3D Printer Design and Build

CoreXY is a motion system where both XY motors work together for every move. Moving X: motor A forward + motor B backward. Moving Y: motor A forward + motor B forward. Moving diagonal: only one motor runs. This eliminates the moving heavy motor common in bed-slinger printers (Ender 3 style), reducing moving mass — enabling faster, cleaner prints. Mathematically: motor_A = X + Y, motor_B = X - Y. Implementation: belts form a unique crossed path with idlers at specific positions.

Design in Fusion 360 using standard extrusion lengths (200, 250, 300, 350mm — minimizes cuts). Key dimensions: bed size = print volume target × 1.3 for frame. Z-height: print volume + 150mm for gantry. Use corner cubes and L-brackets for all joints — critical for squareness. Frame squareness: measure diagonals with tape measure, tighten corner brackets until diagonals are equal within 0.5mm. Square frame is essential for accurate first layer.

MGN12H rails for XY: rails mounted on X beam and Y axis. Carriage moves on hardened steel balls — much more rigid and accurate than V-wheels. Rail parallelism: both Y rails must be parallel within 0.1mm — use a precision jig or DFM spacing method (print test blocks). Belt tension: equal tension on both A and B belts is critical for correct CoreXY kinematics. Gates 2GT belt: tension to ~110Hz when plucked (measure with phone app).

Klipper runs the motion planning on Raspberry Pi (ARM) and sends step/direction pulses to the MCU. This enables complex computations impossible on ATmega328. Configure printer.cfg: set stepper positions, motor currents, thermistor types, PID values for heaters. Calibrate: rotation distance (steps/mm), e-steps (extruder calibration), Z offset (nozzle-to-bed distance). Klipper enables: resonance compensation, pressure advance, exclude objects, firmware retraction, and mesh bed leveling.

At high speeds, printer vibrations cause ringing artifacts (waves or ghosting in prints). Input shaping measures and compensates for resonances. Mount ADXL345 on print head. Run TEST_RESONANCES command in Klipper. Python script generates frequency spectrum, identifies resonance peaks (typically 20–80Hz). Configure input shaper type (MZV, ZV, EI, 2HUMP_EI) and frequency. Result: print at 200–300mm/s with clean quality vs 50–80mm/s without shaping.

Manual tramming: adjust 4 bed screws until all corners are equal distance from nozzle (paper method: slight drag). Automatic mesh leveling: PROBE_ACCURACY test (probe 5× at same point, std dev < 0.01mm indicates good probe repeatability). BED_MESH_CALIBRATE samples 5×5 or 7×7 grid, stores height map. Applied during print to compensate for bed warp. Critical calibration: Z offset (live adjust during first print layer) — correct first layer is foundation of print quality.

Pressure advance (PA) compensates for filament pressure lag in bowden/direct drive. At corner: nozzle must decelerate before corner, then accelerate — without PA, corners have blobs. Print a calibration pattern: tower with varying PA values printed along height. Examine: find where corners are sharpest without gaps on straight sections. Set PRESSURE_ADVANCE=0.035 (typical for direct drive). Klipper computes smooth velocity profile incorporating PA automatically.