CNC Controller based on Microcontroller ATmega1284P

Transcription

1 CNC Controller based on Microcontroller ATmega1284P Sushama A.Kolhe 1, Deepak V. Varde 2, DevyaniS.Khairnar 3, Anushka M. Aware 4 1, Head of Department, Department of Electronics and Telecommunication, Guru Gobind Singh Polytechnic Nashik, (India) 2, 3, 4, Students, Department of Electronics and Telecommunication, Guru Gobind Singh Polytechnic Nashik, (India) ABSTRACT CNC Controlleris an enhanced version of GRBL firmware which is originally compiled for Arduino UNO. To enhance the performance we used ATmega1284P microcontroller which is more powerful than the microcontroller on Arduino UNO (ATmega328p). CNC is a no -compromise, high-performance, low cost alternative to parallel-port based motion controllers. Which uses a high performance microcontroller ATmega1284P from AVR series by Atmel. The controller firmware is written in highly optimized C language utilizing clever features of AVRMicrocontroller to achieve precise timing and asynchronous operation it is able to maintain up to 30 khz of jitter free pulses to drive the stepper motors. It accepts the standardcompliant G-Code with no problem as well as all primary G-Code commands are supported. CNC Controller also supports laser mode which can be used to build a low cost laser cutter or engraver. Important safety and control features for large machines such as hard limits and soft limits, feed hold, pause, start and stop are included in the firmware. CNC includes full acceleration management with look ahead as it is part of GRBL firmware it is also included in CNC controller. That means the controller will look up to 25 motions (18 for Arduino version) in to future and plan its velocities ahead to provide smooth acceleration and jerk-free cornering. We Modified GRBL firmware to with other AVR series microcontroller. Our aim is to develop CNC firmware using by GRBL as base firmware. To lower the cost for the build.we are not using any expensive IDE software instead of that we are using AVR-GCC which the base program on which all IDE for AVR microcontroller works. It is available for free. We are using Linux (fedora and debian) as our operating systems instead of using windows operating systems to lower the cost. KEYWORDS Computer numerical control (CNC), AVR Microcontroller ATmega1284P, Integrated Development Environment (IDE), G-Code. INTRODUCTION CNC Controlleris an enhanced version of GRBL firmware which is originally compiled for Arduino UNO. To enhance the performance we used ATmega1284P microcontroller which is more powerful than the microcontroller on Arduino UNO (ATmega328p). CNC is a no -compromise, high-performance, low cost alternative to parallel-port based motion controllers. Which uses a high performance microcontroller ATmega1284P from AVR series by Atmel. The controller firmware is written in highly optimized c language utilizing clever features of AVR-Microcontroller to achieve precise timing and asynchronous operation it is able to maintain up to 30 khz of jitter (noise) free pulses to drive the stepper motors. It accepts the standardcompliant G-Code with no problem as well as all primary G-Code commands are supported. CNC Controller also supports laser mode which can be used to build a low cost laser cutter or engraver Important safety and control features for large machines such as hard limits and soft limits, feed hold, pause, start and stop are included in the firmware. CNC includes full acceleration management with look ahead as it is part of GRBL firmware it s also included in CNC controller. That means the controller will look up to 25 motions (18 for Arduino version) in to future and plan its velocities ahead to provide smooth acceleration and 104 Sushama A.Kolhe, Deepak V. Varde, DevyaniS.Khairnar, Anushka M. Aware

2 jerk-free cornering. We Modified GRBL firmware to with other AVR series microcontroller. Our aim is to develop CNC firmware using by GRBL as base firmware. To lower the cost for the build.we are not using any expensive ideal software instead of that we are using AVR-GCC which the base program on which all ide for AVR microcontroller works. It s available for free. We are using Linux (fedora and debian) as our operating systems instead of using windows OS to lower the cost. To provide a low cost CNC controller to small scale industries and hobby purpose with accuracy, precision and 3 axis control with PWM laser support. The objective of our project is to provide a low cost solution to old Parallel Port Based CNC Controllers. By improving the existing GRBL firmware and adding new features to it. SYSTEM REQUIREMENTS The system in this paper proposes consist of consists of microcontroller ATmega1284P, stepper motor (NEMA17),Stepper Motor Drivers A4988.The block diagram of proposed system is as follows. Figure1. Block diagram of CNC Controller SPECIFICATIONS ATMega1284P Microcontroller The Atmel ATmega1284P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega1284P achieves throughputs close to 1MIPS per MHz this empowers system designed to optimize the device for power consumption versus processing speed. a) Operating Voltage 5v b) PWM Digital I/O Pins - 8 c) RAM 16KB 105 Sushama A.Kolhe, Deepak V. Varde, DevyaniS.Khairnar, Anushka M. Aware

