Task	Person Responsible
Designing Engraving & Cutting Test	Camila
Testing engraving and cutting on acrylic & plywood	Both
Designing the Kerf Comb Test	Alfredo
Writting: Laser Cutter Safety Guide	Camila
Writting: Laser Cutter Calibration & Material Testing	Camila

Task	Person Responsible
Compare the toolchains and development workflows	Both
Xiao	Alfredo
micro:bit	Camila
Raspberry	Alfredo
Arduino	Camila

Fabruary 19, 2025

Week 5
3D scanning and printing

Group assignment:
Test the design rules for your 3D printer(s)

For this week’s Group Assignment , we explored the design rules of multiple 3D printing technologies, with the Prusa mini, Bambu A1 Mini and resin printing (SLA). The goal was to understand how different printers and materials handle overhangs, wall thickness, bridging, infill, and support structures.

3D Extrusion Printers

Some important printer characteristics can be found below:

Nozzle diameter: will impact the layer thickness of the material being deposed. The tip of the noozle also pushes the material being extruded. The layer should not be larger than the nozzle diameter. Nozzle diameters vary from 0.25 to 0.8mm.
Working area: important to select the right area for the size of model you are building.
Table positioning: can impact the attachment of the piece to the surface. Auto leveling helps control this.
Chamber: a chamber is useful with materials that shrink when cooling which produce breakage if different parts of the model cool at different rates.
Temperature: different materials might need different temperatures for being struded.
Material extruder: whether is direct or bowden.

Slicer Characteristics

Some print characteristics that can be controlled through the slicer are:

Layer height, however is related to the nozdle size.
Infill percentage will determine the percentage of material inside the object being printed.
Number of horizontal and vertical walls.

Nozzle diameter will affect the definition/detail on the horizontal plane while layer height will affect the detail on the vertical and slanted sides . As a rule of thumb layer height should not exceed 80% of nozzle diameter (Prusa’s blog).

https://blog.prusa3d.com/everything-about-nozzles-with-a-different-diameter_8344/

Nozzle horizontal plane definition(source=Prusa’s blog)

Layer height and definition(source=Prusa’s blog)

In addition to layer height a slicer will let you specify vertical and horizontal walls as number of layers. For the vertical walls in the image below subtract the shown vertical outside walls rom the walls above the purple surface which should give 3. It is adviced to have more top layers compared to bottom ones as the top will have only the infill for support which could cause the filament to drip contrary to the bottom wich is supported by the printer’s platform. In general the amount of material will vary between a functional print and a aesthetic one.

Similarly, one can specify infill as a percentage are the red layers (rhomboid shape) inside the cube.

Below you can find a picture of useful utensils that come handy with an extrusion printer.

Safety Guidelines for Extrusion 3D printing [in our lab]

Materials needed for operation

Filament.
IIsopropyl alcohol (>90%).
Spatulas, forceps, cutting tools and tools to dislodge filament.
Cleaning wipes

Personal Protective Equipment

Depending on the material being printed you may need:
Respirator
Apron
Gloves

Operation sequence

Unload filament if a new one is to be used.
Load filament and
Purge the remaining filament
Slice stl file and according to your application adjust for:
- Vertical and horizontal walls
- Infil
- Material,
- Nozzles size,
- Temperature
- Supports
- Etc..
Make sure it fits on the plate!
Check your sliced object to make sure there are not problems
Print G file and save it to a USB or send it throught wifi depending on the printer.
Keep an eye from time to time on the printer
Collect your print and clean the area.

Operation Precautions (People)

Be aware of the characteristics and safety guidelines of the materials you are using.
Use filaments that correspond to the printer settings and if possible use ones that have lower emissions.
Operate the printer in a well ventilated place.
Avoid standing close to the printer for long periods of time.
Be careful if you use alcohol to clean the printer’s plate as it is highly flammable.
Avoid touching heated platforms or hot nozzles.
Wash your hands after/before utilizing the printer
Disconnect the printer if changin/repairing printer pieces to avoid electric shock.

