A Year On A
Lead Strip Line.
One gauge, four lanes, 157,420 scans. Part of the year ran under closed-loop control and part ran under manual operation, which makes this the comparison you almost never get: the same line, the same year, the same specification window, with and without the loop.
One Scan In Eight,
Or One In Three.
Every scan of the year, split by control mode and plotted against the same 0.700 to 0.760 mm window. Both curves are shown together first. Isolate either one and note what does not move: the target. Both modes aimed at the same place. What changes is the spread.
Curves are the normal fits published with the original figures. In-specification percentages are the measured values from the scan data, not read off the curves.
The means land 1.6 microns apart, 0.7488 mm against 0.7472 mm. The standard deviations land 0.0132 mm against 0.0290 mm, a spread 2.2 times tighter with the loop closed. Against a 60 micron window, a 29 micron standard deviation simply does not fit, and a third of manual production fell outside as a result.
Tighter Control Buys You Room To Move.
Both modes aimed high, well above the product nominal. Under manual control that made sense as insurance against running thin. With the spread cut in half, that insurance is no longer needed, and the target can come down. Drag it and see.
Modelled, holding the standard deviation at the measured 0.0132 mm and assuming a normal distribution. The modelled figure at the actual target reads lower than the measured 88.2% because real production is not perfectly normal. Treat the direction as the finding, not the decimal.
The Operators Voted.
Nobody was told to use the loop. Scan volume by month shows manual operation carrying the line through the spring, then the balance flipping. By the second half of the year closed loop was running almost everything.
Monthly values read from the published figure. Annual totals are exact.
All Heavy. All Manual.
The year had three major out-of-spec events. Each ran heavy, each peaked more than 100 microns above the 0.760 mm limit, and each happened under manual control. Pick one.
The Advantage Of Records
The gauge measured through all three events regardless of mode. Roughly 800 scans across the three windows, logged continuously, means every excursion is profiled from ramp to recovery whether or not the loop was on.
One Excursion, Priced.
This is the late shift of 14 February, scan by scan, straight out of the results file. 253 scans, one every nine seconds, 37 minutes of production. The gauge was recording in manual mode throughout, so nothing corrected the drift.
Two things cost money here, and they are different things. Strip above the target line is lead bought and not sold. Strip outside the specification window has to come back and be remelted. Drag through the window and both add up.
And Then The Part Nobody Invoices
The figures above are lead and remelt charges only. On top of them sits the furnace time to put three tonnes back through, the handling to pull and stage the coil, the line availability lost while it happens, and the scheduling knock-on for everything queued behind it. Those are real and they are not small, but they are not in the results file, so no number is put on them here.
Every figure is measured. Target 0.730 mm with a 0.700 to 0.760 mm window, taken from the product record in the file. 253 scans at a nine second interval, 218 of them outside the window, peak 0.877 mm. Line basis 333.8 mm of strip across four lanes at 30.48 m/min with lead at 11.34 g/cm³, which is 5,053 kg an hour. Lead is held at $2.40 per kg and remelt at $0.15 per kg throughout. One caveat: there is a 21 minute gap in the middle of this window. It is treated here as the line being stopped, which is the conservative reading. If the line was running and the gauge was not recording, every figure below is roughly 60% higher.
A thousand dollars in thirty-seven minutes is not what sinks a plant. What matters is that this happened 123 times in February and March alone, every one of them under manual control, and that nobody knew the cost of any of them until the gauge was logging every nine seconds.
The Gauge Moved Less Than The Process Does.
A year-long comparison is only meaningful if the instrument held still. The gauge tracks its own probe separation, the measured distance between the upper and lower sensors that every thickness calculation depends on.
Under a micron of drift on the annual mean, across 169 production days. The C-frame carrying the sensors moved less over twelve months than the process moves between two consecutive scans.
Eighteen Months, 673,640 Scans.
Different plant · A North American battery manufacturerThe South African year answers whether the loop helps. A separate reference site in the United States answers the question that comes next, which is whether any of this is still running in eighteen months on a casting floor.
One gauge, one installation, a scan roughly every sixteen seconds of active production, and 99.4% of those scans produced a valid measurement. The recipe nominal did not move all year, which is what makes the trend readable at all.
They Run Thin On Purpose
Here is the year in one chart. The mean does not sit in the middle of the band. It sits 1.5 standard deviations off the lower limit and 3.8 off the upper one, which means every bit of the risk is on the thin side and there is nearly four sigma of unused headroom above. Nobody lands there by accident.
Specification limits read from the plotted positions on the source chart, whose legend rounds them to three decimals. The standard deviation and mean used here are the values that reproduce the reported Cp of 0.88 and Cpk of 0.51 exactly; the report itself rounds them to 0.0004 in and 0.0249 in.