3 d) EPROM 4KB e) Flash Memory 128KB f) Clock Speed 16-20MHz g) Digital Input/output Pins 32 h) Analog Input 10 Bit Stepper Motor Stepper motors are DC motors that move in discrete steps. They have multiple coils that are organized in groups called "phases". By energizing each phase in sequence, the motor will rotate one step at a time. With a computer controlled stepping you can achieve very precise positioning and/or speed control. For this reason, stepper motors are the motor of choice for many precision motion control applications. a) Step angle b) Phase/Winding - 4/2 c) Current /Voltage - 12V d) Holding torque 2Kg-cm e) Mounting screw 3mm f) Steps/rotation 200/1Rev A4988 Drivers The A4988 is a complete micro stepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, eighth-, and sixteenth-step modes, with an output drive capacity of up to 35 V and ±2 A. a) Working voltage DC5v b) Working current 15Ma c) Working frequency 40hz d) Maximum range 4cm e) Minimum range-2cm f) Measuring angle 15degree METHODOLOGY G-Code Generation from Image or Vector Design.The G-Code is a set of command which is generated by CAM software. For our project we are using inkscape. Inkscape is professional vector graphic editing software. The software is written in python language which allows users to create plugins. For various purposes. We are using two plugins for CNC machining 1. Raster to G-Code (Varade CNC Controller) (for image engraving) 2. Design To G-Code (for vector design engrave and cutting) Raster to G-Code Raster to laser G-Code generator is an extension to generate G Code for a laser cutter/engraver (or pen plotter), it can generate various types of outputs from a simple b & w (on/off) to a more detailed grayscale (PWM) Design to G-Code The laser plug-in allows for multiple commands for laser on and off for all the different versions of machines as well as the ability for multiple passes for cutting. Sending G-Code to V-CNC Controller from PC. The G-Code generated by the CAM software is stored in a.txt or G Code file the G-Code is in text the form of strings. Example (G00 X Y10.10\r\n) the lines are separated by newline char (\n) and carriage return 106 Sushama A.Kolhe, Deepak V. Varde, DevyaniS.Khairnar, Anushka M. Aware

4 char (\r). We have our own software to interpret the G-Code to the controller. The software Varade CNC Controller is written in python language which makes the software cross-platform. the software works in command line interface and arguments from the user such as Filename, Serial Port Name, Baud rate.the software reads the G-Code strings from the generated file one by one discards any comment lines (starts with ( and ends with ) ) and spaces and sends the resultant string to the V-CNC Controller after execution is done by the Controller it returns a OK string as a acknowledgement. The software reads the returned string and if the string is OK the software reads next line from the file and the whole process is repeated until the end of the file Figure 2: Circuit diagram of CNC Controller Figure 3: CNC Controller CNC CONTROL SOFTWARE (GCODE Sender) Gcode Sender is used to send the G-code files to an integrated hardware interpreter(atmega 328).Gcode Sender will take a G-code program in file and send it line-by-line to the Atmega 328 microcontroller. The 107 Sushama A.Kolhe, Deepak V. Varde, DevyaniS.Khairnar, Anushka M. Aware

5 Gcodes will send over the serial ports through USB communic ation between the computer and microcont roller.grb l Controller is software that is designed to send GCode to CNC machines is, such as 3D milling machines. Figure 4 :CNC Control Software Window RESULTS AND DISCUSSION We have designed 3D printed assembly. ABS plastic material is used for making the assembly. For motion we have used NEMA17 motors with a combination of GT2 pulley and belt system. The size of assembly is 250 x 250mm and the thickness of glass is 3mm 108 Sushama A.Kolhe, Deepak V. Varde, DevyaniS.Khairnar, Anushka M. Aware

6 Figure 5 : Engraving process CONCLUSION The CNC router machine was successfully built using ATmega328p and IC4988 microcontrollers combined with 3 Nema 17 stepper motors, with 20x20cm cross-sectional area and using 500 Watt Spindle Air Cooled drill type.the CNC machine can be used for cutting, engraving and marking on wood to form 2D or 3D objects with 98.5% carving accuracy and 100% depth accuracy. The process of synchronizing the 3 stepper motors was controlled using GRBL library and Universal Gcode Sender Software. REFERENCES [1] Yung C. Shin, Henry Chin, Michael J. Brink, Characterization of CNC machining centers,ǁ Journal of Manufacturing Systems,1991 [2] Heisel, M Gringel, Machine Tool Design Requirements for High Speed Machining,1999 [3] M Kumar, V Puttige, low cost automation for CNC machining centerǁ, IJMET, Vol. I. Pahole, L. Rataj, M. Ficko, S. Klancnik, S.Brezovnik, M. Brezocnik, and J. Balic,"Construction and evaluation of lowcost table CNC milling machine",2009 [4] V.K. Pabolu and K.N.H. Srinivas, "Design and implementation of a three dimensional CNC machine",2010. [5] T. Andrei and I. Nae, "Practical applications performed by a stepper motor CNC router", Sushama A.Kolhe, Deepak V. Varde, DevyaniS.Khairnar, Anushka M. Aware