A Build-Your-Own Three Axis CNC PCB Milling Machine Fabrication and User Manual Teaching Learning Centre for Design and Manufacturing Education Indian Institute of Information Technology, Design and Manufacturing-Kancheepuram Chennai 600127 July 20, 2016.
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A Build-Your-Own Three Axis CNC PCB Milling Machine · 1.2. Reconfiguring CNC Milling Machine as PCB Prototyper The design of the CNC milling and drilling machine used in the proposed
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A Build-Your-Own Three Axis CNC PCB
Milling Machine
Fabrication and User Manual
Teaching Learning Centre for Design and Manufacturing Education
Indian Institute of Information Technology, Design and
Manufacturing-Kancheepuram
Chennai 600127
July 20, 2016.
Teaching Learning Centre for Design and Manufacturing Education
Teaching Learning Centre for Design and Manufacturing Education
3
1. INTRODUCTION The need for fabricating a prototype circuit arises frequently in electronics, including education and
research laboratories. In resource-poor countries in the developing world, this is hindered by the high cost
of commercial Printed Circuit Board (PCB) prototyping machines and long turn-around commercial
fabrication process. Practical, hands-on laboratory teaching and experimentation becomes necessary to
improve learning in electronics. In this project and in the following series of tutorials, a low-cost build-
your-own (BYO) semi-automated three-axis PCB milling machine for double-sided PCB prototyping is
developed using commercial components and open source hardware and free open source software to
provide students, teachers, and engineers an understandable, affordable source for PCB prototyping. Also,
the main problems encountered during fabrication of PCB have been mentioned and the techniques used to
solve are discussed in detail.
1.1. Need for PCB Prototyper in Engineering Institutions
The semiconductor industry is one of the fastest growing industries in our country and thereby. With
this, the production and the standard of printed circuit boards (PCB), which is the heart of every
electronic product, are on the rise. PCBs not only provide mechanical support for the electronic
components and also provide other services like electrical impedance matching, electromagnetic
shielding and heat conduction. Specialized courses and curriculum in PCB design and electronics
assembly are introduced in electronics engineering education. However, due to high cost of
commercial and often imported PCB prototyping equipment, there is a severe lack of practical hands-
on PCB design teaching and learning in India. This situation can be remedied with the increasing
affordability and versatility of open source hardware like microcontrollers and microcomputers,
commercial off-the-shelf components like actuators, sensors as well as free, open source software, which can be integrated for design of low-cost PCB prototyping machines for electronics education.
Do-it-yourself (DIY) PCBs can be designed using simple techniques such as using an iron to transfer
ink printed on a transparency to a PCB with chemical etching. Such as like the one presented in this
YouTube video at www.youtube.com/watch?v=6uInan-TjiA. But these methods lack sufficient
consistency for surface mount devices (SMDs) and the drilling of holes is tedious since it has to be
done manually. Further, the environmental and health hazards from chemicals used in these processes are significant.
Fig.1.1. Showing the process of chemical etching
Development of safe and high resolution milling and drilling of PCBs is enabled using isolation
routing which overcomes many of the above mentioned drawbacks. In Isolation milling, the copper
from the board is first removed to recreate pads, which are signal traces and structures based on the pattern generated by a PCB parts layout file.
Teaching Learning Centre for Design and Manufacturing Education
4
In this project, a BYO PCB prototyping machine has been developed and deployed to make both single- and double-sided boards for through-hole technology and Surface Mount Technology (SMT).
The common problems encountered while soldering the components on the PCB and aligning the
board layers have been discussed. Modern and innovative approaches used on an industrial level to
overcome these problems have been implemented in our machine and studied. Commercial techniques
used in easy and comfortable operation of PCB prototyping machines have been incorporated in the
machine.
The above features have been implemented using open source software programs so that teachers and
students themselves would be able to fabricate high-resolution PCBs in an academic environment
matching near-commercial quality. A major advantage of the proposed system is that users can
maintain and repair the machine on their own, without expensive annual maintenance contracts or
import of costly spare parts. With the understanding and experience gained, the users can also
gradually add advanced features like fully automated PCB machines with pick and place assembly, vision feedback, etc.
1.2. Reconfiguring CNC Milling Machine as PCB Prototyper
The design of the CNC milling and drilling machine used in the proposed PCB prototyping system is based on
our earlier developed 3-axis CNC milling system, presented in our other tutorial on Making Your Own 3-Axis
CNC Milling machine. A detailed explanation about the mechanical design, hardware and the software can be
found in that.
The main specifications of the milling machine are listed below:
Table 1. PCB milling machine specifications.
