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Proposal
11/10/2021
Andrew Gerber & Erik Neilson
For our project we are going to build a small CNC router capable of cutting wood, acrylic, and possibly aluminum as well as mill custom PCBs. The objective is to implement a design capable of accepting G-Code input to control the spindle and three axes of motion.
Mechanical. The frame will be built using t-slot extruded aluminum and be approximately 300x300 mm. This should be able to provide a working area of at least 200x200 mm. Lead screws will be used for the axis as it is much more rigid than a belt driven design. The Y-axis will be a gantry moving along the frame. The X-axis will a be a carriage moving across the gantry. The Z-axis will hold the spindle and be mounted to the carriage.
Electrical. The three axes will use NEMA 17 stepper motors driven by A4988 current-limiting driver ICs. Power will be supplied using 12 V and 5 V rails of a standard computer power supply. The microcontroller will be the STM32L476. Limit switches will also be used to home and calibrate the stepper motors.
G-Code. The G-Code will be sent to the microcontroller via UART communication from a PC. Due to the extensive number of G-Code commands a simplified subset of these commands will be the primary target for implementation in this project. It is also possible that an external library may be used to interpret the commands to positional data.
Motors. Driving the stepper motors is greatly simplified thanks to the A4988 driver chips. These chips provide step and dir pins to control the stepping of the motors. Proper values for maximum speed and acceleration will be determined through experimentation.
Currently, there are two team members on the project, Andrew Gerber and Erik Neilson. Due to the ambitious scale of the project, a third team member is desired. We have attempted to find an additional person, but have not found one. If you know anyone needing a team, we may be interested.
The primary objective of this project is to provide 3-axes control of a spindle via UART interface. The commands will be some implementation of G-Code.