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3.02 Drawing Arm

Front view of the MDA's drawing arm with the drawing pen extended.If you move your hands along the sides of the MDA you’ll encounter the arm supports. Following these supports upwards you’ll come across the drawing arm. The drawing arm is covered by a black plastic cover which features the Thinkable logo on the front. The arm moves from the back to the front of the MDA as needed. This is done automatically, so be careful not to get your hands caught by the MDA as this can result in injury.


Cross section view of the inside of the arm. Timing belt displayed translucent.If you were to remove this cover you’d find an aluminium frame housing two motors. The motor located on the left side of the arm is called the x-motor and is responsible for moving the sketching stylus from left to right. The other motor, which is part of the drawing stylus, is called the pen-motor and moves the drawing pen up and down. On the bottom left of the arm, inside the aluminium frame, you’ll find a mechanical endstop. This endstop is used for homing the pen after the MDA has finished drawing. It also prevents the pen-motor from colliding with the aluminium frame. Inside the aluminium frame you’ll also find several other features: a linear rail, for moving the pen-motor and its assembly from left to right; a cable chain, for housing the wires of the pen-motor without damaging them; two pulleys and a black rubber timing belt, which is attached to the pen assembly and makes the assembly move along the linear rail.


! Be careful when the MDA is sketching because the arm and pen point will move independently and can crush your fingers. !