Planet Arduino

We all know how annoying a ceiling fan can be when it isn’t balanced well and that annoyance perfectly demonstrates the necessity of a good, sturdy bearing. A ceiling fan’s bearing needs to allow for smooth rotational motion with as little friction as possible, while completely constraining movement in every other axis. Those properties make a ceiling base a surprisingly good starting point for a SCARA, as demonstrated in tuenhidiy’s recent Instructables write-up.

In their tutorial, tuenhidiy refers to this as a “Spaceship Scara Arm.” It isn’t exactly clear why they chose the “spaceship” terminology, but it is similar to a conventional SCARA (Selective Compliance Assembly Robot Arm) — just one with only two degrees of freedom (DOF).

The entire point of a SCARA is that it is fully constrained, except for rotation around the Z axis at each joint. After their ceiling fan broke, tuenhidiy noticed that the fan’s base with its beefy bearing would be perfect for this application. They took that, added a couple of stepper motors and belts, some aluminum extrusion, and a couple more bearings to create this simple SCARA.

An Arduino UNO Rev3 board controls those motors through a CNC Shield V3. Grbl firmware makes it easy to control the positions of the motors using just about any software a user could possibly want. Some simple calculations regarding the arm’s geometry and gear ratios should let appropriate software determine exactly where it is in space. For a demonstration, tuenhidiy added a DC solenoid for its magnetic capabilities. But anyone replicating this project can add their own end effector to suit their needs.

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Robots come in all shapes and sizes, but one of the most popular styles for industrial applications is the SCARA (Selective Compliance Assembly Robot Arm). These have multiple degrees of freedom, each of which rotates around the vertical Z axis. But they’re otherwise constrained, which can have advantages for certain applications. For example, they tend to have relatively high payload capacities. If you’re on a budget but want to dip your toes in, tuenhidiy’s SCARA plotter is a great way to start.

This is a follow-up to tuenhidiy’s previous SCARA design from a couple of years ago. The new version is more robust and includes a homing feature, which is important for repeatability. This is set up as a plotter and the firmware reflects that, but it would be possible to adapt the mechanical design for other purposes. 

To keep costs down, most of the structure is PVC pipe. Stepper motors provide actuation via GT2 timing belts and pulleys. An Arduino Mega 2560 board controls those steppers through a RAMPS 1.4 board with A4988 stepper drivers. An interface module with a 2004 LCD, rotary encoder, buzzer, and button lets the user start jobs.

In this case, those jobs are G-code files containing the movement commands to reproduce the drawings. That works because the Arduino runs Marlin firmware (popular in the 3D printing community). The use of Marlin made homing easy and it accepts g-code that users can create with most of the standard software tools. 

The post Building your own affordable SCARA plotter with Arduino appeared first on Arduino Blog.

SCARA robots are often used in industrial settings to move components in the proper location. In order to demonstrate the concept to students, Nicholas Schwankl has come up with a simple unit that employs three servos and 3D-printed parts to dispense 4.5mm bearings.

The device runs on an Arduino Mega (though an Uno or other model would work) and as seen in the video below, it twists its ‘shoulder’ and ‘elbow’ joint to position its dispenser tube. Once in place, a micro servo releases a bearing, allowing the tiny steel ball to drop into an empty slot.

STL files, a parts list, and Arduino code are available in the Schwankl’s write-up.