tightening the bolts can only temporarily alleviate the problem; it cannot completely eliminate the hidden danger."

He then offered three practical suggestions for improvement: "First, reinforce all the anchor bolts of the equipment; second, increase the distance between precision machine tools and vibrating equipment; third, dig a vibration isolation trench between the roughing and finishing areas, with a depth of 30 centimeters and a width of 10 centimeters, and fill it with dry sand."

Ye Bingwen frankly revealed his thoughts: "I also thought of the third option during class, but the ground was only recently completed, so it would be a real shame to start excavating."

Professor Zhao smiled and reassured him, "If you want to do things and develop in a down-to-earth manner, don't get bogged down in superficial appearances. Precision machining values ​​vibration control the most. The parts wear and maintenance costs saved by digging this vibration isolation trench far exceed the construction costs. It's definitely worth it."

In the afternoon, Ye Bingwen drove back to the factory and immediately summoned Chen An, Master Li, and Liu Xiaojun. He relayed the resonance case, theoretical knowledge, and rectification suggestions from the class.

The three men immediately divided the work and checked the bolts of the equipment one by one. Sure enough, they found that two bolts on the old milling machine were loose. Master Li picked up a wrench and turned it more than two turns before he could finally fix the bolts securely.

Chen An used an instrument to re-measure the vibration data of the machine tool. After reinforcing the bolts, the vibration amplitude decreased significantly, but there was still slight ground-transmitted vibration.

Ye Bingwen bent down and walked around the precision machine tool along the ground. Then he drew a long line on the brand-new ground, running across the east and west walls, which separated the two work areas.

He stood up and decisively finalized the plan: "Dig a vibration isolation trench here, thirty centimeters deep and ten centimeters wide. We'll start working again when we stop at night, and continue production as usual during the day. It won't delay the order schedule."

Looking at the intact and flat ground, Mr. Li couldn't help but feel a little heartache, but when he thought about how it could completely eliminate the hidden danger of resonance and stabilize the precision of the product, he quickly dispelled his concerns and nodded in agreement.

Ye Bingwen immediately arranged for people to contact the construction workers and borrow cutting equipment. The other party replied that they could start construction the next evening.

The meticulous Chen An took out the workshop floor plan and accurately marked the excavation location, size, and safety distance between the vibration isolation trench and the surrounding equipment.