X,Y,Z axes travel 180 x 180 x 50 mm
Motors Steppers: 3x NEMA 17,200 step/rev, 2-phase,
1.3A
Spindle motor: 5000rpm @24 V DC, 0.3A no
load
Lead screws Stainless steel, 3xM8x1.25, 20 tpi
Stepper drivers 3 x single axis, rated 3A, up to 1/16 micro
stepping
Speed X, Y axes: 8 mm/sec
Resolution Electrical: 1.8° (0.0062 mm/step)
Mechanical: 0.01mm/step
Weight 14 kg
USB microscope Resolution: 640x480 pixel
Microcontroller Arduino Uno
Fig.1.2. Mechanical Setup of the Machine Fig.1.3. Electronics Hardware Assembly
Teaching Learning Centre for Design and Manufacturing Education
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A camera is mounted parallel with the spindle axis using a as shown in the below figure. A high speed spindle
motor of RPM 5000 is used and is powered by the 24V uniform supply from the SMPS used for CNC. The
milling and drilling tool bits are mounted to a high speed spindle motor with a precision ER-11 chuck which
holds bits with 1/8 shank dia. A 30° V-engraving bit with end width of 0.1mm is used for routing. A 0.6mm
single-fluted drill bit is used for making holes and a 0.6mm end mill bit is used for copper rubout and for cutting
sections of the boards. All the tool bits used for the operation are made constant in their height by adding a
depth setting ring. All bits used are tungsten carbide bits because of their extended tool life.
Rest of the machine settings and tools used in this PCB milling machine are same as the generic CNC milling
machine explained in the previous tutorial.
1.3. Isolation Routing Procedure
The outline of the procedure for fabricating PCB is as follows. The detailed explanation of the softwares
used and the design procedure is explained in the individual sections of the Manual.
The PCB design is first generated using a Computer Aided Drawing Software by the name Autodesk
Eagle CAD. The design of the circuitry is first drawn in a schematic file which is something like a
typical circuit diagram.
The circuit design is then transferred into the Board layout file in the same software where the exact
positions of the components of the circuit and the mounting holes and vias of the board are placed. The
components are connected by the copper traces here where they can be set in different bent styles,
angles, width, distances, etc.
The board layout is input into Computer Aided Manufacturing (CAM) Software called as FlatCAM
which converts it into a G-Code file which has the machine readable form of instructions for the CNC.
The CAM software simply analyses the position of the copper tracks and the position of the
components and generates tool paths to route and drill the board matching the board layout. Other
machining parameters for milling are also adjusted here.
The converted G-Code files are then fed into the machine using G-Code sender program called
Universal G-Code converter which controls the CNC controller.
The tool is first moved and set to an arbitrary origin position (with respect to all three axes). Now the
Etching G-code file is run which cuts out the tracks and the pads. Now the tool is moved again to its
previously set origin position and the drilling G-code file is run.
In case of double-sided boards, the same procedure is followed for generating G-Code data; the top
side is engraved first and then the board is flipped and aligned to the axis of the top layer and the
bottom layer is engraved and drilled.
Fig.1.4. Camera mounted parallel to Spindle Fig.1.5. Tool bits used
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2. Installation and Configuring EAGLE
2.1. Download & Installation.
EAGLE is available on Cadsoft’s download page https://www.autodesk.com/products/eagle/overview.
Please download the most recent version that matches your operating system (the software is available for
Windows, Mac and Linux). It’s a relatively light download – about 45MB.
EAGLE installs just like any ordinary .exe program, it’ll self-extract and then present you with a series of
dialogs to configure the installation.
Note: Few contents of this manual have been excerpted from Official Eagle Manual. For more detailed
instructions, you can look up the Documentation page of eagle.autodesk.com.
2.2. Using EAGLE as a Freeware
On the last screen of the installation process, you should be presented with a window like this:
The alternatives used in the place of Eagle are Fritzing, KiCAD, Cadense OrCAD and Proteus PCB Design
mostly. While the former two are open-source the later too are professional but highly commercial. Eagle
has been found to be ample enough for designing even complex PCB boards unless they are very much
multi-layered like covering 8 layers or so. However, there are a few limitations when using the free
version:
Your PCB design is limited to a maximum size of 100 x 80mm of PCB board area, which is still
pretty big. Even if we’re designing a big Arduino shield, we would still be under the maximum size.
Only two signal layers allowed. If you need more layers check into the Hobbyist licenses.
Can’t make multiple sheets in your schematic editor.
If you need to upgrade your license there are a few versions available. Most licenses are still incredibly
The first time you open up EAGLE, you should be presented with the Control Panel view. The Control
Panel is the home window for Eagle, it links together all of the other modules in the software.
You can explore the six separate trees in the control panel, which highlight separate functions of the
software:
Libraries – Libraries store parts, which are a combination of schematic symbol and PCB footprint.
Libraries usually contain a group of related parts, e.g. the atmel.lbr stores a good amount of Atmel
AVR devices, while the 74xx-us.lbr library has just about every TTL 74xx series IC there is.
Design Rules – Design rules are a set of rules your board design must meet before you can fabricate
your PCB. In this tree you’ll find DRU files, which are a pre-defined set of rules.
