Prismatic Scara

Description

Prismatic Scara is an Open Source and printable robotic arm with four degrees of freedom. It has two rotations and two linear movements; one in the radial direction and the other one in the vertical direction. The radial direction doesn´t expand the C-Space of the robot (it has the same as a regular scara) but allows the brush strokes to be clean and fast. The vertical movement allows the brush to apply different pressure to get thin or thick strokes.

Details

Update: the C-Space of the pristmatic is bigger than the C-Space of a regular Scara. This, due to the linear movement. It's expanded with lines of different slopes, but it leads to difficult poses to the manipulator that makes hard controlling it's cinematic.

The correction now is that the W-Space is the same as the W-Space of a regular Scara since it allows to work corectly with the cinematic of the robot.

Files .f3z link: https://www.thingiverse.com/thing:5733435

To do:

Software:

1) Test the code in python, wich contains the inverse kinematic of the manipulator.

2) Check that the serial communication (between python and arduino) is working.

3) Program in python the 8 basic strokes in chinese calligraphy.

Hardware:

1) Properly accommodate the wires in the robot. Some movements tangle the wires, this is a critical problem and must be fixed.

2) Improve the pieces of the brush, because they break easily, thus, must be replace often. This can be due to problems in design or because of quality of 3D printing.

Files

VID_20221214_172510 (1).mp4

home and zero function

MPEG-4 Video - 24.08 MB - 12/22/2022 at 02:39

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VID_20221214_160349.mp4

Brush control

MPEG-4 Video - 2.34 MB - 12/22/2022 at 02:38

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Scaraprismatico.zip

Inventor CAD files

x-zip-compressed - 43.54 MB - 12/22/2022 at 01:24

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WhatsApp Video 2022-12-15 at 15.12.43.mp4

Show of the movement of the manipulator

MPEG-4 Video - 5.23 MB - 12/15/2022 at 19:15

Download

manipuladores_final.ino

Communication between python code and arduino

ino - 4.18 kB - 12/15/2022 at 19:06

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Components

3 × Motor stepper nema 17

1 × Motor servo MG995

1 × Aluminum V-slot profile

3 × 16 teeth pulley GT2 6mm

3 × GT2 drive belt

Build Instructions

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1
3D printing
To manufacture the parts, a 3D printer is used, specifically the CR-10 printer, using the Cura 4.11 software with the following parameters:
- Layer Height: 0.2mm
- Nozzle: 0.4mm
- Tree supports with 60° overangle
- Horizontal expansion: -0.05mm
- Material: PLA
- Weight of material: 700 g
- Infill: 20%
The pieces corresponding to the bearings of the project, the rodtest piece is printed, so that the tolerances of the 6mm balls and the bearing tracks are adjusted, varying their horizontal expansion.
2

Assembly of pieces

The assembly between the vslot profiles is carried out by means of localized blows normally to the section plane, in order to achieve a pressure joint without glue. The following image illustrates the assembly of the vertical bar that is the axis of the rotating base.
3

Assembly of bearings

To assemble the bearings, the pieces are arranged in an aligned manner and the balls are inserted through the hole provided to load the bearing with balls. Also remembering to insert the closed band in the section arranged to achieve transmission with the shaft.

Performing the same procedure for the lower section.

In addition to a cover so that the balls cannot come out of the bearing. The second bar bearings can be seen below:

Then the bars are linked as you can see in the image:

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Prismatic Scara

Description

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