TL;DR
Scanner calibration drift causes the optimizer to misread log dimensions and reduce lumber value recovery. Run the calibration procedure with a certified target and compare optimizer outputs to measured dimensions.
What you might see
- optimizer solution dimensions not matching sawn lumber measurements
- lumber value recovery declining with no log quality change
- scanner error flags in the optimizer log
- consistent over or undercut in one axis across multiple logs
Likely causes
Laser emitter or receiver thermal drift from temperature changes in the scan zone
Vibration loosening scanner mounting hardware and shifting sensor alignment
Sawdust accumulation on scanner lenses attenuating the signal
Encoder drift on the log carriage giving incorrect length data
Required tools
- USNR calibration target
- Lint-free lens cleaner
- Optimizer software calibration routine access
- Tape measure for reference log hand measurement
Safety first
- LASAR scanners emit Class 3B or 4 laser radiation. Never look into the laser aperture. Use appropriate laser safety eyewear when working near the scan zone.
- Lock out the log carriage and headrig before entering the scan zone for any physical inspection or mounting hardware checks.
Procedure
- 1
Clean all scanner lens windows with a lint-free cloth and approved lens cleaner before starting calibration. Dust attenuation is the most common cause of gradual scan errors.[1]
- 2
Obtain the USNR calibration target for the installed scanner model.
- 3
Place the calibration target at the scan zone center per the calibration procedure in the scanner maintenance manual.
- 4
Run the scanner calibration routine from the optimizer software. The routine measures the known target dimensions and adjusts the offset coefficients.[1]
- 5
After calibration, scan a reference log of known dimensions and compare the optimizer output to hand measurements at three cross-sections.
- 6
If dimension error exceeds 3 mm after calibration, inspect scanner mounting hardware for looseness and re-torque before repeating calibration.
- 7
Log calibration date, target readings, and post-calibration dimension check results in the maintenance record.
Warning: LASAR scanners emit Class 3B or 4 laser light. Never look into the laser aperture or direct the beam at personnel. Follow laser safety procedures for the installed scanner class.
Sources
USNR USNR LASAR scanner & headrig Sawmill Headrig / Optimization System general technical documentation, USNR
Sawmill log scanner calibration and dimension verification, general sawmill optimization system practice (general)
More guides for USNR USNR LASAR scanner & headrig
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How to fix log carriage positioning error on a USNR Sawmill Headrig
Carriage positioning error results in off-dimension lumber and reduced yield. Check the setworks encoder, drive chain, and carriage rail alignment before running a dimension cut test.
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