User Language Programs (ULPs) – ULPs are scripts written in EAGLE’s User Language.
ftp://ftp.cadsoftusa.com/eagle/userfiles/doc/ulp570_en.pdf. They can be used to automate processes
like generating bill of materials (bom.ulp), or importing a graphic (import-bmp.ulp).
Scripts – Script files can be used to customize the EAGLE user interface. In one click you can set the
color scheme and assign key bindings.
CAM Jobs – CAM jobs can be opened up by the CAM processor to aid in the creation of gerber
files.
Projects – This is where each of your projects is organized into a single project folder. Projects will
include schematic, board design, and possibly gerber files.
2.4. Using the Libraries
Included with EAGLE is a list of part libraries, which you can explore in the Control Panel view. There are
hundreds of libraries in here, some devoted to specific parts like resistors, or NPN transistors, and others
are devoted to specific manufacturers. This is a great and a comprehensive resource, but it can also be a bit
confusing. For example, even if you just want to add a simple through-hole electrolytic capacitor, there are
dozens of libraries and parts to sort through to find the right thing.
In many cases you will need to download and use the additional libraries suited for specific purpose. For
example if you are designing a Arduino board based on the manufacturing designing from Sparkfun, you
can use the Sparkfun libraries, which are filtered down to only include the parts that they’ve used in their designs only. So, in the following example we will see how to install Sparkfun libraries and use them.
Click on Choose under Create CNC Job to open a selection window with the list of tools. Each has the
format id: diameter, where the diameter is in the project’s units. Check the boxes by the tools you want to
include in the job. The comma-separated list of tools should appear in the Tools entry box.
3. Adjust Drill Z (Drilling depth), Travel Z (Height for X-Y movement) and Feed rate (Z-axis speed in
project units per minute) to your desired values, and click on Generate.
A CNC job will be created and the tool-path will be shown on the screen. Click on the “Export” button
under “Export G-Code”. This will open a dialog box for you to save to a file. This is the file that you will
supply to your CNC G-Code sender.
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6. PCB Isolation Routing and Drilling
(A video demonstration of Isolation Routing for fabricating Double-sided PCB is given in the TLC project Webpage)
6.1. Universal G-Code Sender
A detailed explanation on how to use the universal G-code sender and calibration of CNC using it has been
given in the previous tutorial. So, for now let us just assume that the CNC machine is properly calibrated and
the user has enough idea on what the UGS does. The figure below shows the UGS opened in PC and
connected to the CNC Arduino controller. And we know that the UGS can open and execute any .nc files
generated by CAM software and the live visualization can be viewed in the G-Code sender when the machine
is running.
Fig.6.1. Showing UGS open with file mode.
Before we move on to making our own PCB there are few fundamental theories and practices to be learnt on how a
copper bare-board is captured and measured or aligned by a CNC machine.
6.2. Zeroing the Tool Tip
Moving the CNC tool tip to its exact origin position is known as Zeroing the CNC. Several methods and
devices have been proposed for doing this precisely but the best and convenient solution is to use a
microscope/camera mounted parallel with the tool axis(as parallel as possible). The camera points downwards
facing the PCB surface and shows an image of the part of the PCB focussed on the computer screen including
crosshairs.
6.2.1. Calibrating Camera Offset
We know that the tool centre represents the centre of the axes and that the camera is mounted at a distance
parallel with the tool axis. This distance is known as camera offset and this offset should be balanced every
time when zeroing the CNC. The software we recommend to use for camera video streaming is AMCap
which has a feature of always staying on top of the other running programs in your computer screen and
shows a magnified image with cross-hairs in the image.
In order to measure the camera offset, a hole is first drilled on the board surface using a drill tool and the spindle is moved until the crosshairs of the camera image line up with the center of the hole. The offset
distance is now measured from the position displayed in Universal G-Code Sender (UGS) as shown in
Fig.6.2. We then save these coordinates into the macros tab of UGS (shown in the figure 6.3) which when
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executed tells to set a position as offset point with respect to origin using command G92.Now, In order to set
an arbitrary drill hole as origin, we just need to position the hole in camera and press the macro button with
the corresponding macro. For example, the figure below 6.2 shows how to measure the camera offset in UGS
and the figure 6.3 shows how to set camera offset using the Macro. The macro G92 X44.5 Y35.1 sets the drill
hole viewed under camera currently to be origin since the camera is at a distance of (44.5,35.1) from tool
centre. The above procedure will accurately set desired any desired location to X, Y = 0.
Fig.6.2. Showing to measure current work position in UGS.
Fig.6.3. Showing macro to set offset.
6.2.2. Probing for Z-Axis
Fig.6.4. Showing macro to set offset.
