Arduino XY Plotter Drawing Robot: Build & Program Tutorial

This video demonstrates how to determine the Denavit-Hartenberg (DH) parameters for a SCARA robot manipulator, which consists of three rotational joints and one translational joint. The DH parameters include: theta (rotation angle about the z-axis to align x-axes), d (distance along the z-axis between origins), a (distance along the x-axis between origins), and alpha (rotation angle about the x-axis to align z-axes). For the SCARA robot shown, the parameters are calculated as follows: theta₁ = 30°, d₁ = l₁, a₁ = l₂, alpha₁ = 0°; theta₂ = 0°, d₂ = 0, a₂ = l₃, alpha₂ = 180°; theta₃ = 0°, d₃ = 0, a₃ = 0, alpha₃ = 0. The final DH matrix is constructed by substituting these values into the general DH matrix formula and multiplying the individual transformation matrices in sequence to obtain the global transformation from the base frame to the end effector.

The Denavit-Hartenberg method provides an industry-standard shortcut for computing homogeneous transformation matrices in robotics. Unlike the direct method of separately finding rotation matrices and displacement vectors, this approach obscures the underlying meaning but offers computational efficiency. The method requires three essential steps: (1) drawing the kinematic diagram with frames assigned according to D-H rules, (2) creating a parameter table with four columns (theta, alpha, R, D) and rows equal to frames minus one, and (3) using this table to compute transformation matrices. The four parameters—theta (rotation around z(n-1) to align x-axes), alpha (rotation around x(n) to align z-axes), R (distance between centers along x(n)), and D (distance between centers along z(n-1))—systematically capture both rotational and translational relationships between consecutive frames.

Polar 3D printers use a rotating build platform instead of stationary axes, employing r (radius), theta (angle), and z (height) coordinates rather than traditional Cartesian x, y, z. The Sculpto 2 Pro exemplifies this design, where the r value controls distance from the center point and theta describes angular position. This system holds all motion components within a fixed envelope, preventing size changes during printing. The printer features an authentic E3D hot end with holographic authenticity verification and a removable flexible build plate for easy part release without scrapers.

The Denavit-Hartenberg (DH) representation is a systematic method for describing the position and orientation of robotic joints using four parameters: a_i-1 (link length, distance between joint axes along the common perpendicular), alpha_i-1 (link twist, angle between joint axes about the common perpendicular), d_i (link offset, distance between origins along the previous joint axis), and theta_i (joint angle, rotation about the current joint axis). For prismatic joints, d_i is non-zero while theta_i is zero; for revolute joints, theta_i is non-zero while d_i is zero. These four parameters are organized into a DH table, which enables the calculation of transformation matrices that describe the spatial relationship between consecutive frames in a robotic manipulator.

Robot kinematics studies how robots move using joints (rotating parts like hips, knees, feet) and links (rigid connecting parts like thighs and feet). Forward kinematics tells each servo where to move, resulting in predictable foot positions but becoming impractical for complex movements. Inverse kinematics reverses this: specify desired foot position, then calculate required joint angles. A right-handed coordinate system is standard for robotics, with x-axis forward, z-axis up, and y-axis left when viewed from behind. Angles can be calculated in radians (Arduino default, full rotation = 2π) or converted to degrees for easier visualization. Three mathematical operations suffice for inverse kinematics: calculating angles from single lines using arctan, solving right triangles with known sides, and calculating any triangle's angles when all three sides are known.

Adding an encoder to a stepper motor system enables closed-loop control, providing two key benefits: stall detection (which immediately notifies the user when a motor stall occurs) and stall prevention (which dynamically adjusts motor current and speed to maintain torque and prevent stalling), thereby eliminating the uncertainty of whether the motor reached its target position and enabling advanced control schemes like torque-limited velocity and position control.