1.32% Off Every Coil.
What Would Yours Be?
Lead is bought by weight, so a percentage off the thickness is a percentage off the lead bill. How far you can move your target depends on your own spread, your own spec window and your own line speed. The estimator shows the math it used, so you can check every number.
No sign-up. Runs in your browser.
Why The Cpk Is Low, And Why That Is A Choice
A Cpk of 0.51 looks like a process out of control. It is not. Cp is 0.88, so the spread would nearly fit if it were centred. The 0.51 is the price of sitting deliberately close to the lower limit in order to keep that 1.32%. Drag the mean to the centre of the band and watch both numbers move, because they move in opposite directions.
Cp and Cpk as reported for the 2025 window. The slider interpolates Cpk toward Cp as the mean is centred, which is what the two numbers become at perfect centre. Cp is the ceiling this spread allows, and 1.33 is the figure most quality systems ask for. No equipment change is modelled.
Centring buys 0.37 of Cpk and costs 1.92% of the lead on every coil, and it still lands short of 1.33. That is the trade in front of the plant, and it is only visible because something has been measuring every sixteen seconds for eighteen months. A gauge does not make strip thinner. It makes running thin survivable.
What This Does Not Prove.
This is production data, not a designed experiment. Operators chose when to engage the loop, and because adoption grew through the year, the comparison between modes partly overlaps a comparison of early 2022 against late 2022.
Two product nominals, 0.730 mm and 0.750 mm, share a single specification window, so the in-specification percentages blend both products. The closed-loop mean of 0.7488 mm sits close to the 0.760 mm upper limit, which is where most of the remaining out-of-spec fraction lives. An 88.2% in-specification rate is a large improvement, not a finished process.
The clustering of all three excursions in manual operation is consistent with the value of closed-loop control without being controlled proof of it.
This window also covers the period when the system was being commissioned, tuned, and integrated. Unusual events and production mistakes were more likely during that time, and the specification window may have been set incorrectly on some days. Parts of it may not represent an established line in either mode.
What it does establish: the gauge held its reference within a micron on the annual mean across 169 days, and on the same line against the same window, closed-loop operation ran 2.2 times tighter and converted that into 23 more percentage points of in-specification production.
Same line, same year, same window. One scan in eight out of specification with the loop closed. One in three without it.
Ask About A Report For Your Line →A Year On A
Lead Strip Line.
One gauge, four lanes, 157,420 scans. Part of the year ran under closed-loop control and part ran under manual operation, which makes this the comparison you almost never get: the same line, the same year, the same specification window, with and without the loop.
One Scan In Eight,
Or One In Three.
Every scan of the year, split by control mode and plotted against the same 0.700 to 0.760 mm window. Both curves are shown together first. Isolate either one and note what does not move: the target. Both modes aimed at the same place. What changes is the spread.
Curves are the normal fits published with the original figures. In-specification percentages are the measured values from the scan data, not read off the curves.
The means land 1.6 microns apart, 0.7488 mm against 0.7472 mm. The standard deviations land 0.0132 mm against 0.0290 mm, a spread 2.2 times tighter with the loop closed. Against a 60 micron window, a 29 micron standard deviation simply does not fit, and a third of manual production fell outside as a result.
Tighter Control Buys You Room To Move.
Both modes aimed high, well above the product nominal. Under manual control that made sense as insurance against running thin. With the spread cut in half, that insurance is no longer needed, and the target can come down. Drag it and see.
Modelled, holding the standard deviation at the measured 0.0132 mm and assuming a normal distribution. The modelled figure at the actual target reads lower than the measured 88.2% because real production is not perfectly normal. Treat the direction as the finding, not the decimal.
The Operators Voted.
Nobody was told to use the loop. Scan volume by month shows manual operation carrying the line through the spring, then the balance flipping. By the second half of the year closed loop was running almost everything.
Monthly values read from the published figure. Annual totals are exact.
All Heavy. All Manual.
The year had three major out-of-spec events. Each ran heavy, each peaked more than 100 microns above the 0.760 mm limit, and each happened under manual control. Pick one.
The Advantage Of Records
The gauge measured through all three events regardless of mode. Roughly 800 scans across the three windows, logged continuously, means every excursion is profiled from ramp to recovery whether or not the loop was on.
One Excursion, Priced.
This is the late shift of 14 February, scan by scan, straight out of the results file. 253 scans, one every nine seconds, 37 minutes of production. The gauge was recording in manual mode throughout, so nothing corrected the drift.
Two things cost money here, and they are different things. Strip above the target line is lead bought and not sold. Strip outside the specification window has to come back and be remelted. Drag through the window and both add up.