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But, the vertical position of the spindle, Z axis is also an important axis to zero out properly. For this, one
wire is connected to the probe which as the positive terminal of the circuit. This terminal is pulled high with a
10K resistor and connected to an input pin (Ex: A5) of Arduino. Another wire connected to the ground pin is
attached to the surface of the PCB when we mount it. We then use probing command “G38.2 Z-20 F20” in
UGS which moves the tool towards the board at a feed rate of 20mm/sec upto 20mm until the tip touches the
board and makes an electrical contact through the wire. Now, this way the CNC easily determines the exact
top of the surface and sets the origin position for Z axis.
Fig.6.5. Showing macro to set offset.
6.3. Making Double-Sided PCBs
In case of prototyping single-sided PCBs, the tool is moved and set to any arbitrary origin position (usually
on the lower left corner of the board) and probed for Z-axis. Then the Etching G-code file is run which cuts
out the tracks and the pads. Now the tool is moved again to its previously set origin position using the
“Return to Zero” option in UGS and the drilling G-code file is run.
But In case of double-sided boards, the same procedure is followed and the top side is engraved. Next, the
board is flipped and aligned to the axis of the top layer and the bottom layer is engraved and drilled. In any
cases, it is not possible to align the board accurately with the x-axis with the help of alignment pins or
markings; therefore the angle through which the board is rotated has to be measured to account for minute
variations. For this purpose, three reference holes are drilled on the four corners of the PCB board first along
x and y axis. The two holes serve to measure the alignment angle while the third hole helps us easily detect
which layer is up. The experimental procedure to do that is as follows.
Manually jog the tool along the four corners of your job using the command “G0” and drill the holes
corresponding to the thickness of your board using Z- button on UGS. The below picture shows to
manually jog to various corners of the PCB and drill hole using the Rapid positioning command with the
length of the sides of the PCB being 60 mm.
Fig.6.6. Showing macro to manually move to all corners of the PCB.
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Now measure the value of camera offset as explained in the top section and execute auto-levelling and
warp the board if you feel the board is bent. Run the g-code file for the top layer exported from your
FlatCAM.
Fig.6.7.UGS showing the visualization top layer of PCB.
For the bottom layer, turn the board around and capture the alignment holes along the edge of a board to
measure how much the board is skewed. The work position is measured in the UGS under UGS tab as
explained in previous section. The G-Code file for the bottom layer is rotated through this angle
measured using the G-Code command G-68.Example: The below picture shows the macro to rotate the
board just about the origin to 2.3 degrees.
Fig.6.8. Showing macro to rotate the co-ordinate system and hence the G-Code file.
The tool is moved to the origin position again using the camera-zeroing and camera offset macro in the
UGS. Now the G-Code file for the bottom layer is run. Once the bottom routing is done, the drill g-code
file is run successively. This takes care of both translation and rotation while flipping the PCB and the
tracks and holes would match each other on both the sides.
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Fig.6.9. UGS showing the visualization top layer of PCB.
Fig.6.10. UGS showing the visualization drill file of PCB.
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7. Special Procedures Often in PCB designing, there arise special needs to make complicated circuits that involve PCB traces on
both of the sides. There are also other problems while fabricating PCBs such as uneven bed flattening etc.
In this section of the tutorial, we will see how to use convenient techniques for easy calibration and
adjustments in PCB fabrication.
7.1. Autolevelling
One problem that exists while trying to create finely etched traces is the inconsistency in the height across the
surface of the board. Reasons for this are that the CNC bed may not be flat or that the boards could be warped or
bent, which is usually the case if the boards are larger in size. Even minute height variations such as 1mm would
increase the groove width to 0.672mm.This can in turn cause the copper tracks between grooves to become too
narrow, or create shallow “aircuts” forming incomplete traces when the height reduces. The technique used here
to solve this is to probe the PCB surface in a grid pattern for height variations and modify the G-code so that
there is uniform depth while milling. A figure depicting PCB board milled without and with the use of
Autoleveller respectively when the bed is not flat is shown above.
The software used here to do this is Autoleveller which interacts with the CNC controller and modifies and
outputs a G-Code file for us to run with UGS eliminating the height variations. Load the G-Code into the
autoleveller software using the Browse button; you would see that the Probe settings vary automatically
matching the dimensions of the PCB file loaded. You can change the default settings such as probe spacing(the
space between the points of the probing grid, probe depth(the maximum distance the probe will go down if no
contact on board is made) and probe clearance(the distance between the board surface and the probe tip as it
moves up before going to the next point of the grid).
Note: Make sure that you connect the probe clip to the tool tip before you run the Autoleveller else the tool will
bury itself into the board and break. Also shrink the board dimension by 5mm in X Length and Y length tab of
your Autoleveller for the bottom layer of a double-sided board as we drill holes in to the origin position of the
PCB in top layer.
Fig.7.1. Showing the making of PCB board with and without the use of Autoleveller on a skewed platform.
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7.2. Copper Area Clear
Removing large areas of copper is necessary when trying to avoid shorts due to dust, isolating components
or in RF circuits, where the remaining unused copper is just unwanted core load. We will see how to
eliminate all copper that is not specified in the Gerber source, while still being able to selectively choose
what to clear.
