DrawBot - Android Thing CNC Plotter

DRAWBOT – A MINI CNC PLOTTER MAIN PROJECT
DEPARTMENT OF IT iii LBSCEK
TABLE OF CONTENTS
CHAPTER 1................................................................................................................................ 1
INTRODUCTION........................................................................................................................ 1
1.2 Computer Numerical Control (CNC) ................................................................................ 1
1.2.1 Cartesian Coordinate System................................................................................... 2
1.3 DrawBot – A Mini CNC Plotter........................................................................................ 4
CHAPTER 2................................................................................................................................ 5
BLOCK DIAGRAM..................................................................................................................... 5
2.1 Description.................................................................................................................... 5
2.1.1 Android Things.......................................................................................................6
2.1.2 Arduino.................................................................................................................. 6
2.1.3 Motors................................................................................................................... 7
2.2 Working........................................................................................................................ 8
CHAPTER 3................................................................................................................................ 9
CIRCUIT DIAGRAM AND WORKING....................................................................................... 9
3.1 Description.................................................................................................................. 10
3.2 Circuit Components ..................................................................................................... 10
3.2.1 Android Thing (Picoi.MX7 Dual Development Board).............................................. 10
3.2.2 Arduino UNO........................................................................................................ 12
3.2.3 Breadboard (for Ground &VCC)............................................................................. 14
3.2.4 Motor Driver IC.................................................................................................... 15
3.2.5 Servo Motor......................................................................................................... 16
3.2.6 The LED status light.............................................................................................. 17
3.2.7 Stepper Motor...................................................................................................... 17
3.2.8 DVD/CD Drive....................................................................................................... 18
3.2.9 Connector............................................................................................................ 19
3.3 Working...................................................................................................................... 19
3.4 Design......................................................................................................................... 20
CHAPTER 4.............................................................................................................................. 23
SOFTWARE.............................................................................................................................. 23
4.1 G-code........................................................................................................................ 23
4.2 Inkscape.......................................................................................................................... 26
4.3 Android Program............................................................................................................... 27
4.3.1 Algorithm................................................................................................................... 27

DEPARTMENT OF IT iv LBSCEK
4.3.2 Flow Chart.................................................................................................................. 28
4.3.3 User Interface of Android Program........................................................................ 29
4.4 Android Studio............................................................................................................. 31
4.5 Arduino Program......................................................................................................... 34
4.5.1 Algorithm............................................................................................................. 34
4.5.3 Arduino IDE.......................................................................................................... 36
5.1 Advantages.................................................................................................................. 37
5.2 Disadvantages ............................................................................................................. 38
5.3 Applications................................................................................................................. 38
CHAPTER 6.............................................................................................................................. 40
CONCLUSION.......................................................................................................................... 40
6.1 Future Scope............................................................................................................... 40
REFERENCE............................................................................................................................. 41

DEPARTMENT OF IT v LBSCEK
TABLE OF FIGURES
Figure Title Page
1.1 Intersecting lines form right angles and establish the zero point
(Allen- Bradley)
2
1.2 The three-dimensional coordinate planes (axes) used in CNC 2
1.3 The quadrants formed when the X and Y axes cross are used to
accurately located
3
2.1 Block Diagram 5
3.1 Circuit Diagram 9
3.2 Pico i.MX7 Dual Development Board 10
3.3 Pin out Diagram 11
3.4 Arduino board 12
3.5 Arduino Pin out Diagram 13
3.6 Breadboard 14
3.7 L293D Motor Driver IC 15
3.8 L293D Pin out diagram 15
3.9 Servo Motor 16
3.10 28BYJ48 Stepper motor 18
3.11 DVD Drive 20
3.12 Pen setup 21
3.13 Final setup 22
4.1 Booting Screen 29
4.2 Android Program UI 29
4.3 GCode Selection 30
4.4 External Input Selection 30
4.5 Start Drawing Button Activity 31
5.1 Plotted output image 37

DEPARTMENT OF IT 1 LBSCEK
CHAPTER 1
INTRODUCTION
CNC stands for Computer Numeric Control and typically refers to a machine whose
operation is controlled by a computer. The most common usage of CNC, and the one relevant
to us, is the name given to devices that, under computer control are able to cut, etch, mill,
engrave, build, turn and otherwise perform manufacturing operations on various materials.
Typically, a CNC machine has the ability to move a cutting or 3D printing head in 2 to 6
axes, meaning that it can position that tool head at a precise point in or on the material to
create the cut or operation desired at that point. By moving the head through multiple points,
the cutting head can cut or sculpt the design represented by a data stream of positioning
points being sent by the PC. By controlling a CNC machine through a PC it is possible for the
user to design a product on-screen, convert it to CNC-reliable code and then send that data to
the CNC machine for it to produce a physical copy of the item designed.
1.2 COMPUTER NUMERICALCONTROL(CNC)
The term numerical control is a widely accepted and commonly used term in the machine
tool industry. Numerical Control (NC) enables an operator to communicate with machine
tools through a series of numbers and symbols.
NC which quickly became Computer Numerical Control (CNC) has brought tremendous
changes to the metal working industry. New machine tools in CNC have enabled industry.
New machine tool is CNC have enabled industry to consistently produce parts to accuracies
undreamed of only a few years ago. The same part can be reproduced to the same degree of
accuracy any number of times if the CNC program has been properly prepared and the
computer properly programmed.
The operating commands which control the machine tool are executed automatically with
amazing speed, accuracy, efficiency and repeatability. The ever-increasing use of CNC in
industry has created a need for personnel who are knowledgeable about and capable of
preparing the programs which guide the machine tools to produce parts to the required shape
and accuracy.

