The sign for the "Export Product Quality Improvement Task Force" was hung overnight at the entrance of a large office vacated next to the factory's conference room. There was no grand opening ceremony, only an invisible, tense atmosphere that quickly gathered.
Liu Li acted swiftly and decisively. On the morning of the day the organization was officially established, she convened the first plenary meeting in this temporary command center. Attendees included her personally selected technical elites (centered around Fu Jingchen), technical directors from each workshop, key personnel from the quality control department, and several experienced and highly respected level-eight workers like Master Wang Jianguo. Zhang Shulan, due to her meticulousness and strong practical skills, was also selected to join the task force to track and record the assembly process.
In the office, the walls were covered with assembly drawings, component drawings, and process flow diagrams of the gearbox. Several tables were pushed together and piled with test data of the first batch of failed samples, gear samples of various materials, and foreign language technical documents.
Standing before the blueprints, Liu Li glanced at each member present and cut to the chase: "Let's skip the formalities. We're all in this together now, with only one goal: to produce a fully qualified export gearbox within the allotted time. Time will be measured in hours."
She didn't waste time boosting morale, getting straight to the point: "The initial inspection failed because of noise and lifespan issues. But the root cause may lie in every step from raw materials to finished product. So, our first step isn't to rush into changing the process, but to 'dissect' it! We need to examine the entire production process from beginning to end, like using a magnifying glass, inch by inch!"
She divided the commando team into three groups:
The first group, Materials and Heat Treatment Group, led by Fu Jingchen, focuses on tracking the fluctuations in the chemical composition of gear steel, forging flow lines, and the most critical heat treatment process—carburized layer depth, hardness gradient, and metallographic structure—to find potential microscopic hazards that may lead to early pitting and wear.
The second group, the Machining and Precision Group, was personally led by Liu Li, with Master Wang Jianguo serving as consultant. They focused on the entire gear machining process. From the precision of hobbing and shaving (or shaping), to the surface finish of the gear teeth, and then to the dimensions and geometric tolerances of every related shaft, hole, and end face, they left no stone unturned in terms of precision deviations that could cause vibration and noise.
The third group, the assembly and cleanliness group, is led by Zhang Shulan and experienced assembly workshop workers. They closely monitor the assembly environment, parts cleaning process, bolt tightening torque, bearing clearance adjustment, and any minor impurities that may be introduced during the assembly process.
“Remember,” Liu Li emphasized, “data must be shared between groups in real time. Any anomaly, no matter how small, must be reported immediately and cross-validated. What we’re looking for may not be a big problem, but rather the ‘resonance’ effect of several small problems accumulating.”
Once the order was given, the entire Red Star Factory seemed like a sophisticated machine, operating at high speed around the assault team.
Fu Jingchen and his team immersed themselves in the heat treatment workshop and the physical and chemical laboratory. They collected steel samples from different batches to compare the differences between imported and domestic materials; they recorded the temperature control curves and carbon potential changes of each heat treatment furnace; they sliced the failed gears and carefully observed their carburized layer and martensite morphology under a microscope to look for evidence of uneven microstructure or excessive residual austenite.
Liu Li and Master Wang dedicated themselves to the machining workshop. They reviewed the precision calibration records of all the machining equipment, personally operated the instruments, and re-inspected the tooth profile error, tooth direction error, and cumulative pitch error of the machined gears. With decades of experience, Master Wang could even discern subtle differences in the cutting sound under different tool wear conditions, guiding younger workers to adjust parameters. They discovered that due to equipment aging, the surface roughness of some gears did indeed fluctuate, and the cylindricity of some shafts was also at the edge of the tolerance zone.
Zhang Shulan's work was equally tedious yet crucial. She led several female workers, strictly adhering to the new assembly and cleaning procedures. They wiped every part with white silk cloths, checked the cleanliness of the cleaning solution, and used torque wrenches to standardize the tightening sequence and torque of each bolt. They discovered that the old assembly practices were indeed arbitrary; the adjustment of bearing preload relied more on the experienced workers' feel, lacking quantifiable standards.
Data flowed like streams into the commando office from all directions. Liu Li stood before the walls covered with data and charts, like a commander facing a battle table, her sharp eyes capturing the connections between various pieces of information.
After several days and nights of continuous work, countless meetings were held, and debates frequently erupted. Fu Jingchen, based on theoretical calculations, believed that heat treatment deformation was the main cause of the decrease in gear meshing accuracy; while Master Wang, based on practical experience, insisted that the precision deviation of the machining itself was an "inherent deficiency," amplifying all subsequent problems. Zhang Shulan provided evidence of the uncertainties in the assembly process.
Liu Li did not blindly trust either side; she demanded that each group provide more detailed supporting data. Finally, after cross-referencing massive amounts of data, two core and interconnected issues emerged:
First, the deformation pattern of gears after heat treatment is unstable and difficult to predict. Gears treated in the same furnace exhibit discrete deformation of their inner bore and end face, which leads to distortion of the positioning reference during subsequent finishing processes (such as gear grinding), making it difficult to correct to the ideal state. This is one of the root causes affecting the final meshing accuracy and is directly related to noise.
Secondly, there is a lack of systematicness and consistency in assembly precision. Key dimensions such as bearing installation clearance and gear shaft axial positioning rely excessively on the personal experience and feel of assembly workers, lacking effective tooling guarantees and quantitative control. This results in fluctuations in the relative positional relationships of core transmission components even for properly machined parts after assembly into an assembly, directly affecting transmission smoothness and lifespan.
The problems were identified, but solving them meant undertaking a major overhaul of the existing, mature but crude processes—a task no less difficult than redesigning a product. However, Liu Li's eyes shone even brighter than before. Having found the bullseye, the remaining task was to mobilize all resources to fire the bullets precisely. The real battle was about to begin.
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