Closed-loop position control compares actual rotor position (from encoder) against a setpoint to compute error. Maximum torque requires 90-degree phase advance relative to rotor position, implemented as +12 or -12 steps in the 48-value array. SPI-based encoder reading eliminates PWM noise, providing stable position tracking. The control algorithm maps encoder values to electronic shaft positions, applies proportional torque based on error magnitude, and includes experimental offset compensation for mechanical misalignment. This enables precise motor positioning with minimal vibration.

This comprehensive segment explains the implementation of closed-loop motor systems with encoder feedback and demonstrates complete CNC system operation. Closed-loop stepper motors incorporate encoders on their shafts that provide feedback confirming actual rotation matches commanded output, ensuring precise positioning. The system uses three closed-loop drivers powered by 60-volt supplies and one open-loop driver powered by 48 volts for the Z-axis. Encoder cables require shielding and should be separated from motor cables to prevent electromagnetic interference. The video demonstrates soldering encoder connectors to panel-mounted receptacles using the wire combing technique for organized cable routing. Each encoder connector requires careful alignment with matching notches and secure fastening to prevent disconnection during operation. The final assembly includes preparing and soldering 50 feet of motor cable and encoder cable with heat shrink tubing protecting soldered sections. Dip switches on each driver control microstepping and current settings, requiring adjustment based on specific motor requirements. Voltage testing verifies power supply outputs before powering on the complete system. The demonstration shows jogging axes using keyboard arrow keys with audible motor operation confirming successful movement. Output signals are configured through Mach3 Ports and Pins settings, assigning outputs to specific ports and pins with active-low configuration. One relay controls both spindle directions while another controls both flood and mist functions simultaneously. Input capabilities include limit switches, home switches, and e-stops connected through dedicated input connectors. Ground connectors are essential for completing all electrical circuits. Analog voltage inputs (0-10V) enable PWM-controlled spindle speed adjustment.

A closed-loop stepper motor includes an encoder mounted on the back of the motor, connected via an extra cable. This encoder enables bidirectional communication between the motor and controller, allowing the motor to report its position and status. When the motor cannot move as commanded or misses steps, it can signal the controller about the problem.

Advanced builds require scaling blocks in multiple axes simultaneously. A block can be scaled inward, then downward, then outward in a sequence. This multi-axis scaling creates complex shapes from simple rectangular blocks and is essential for creating detailed mechanical components.

This segment explores the critical relationship between scaling and mechanical system functionality. The presenter explains that scaling 3D printer designs requires careful consideration of all axes simultaneously, as scaling the Z-axis differently from X and Y can cause component misalignment. The distance between angled components may become too large or too small, and glide axes may become too short, preventing proper compensation. The segment demonstrates how original parts must be scaled proportionally to maintain functional geometry, and how improper scaling creates mechanical problems that cannot be easily corrected.

Modular manufacturing equipment allows manufacturers to extend functionality through interchangeable modules without redesigning the entire product. The Snapmaker 2.0 demonstrates this by offering a base unit that transforms into different machines (3D printer, laser engraver, CNC mill) through module additions. The rotation module extends laser and CNC functions by adding a fourth axis, enabling complete figure creation through circular laser cutting or multi-axis milling. CNC milling requires systematic setup including freeing the CNC plate, mounting with four screws, connecting via combo plug, and performing coordinate calibration (X1, X2, Y, Z, B-axis). The B-axis defines rotation reference points for materials with seams. The machine uses standard vice clamps for material securing. Software provides step-by-step guidance, and automatic WiFi updates ensure the machine remains current. This systematic approach ensures accurate and safe operation while providing users with flexibility and manufacturer adaptability.

After adding a primitive shape, users can scale it to approximate size using the scale tool, then position it precisely using the move tool. Multiple primitives can be added and positioned to create completely original designs by combining and modifying existing parts.

A universal CNC machine frame can be constructed using MDF board, 8mm linear rods, stepper motors, linear bearings, lead screws, and couplers, creating a versatile platform that can be adapted into various machines such as a laser cutter, 3D printer, PCB milling machine, or pen plotter by modifying the tool and software components.