Fig 1.1: Intersecting lines form right angles and establish the zero point (Allen- Bradley)
Fig 1.2: The three-dimensional coordinate planes (axes) used in CNC.
1.2.1 Cartesian Coordinate System
Almost everything that can be produced on a conventional machine tool can be produced on a
computer numerical control machine tool, with its many advantages. The machine tool

movements used in producing a product are of two basic types: point to point (straight-line
movements) and continuous path (contouring movements).
The Cartesian, or rectangular, coordinate system was devised by the French mathematician
and philosopher Rene’ Descartes. With this system, any speciﬁc point can be described in
mathematical terms from any other point along three perpendicular axes. This concept ﬁts
machine tools perfectly since their construction is generally based on three axes of motion
(X, Y, Z) plus an axis of rotation. On a plain vertical milling machine, the X axis is the
horizontal movement (right or left) of the table, the Y axis is the table cross movement
(toward or away from the column), and the Z axis is the vertical movement of the knee or the
spindle. CNC systems rely heavily on the use of rectangular coordinates because the
programmer can locate every point on a job precisely.
Fig 1.3: The quadrants formed when the X and Y axes cross are used to accurately located
The three-dimensional coordinate planes are shown in Fig. 1.2. The X and Y planes (axes)
are horizontal and represent horizontal machine table motions. The Z plane or axis represents
the vertical tool motion. The plus (+) and minus (-) signs indicate the direction from the zero
point (origin) along the axis of movement. The four quadrants formed when the XY axes
cross are numbered in a counterclockwise direction (Fig. 1.3). All positions located in
quadrant 1 would be positive (X+) and positive (Y+). In the second quadrant, all positions
would be negative X (X-) and positive (Y+). In the third quadrant, all locations would be

negative X (X-) and negative (Y-). In the fourth quadrant, all locations would be positive X
(X+) and negative Y (Y-).
In Fig. 1.3, point A would be 2 units to the right of the Y axis and 2 units Fig 1.3: The
quadrants formed when the X and Y axes cross are used to accurately located above the X
axis. Assume that each unit equals 1.000. The location of point A would be X + 2.000 and Y
+ 2.000. For point B, the location would be X + 1.000 and Y - 2.000. In CNC programming it
is not necessary to indicate plus (+) values since these are assumed. However, the minus (-)
values must be indicated.
For example, the locations of both A and B would be indicated as follows:
A X2.000 Y2.000
B X1.000 Y-2.000
1.3 DRAWBOT – A MINI CNC PLOTTER
Robotics is the branch of technology that deals with the design, construction, operation, and
application of robots, as well as computer systems for their control, sensory feedback, and
information processing. The design of a given robotic system will often incorporate
principles of mechanical engineering, electronic engineering and computer science
(particularly artificial intelligence).The term ’robotics’ was coined by Isaac Asimov in his
science fiction short story called ’Liar’. Robot is an electro-mechanical machine which is
guided by an electronic circuitry or computer program to perform various tasks. A robotic
arm is a robotic manipulator, usually programmable, with functions similar to that of human
arm. DrawBot is a mini CNC plotter that offers the fastest way to efficiently produce very
large drawings. Pen plotters will be able to print by moving pen or other writing device
across the surface of a piece of paper. This means that plotters are vector graphics devices,
rather than raster graphics. Pen plotters can draw complex line art, including text, but do so
slowly because of the mechanical movement of the writing device such as pen.

CHAPTER 2
BLOCK DIAGRAM
Fig 2.1: Block Diagram
2.1 DESCRIPTION
A picture of what to be printed is send to the android things where it is converted to the G-
code form and is send to the Arduino serially. Inside the Arduino there is a coordinate
separator which then divides our input that it receives to X, Y, Z coordinates. The coordinates
of Z, Y is made to go through the PWM generator. This is done for encoding the amplitude of
the signal right into a pulse width or duration of another signal, usually a career signal for
transmission. Then it is send to a motor, in which the Z coordinate move to the Servo motor
that directs the movement of pen, Y coordinate is send to the Stepper motor 1 that directs the
horizontal movement of the DVD rail, Z coordinate is send to the Stepper motor 2 that directs
the vertical movement of the DVD rail.

2.1.1 Android Things
Android Things (codenamed Brillo) is an Android-based embedded operating
system platform by Google, announced at Google I/O2015. It is aimed to be used with low-
power and memory constrained Internet of Things (IoT) devices, which are usually built from
different MCU platforms. As an IoT OS it is designed to work as low as 32–64 MB of RAM.
It will support Bluetooth Low Energy and Wi-Fi. Along with Brillo, Google also introduced
the Weave protocol, which these devices will use to communicate with other devices and
which it hopes will be adopted by other IoT operating systems. Every Android device can
automatically recognize any Brillo OS or Weave API based device. Users can choose a
device, set it up and use it immediately. Google describes Android Things as "a
comprehensive way to build IoT products with the power of Android," and of course that
sounds very familiar to its stance on letting manufacturers use Android to build phones,
tablets, TV boxes and more. Android Things is effectively a rebranding and expansion of its
previous Brillo platform, which itself was a stripped-down version of Android designed for
IoT device. Well, the biggest difference is that hardware and software developers can now
create IoT devices using the same Android APIs and Google Services they already know.
Android Things is now available to work with inside of Android Studio with the Android
SDK, Google Play Services and Google Cloud Platform. Google will also start releasing
updates to Android Things similarly to how it handles other Android releases, with patches
and security fixes. In many ways this turns IoT development into a first-class citizen right
next to creating apps for Android phones and tablets.
2.1.2 Arduino
Arduino is an open-source electronics platform based on easy-to-use hardware and
software. Arduino boards are able to read inputs - light on a sensor, a finger on a button, or a
Twitter message - and turn it into an output - activating a motor, turning on an LED,
publishing something online. You can tell your board what to do by sending a set of
instructions to the microcontroller on the board. To do so you use the Arduino programming
language (based on Wiring), and the Arduino Software (IDE), based on Processing.
Over the years Arduino has been the brain of thousands of projects, from everyday objects to
complex scientific instruments. A worldwide community of makers - students, hobbyists,
artists, programmers, and professionals - has gathered around this open-source platform, their