Open a Gerber file in your FlatCAM software. In the Selected tab for the Gerber Object, under Non-
copper regions, provide Boundary Margin and click Generate Geometry. This creates a new Geometry
Object containing a bounding box around the Gerber object, with the given margin. Then subtract the
The USB HANDHELD MICROSCOPE is a new electronic product for themicro object observation. It is a tubular imaging system consisting of anoptical lens, an image sensor, an illumination mechanism, and an imagetransfer control circuit connected to a computer. You can display the imagescaptured by the USB HANDHELD MICROSCOPE on the computer screen,store them on the computer, print them, or send them over the Internet.
AAAApplicationspplicationspplicationspplications
As a USB microscope, it can magnify stamps, coins, antiques, insects,electric circuits, machines, hair, skin, fabrics, food, decorations, etc.
AttentionAttentionAttentionAttention
Before installation and use of this product, please read the instructions inthis manual to ensure its correct use.
Before using this product, please carefully read the following safetyinstructions.
1. The socket that the computer is plugged in must be properly grounded,as the computer supplies power to this product. If in any doubt, pleasehave a professional electrician check and verify the grounding to ensuresafety.
2. Never use this product in stormy weather.
3. This product contains delicate and precision components. Be gentlewhen using it and avoid harsh handling or excessive force that maycause damage to the product.
4. The temperature of the handle increases slightly during use and it feels alittle warm. This is normal. If the product is overheated and hot to thetouch, immediately cut off the power and contact us for repair.
5. Never leave the product on unattended. Unplug from the USB port afteruse.
6. Do not disassemble this product. Disassembling this product will result inirreparable damage. The company is not responsible for damageresulting from disassembly of the product by the user. In case of anydifficulties in using the product, please contact us.
7. This product may only be used by children under supervision of an adult.Never give this product to a child to use or play by him or herself. Keepthis product out of reach of children.
8. Do not let this product come in direct contact with steam, vapor, water, orliquids of any kind. Such contact can cause irreparable damage that isnot covered by warranty.
9. When not in use, put the handle in the transparent sleeve and store it in atightly sealed box to avoid moisture and decay. Damages resulting from
improper storage are not covered by the warranty.10.The cable with this product has been strictly tested. To ensure safe use,
do not replace it.
SystemSystemSystemSystem RequirementsRequirementsRequirementsRequirementsFor best picture quality, the following specifications are recommended:1. Windows XP, Vista ,windows 72. 128M RAM or above3. At least one USB port (For best effect, USB 2.0 port is recommended).4. CD-ROM and a 40G or higher hard disc.
TechnicalTechnicalTechnicalTechnical SpecificationsSpecificationsSpecificationsSpecifications1. DSP: Digital Image Monarch Processor.2. Sensor: high-quality CMOS sensor3. Resolution: 640*4804. Colors: true color 24bit (RGB)5. Interface: USB2.0.6. Frame rate: 30 frames/sec (CIF and VGA).7. Magnification: 200×8. Size: 12mm in diameter,9. USB cable length: 1.6 meters
InstallationInstallationInstallationInstallationTo avoid mistakes in the installation process, please strictly follow thesesteps:Place the included CD into the CD-ROM drive.Find the icon of ‘amcap.exe’.Copy the ‘amcap.exe’ to your PC. Just copy but never try to install it.
Plug the HANDHELD MICROSCOPE into the USB port, and double click onthe icon of ‘amcap.exe’ to open the image window.
Properly connect the USB HANDHELD MICROSCOPE to the computer andto rotate the dial on the USB cable to controls the brightness of the LED onthe USB HANDHELD MICROSCOPE. After a short while you should seethe image captured by the USB HANDHELD MICROSCOPE on thecomputer monitor.
Double click on the icon and open an image window on the screen. After afew seconds the USB HANDHELD MICROSCOPE will begin to take imagesin the window. Click on ‘OPTIONS’ and click on ‘VIDEO CAPTURE PIN’.Choose one of image window size in the drop-down menu and click on ‘OK’to confirm.
FOCUSINGFOCUSINGFOCUSINGFOCUSING
The focusing ring is at the handle of the USB HANDHELD MICROSCOPE....When the focusing ring is rotated it adjusted the distance between lens andsensor for getting the clear image.
Please keep the head of USB HANDHELD MICROSCOPE tightly andsnugly touching the surface of the object during the focusing andobservation.
TAKETAKETAKETAKE PHOTOSPHOTOSPHOTOSPHOTOSPush down the snap key on the handle or pushdown the button of the dimmer that located onthe USB cable to freeze an image. Or click‘snap’ on the top of image window, or pushdown the ‘return key’ of keyboard to freeze animage.The photos you have taken will be saved in thecomputer and display an icon on the screen.