And Then The Part Nobody Invoices
The figures above are lead and remelt charges only. On top of them sits the furnace time to put three tonnes back through, the handling to pull and stage the coil, the line availability lost while it happens, and the scheduling knock-on for everything queued behind it. Those are real and they are not small, but they are not in the results file, so no number is put on them here.
Every figure is measured. Target 0.730 mm with a 0.700 to 0.760 mm window, taken from the product record in the file. 253 scans at a nine second interval, 218 of them outside the window, peak 0.877 mm. Line basis 333.8 mm of strip across four lanes at 30.48 m/min with lead at 11.34 g/cm³, which is 5,053 kg an hour. Lead is held at $2.40 per kg and remelt at $0.15 per kg throughout. One caveat: there is a 21 minute gap in the middle of this window. It is treated here as the line being stopped, which is the conservative reading. If the line was running and the gauge was not recording, every figure below is roughly 60% higher.
A thousand dollars in thirty-seven minutes is not what sinks a plant. What matters is that this happened 123 times in February and March alone, every one of them under manual control, and that nobody knew the cost of any of them until the gauge was logging every nine seconds.
The Gauge Moved Less Than The Process Does.
A year-long comparison is only meaningful if the instrument held still. The gauge tracks its own probe separation, the measured distance between the upper and lower sensors that every thickness calculation depends on.
Under a micron of drift on the annual mean, across 169 production days. The C-frame carrying the sensors moved less over twelve months than the process moves between two consecutive scans.
Eighteen Months, 673,640 Scans.
Different plant · A North American battery manufacturerThe South African year answers whether the loop helps. A separate reference site in the United States answers the question that comes next, which is whether any of this is still running in eighteen months on a casting floor.
One gauge, one installation, a scan roughly every sixteen seconds of active production, and 99.4% of those scans produced a valid measurement. The recipe nominal did not move all year, which is what makes the trend readable at all.
They Run Thin On Purpose
Here is the year in one chart. The mean does not sit in the middle of the band. It sits 1.5 standard deviations off the lower limit and 3.8 off the upper one, which means every bit of the risk is on the thin side and there is nearly four sigma of unused headroom above. Nobody lands there by accident.
Specification limits read from the plotted positions on the source chart, whose legend rounds them to three decimals. The standard deviation and mean used here are the values that reproduce the reported Cp of 0.88 and Cpk of 0.51 exactly; the report itself rounds them to 0.0004 in and 0.0249 in.
1.32% Off Every Coil.
What Would Yours Be?
Lead is bought by weight, so a percentage off the thickness is a percentage off the lead bill. How far you can move your target depends on your own spread, your own spec window and your own line speed. The estimator shows the math it used, so you can check every number.
No sign-up. Runs in your browser.
Why The Cpk Is Low, And Why That Is A Choice
A Cpk of 0.51 looks like a process out of control. It is not. Cp is 0.88, so the spread would nearly fit if it were centred. The 0.51 is the price of sitting deliberately close to the lower limit in order to keep that 1.32%. Drag the mean to the centre of the band and watch both numbers move, because they move in opposite directions.
Cp and Cpk as reported for the 2025 window. The slider interpolates Cpk toward Cp as the mean is centred, which is what the two numbers become at perfect centre. Cp is the ceiling this spread allows, and 1.33 is the figure most quality systems ask for. No equipment change is modelled.
Centring buys 0.37 of Cpk and costs 1.92% of the lead on every coil, and it still lands short of 1.33. That is the trade in front of the plant, and it is only visible because something has been measuring every sixteen seconds for eighteen months. A gauge does not make strip thinner. It makes running thin survivable.
What This Does Not Prove.
This is production data, not a designed experiment. Operators chose when to engage the loop, and because adoption grew through the year, the comparison between modes partly overlaps a comparison of early 2022 against late 2022.
Two product nominals, 0.730 mm and 0.750 mm, share a single specification window, so the in-specification percentages blend both products. The closed-loop mean of 0.7488 mm sits close to the 0.760 mm upper limit, which is where most of the remaining out-of-spec fraction lives. An 88.2% in-specification rate is a large improvement, not a finished process.
The clustering of all three excursions in manual operation is consistent with the value of closed-loop control without being controlled proof of it.
This window also covers the period when the system was being commissioned, tuned, and integrated. Unusual events and production mistakes were more likely during that time, and the specification window may have been set incorrectly on some days. Parts of it may not represent an established line in either mode.
What it does establish: the gauge held its reference within a micron on the annual mean across 169 days, and on the same line against the same window, closed-loop operation ran 2.2 times tighter and converted that into 23 more percentage points of in-specification production.
Same line, same year, same window. One scan in eight out of specification with the loop closed. One in three without it.
Ask About A Report For Your Line →