contributions have added up to an incredible amount of accessible knowledge that can be of
great help to novices and experts alike.
Arduino was born at the Ivrea Interaction Design Institute as an easy tool for fast prototyping,
aimed at students without a background in electronics and programming. As soon as it
reached a wider community, the Arduino board started changing to adapt to new needs and
challenges, differentiating its offer from simple 8-bit boards to products for IoT applications,
wearable, 3D printing, and embedded environments. All Arduino boards are completely
open-source, empowering users to build them independently and eventually adapt them to
their particular needs. The software, too, is open-source, and it is growing through the
contributions of users worldwide.
2.1.3 Motors
A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides
a full rotation into a number of equal steps. The motor's position can then be commanded to
move and hold at one of these steps without any position sensor for feedback (an open-loop
controller), as long as the motor is carefully sized to the application in respect to torque and
speed.
Switched reluctance motors are very large stepping motors with a reduced pole count, and
generally are closed-loop commutated.
Brushed DC motors rotate continuously when DC voltage is applied to their terminals. The
stepper motor is known by its property to convert a train of input pulses (typically square
wave pulses) into a precisely defined increment in the shaft position. Each pulse moves the
shaft through a fixed angle.
Stepper motors effectively have multiple "toothed" electromagnets arranged around a central
gear-shaped piece of iron. The electromagnets are energized by an external driver circuit or
a micro controller. To make the motor shaft turn, first, one electromagnet is given power,
which magnetically attracts the gear's teeth. When the gear's teeth are aligned to the first
electromagnet, they are slightly offset from the next electromagnet. This means that when the
next electromagnet is turned on and the first is turned off, the gear rotates slightly to align
with the next one. From there the process is repeated. Each of those rotations is called a
"step", with an integer number of steps making a full rotation. In that way, the motor can be
turned by a precise angle.

The circular arrangement of electromagnets is divided into groups, each group called a phase,
and there is an equal number of electromagnets per group. The number of groups is chosen
by the designer of the stepper motor. The electromagnets of each group are interleaved with
the electromagnets of other groups to form a uniform pattern of arrangement. For example, if
the stepper motor has two groups identified as A or B, and ten electromagnets in total, then
the grouping pattern would be ABABABABAB.
Electromagnets within the same group are all energized together. Because of this, stepper
motors with more phases typically have more wires (or leads) to control the motor.
2.2 WORKING
A picture of what to be printed is send to the android things through a mobile phone. The
picture is then converted to G-code from the android phone or Android things and are send to
the Arduino through USB. Arduino parses the G-code, i.e. it takes the X, Y, Z axis values and
converts it to the corresponding motor movement. Inside the Arduino there is a coordinate
separator which then divides our input that it receives to X, Y, Z coordinates. The coordinates
of Z, Y is made to go through the PWM generator. This is done for encoding the amplitude of
the signal right into a pulse width or duration of another signal, usually a career signal for
transmission. Then it is send to a motor, in which the Z coordinate move to the Servo motor
that directs the movement of pen, Y coordinate is send to the Stepper motor 1 that directs the
horizontal movement of the DVD rail, Z coordinate is send to the Stepper motor 2 that directs
the vertical movement of the DVD rail.
As the pen touches the paper, according to the values of X, Y and Z axis it starts to move to
the coordinates and draws the Fig .As the movement of pen to paper, i.e. pen down is the Z
axis the pen moves only according to X and Y axis After drawing the Fig , pen direction
moves to the value 1,i.e. it moves up from the drawing pad and X,Y axis moves to its default
values. Thus we obtain a print of the image on the paper.

CHAPTER 3
CIRCUIT DIAGRAM AND WORKING
Fig 3.1: Circuit Diagram

3.1 DESCRIPTION
The base circuit of the system shown above. The proper arrangement of above circuit will
help us to maintenance as well as operation of CNC plotter. The pen arrangement of the
circuit is controlled by servo meter. Which provide a motion of 180 degree shift. So the break
in circuit is easily achievable.
3.2 CIRCUIT COMPONENTS
The block explanation of each section of a CNC Plotter as follows.
3.2.1 Android Thing (Pico i.MX7 Dual Development Board)
The i.MX 7 Dual delivers high-performance processing for low-power requirements with a
high degree of functional integration. The i.MX 7 Dual features an advanced implementation
of two ARM Cortex A7 cores, which operate at speeds of up to 1.2 GHz, as well as the ARM
Cortex 4 core. The Pico variant is pin-compatible with the Intel Edison for sensors and low-
speed I/O, but also adds additional expansion possibilities for multimedia and connectivity,
giving you cutting edge technology that can easily be expanded and implemented for IoT
designs.
Fig 3.2: Pico i.MX7 Dual Development Board
Before you begin flashing, you will need the following items in addition to your board:
 USB-C cable
 Ethernet cable (if not connecting with Wi-Fi)