If your system could not freeze an imageplease follow steps to make it work:
1, Open the image window
2, Click on ‘capture’ on top line of the window
3, Click on ‘still’ in the pull down window
3, Click on ‘folder’
4, Designate the folder for your photos location
5, Click right mouse button to confirm
The photos can be taken by push down the button of the dimmer or justpush down the return key of the keyboard.
There is a LED light dimmer on the USB cable.Turning the dimmer can adjust the light power to aproper level according the demand of observation.
With the different display,resolution ratio and contrast,the definiton of the picture
will be different.So do the light, point of view.
MOVIEMOVIEMOVIEMOVIE RECORDRECORDRECORDRECORDFor making a record of still image please follow below procedures.1, Click on the ‘capture’ that located on the top line of image window2, Click on the ‘set time limit’ in the pull down window3, Click on the ‘use time limit’4, Input the number of seconds that you want to delay the record5, Click right mouse button to confirm6, Click ‘capture’ again7, Click ‘start capture’8, Click ‘ok’ to start the recorderThe movie record will be stopped while time is off.
Please keep all the receipts of your purchase in a safe place. You need toproduce the unaltered and original receipts to receive warranty coverage.Otherwise, the warranty is voided.
The warranty only covers the product if it is used under normal operationconditions. However, the following are not covered by the warranty:
Damages resulting from unauthorized disassembly or assembly of theproducts by the customer
Damages caused by fitting of improper components to the product
Damages resulting from unauthorized attempts to repair or to alter theproduct
Gross distortion, scratches, discoloration, or damage of the covering
Cracks, scratches, and mold spots on the lens
COMS sensor is burned or apparently scratched
Damages to the PCB board (such as burned PCB board) due to misuse
With vigorous shaking, the tiny dust may drop on the imaging sensor.Wecan ’ t see it with our eyes but it only showed on the picture aftermicroscopic’s magnifying,PLS don’ t repaire it unless you have enoughprofessional maintain experience and patience.If you want to repair it,pls refer the documents below1. PLS turn left of the camera lens, and do not touch the LED light.Or it willbe damaged.2. PLS safekeep the camera lens,and do not let it touch the alcohol.
3. PLS adjust the focal distance, let the imaging sensor move into a bestposition.In order to wash easily.we suggest that adjust the imaging sensor into the nearest distance4. Dip in a little absolute alcohol with fine cotton swab,using fine cottonswab clean the imaging sensor gently.If you are unexperienced,pls ask thehelp of the professional .(Notes:Don ’ t dip in too much absolutealcohol,protecting the alcohol from flowing itno circuit board and LED lightand don’t be too strong when cleaning)5.After confirimg dustout,pls turn on the LED ligth and keep for 15-20min tofast the alcoho volatilization.Because the alcohol will dissolve the gluearound the camera lens,pls make sure after volatilization totally,then installthe camera lensIf the lens need washing,don’t use absolute alcohol.Just clean the lens withcotton swab.To avoid the drop of the lens,pls don’t be too strong .For the unprofessional,it is difficult to maintain.We can’t see the tiny dustwith our eyes.This work need patience and professional technology.
2. Generation - The settings under this allow you to specify if you are fabricating a single or double-sided board,
which side you want the drilling process to happen, mirroring the pattern, etc.
3. Drill - Changes the depth of drills and mounting holes and drill dwell time.
4. Feed rates - These settings control how fast the CNC mill will cut and drill the board. As the feed rate
increases, the stress on the tool increases. Also, slower feed rates will ensure a smooth and clean cut on the board.
5. G-Code profiles - Altering the files under this helps you change the formats used by the program to generate
the G-codes to suit your machine.
Once all the input parameters are entered correctly, the software shows the preview and generates G-Code files
that cut out tracks individually for top and bottom layer, drill holes, engrave texts, and mill out sections of the board.
3.3. CNC machine control
The G-Code program is sent to Arduino from control computer (typically, a PC) by serial communication. Few
standard GUI open source software packages available for this are bCNC, Universal G Code Sender [10] or CNC
Grbl controller. These programs are very versatile and control the machine in manual mode or file mode. Options
similar to the human-machine interface (HMI) of expensive commercial CNC machines are included which help in
moving each axis individually, setting workspace origin, and homing cycles. Also, current position of world
coordinates and job coordinates are displayed based on signals sent from the software.
The software has options to set the current position to origin, return the machine to origin position, as well as
write and save complex commands under the macros tab used for tool and work offsets. The files generated by the
CAM software are loaded one by one and the tool is moved to the origin position and the job is run.
3.4. Isolation routing
In prototyping single-sided PCBs, the tool is moved and set to an arbitrary origin position (usually on the lower
left corner of the board). Now the etching G-code file is run which cuts out the tracks and the pads. Now the tool is
moved again to its previously set origin position and the drilling G-code file is run. Usually the option in the PCB G-
code software to create spot drills in the etching stage is used and then the actual drilling G-code file is run. Spot
6 Author name / Materials Today: Proceedings 00 (2017) 0000–0000
drills create ‘dimples’ or dents in the drill points so that the actual drill tool tip does not deflect and walk-off center
and the hole is drilled correctly. In case of double-sided boards, the same procedure is followed and the top side is
engraved. Next, the board is flipped and aligned to the axes of the top layer and the bottom layer is engraved and
drilled.
