Technical Specification
This project involved the successful creation of an automated system capable of interpreting and realizing a computer image into a physical object by manipulating the position of a carving blade along a soft material, which is spun at high speeds. The system was built around the Axiom CMD-2001 Development Board, which contains the Motorola MMC2001 MCORE Microcontroller, two stepper motors, and a variable speed direct-current (DC) motor. The user interface components for this system consist of a liquid crystal display (LCD) and a keypad to control the lathe and provide feedback to the user during the carving process, both of which are directly controlled by the MCORE. In addition, an adjustable knob to vary the speed of the rotating material on the lathe is provided using an analog circuit. The general purpose input/output (GPIO) pins and pulse-width modulation (PWM) pins on the development board were used to provide an interface between the microcontroller and the stepper motors. To limit the displacement of the carving blade limit switches were used and interfaced to the development board using the interrupt port. These components are connected together at the software level to automate carving of an object using a computer graphic from a PC. A manual carving feature was also added to the system’s capability. Comprehensive testing ensured that the automated carving system met all specifications.
Rotating Plate Control
A variable speed direct-current motor, from Clifton Precision (DH-2250-C-1), that operates at 24V (2A), with a minimum speed of 120 RPM, is used to rotate the plate that spins the material to be carved. This motor was geared by a factor of 5 to increase the torque of the rotating plate. The control unit for this motor is realized using a potentiometer in an analog circuit created using concepts of voltage division and the current-emitter follower transistor configuration.
Carving Tool Control
Two stepper motors are used in this system to control the position of the cutting blade with respect to the axis of the rotating plate and the top surface of the plate.
Mechanical Limits
Four limit switches were used to interrupt the MCORE Microcontroller. This interrupt signifies to the microcontroller that a motor has attempted relocate itself to a position outside the designed boundary of the apparatus. The limit switches are enabled during an active-low state, and therefore, they are pulled high using a resistor to 3.3V when the switch is open.
System Power Supply
There are many independent electronic units that comprise this system. In turn, there is several power supplies used throughout the construction of the system. First, a standard 9.0V power adapter used to power the Axiom CMD-2001 Development Board. This board has a voltage regulator that provides 5V and 3.3V power supplies on two pin-outs. Both of these supplies, in addition to the board’s ground signal, are supplied the system’s vector board that contains the control units for each motor. Separate power supplies were used for each motor to help maximize their torque during operation, as sharing the current across several devices decreases the amount of current through each device (in comparison to a dedicated power supply).