Fig 3.3: Pin out Diagram

Internet access
It is strongly recommended to connect the board to the internet. This allows your device to
deliver crash reports and receive updates.
Do either of the following:
To connect to a wired network, attach an Ethernet cable.
Connecting Wi-Fi
After flashing your board, it is strongly recommended to connect it to the internet. This
allows your device to deliver crash reports and receive updates.
To connect to Wi-Fi, do one of the following:
 Run the setup utility and select the Wi-Fi setup option.
 Connect a display and conFig Wi-Fi though the launcher app.
 Connect to Wi-Fi with adb.
Serial Debug Console
The serial console is a helpful tool for debugging your board and reviewing system log
information. The console is the default output location for kernel log messages (i.e. dmesg),
and it also provides access to a full shell prompt that you can use to access commands such
as logcat. This is helpful if you are unable to access ADB on your board through other means
and have not yet enabled a network connection.
3.2.2 Arduino UNO
Fig 3.4: Arduino board

It plays an important role in this system. The required program is dumped in the
Microcontroller. It always takes the input from G-code executer and performs operations in
controlling motors. Here we are using Arduino UNO R3.
The Arduino Uno is a microcontroller board based on the AtMega328. It has 14 digital
input/output pins(of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal
oscillator, a USB connection, a power jack, an ICSP header and a reset button. It contains
everything needed to support the microcontroller. Simply connect it to a computer with a
USB cable or power it with an AC to DC adapter or battery to get started. The UNO differs
from all preceding boards in that it does not use the FTDI USB to serial driver chip. Instead,
it features the AtMega8U2 programmed as a USB to serial converter.
Fig 3.5: Arduino Pin out Diagram

3.2.3 Breadboard (for Ground &VCC)
Fig 3.6: Breadboard
A breadboard is a construction base for prototyping of electronics. Originally it was literally a
bread board, a polished piece of wood used for slicing bread. In the 1970s the solder less
breadboard (a.k.a. plug board, a terminal array board) became available and nowadays the
term "breadboard" is commonly used to refer to these.
Because the solder less breadboard does not require soldering, it is reusable. This makes it
easy to use for creating temporary prototypes and experimenting with circuit design. For this
reason, solder less breadboards are also extremely popular with students and in technological
education. Older breadboard types did not have this property. A strip board (Vero board) and
similar prototyping printed circuit boards, which are used to build semi-permanent soldered
prototypes or one-offs, cannot easily be reused. A variety of electronic systems may be
prototyped by using breadboards, from small analog and digital circuits to complete central
processing units (CPUs).

3.2.4 Motor Driver IC
Fig 3.7: L293D Motor Driver IC
L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as current
amplifiers since they take a low-current control signal and provide a higher-current signal.
This higher current signal is used to drive the motors.
L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two
DC motors can be driven simultaneously, both in forward and reverse direction. The motor
operations of two motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input
logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise
and anticlockwise directions, respectively.
Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to start
operating. When an enable input is high, the associated driver gets enabled. As a result, the
outputs become active and work in phase with their inputs. Similarly, when the enable input
is low, that driver is disabled, and their outputs are off and in the high-impedance state
Fig 3.8: L293D Pin out diagram

3.2.5 Servo Motor
The servo motor is attached to the stand where the camera sits and rotates the camera to align
with the active PIR sensor.
Using the pin out for our motor, connect one pin to power, another pin to the Arduino digital
input 7, and the last pin to ground.
Before powering the Arduino, make sure to connect a 100µF capacitor between the power
and ground of the motor to help protect the board from the power surges that occur when the
motor moves.
One thing to note about servo motors is that not all have a full 180º range of motion.
To fully understand how the servo works, you need to take a look under the hood. Inside
there is a pretty simple set-up: a small DC motor, potentiometer, and a control circuit. The
motor is attached by gears to the control wheel. As the motor rotates, the potentiometer's
resistance changes, so the control circuit can precisely regulate how much movement there is
and in which direction.
When the shaft of the motor is at the desired position, power supplied to the motor is stopped.
If not, the motor is turned in the appropriate direction. The desired position is sent via
electrical pulses through the signal wire. The motor's speed is proportional to the difference
between its actual position and desired position. So if the motor is near the desired position, it
will turn slowly, otherwise it will turn fast. This is called proportional control. This means the
motor will only run as hard as necessary to accomplish the task at hand, a very efficient little
guy.
Fig 3.9: Servo Motor

Servo control mechanism
Servos are controlled by sending an electrical pulse of variable width, or pulsewidth
modulation (PWM), through the control wire. There is a minimum pulse, amaximum pulse,
and a repetition rate. A servo motor can usually only turn 90° in either direction for a total of
180° movement. The motor's neutral position is defined as the position where the servo has
the same amount of potential rotation in the both the clockwise or counter-clockwise
direction. The PWM sent to the motor determines position of the shaft, and based on the
duration of the pulse sent via the control wire; the rotor will turn to the desired position. The
servo motor expects to see a pulse every 20 milliseconds (ms) and the length of the pulse will
determine how far the motor turns. For example, a 1.5ms pulse will make the motor turn to
the 90° position. Shorter than 1.5ms moves it in the counter clockwise direction toward the 0°
position, and any longer than 1.5ms will turn the servo in a clockwise direction toward the
180° position.
3.2.6 The LED status light
We used a mini breadboard to keep the LED lights separate from the rest of the circuitry in
order to allow for easier removal if needed. Each LED responds to a different PIR sensor and
will light up anytime it detects motion. Simply connect each LED to a separate digital input
(9-13) on the Arduino and ground them through a 220 ohm resistor.
 Here's what everything looks like after the PIR sensors have been installed
and all the circuitry completed.
 We used breadboards to complete our project. The reason for this being that
it made it. Extremely easy to fit them inside the base, as well as pick and
choose which one to remove while troubleshooting and expanding upon later.
3.2.7 Stepper Motor
A stepper motor is an electromechanical device which converts electrical pulses into discrete
mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step
increments when electrical command pulses are applied to it in the proper sequence. The
motors rotation has several direct relationships to these applied input pulses. The sequence of
the applied pulses is directly related to the direction of motor shafts rotation. The speed of the
motor shafts rotation is directly related to the frequency of the input pulses and the length of
rotation is directly related to the number of input pulses applied. One of the most significant
advantages of a stepper motor is its ability to be accurately controlled in an open loop system.

