The process view of quality professionals: The quality code hidden in the temperature of metals
I. Craftsmanship is never "fabricated"; it is "gained through hands-on experience"
My understanding of craftsmanship began with the first set of process cards for titanium alloy special-shaped brackets that I learned to compile from the chief process engineer twenty years ago. At that time, I had just been transferred from the workshop. Thinking highly of my three-year experience in operating lathes and being able to recite the spindle speeds of all the equipment by heart, I thought that compiling process was simply "writing down the processing steps in words". It wasn't until I got the drawing – there were three deep holes slanted at 15°, with a hole diameter tolerance of ±0.01mm, and the material was difficult-to-machine titanium alloy. I spent three hours poring over the equipment ledger:
- Use a drilling machine? Custom fixtures are required for oblique hole positioning, but there is no five-axis linkage drilling machine in the workshop. Manual alignment will result in a deviation of more than 0.05 mm.
- Use a milling machine? The overhang length of the cutting tool is 8 times the hole diameter. It will "chatter" during rotation, and there will be spiral marks on the hole wall.
- Use the machining center? The four - axis turntable in the workshop just broke down. We have to wait for the spare parts for two weeks.
I was sitting on the steps at the workshop door, staring blankly at the blueprint in my hand. Technician Wang, who had been re - employed after retirement, passed by and tapped the corner of the blueprint. "Kid, is there anything we can borrow from the old processes? Have you forgotten that our factory made aviation parts in the 1980s?" He was referring to the dusty universal angle head in the warehouse - an old tooling from the 1980s that could turn the vertical spindle to any angle.
I grasped it like a drowning man clutching at a straw: Install the angle head on the radial drill, use a discarded grinding wheel as the "guide positioning block", first cut a 15° shallow groove on the end face of the workpiece, and then use a carbide drill for slow feed (50 revolutions per minute). Three days later, the measured hole diameter tolerance of the first prototype was ±0.008mm, which just hit the middle value required by the customer.
When handing in the work, the chief technologist flipped through the process card, nodded and said, "You're on the right track." But his fingertips stopped at the "Deep-hole machining" section. "You used an angle head, but have you tried the sand-embedded guide sleeve? In the old process, brass sleeves were embedded with emery, which can automatically center and are three times more stable than the positioning blocks."
That was an almost lost craft. There was only half a page of records about it in the craft manual from the 1980s. I had to ask the retired Master Li for details, rummage through the tooling drawings from 1983 in the warehouse, and even make the guide sleeve by turning a brass rod myself and then manually embed emery. For seven days, I spent every day in the workshop:
- Late at night, I flipped through the *Handbook of Mechanical Technology* (1985 edition). The pages were tinged with the yellow of an old book, and there were annotations by an old craftsman on the edges.
- Ask Master Li about "how to control the density of the embedded sand". He said, "It's like kneading dough. The sand grains need to be evenly distributed so that the cutter won't get stuck."
- When trying out the tooling fixture, as soon as the guide sleeve was installed on the drill press and the drill rod was inserted, it got "stuck". It turned out that the sand grains were embedded too densely. I used sandpaper to grind off a layer on the surface. Then, when I tried again, the sound of the drill rod's rotation suddenly became "steady", and the iron filings were in a uniform "needle shape".
When I typed the last full stop on the process card, I suddenly understood: technology is never "fabricated in the office". It is felt out by getting close to the temperature of the metal - it is hidden in the experience of old workers, the patterns of old tooling, and even the shape of iron filings. Just as the chief process engineer said, "Do you think technology is new? No, it's old. You just haven't rummaged through the old boxes."
II. The craftsmanship is the root of quality, not the branches and leaves
Later, when I switched to working in quality control, I came to understand a harsh truth: The answers to all quality problems lie in the manufacturing processes.
Many quality engineers like to focus on reports and measure data, but forget that data is the "result" while the process is the "cause". For example, three years ago, we dealt with a complaint about scratches on the motor shaft:
- The production line said, "There was no contact during assembly." The quality department checked the packaging and said, "The foam pad is thick enough." I squatted beside the centerless grinder and watched for half an hour: The rubber layer of the guide wheel was worn unevenly, causing the workpiece to slightly "wobble" when rotating. There were spiral marks of 0.005 mm on the surface of the ground shaft. When assembled, it rubbed against the end cover and became visible scratches to the naked eye. After adjusting the radial clearance of the guide wheel by 0.02 mm and replacing the new rubber layer, the scratches immediately disappeared.
Another example is that the strength of the aluminum alloy brackets did not meet the standards last year.
- Material analysis shows that the composition is qualified, and mechanical tests show that the tensile strength is 10 MPa short. When I checked the process card, I found that the production department skipped the "stress relief annealing" to speed up the progress. There will be micro - cracks inside the aluminum alloy after welding, and these cracks will expand without annealing. After adding back the annealing process at 180°C for 2 hours, the strength just meets the standard.
