Digital Pulse in Mortise-Tenon Joints: Stepper Motors Reanimate Millennia-Old Dougong

Ying County, Shanxi Report: In the dappled shadows of Yingxian Wooden Pagoda, 73-year-old intangible heritage bearer Li Qingshan sets down his ink marker, gazing at the pulsing 3D model on the control screen. As he presses "confirm," six stepper-driven carving arms descend, sandalwood dust shimmering like gold powder—this dance between modern technology and ancient craftsmanship is granting a new millennium to endangered Liao Dynasty bracket systems.

Guardians of Breathing Timber
"Listen closely," Li murmurs, stroking a newly finished corner bracket set. "Old masters' chiseling coughs, but motor carving breathes steadily." Behind him, stepper-controlled alloy cutters vibrate at 400 cycles/minute, carving 0.12mm-wide mortises into rosewood. This hair-thin precision makes new components interlock seamlessly with eight-century-old timbers.

Rescuing Time's Fractures
Three years ago, structural sensors sounded the alarm: a 2.8mm displacement was found in southwest column brackets. "Like arthritis in an elder's joints," explains heritage architect Wang Zhenyu. "We couldn't replace the bones nor ignore the decay."

Traditional restoration faced dual traps:

• Hand-carving couldn't replicate micron-level ancient joinery

• CNC vibrations risked accelerating wood fatigue

The breakthrough emerged from Tsinghua's architecture lab. Researchers discovered stepper motors' incremental motion mirrored the "three-chisels-two-measurements" tradition—each 0.00015° rotation letting cutters pirouette on brittle timber.

Twin Narratives on Dougong Brackets
The most nerve-wracking repair unfolded beneath sixth-layer eaves:

• 3D scanners detected insect-damaged hidden tenons

• Steppers engaged "termite-boring mode": advancing 3μm then retreating 0.5μm

• Micro-injectors simultaneously infused sandalwood-epoxy resin
  "See these linggong brackets," Li points to microscopic views. "New maple wood grain grows with 800-year-old patterns, even duplicating spring-autumn density variations."

Digital Echoes of Ancient Wisdom
The team digitally archived Li's axe techniques. When demonstrating his signature "wrist-lift axe-sink" method:

• Motion sensors captured 21 joint angles

• Steppers reproduced 0.3-second force curves

• Cutters traced undulating grooves in rosewood
  "It remembers my father's hands," Li fits a new shuatou bracket. "This machine carries three generations of embodied warmth."

As sunset gilds the 72-meter pagoda spire, drones scan the restored structure. On monitors, structural stability graphs stretch straight as dawn—this silent timber revolution lets Yingzao Fashi's wisdom breathe anew in the digital renaissance.