Open loop control means no feedback information about position is needed. This type of
control eliminates the need for expensive sensing and feedback devices such as optical
encoders. Your position is known simply by keeping track of the input step pulses.
Fig 3.10: 28BYJ48 Stepper motor
3.2.8 DVD/CD Drive
Short for Digital Versatile Disc or Digital Video Disc, a DVD or DVD-ROM is
a disc capable of storing large amounts of data on one disc the size of a standard Compact
Disc. CD/DVD drives were first sold in 1997. They are widely used for storing and viewing
movies and other data. To play DVDs on a computer, you must have a DVD drive and a
software DVD player.
 There are several capacities a single DVD disc is capable of holding. Below is a
listing of the different types of DVD's and each of their total capacity.
 One of the most common DVD's is the single-sided, single-layer disc, capable of
holding 4.7 GB.
 The single-sided, double-layer disc is capable of holding between 8.5 - 8.7 GB.
 The double-sided, single-layer disc is capable of holding 9.4 GB.
 Although rare, the double-sided, double-layer disc is capable of holding up to 17.08
GB.

3.2.9 Connector
 Electrical connector, a device for joining electrical circuits together (sometimes known as
ports, plugs, or interfaces)
 Gender of connectors and fasteners
 AC power plugs and sockets, devices that allow electrically operated equipment to be
connected to the primary alternating current power supply in a building
 RF connector, an electrical connector designed to work at radio frequencies in the multi-
megahertz range
 Circular connector
 Cigarette lighter receptacle
 Blind mate connector, a connector with self-aligning features
 Board - to-board connector, for connecting printed circuit boards
 Structural connector, in engineering
3.3 WORKING
Our CNC machine consists of three axes X, Y, Z - axis for three dimensional motion of tool.
The numerical data required for working of the plotter is provided by a program called part -
program which in turn converts the numerical data to electrical signals. These electrical
signals are then given as input to stepper motors. Each signal specifies a specific point in the
coordinates and according to the point the tool moves. As mentioned earlier input device used
is serial communication port DB9. Machine control unit (MCU) consists of data processing
unit (DPU) and control loop unit (CLU). On receiving part program DPU interprets and
encode it into internal machine codes. Then intermediate position of the motion in Basic
length unit (BLU) is calculated by interpolator of DPU. Then it is passed to CLU for further
process. To control driving system and to perform required motion data from DPU are
converted in to electrical signals in CLU. Machine tool can be of any type, machine slide
should be of high accuracy and repeatability and also coated with anti-frictional material.
Here we use open loop control system in which there is no feedback and uses stepping motor
whose output angle rotates through a fixed angle in accordance with an input Pulse. The
accuracy depends upon the motor’s ability to step through correct number and the frequency
on load torque, they have an inverse relation. Driving system includes stepper motor, which
converts electric pulses into discrete mechanical rotations of motor shaft. These pulses are
provided by the machine control unit. Stepper motor would be the best simple device that can

be applied to CNC as it converts digital data to actual mechanical displacements. They are
mainly used because of slow speeds, low torque, and low resolution and easy to slip in case
of over load.
3.4 DESIGN
The complete mechanical system was designed in the metallic DVD/CD drive cover. The
designs in the project are:
 X – Y Direction.
 Pen Setup.
 Stand holding the Whole.
 Final Setup.
Y axis: basic axis carries X axis move from front to back.
X axis: carries Z axis move from left to right.
Z axis: carries pen part move up and down.
X – Y Direction:
In computing, an optical disc drive (ODD) is a disk drive that uses laser light or
electromagnetic waves or near the visible light as spectrum as part of the process of reading
or writing data to or from optical discs. Compact discs, DVD and Blu-ray discs are common
types of optical media which can be read and recorded by such drives. Optical disc drives that
are no longer in production include CD-ROM drives. As of 2015, DVD writer drive is the
most common for desktop PCs and laptops. There are also the DVD-ROM drive, CD-ROM
drive and Blu-ray. Disc combo (CD-ROM/DVD-RW/CD-RW) drive.
The DVD Rails are used for X and Y planes of the setup.
Fig 3.11: DVD Drive

Stand Holding the Whole
The stand holding all the parts are made by the outer metallic cover of the CD drive. Two
covers are welded together perpendicularly for holding the X and Y axis.
Pen Setup (Zaxis)
Fig 3.12: Pen setup
For pen setup (Z axis) High Density Fiberboard (HDF) is used. It is a type of fiberboard,
which is a petroleum product. It is of light weight. Servo motor is adjusted inside the HDF to
get the up and down movement required to plot the object.

