AutoSAW — Automated Abrasive Saw with Atmega 32A
An Invention to Automate the Industrial Metal Cutting Process by a Group of Undergraduates of the Faculty of IT, University of Moratuwa (Level 01 Hardware Project)
The first-year hardware project was one of the unforgettable assignments carried out by all the undergraduates of the Faculty of IT, University of Moratuwa. It is a 4–5-member group project with lasts for one year period. For most students, it is the place where they experience the real-world application of IT and technology to solve a critical problem for the first time in their life. This article is a brief overview of such a project carried out by a group of fresh undergraduates of the faculty in 2020. The project was selected among the top 5 hardware projects carried out by the faculty in 2020.
1. Project Overview
Aluminum is a material having thousands of applications from door frames in buildings to aircraft components. Aluminium bars available in the market are formed into usable products through ‘Aluminum fabrication’. Aluminium fabrication is the creation of Aluminum structures by cutting, bending, and assembling cut sections together by means of welding, riveting, etc.
To maintain an efficient and constant supply that will not be affected by circumstances such as human resource management issues, automation should be introduced to this industry. Therefore, as a pioneering step, we, as IT and Management students expect to automate the first step in Aluminum fabrication which is to cut a necessary number of pieces of Aluminum sections of required lengths, from standard-size Aluminum bars available in the market.
‘Automated Abrasive Saw’ is the name of the proposed automated aluminium cutting machine. As the name suggests, the device utilizes an abrasive disc for the cutting purpose.
With the user inputs of length and required number of pieces, the machine is capable of feeding an Aluminum bar while measuring the length, cutting the measured section, and finally ejecting the cut section out of the machine. The machine carries out the above activities automatically and precisely, minimizing human involvement.
Approximately, there are about 1000 small- and large-scale Aluminum fabricating workshops located island-wide where manual abrasive saws are used. There are many drawbacks to using manual abrasive saws such as being time-consuming, labor-intensive, and having safety issues which ultimately bring negative impacts on productivity as well as on the quality of the workmanship.
The introduction of ‘Automated Abrasive Saw’ to the Aluminum fabrication industry will probably bring about a notable change since it holds the power to save human labor, time, and money which can be invested in further development and expansion of the industry.
2. The Design
2.1 System Designing
Accordingly, in the block diagram [Figure 2], the proposed system has 04 primary sensors to the input feedback signal to manipulate the control of 05 output modules. The IR sensor 1 and 2 input the positions of the cutting arm. The wheel encoder (Photoelectric Encoder) connected to one of the rolling pins measures the length of the object that needs to be cut. The limit switch is used to check the presence of the object to be cut on the platform.
LCD display acts as the major output device which displays the user inputs and functional status of the machine. Nevertheless, to meet the main aim of the machine, the five motors (two low rpm DC gear motors, a stepper motor, a high rpm DC motor, and the servo motor) act as the main output devices of the machine. Every data received through input devices to the microcontroller is processed and output command signals to respective motor drivers and relay modules to control the functioning of motors.
2.2 PCB Designing
The schematic design of the PCB was carried out as follows using Easily Applicable Graphical Layout Editor: EAGLE. Next, the Routing of the PCB was carried out using the same application.
The Final PCB layout was carried out with manual routing of the wires as follows.
3. Implementation
3.1 Control Panel
To interface the 20×4-character LCD to the Atmega32A microcontroller we had to use an I2C converter to minimize the number of pins directly connected to the microcontroller from the LCD module. By using the I2C, only two pins SCL and SDC in the microcontroller were used, instead of using 8 pins as an indirect interface.
To get the user inputs, i.e., the unit length and the total number of pieces to be cut from a single box bar, a set of push-button is used. There are 04 push buttons where all the buttons are pulled down across 10 kΩ resistors. Hence, unless the buttons are pressed, 0V/low signal is sent to the microcontroller. Once a push button is pressed a +5V/high signal is sent to the microcontroller, enabling the assigned function to each push button. The functions assigned are, number increment when pressing the push button 01, decreasing the count when push button 02 is pressed, moving forward/’OK’ push button 03 is assigned and finally moving back & cancel the operation push button 04 is assigned.
3.2 Stepper motor module
The stepper motor model Nema-23 is connected to the stepper motor driver TB-660. The pulse (+), direction (+), and enable (+) pins of the stepper driver are connected to the pins of the microcontroller while the pulse (-), direction (-) and enable (-) terminals of the stepper driver are grounded together. The stepper motor is in bipolar mode where only 04 wires of the stepper motor are connected to the stepper driver. The stepper motor is provided with 12V DC voltage through the stepper driver.
3.4 High rpm motor module
In interfacing the high rpm motor module with the Atmega32A microcontroller, it was a challenge to control the motor using the relays. The high rpm motor ideally works at 24V drawing 10–15A of current. To switch ON/OFF the motor, a relay that can withstand the mentioned current rates should be supplied. The problem was that the coil voltage of such a relay is about 12V whereas the maximum output pulse from the microcontroller is +5V. Hence, we have to use another relay which is operated under +5V (which can be easily supplied across the microcontroller), to enable the functioning of the high current relay, which eventually controls the functioning high rpm motor.
Therefore, two relays were used (Relays 1 & 2). The ‘Relay 02’ is resistant to high currents and directly connected to the high rpm motor. The ‘Relay 01’ is operated at a lower voltage and directly connected to the microcontroller. The output of the first relay acts as the input to the second relay. With this method, the microcontroller is not affected by the back EMF which could be generated as a result of induced current.
3.5 Low RPM DC motor modules
There are two low-rpm motor modules are used in the machine. One gear motor is used to rotate a shaft to fasten the box bar to be cut temporarily to the machine to prevent it from wobbling. The other gear motor is used to rotate the shaft which feeds the box bar to be cut, into the machine. Both motors are controlled by a single-motor driver YXY-160D motor driver.
The motor driver is connected to the microcontroller by 03 terminals named two initialization pins and one enables pin from the motor driver. The motor driver is given a 12V DC and the output signals from the microcontroller enable the switching action of the motor driver. Two motors are named as ‘fastener motor’ which is used to fasten the box bar and the ‘feeder motor’ which is used to feed the box bar into the machine.
3.6 Sensor modules
The photoelectric encoder (Wheel encoder) is high resolution, short response speed, and Digital output speed measurement module. It can measure the motor speed when it works with the slit disk. This encoder uses a through-beam sensor. It has high resolution and the output signal is a standard square wave. We use this encoder to measure the box bar length to be cut (a linear length) by converting the circular length measured by the encoder.
When we placed the object in front of the IR proximity sensor, we observed the change in the LED connected to the output terminal. When we removed the object, it gets turned off. The sensor outputs a logic 1 (+5V) at the digital output when an object is placed in front of the sensor and a logic 0 (0V) when there is no object in front of the sensor.
4. Team
GitHub Repository Link: https://github.com/aLLUPS/AutoSaw
Thank you for reading!
