Liu Li was doing well in the technical department, but she always had her heart set on the group in the workshop—the QC team she had led. Every Tuesday and Thursday evening, as long as they weren't working overtime, the light would be on in the little, unused tool room in the corner of the machining workshop. The place was very simple; old wooden boards were painted black and used as a blackboard, the long bench was crooked, and parts, drawings, and calipers were piled on the workbench. Even the air smelled faintly of machine oil, but every time you entered, you could hear noisy discussions, much more lively than in the office.

Tonight was another activity day. Liu Li put the process drawings for the "hydraulic coupler housing" into a folder, glanced at the wall clock—the work bell had just rung—grabbed her canvas bag, and ran downstairs. Before she even reached the tool shed, she heard Zhang Shulan's loud voice: "If you ask me, it's because the annealing wasn't thorough enough! The internal stress wasn't completely eliminated. No matter how smooth you machine it later, it'll still bend! I bet you it'll be like this next time!"

Liu Li pushed open the door, and the dim yellow light from the incandescent bulbs shone on the room. Seven or eight team members were there. Zhang Shulan stood with her hands on her hips, staring at a bent, thin shaft on the table; Fu Jingchen stood beside her, holding a process card and inspection record in his hand, his brows furrowed; the other young workers surrounded them, chattering noisily.

"The team leader is here!" As soon as Zhang Shulan saw her, she immediately pulled her over. "Take a look at this tough nut to crack! We've been arguing about this for ages!"

This "tough nut to crack" is the shift fork shaft in the gearbox. It's made of 45# steel, thin and long, and requires milling keyways and machining steps. Recently, the scrap rate has been almost 30%. All of them bend after being precision machined and left to rest for a while, making them unusable during assembly.

"How's it going?" Liu Li picked up the shaft, her fingertips brushing against the bending data marked on it, and then took the notebook that Xiao Chen handed her—that was what she required, every piece of scrap had to have the date, operator, and machine number recorded, "data speaks for itself."

“Team leader, look at this data,” Xiao Chen pointed to the notebook, “The curves are irregular, sometimes more, sometimes less, but there are too many that are out of tolerance.”

Fu Jingchen pushed the process card over and pointed to the heat treatment section: "The process says to perform stress-relief annealing after rough turning. I checked the records in the heat treatment workshop, and the furnace temperature and time are correct, there's nothing wrong with them. But Shulan said that maybe they didn't do it properly during operation."

"Standards are rigid, but people are flexible!" Zhang Shulan interjected. "What if the furnace was packed too tightly during loading, causing uneven heating? We didn't even see the scene!"

Liu Li didn't rush to take sides. She listened to everyone's comments first, then flipped through her notebook. Afterward, she walked to the blackboard, picked up the chalk, and drew as she spoke: "Look, everyone, according to the date and operator, when Master Wang and Master Li are on duty, there are fewer defective products; when Master Zhao and Master Sun (another Master Sun) are on duty, there are more defective products—that's the first thing that's not right. And look at the bending direction, most of them bend towards the keyway, that's the second thing."

The moment the table and arrows were drawn on the blackboard, the previously chaotic discussion suddenly fell silent. Fu Jingchen stared at the blackboard: "Different operators... could stress be introduced during processing?"

"It must have been because too much force was used when milling the keyway!" Zhang Shulan's eyes lit up.

“Then let’s verify it.” Liu Li put down the chalk. “Xiao Chen, tomorrow ask Master Wang and Master Li if they let the shaft rest for a while after rough machining before sending it for heat treatment. Do they have any ‘makeshift methods’? Shulan and Engineer Fu, tomorrow at noon we’ll go to the heat treatment workshop to see how they load the furnace. Also, Engineer Fu, does the materials lab in the technical department have strain gauges? Let’s find a few rough-machined blanks, attach strain gauges, and measure the stress during keyway milling—the data will be the most reliable.”

Once the idea was proposed, no one argued. Xiao Chen patted his chest and said, "I'll make sure to find out!" Fu Jingchen also nodded and said, "I'll borrow the strain gauges, and we can coordinate the measuring instruments as well."

Over the next few days, the team was extremely busy. Xiao Chen kept asking Master Wang for advice and finally learned the old worker's "secret": after rough machining, don't rush to send it for heat treatment. First, loosen the chuck, hang the shaft vertically, and let it rest for half a day to allow the stress to dissipate on its own—this trick wasn't written in the books, but it was old experience.

A visit to the heat treatment workshop revealed a problem: the shift fork shafts were piled up densely, squeezed together during furnace loading, resulting in uneven heating and slow cooling. Although the records showed compliance, the actual effect was far from ideal. The strain gauge data was even more telling: when milling keyways, if the rotation speed was too low, the feed rate too high, or the tool dull, the stress could be 50% higher than the specification value—no wonder it bent!

The cause has been found, and the solution is simple:

1. Add the sentence "After rough machining, hang vertically and let stand for more than 4 hours to release stress" to the process card;

2. When milling keyways, slow down the feed rate, ensure the tool is sharp, and check it regularly;

3. Tell the heat treatment workshop to use supports to separate the shift fork shafts when loading them into the furnace, and not to stack them too densely.

With minimal expense and some operational changes, the scrap rate dropped from 30% to less than 30% in just two weeks! Even the workshop foreman, Zhao Dahai, came to praise them: "Your QC team has truly solved a major problem!"

Later, at the factory's quarterly commendation meeting, the QC team was awarded "Outstanding QC Team," receiving a banner, a new notebook, and a pen from each member. Liu Li stood on the stage to receive the banner, her palms sweating. Zhang Shulan waved vigorously from below the stage, Fu Jingchen nodded with a smile, and even her colleagues from the technical department gave her a thumbs up.

But just as he stepped off the stage, the workshop's loudspeaker suddenly blared, with an urgent voice: "Urgent notice! Heads of the technical department, machine repair workshop, and electrician team, assemble immediately in workshop number three! There is a major equipment malfunction in workshop number three!"

Liu Li's heart skipped a beat—that gantry planer in Workshop No. 3 was specifically used for producing core military components! She and Fu Jingchen exchanged a glance, both panicking. She shoved the banner into Zhang Shulan's hands, saying, "You keep it for now!" and followed Section Chief Chen to Workshop No. 3.

It looks like we're in for another tough battle.