Final Setup
All the sections are integrated together to get a good output.
Fig 3.13: Final setup

CHAPTER 4
SOFTWARE
4.1 G-CODE
G-code is a programming language for CNC that instructs machines where and how to move.
Most machines speak a different “dialect” of g-code, so the codes vary depending on type,
make, and model. Each machine comes with an instruction manual that shows that particular
machine’s code for a specific function. G-code stands for “geometric code,” and follows
some variation of the alpha numeric pattern:
N## G## X## Y## Z## F## S## T## M##
N: Line number
G: Motion
X: Horizontal position
Y: Vertical position
Z: Depth
F: Feed rate
S: Spindle speed
T: Tool selection
M: Miscellaneous functions
I and J: Incremental center of an arc
R: Radius of an arc
Alpha numeric codes are used for programming as they are a simple way to:
Define motion and function (G##)
Declare a position (X## Y## Z##)
Set a value (F## and/or S##)
Select an item (T##)

Switch something on and off (M##), such as coolant, spindles, indexing motion, axes locks,
etc.
For example,
G01 X1 Y1 F20 T01 M03 S500
Generally indicate a linear feed move (G01) to the given XY position at feed rate of 20. It is
using Tool 1, and the spindle speed is 500. Miscellaneous functions will vary from machine
to machine, so in order to know what the m-code means, the machine’s instruction manual
will need to be referenced.
Machine Motion.
Everything a machine can do is based on three basic types of motion:
Rapid move: a linear move to an XYZ position as fast as possible
Feed move: a linear move to an XYZ position at a defined feed rate
Circular move: a circular move at a defined feed rate
Every g-code tells the machine which variation of these basic motions to perform, and how to
perform it.
X and Y are Cartesian coordinates for horizontal and vertical position, and Z represents the
depth of the machine. These alpha numerals will follow the motion/function command (G) to
declare the position of the machine.
Next, F determines the feed rate (for feed moves or circular moves), while S determines the
spindle speed. T is used to select a tool. Other alpha numerals used in programming might
include I, J, and R, which have to do with arc centers and radii.
Miscellaneous Codes.
The line of a program might also include m-codes, which are generally codes that tell a
machine how to perform an action. While not guaranteed to be the same across machines,
some common, standard m-codes are:
M00: Program stop
M01: Optional program stop

M02: End of program
M03: Spindle on clockwise
M04: Spindle on counterclockwise
M05: Spindle stop
M06: Tool change
M08: Flood coolant on
M09: Flood coolant off
M30: End of program/return to start
M41: Spindle low gear range
M42: Spindle high gear range
Example of g code
For example, say a code begins with a linear rapid move at X1 Y1 (G00 X1 Y1). If the next
function is another linear rapid move, it is not necessary to write G00 again. All that is
needed on the next line of code is the new position (say, X2 Y2) because the modal condition
is the same. Then, to change the function to a linear feed (G01), programming G01 on the
following line would deactivate the linear rapid move and activate the linear feed.
Once a condition is set, it stays active until it is turned off or another condition overrides it.
The modal groups for g-codes are:
Group 1 (motion): G00, G01, G02, G03, G80, G81, G82, G84, G85, G86, G87, G88, G89
Group 2 (plane selection – XY, YZ, ZX): G17, G18, G19
Group 3 (absolute/incremental mode): G90, G91
Group 5 (feed rate mode): G93, G94
Group 6 (units – inches/millimeters): G20, G21
Group 7 (cutter radius compensation – CRC): G40, G41, G42
Group 8 (tool length offset – TLO): G43, G49

Group 10 (return mode in canned cycles): G98, G99
Group 12 (work coordinate system selection – WCSS): G54, G55, G56, G57, G58, G59)
4.2 INKSCAPE
Inkscape is a Free and Open Source vector drawing program oriented towards the creation of
SVG (scalable vector graphics). It can export to DXF for use in other CAD/CAM software,
or directly to G-code using the G-code tools extension. It has a broad variety of import and
export formats, so is useful to have for conversion, even if one doesn't use it to draw.
Converting Text to Objects:
This is necessary to import into Carbide Create and many other tasks, most notably the Path
commands noted below. View | Display Mode | Outline (this gets one a view which shows
objects more or less as CC will import them
Select all text objects which one wishes to convert (shift-click on each in turn after the first or
click drag-select to do multiples)
| Path | Object to Path --- this should convert most other objects as well (arguably one could
just select all and then do this).
Path commands:
The Path commands are even more important and one needs to understand all of the options:
 Union
 Difference
 Intersection
 Exclusion
 Division
 Cut path
Work and how stacking order interplays w/ them in order to accomplish anything non-trivial
w/o going to a lot of unnecessary work.

Scaling Factor for SVG Files:
SVG files will include a statement which notes how many internal (file) units there are per
inch. Different programs use different numbers --- most programs on import will ignore this
value and instead directly map to their own (possibly different) value.
Values for some programs:
Previewing Cuts
Dupe the paths: Edit | Select All, Edit | Copy, Edit | Paste in Place
Offset them in the appropriate direction by half the bit diameter, for profiles this is out (Path |
Outset), for pockets, in (Path | Inset) Unfortunately, Inkscape doesn't afford one much control
over this --- you'll have to do it multiple times (seems to be 1 pixel each time) until you get
close --- draw in an appropriately sized circle first. FYI Dynamic offset is buggy and may be
removed.
Set the stroke to the width of the bit and rounded ends and corners. Object | Fill and Stroke ---
set Width appropriately, Join and cap should be the middle (rounded) options.
4.3 ANDROID PROGRAM
4.3.1 Algorithm
Step 1: Start
Step 2: Generating G- code files using Inkscape. These G-codes are stored on Android Things (Pico
i.MX7 Dual Development Board).
Step 3: Display 3 buttons:
1. Explore
2. G-code
3. Start Drawing.
Step 3.1: Click on Explore button.
Connecting a mobile phone to Android Thing by using USB cable and copying a G-
code file from mobile phone to Android Thing’s G-code folder. Go to Step 3.2.
Step 3.2: Click on G-code button.
We get a list of G-code files and select a G-code from list. Go to Step 3.3.
Step 3.3: Click on Start Drawing button.
Start drawing button disable and Android Thing passes G-code into Arduino.
Step 4: Stop.