Operation Precautions (Machines)

Clean the machine’s plate with alcohol after each print in order to avoid grease build up.
Use appropriate filaments with their correct settings.
Avoid build up of dust as this increases.
If you change a nozzle make sure you update your slicer settings.
Let the model print cool down before removing it from the printer’s platforms.
Clean the work area thoroughly when finished.
Dispose residual filament appropriately.

Our Lab Safety Guidelines for Extrusion Printing

Prusa Mini

Below you can find a diagram of the Prusa Mini from:

https://help.prusa3d.com/article/glossary-mini_125081

From this article is important to note:

8-Main PTFE tube (Bowden-tube): leads the filament strand from the extruder into the print head/nozzle. Inspect it from time to time to make sure there is no debris inside that would prevent the filament strand from reaching the nozzle.
10-Print fan: cools the printed object, and improves print quality. Comes with RPM monitoring.
11-Print head: Lightweight print head consisting of the hotend (printing nozzle), M.I.N.D.A. sensor, and two fans. The heaviest parts of the extruder were moved onto the Z-axis tower to improve print quality.
14-Extruder / Extruder motor: as opposed to 3D printers like MK2 or MK3S, the extruder motor is not moving along the X-axis. Instead, it’s fixed on the side and pushes filament through the PTFE tube towards the print head.

which make the Prusa Mini is a bowden extruder. Bodwen extruders present the following pros and cons:

Pros: - Cleaner movements: as the extruder is not located in the printer head allowing faster movements and better print quality. - Larger build volume: as it allows for a smaller head carriage.

Cons: - Needs a more powerful motor. - Slower response times due to the distance between the print head and extruder. - Material complications flexible materials can bind or wear in bowden tubes.

from: https://all3dp.com/2/direct-vs-bowden-extruder-technology-shootout/

The slicer for the Prusa Mini was configured as:

with an infill of 15% and using the generic PLA setting for type of material.

Bambu A1 Mini (Q) - General Features

The Bambu A1 Mini (Q) is an advanced entry-level 3D printer that offers high-speed and high-precision printing with an easy-to-use interface. This model is designed to provide a seamless printing experience with minimal setup time.

The A1 Mini (Q) is an excellent choice for beginners and professionals alike, offering reliability and ease of use with features that make 3D printing more efficient and precise.

Key Features:

Build Volume: 180 × 180 × 180 mm
Nozzle Diameter: 0.4 mm (default), supports 0.2 mm and 0.6 mm
Layer Height: 0.1 - 0.3 mm
Extruder Type: Direct Drive for improved performance with flexible filaments
Printing Speed: Up to 500 mm/s
Acceleration: 10,000 mm/s² for ultra-fast movements
Temperature: Max extruder temperature 300°C, heated bed up to 100°C
Auto Bed Leveling: Uses LIDAR-assisted calibration for precise first-layer adhesion
Multi-Color Printing: Compatible with the AMS (Automatic Material System) for seamless filament changes
Filament Compatibility: PLA, PETG, TPU, ABS, ASA, and more
Connectivity: Wi-Fi, SD card, and USB support
Software: Works with Bambu Studio and third-party slicers

Resin 3D Printers (SLA)

Important Resin Printer Parameters

The documents that follow describe some key parameters of resin printers:

https://store.anycubic.com/blogs/3d-printing-guides/3d-printing-parameters-of-resin-printer?srsltid=AfmBOooAoccop8OxJFcS33-srpdOZS5MyuufMflMYK0Aj16zgqottKCG

and

https://store.anycubic.com/blogs/3d-printing-guides/common-parameters-description-of-resin-printer?srsltid=AfmBOor3nFigVD1I4lttoq839dnrujBsUfNk5XFMOtClglgzMIOD_bjd

I have summarize these in ChatGPT with the following prompts: Summarise in 3 to 4 lines:…

Exposure time: controls how long resin is cured with UV light, affecting print quality and accuracy. Too short or too long exposure can cause weak, brittle, or swollen prints. Factors like resin type, temperature, and layer thickness influence the ideal exposure time.