These problems can be solved not because I "understand FMEA" or "can calculate SPC control limits", but because I "understand the logic of the process".
- The root cause of the scratches is "wear of the grinding machine guide wheel", not "assembly collision".
- The root cause of the strength issue is "skipping the annealing process", not "poor material quality".
Quality is like a tree, and craftsmanship is its root. If the root doesn't go deep enough, the tree will fall even if it grows very tall. If you don't even know "how the parts are ground", how can you find out the reason for "the scratches"? If you don't even understand "annealing after welding", how can you solve the problem of "insufficient strength"?
III. Process engineers are "invisible translators", but their value is hidden in every process
I often say that process engineers are "interpreters between design and production":
- What is designed is an ideal on paper (for example, this hole should have a tolerance of ±0.01mm).
- The process needs to be translated into a language that machines can understand (e.g., using a sand-embedded guide sleeve + slow-feed drilling).
But only those who have worked as interpreters can understand the grievances of an interpreter.
- After the design drawings are completed, others praise, "You're amazing! You've created a new product."
- When it comes to production and shipment, others praise, "You're amazing! You've achieved remarkable results."
- What about the process engineer? They turn the design drawings into 20 processes and adjust 5 sets of tooling. No one pays attention to this process, but when production gets stuck, the first thing people say is There's a problem with the process planning.
- If the design size is changed, the process engineer has to rearrange 15 processes. No one asks, "Are you tired?" But when the size is out of tolerance, the first one to be blamed is "the process calculation was inaccurate."
I used to work as a designer for six months. At that time, I thought "design is the coolest" because it involves creating something new from scratch. However, after working in the field of craftsmanship for ten years, I've come to understand that design is about "giving the world a new look", while craftsmanship is about "bringing that look to life". The bottleneck of design is "being able to conceive", and the bottleneck of craftsmanship is "being able to execute" - you can draw a hole with a diameter of 0.005mm, but can you make a lathe "consistently turn out such a hole"? You can design complex curved surfaces, but can you make a milling machine "move the cutter along the curve of the surface"?
Last year, when recruiting process engineers, I selected a graduate who "could adjust the change gears of a lathe" - not because he could adjust the change gears, but because he "had felt the pulse of the process". Many young people think that "the process has no future" because "the results are invisible", but they don't know that when you turn an "impossible design" into a "manufacturable product", the sense of achievement of "making the machine understand what I say" is more precious than any "visible results".
IV. Quality personnel should "go deep", because the craftsmanship lies in the iron filings in the workshop
Nowadays, many quality engineers are like "Zhao Kuo" – they can recite the VII steps of FMEA and talk about the control limits of SPC, but they don't even know how to adjust the concentricity of a three - jaw chuck; they are also like "Ma Su" – they are eloquent in theoretical discussions but are completely at a loss when they get to the workshop.
I have an engineer under my command. Last time when dealing with the problem of the out-of-tolerance roundness of the bearing sleeve, he spent three days checking the data and then said, "We need to use a roundness measuring instrument for detection." I took him to the workshop and asked him to feel the lathe spindle. The spindle bearing was worn out, and there was a slight "shaking" when it rotated. That's why the roundness of the machined parts was off by 0.02 mm. After replacing the spindle bearing, the roundness immediately met the standard. He stared with wide eyes and said, "It turns out that the problem lies not in detection but in the process."
I often tell them: Quality control personnel should "immerse themselves" - immerse themselves in the iron filings in the workshop, in the roar of the machines, and in the smell of the old workers' cigarettes. You have to know:
- If the cutting speed of the lathe increases by 10%, how much will the thermal deformation increase?
- If the feed rate of the milling machine is 20% slower, how much will the tool marks be reduced?
- If the welding current is 5A larger, how thick of the steel plate will be burned through?
V. All the answers regarding quality lie in the craftsmanship
Yesterday, the customer came to inspect the factory. He saw the note I wrote on the process card: "Increase the flow rate of the cooling pump by 20% in this process to reduce thermal deformation." The customer pointed at the note and said, "Your quality is 'built', not 'inspected'." I smiled and said, "Because our quality control personnel all understand the process."
What is craftsmanship? It is the pattern left by a file in the hands of an old worker, the slight vibration when the machine is running, the lamp in the workshop during a trial run of tooling late at night, and the metallic smell on the fingertips after touching iron filings. What is quality? It is "doing every step right" in craftsmanship and "being a little better than the last time every time".
As quality professionals, our "process view" is actually very simple:
- Immerse yourself and feel the temperature of the craftsmanship.
- Drill in and find the root of quality.
Because - all the answers regarding quality lie in craftsmanship.