4.3.2 Flow Chart
2. G- code
Yes
No
o Yes
No
Start
3 Buttons:
1. Explore
2. G-code
3. Start Drawing
Connect Mobile
Device
Select G-
code?
G-code passes to
Arduino
Button
disable?
Stop
Copyinga G-code file
from mobile to
Android Thing
2. G-code 3. Start
Drawing
1. Explore

4.3.3 User Interface of Android Program
4.3.3.1: Android things Booting Screen
Fig 4.1 Booting Screen
4.3.3.2: UI and Touch input Select Screen.
Fig 4.2 Android Program UI
Click on GCODE button then go to 4.3.3.3.
Click on EXPLORE button then go to 4.3.3.4.
Click on START DRAWING button then go to 4.3.3.5.

4.3.3.3: GCode selected from the Library using this touch Input.
Fig 4.3 GCode Selection
4.3.3.4: External Device Input Selection
When a mobile phone is connected to Android things then it shows connected device and
contents or files in the device. Select and copy a file from connected device and it stored on
GCode folder of Android things.
Fig 4.4 External Input Selection

4.3.3.5: Button: START DRAWING
This button disable when plotter starts to draw. Then Android things start to pass these
GCode into Arduino by serially.
Fig 4.5 Start Drawing Button Activity
4.4 ANDROID STUDIO
Android Studio is the official integrated development environment (IDE) for Google's
Android operating system, built on JetBrain’s IntelliJ IDEA software and designed
specifically for Android development. It is available for download on Windows, macOS and
Linux based operating systems. It is a replacement for the Eclipse Android Development
Tools (ADT) as primary IDE for native Android application development.
Features:
The following features are provided in the current stable version:
 Gradle-based build support
 Android-specific refactoring and quick fixes
 Lint tools to catch performance, usability, version compatibility and other
Problems
 ProGuard integration and app-signing capabilities
 Template-based wizards to create common Android designs and components.

 A rich layout editor that allows users to drag-and-drop UI components, option to
preview layouts on multiple screen configurations.
 Support for building Android Wear apps.
 Built-in support for Google Cloud Platform, enabling integration with Firebase Cloud
Messaging (Earlier Google Cloud Messaging') and Google App Engine.
 Android Virtual Device (Emulator) to run and debug apps in the Android studio.
Android Studio supports all the same programming languages of IntelliJ, and PyCharm e.g.
Python, and Kotlin and Android Studio 3.0 supports "Java 7 language features and a subset
of Java 8 language features that vary by platform version. External projects backport some
Java 9 features.
Requirements:
Version 3.x
Criterion Description
OS version
Microsoft® Windows® 7/8/10 (32-bit or 64-bit)
Mac® OS X® 10.10 (Yosemite) or higher, up to 10.13 (macOS High Sierra)
GNOME or KDE desktop Linux (64 bit capable of running 32-bit applications)
(GNU C Library (glibc) 2.19+)
RAM
3 GB RAM minimum, 8 GB RAM recommended; plus 1 GB for the Android
Emulator
Disk space
2 GB of available disk space minimum,
4 GB recommended (500 MB for IDE + 1.5 GB for Android SDK and emulator system
image)
Java version Java Development Kit (JDK) 8
Screen
resolution
1280×800 minimum screen resolution

Version 2.x
OS version
Windows 7 or later
Mac OS X 10.9.5 or later
GNOME or KDE desktop Linux
RAM 8 GB RAM recommended; plus 1 GB for the Android Emulator[20]
Disk space
500 MB disk space for Android Studio, at least 1.5 GB for Android SDK, emulator
system images, and caches
Java version Java Development Kit (JDK) 8
Screen
resolution 1280×800 minimum screen resolution.
Version 1.x
OS version
Mac OS X 10.8.5 or later
GNOME, KDE or Unity desktop on Ubuntu or Fedora or GNU/Linux
Debian
RAM 3 GB RAM minimum, 4 GB RAM recommended
Disk space 500 MB disk space
Space for Android
SDK At least 1 GB for Android SDK, emulator system images, and caches
JDK version Java Development Kit (JDK) 7 or higher
Screen resolution 1280×800 minimum screen resolution

4.5 ARDUINO PROGRAM
4.5.1 Algorithm
Step 1: Start
Step 2: Read TX /RX pin.
Step 3: Execute G-code command to provide translation.
Step 4: Define constants, variables, pin modes and directions.
Step 5: Self calibrate X, Y, Z to (0, 0, 0).
Step 6: Read the next serial input.
Step 7: Retrieve and map the serial input into drivers.
Step 8: Generate PWM signals according to Z – axis values.
Step 9: Execute line code to move X and Y to new position.
Step 10: Check if the target position is achieved or not.
Step 11: If NO, go to Step 6.
Step 12: If YES, operation completed.
Step 13: Stop.

