10. Mechanical Design

ScaraGraph

The initial idea behind the project is to create a drawing machine inspired by the pantograph, a mechanical linkage connected in a manner based on parallelograms so that the movement of one pen, when tracing an image, produces identical movements in a second pen. The mechanical linkage manages the forces and movement of the pen and will be based on the logic used by articulated arm assembly robots, known industrially as SCARA. A two-link arm layout allows for freedom of movement in the X-Y axes with movement restriction in Z axis. To control them, the machine must be operated by a controlling software. Then several motors move, which guide a pen over a paper via an arm construction

The concept

Dream it.

It all begins with an idea. Maybe you want to launch a business. Maybe you want to turn a hobby into something more. Or maybe you have a creative project to share with the world. Whatever it is, the way you tell your story online can make all the difference.

The machine is made mostly of printed parts. To support the arms and the servomotors, the wooden base is designed with perforations to facilitate the assembly of the different pieces and to give the arms stability and precision. The arms are assembled using nuts and bolts for the joints.

These servo motors will require inverse kinematics for linear interpolated moves to comply with the mathematical logic of SCARAs.

Pantograph, instrument for duplicating a motion or copying a geometric shape to a reduced or enlarged scale. It consists of an assemblage of rigid bars adjustably joined by pin joints; as the point of one bar is moved over the outline to be duplicated, the motion is translated to a point on another bar, which makes the desired copy according to the predetermined scale

Source: Pantograph

The Design

We used the logic of Pantograph and we proposed a design which was made in Fusion360. In this program we made the design of each of the mechanical parts according to their function.

The following materials were considered for this exercise: 2 Stepper Motor Nema 17 model 42BYGH34 of 0.3Nm at 1.3A/12V.
2 Polypropylene sheets of 25cm x 20 cm
1 Arduino Uno
2 DRV8825
6 bolts of 1/4" x 1/2
8 bolts of 1/8" x 1/2" with nuts
4 brass flange bushing of I.D (6mm), O.D(10mm), and Height (8mm)
2 brass flange bushing of I.D (9mm), O.D(16mm), and Height (8mm)
1 Pencil
1 Breadboard
Multiple wires

The result to be able to manufacture the machine is based on 6 parts that will be articulated later:

-First Link
-Second Link
-BushingTest
-BushingTest1
-MotorCoupler
-Pencilholder
-LidPencilHolder