Lithium Battery
Dual-Sensor Online Thickness Measurement after Lithium Electrode Calendering
A dual-sensor laser triangulation method for online electrode thickness measurement after calendering, covering alignment, synchronized sampling, calibration, and uncertainty control.
Background
Electrode thickness after calendering must be monitored without contacting the moving coated foil. Because the web also moves vertically, a single surface-distance reading cannot represent absolute thickness; synchronized opposed sensors are the preferred arrangement.
Pain Points
- • Vertical web motion directly affects a single-sensor thickness estimate.
- • Unsynchronized or longitudinally offset spots create dynamic measurement error.
- • Reflective foil, dark coating, oil mist, vibration, and frame drift affect stability.
Measurement Solution
Measurement geometry: Install one ST-P laser triangulation sensor above the electrode and one below it. After calibrating the fixed sensor separation L, thickness is calculated as T=L-A-B, where A and B are the upper and lower distance readings.
Synchronization and alignment: Trigger both sensors at the same time and align the spots to the same electrode cross-section. A longitudinal spot offset causes the two channels to sample different material positions on a moving line.
Model selection: Evaluate ST-P30, ST-P50, or ST-P80 from the machine opening, mounting space, and required uncertainty. The verified reference distance, range, repeatability, and linearity error are listed below.
Calibration: Use a rigid frame and calibrate the fixed separation with traceable gauge blocks or reference samples. Check the empty gap, a stationary sample, and a moving sample. Include frame temperature drift, vibration, and web tilt in the uncertainty assessment.
Surface and sampling checks: Validate signal quality on actual positive- and negative-electrode materials. Set the sampling rate from line speed and required spatial resolution; selected standard models support rates up to 160 kHz.
Data integration: Send the raw distance channels and calculated thickness to the PLC, host software, or quality system through Ethernet, RS485, or analog output. Complete correlation and gauge repeatability studies before using the result for closed-loop roll-gap control.
| Model | Reference Distance | Measuring Range | Repeatability | Linearity Error |
|---|---|---|---|---|
| ST-P30 | 30 mm | ±5 mm | 0.15 μm | <±3 μm |
| ST-P50 | 50 mm | ±10 mm | 0.25 μm | <±4 μm |
| ST-P80 | 80 mm | ±15 mm | 0.5 μm | <±6 μm |
Technical Advantages
- • Opposed sensing reduces the effect of common vertical web motion on thickness.
- • Synchronized measurements at the same cross-section support high-speed inspection.
- • Raw distances and calculated thickness can both be retained for calibration and traceability.