2-Axis, precision geared drawing arm

By

Dario 0, Cory Towner and Kellen Newby

3D Printing
Junior Design
Spring 2025

A drawing arm that was configured to be gear and chain controlled with specific gear ratios to provide quick and precision movement while drawing. It uses the NEMA17 stepper motor to move/rotate the arm, the A4998 motor driver to coordinate movements and steps for the arms to take. We also used a ESP32 microcontroller as the brain for this arm. It also boasts a deep cycle lithium-Ion battery to allow it to be portable and acts as a weight counterbalance for the arm's weight too. lastly, it uses dual, parallel channel, buck converters to supply the 5V for the ESP and motor drivers and the 12V-24V for the motors themselves, all while supplying a total of 5A. The motors won't draw that much however as the driver are configured to limit the current in each phase to about 1.05A maximum. While the arm never did work when fully assembled, the arm did in work in all of our individual testing blocks. Unfortunately, we were unable to determine the cause of failure for the assembled work but were confident that as each individual block responded as expected on their own, that the cause was most likely some type of damage incurred while we were assembling it together.

0 Lifts 

Artifacts

Name Description
Arm Production models While drafting up the parts for the arm, I ran into a lot of improveable issues with both the production and function of parts. The arm went through several remodels to get where it is now, including chain type, gear types, modular construction, and gear ratios for precision. One such artifact was this schedule #40 chain that I got which proved to be too large and too heavy for the application that the arm needed to do. While the motors could push/pull the chain, it was slow and power intensive. So, it was later replaced with the much smaller and lighter #25 chain instead.   Download
Motor driver L298N The L298N motor driver is a unique and powerful driver that is very easy to use. Initially that was why it was chosen for this project. It is also why the arm has gear ratios, because the L298N is incapable of micro stepping, and in fact, is not a true stepper motor driver, it can be used like one but the issues arose in the code block because this driver doesn't use steps or PWM to move the motors but instead simulates it own faux PWM signal that the Uc cannot keep track of, since it is not pwn but just a series of 1/0 signals that simulates PWM. Since we needed to keep track of steps and direction, we had to replace the L298N with, the much more complicated to use, A4998.   Download
Printed Gears Initially I attempted to print gears for the lighter weight and the more custom gear ratios that I could achieve to allow for the arm to not have to need micro stepping to achieve its precision requirements. The issue with all of these gears though was the same and not really their fault but the NEMA17 motor is actually pretty powerful and fast. If we weren't careful or we moved the motor too fast, it would just split the gear shafts and then I would have to reprint them again and again. So instead, I went and printed the planetary gearbox for the primary arm as there was a lower likely hood of it splitting that one and then I used small 12-teeth hardened steel gears for the secondary arm.   Download
Project Summary Team 22's Project Summary   Download
video Submission Team 22's Video Submission (YouTube)   Link
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