Marlin Bed Leveling: Deterministic Calibration & First-Layer Mesh Engineering

Master Marlin 2.x bed leveling architectures (Unified Bed Leveling UBL, Bilinear ABL, Manual Mesh MBL) to guarantee flawless first-layer adhesion through rigorous G-code phase workflows, probe offset math, and persistent EEPROM compensation.

When to Use This Skill

Activate this skill when:

• Calibrating, tuning, or troubleshooting automatic bed leveling on Marlin 2.x 3D printers (Ender 3, CR-10, Prusa clones, custom CoreXY / Cartesian machines).
• The user asks: "How do I set up UBL in Marlin?", "My printer homes with G28 and ignores the mesh", "Calculate BLTouch Z-probe offset", "Generate G26 validation print G-code", or "Edit warped mesh points with M421".
• Diagnosing first-layer defects: nozzle dragging across PEI sheets, corner detachment, uneven squish, or compensation disabling after homing.
• Sizing slicer start G-code sequences (Cura, PrusaSlicer, OrcaSlicer, Bambu Studio) with thermal soaking and mesh restoration.

Do NOT use this skill when:

• Calibrating Klipper or RepRapFirmware printers (different firmware syntax and mesh compensation systems).
• Fixing gross mechanical skew: loose V-slot rollers, bent Z leadscrews, or wobbly gantry arms (hardware faults cannot be solved by software leveling).
• Delta printer kinematics setup requiring radius and tower endstop adjustments before mesh probing.

Core Mental Models & Non-Negotiable Rules