4.5.2 Flowchart
No
Yes
Start
Read RX/TX
pin
Execute G-code command
to provide translation.
Define constants,
variables, pin modes
and directions.
Self-calibrate X, Y, Z
( 0. 0. 0)
Read next
serial input
Retrieve & map the serial
value into drivers
Generate PWM
signal (z- axis)
Execute line code to
move X & Y to new
position
Target
position?
Stop

4.5.3 Arduino IDE
The Arduino project provides the Arduino integrated development environment (IDE), which
is a cross-platform application written in the programming language Java. It originated from
the IDE for the languages Processing and Wiring. It includes a code editor with features such
as text cutting and pasting, searching and replacing text, automatic indenting, brace matching,
and syntax highlighting, and provides simple one-click mechanisms to compile and upload
programs to an Arduino board. It also contains a message area, a text console, a toolbar with
buttons for common functions and a hierarchy of operation menus.
A program written with the IDE for Arduino is called a sketch. Sketches are saved on the
development computer as text files with the file extension .ino. Arduino Software (IDE) pre-
1.0 saved sketches with the extension .pde.
The Arduino IDE supports the languages C and C++ using special rules of code structuring.
The Arduino IDE supplies a software library from the Wiring project, which provides many
common input and output procedures. User-written code only requires two basic functions,
for starting the sketch and the main program loop, that are compiled and linked with a
program stub main() into an executable cyclic executive program with the GNU tool chain,
also included with the IDE distribution. The Arduino IDE employs the program avrdude to
convert the executable code into a text file in hexadecimal encoding that is loaded into the
Arduino board by a loader program in the board's firmware.
4.6 CAMotics
CAMotics is an Open-Source software which simulates 3-axis CNC milling or engraving. It
is a fast, flexible and user friendly simulation software for the DIY and Open-Source
community. CAMotics works on Linux, OS-X and Windows.
Being able to simulate is a critical part of creating CNC tool paths. Programming a CNC
without a simulator is cutting without measuring; it's both dangerous and expensive. With
CAMotics you can preview the results of your cutting operation before you fire up your
machine. This will save you time and money and open up a world of creative possibilities by
allowing you to rapidly visualize and improve upon designs without wasting material or
breaking tools.

CHAPTER 5
RESULT AND ANALYSIS
Integrating the software along with the hardware and mechanical system makes up an
effective mini CNC plotter.
Fig 5.1: Plotted output image
5.1 ADVANTAGES
 Plotters are able to work on large sheets -- 2 or more feet -- of paper and still maintain
high quality resolution.
 A plotter may print on a wide variety of materials and thus offer its user many
options.

 Materials that a plotter can draw on include sheet steel, plywood, aluminum, plastic,
cardboard and almost any flat sheet material.
 Efficiency, reproducibility, accuracy and speed are all attributes of a plotter.
 Plotters can save all patterns and templates on disk and eliminate the hassle of having
to load the same patterns or templates over and over again.
 Additionally, the same pattern can be drawn thousands of time without any
degradation.
5.2 DISADVANTAGES
 The machine runs in a slow pace and generate excess heat which cause the heat sink
to be heated quickly.
 A slight error may remain on the image file after it has been plotted due to one side of
the Y – axis fixed to the moving mechanism and the other end is free to move.
 The Z – axis is not very rigid. So it causes slight vibration.
5.3 APPLICATIONS
The main applications of CNC machines comes in industrial field. Some of them are
discussed below:
• Metal Removal Applications – CNC machines are extensively used in industries where
metal removal is required. The machines remove excess metal from raw materials to create
complex parts. A good example of this would be the automotive industries where gears,
shafts and other complex parts are carved from the raw material. CNC machines are also used
in the manufacturing industries for producing rectangular, square, rounded and even threaded
jobs. All processes, such as milling, grinding, turning, boring, reaming, etc, can be controlled
and carried out by these CNC machines using specific machine tools for each task.
• Metal Fabrication Industry – Many industries require thin plates for different purposes.
These industries use CNC machines for a number of machining operations such as plasma or
flame cutting, laser cutting, shearing, forming and welding to create these plates. CNC
plasma or laser cutters are used for shaping metal, while CNC turret presses are used for
operations like punching holes. Other operations like bending metal plates can also be carried
out with very high precision using CNC press brakes.

• Electrical Discharge Machining Applications – Electrical Discharge Machines or EDMs
as they are also known, remove metal from the raw material by producing sparks that burn
away the excess metal. EDM machining through CNC automation is carried out in two
diﬀerent ways; ﬁrst through Wire EDM and second through Vertical EDM. CNC automated
Wire EDM is used to punch and then die combinations for creating die sets used in the
fabrication industry. CNC automated Vertical EDM requires an electrode in the same size
and shape as the cavity that needs to be carved out.

CHAPTER 6
CONCLUSION
In modern CNC systems, end-to-end component design is highly automated using computer-
aided design (CAD) and computer-aided manufacturing (CAM) programs. The programs
produce a computer file that is interpreted to extract the commands needed to operate a
particular machine by use of a post processor, and then loaded into the CNC machines for
production. Since any particular component might require the use of a number of different
tools – drills, saws, etc., modern machines often combine multiple tools into a single ”cell”.
In other installations, a number of different machines are used with an external controller and
human or robotic operators that move the component from machine to machine. In either
case, the series of steps needed to produce any part is highly automated and produces a part
that closely matches the original CAD design.
6.1 FUTURE SCOPE
 The pen of the machine can be replaced by a laser to make it work like a laser
engineering or cutting machine.
 Engraving machine can be used on wood.
 The pen can also be used for both milling and drilling purpose.
 The servo can be replaced with a stepper motor and the pen with a 3D pen to make it
a 3D printer which can print objects with dimensions.

REFERENCE
 V.K. Pabolu and K.N.H. Srinivas, "Design and implementation of a three –
dimensional CNC machine", Int. J. Computer Science and Engineering, vol. 2,pp.
2567-2570 2010.
 I. Nae and T. Andrei, "Designing and building a CNC router using stepper motors",
Serial Technical, vo. LXII, pp. 55-62, 2010.
 https://developer.android.com/things/
 www.YouTube.com/
 Wikipedia
 geocities.ws/industrialmarketplace/cnc- machines

DrawBot - Android Thing CNC Plotter

More Related Content

What's hot (20)

Similar to DrawBot - Android Thing CNC Plotter (20)

Recently uploaded (20)

DrawBot - Android Thing CNC Plotter