4. Techniques used in fabrication
4.1. Zeroing the CNC and probing
Moving the CNC tool tip to its exact origin position is known as Zeroing the CNC. Only then, we can ensure the
preciseness of the CNC and it has been a challenge in CNC operation. Several methods and devices have been
proposed for this but the best and convenient solution is to use a microscope/camera mounted in parallel next to the
spindle. The camera points downwards towards the raw material and shows a magnified image on the computer
screen including crosshairs. A hole is first drilled on the board surface using a drill tool and the spindle is moved
until the crosshairs of the image line up with the center of the hole. The offset distance between the camera and the
tooltip is now measured from the position displayed in Universal G-Code Sender (UGS) and then the offsets are
input under the macro tab of UGS. Thus, in order to set any point we want as origin, we move the camera to that
point and use the macro to set the current position as offset point with respect to origin.
The above procedure will accurately set desired X, Y = 0. But, the vertical position of the spindle, Z axis is also
an important axis to zero out properly. For this, one wire is connected to the tool tip, i.e. the probe and the other end
is pulled high with a resistor and connected to an input pin of Arduino (Fig. 6). Another wire connected to the
ground pin is attached to the surface of the PCB when we mount it. We then use probing command “G38.2” in UGS
which moves the tool towards the board with a given feed rate until the tip touches the board and makes an electrical
contact through the wire. Now, this way the CNC easily determines the exact top of the surface and sets the origin
position.
4.2. Autolevelling
One problem while trying to create finely etched traces is the inconsistency in the height across the surface of the
board. Reasons for this are that the CNC bed may not be flat or that the boards could be warped or bent, which is
usually the case if the boards are larger in size. The ideal depth of cut is found to be 0.01” i.e. 0.254 mm. A 30° V-
bit with this depth of cut gives a groove of width of 0.136 mm. Even minute height variations such as 1mm would
increase the groove width to 0.672mm.This can in turn cause the copper tracks between grooves to become too
Fig. 7. Effect of autoleveller in eliminating height variations Fig. 6. Probes attached to tool tip and board
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narrow, or create shallow “aircuts” forming incomplete traces when the height reduces; also increase in the depth of
cut in the dielectric layer causes impedance variations in high-frequency PCBs [11]. The technique used here to
solve this is to probe the PCB surface in a grid pattern for height variations and modify the G-code so that there is
uniform depth while milling. The software used here to do this is Autoleveller [12] which interacts with the CNC
controller and modifies and outputs a G-Code file for us to run with UGS eliminating the height variations. PCB
board milled without and with the use of Autoleveller respectively when the bed is not flat are shown in Fig. 7.
4.3. Alignment for double sided PCB
One of the biggest challenges in making double-sided boards is aligning the board after it is flipped for milling
the bottom layer. Many methods for alignment have been proposed. A reliable best technique used is to drill
reference holes along two corners of the PCB and locate them using the camera and measure by how much angle the
board is skewed. The points in the etch file and drill file are then rotated according to this angle and run [13], [14].
The matrix for rotation of coordinates around the origin by an angle θ from reference axis (X,Y) to rotated
axis(X’,Y’) is given as (Fig. 8.a,b).
[𝑋′𝑌′
] = [ 𝑐𝑜𝑠 (𝜃) 𝑠𝑖𝑛 (𝜃)−𝑠𝑖𝑛 (𝜃) 𝑐𝑜𝑠 (𝜃)
] [𝑋𝑌
]
Fig.8.a. Top side of PCB Fig.8.b. PCB flipped and rotated through an angle
Fig 9. Capture of reference hole in camera image and measuring current work position in UGS
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The angle θ is measured by the work position of the reference points displayed in the UGS. Now instead of
finding the transformation matrix and multiplying it to all the points in the G-Code file, we simply rotate the
machine’s coordinate axis system by the required angle using the macro command (G68) and all the matrix
transformation of the points occurs automatically inside the CNC controller. This step-by-step method ensures
surety in rotating the matrix than using separate software for matrix transformation. Fig. 9 shows the hole drilled being identified with camera and the corresponding work position. The angle θ is
measured by the work position of the reference points displayed in the UGS. Now instead of finding the
transformation matrix and multiplying it to all the points in the G-Code file, we simply rotate the machine’s
coordinate axis system by the required angle using the macro command (G68) and all the matrix transformation of
the points occurs automatically inside the CNC controller. This step-by-step method ensures surety in rotating the
matrix than using separate software for matrix transformation. Fig. 9 shows the hole drilled being identified with
camera and the corresponding work position.
