A 4-DOF desktop robot arm on the proven EEZYbotARM Mk2 kinematic topology: a four-bar parallel linkage keeps the forearm level as the shoulder swings, so the geometry does the work three servos otherwise couldn't.
A mechanism checked joint by joint
Yaw rotates the whole arm on a printed slewing ring; shoulder and elbow servos sit low in a bracket and drive the linkage; a geared two-jaw gripper opens and closes on an SG90. Every joint was swept through its range and checked for collisions, and every servo is captured on a real bearing wall — the flange bears on solid printed material, not a friction fit.
Real components, honest power
The Feather ESP32-S3 and PCA9685 are modeled from genuine vendor CAD; the servos, BMS, buck and battery holder from measured or datasheet-built parts. The power chain is sized for what three MG996Rs actually draw: a 4S 18650 pack → BMS → an 8 A UBEC for the 5 V servo rail, with the logic fed separately.
What's in the pack
Print-ready STL for all 14 printed parts, editable STEP for each, a wired BOM with real parts, an assembly guide covering the linkage and the slewing-ring build, six renders, and a self-contained interactive 3D viewer.