4.4. Soldering
Soldering of SMDs has been found to be difficult and is believed to be a job of the expert. Microwave heating as
described below would enable users to perform the soldering conveniently. Formation of solder bridges are
prevented by routing tracks with high isolation distance and this has been found to provide good soldering without
the need for solder mask in procedure. Lead-free solder paste is first applied on the fluxed tracks and components
are mounted on top of them. This assembled board is then preheated for a while and then baked at moderate
temperature in a microwave oven. The solder joints are formed using reflow process and the components align
themselves precisely with the flux. Use of microwave heating facilitates both simultaneous and selective heating
process which does not cause damage to the components. The quality and reliability of the solder joints formed are
found to be reliable. The other properties and advantages of soldering using microwave heating are explained in
[15], [16].
5. Results and discussions
Different sets of experiments have been done with the designed machine similar to [17] to verify its practical
utility and presented below. But a fabrication method using chemicals has been used in [17] which is unsuitable for
academic environment.
5.1. Wire width and resolution
A series of copper tracks with diminishing width has been tried and the thinnest track line that could be reliably
Fig. 10. PCB fabricated with lines and SMT footprints
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fabricated with the machine is found to 0.2mm. Table 2 shows the calculation of the resolution of the line width
measured using microscope. ∆W is the deviation in the width from the theoretical input width WIN to the actual
routed width on PCB, WPCB. Fig. 10.A. shows the lines routed in the order of diminishing thickness from bottom to
top and a 0.1mm irregular track line at the top.
Table 2. Calculation of line width resolution.
Input unit WIN (mm) WPCB (mm) ΔW (mm)
0.6 0.563 0.037
0.5 0492 0.008
0.4 0.422 -0.022
0.3 0.352 -0.052
0.2 0.212 -0.012
0.1 NIL NIL
5.2. SMT board
Fig 10.B. shows a fabricated board with some of the typical ICs and components used in SMT. It consists of
SMT IC packages such as SOIC, TQFP, SOT23 and resistor and capacitor packages such 0603, 0805, 1206, SMA
etc. It has been inferred that a SMT footprint with a pitch size of as low as 0.3mm can be fabricated reliably with the
machine. In order to implement more precise operation, the machine has been planned to be redeveloped with
stepper or servomotors having optical encoder feedback in future.
5.3. Radio frequency circuits
A conventional branch line coupler is constructed employing four λ/4 transmission line in a ring. By following
the synthesis approach in [18], [19], we have designed and fabricated a branch line coupler (Fig.11) using microstrip
technology working at 2.45 GHz on a low cost 1.65 mm thick FR4 epoxy material with dielectric constant of 4.4
and a loss tangent of 0.02. The physical dimensions were calculated using microstrip line calculator and the board
was drawn in Eagle. Fig.12 illustrates the full-wave simulated S-parameters of the designed branch line coupler.
From the graph, the return loss (S11), throughput (S21), coupled (S31) and isolation (S41) are calculated as -3.7 dB,
-3.7 dB, -27.4 dB, and -31.63 dB, respectively. The experimental measurements of the fabricated prototype and
further calibration are under progress.
6. Conclusion
Thus, a low-cost BYO PCB prototyping machine has been designed and developed for fabrication of both single
and double-sided boards with through-hole and surface mount technology. The resolution of the machine was
Fig.11. Fabricated PCB of a Conventional BLC Fig.12. Full wave simulated S-parameters of BLC
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studied and fabrication of RF circuits has been presented. Commercial techniques used for easy and comfortable
operation of PCB prototyping machines have been incorporated in the procedure. The machine is fabricated with
commercial and inexpensive open source hardware components and freeware and so can be readily disseminated,
adapted and improved for widespread use in electronics education.
Pick and place mechanisms for changing the tool and placing the SMD components can be added in future. A
software program to find the rotation angle for the bottom layer during fabricating double sided boards and to
perform G-code transformation is being developed. It will identify the reference holes on the corners of the board
using computer vision (OpenCV) and send signals to the CNC to move the camera to the centroid of the rectangle
and measure the angle of the axis of bottom layer. It will then create a transformation matrix and modify the G-Code
and run the etch files automatically. This program will also have the ability to interact with the CNC controller and
automatically send macros, find the camera offsets and perform zeroing of CNC and run the whole operation cycle
on its own.
References
[1] S. Sengar, 2015, The rising semiconductor industry in India, http://www.electronicsb2b.com/industry-
buzz/rising-semiconductor-industry-india/
[2] R. S. Khandpur, 2005, Printed Circuit Boards: Design, Fabrication Assembly and Testing, Tata Mcgraw-
Hill Education, Delhi, India.
[3] P. H. Wald and J. R. Jones, (1987), Semiconductor manufacturing: An introduction to processes and
hazards. Amer. J. Industrial Medicine, 11: 203–221.
[4] S. Pandian and S. R. Pandian, 2014, "A low-cost build-your-own three axis CNC mill prototype", Int. J.
Mechanical Engineering and Robotics, 2(1), pp. 6-11.