Bottom Exposure time: The bottom layer is the first printed layer, and its exposure time affects adhesion to the platform. A longer bottom exposure time improves adhesion, preventing warping or detachment. Both bottom exposure time and the number of bottom layers determine print stability. Model size, weight, bottom contact area and resin properties.

The optimal operating temperature for the resin is around 24°C, which may vary slightly depending on the resin type.

Number of Bottom layers: Bottom layers are the initial layers exposed for a longer time to ensure strong adhesion to the platform. More bottom layers increase adhesion but can make the base larger than other layers. Around six layers are recommended, but the ideal count depends on model size, weight, and resin type. Taller models generally require more bottom layers for stability.

Off time: is the interval between the platform stopping and the next exposure, typically 1-3 seconds. It allows resin to flow back and stabilize, ensuring even layer formation. Higher viscosity, low temperatures, or large print areas require longer off times.

Z Lift Distance: Z lift distance is the vertical movement of the build platform between layers, ensuring proper layer separation. A precise distance prevents print or platform damage while optimizing print time. Reducing lift distance speeds up printing but may cause separation issues due to FEP film elasticity. It is generally recommended to use the default settings.

Z lift Speed: Z lift speed is the rate at which the build platform rises between layers, affecting print stability. If too fast, it creates high tensile force, risking cracks or failures; if too slow, it increases print time.

Anti-aliasing: smooths jagged edges in resin prints, improving surface finish and reducing layer stepping. Higher settings enhance edge quality but increase slice time and file size. It works alongside gray level and image blur techniques to refine pixel patterns in each layer.

Safety Guidelines for Resine Printing [in our lab]

Materials needed for operation:

405nm UV-resin. Resin types for the Photon Mono X and printing parameters can be found:https://store.anycubic.com/blogs/news/resin-settings-for-anycubic-3d-printers?srsltid=AfmBOoo1EzQdeN-_s_7_FxLSeghJwu5SCRzCA3sgt_XB7r4Y5dTT5Jfo
Isopropyl alcohol (>90%)
Airtight containers for washing.
Spatulas, forceps, cutting tools.
Funnel
Cleaning wipes
Colanders

Personal Protective Equipment(PPE)

Googles
Gloves
Respirator
Apron

Operation sequence

Raise built area and allow for resin to drain.
Remove cover from the printer
Unlock the build area platform and remove it with care.
Pry the print object apart from the build area with the spatulas [Check with MPI]
Replace build platform and cover to the printer
Perform an initial wash to remove the excess of resin and clean the tools used to pry open the print model.
Open the Anycubic wash container and place the print.
Close the lid of the wash container and set the washing clock, press knob to start.
Once time is over unlock the washer, take out the print and dry it. Replace the cover of the washer so the isopropyl won’t evaporate.
Once dry, place in the curing machine and place the UV protection cover.
Set the timer and wait until the print model is cured.

Operation Precautions (People)

Be aware that many resins are toxic.
UV exposure can be harmful to skin and eyes.
Be also aware that isopropyl alcohol is highly flammable and take appropriate precautions.
Prior to operating the machine read the safety data sheet for the resin to be used and be aware of what are the procedures if you were exposed to them.
Warn someone that you will be working with this resin 3D printer.
Make sure that the area of work is well ventilated.
Wear personal protective equipment described above at all times.
Operate machines with lids closed.
Make sure you close the lids of all containers you open after their use.
Ask the lab manager if you have any doubts.

Operation Precautions (Machines):

Clean equipment and machines if they are contaminated with resin.
Replace the printer resin container if you find a leak.
Remove resin from the printer container if you will not print anything else in the next 48 hours.
Dispose of residues appropriately, do not flush them down the sink.
Clean the work area thoroughly when finished.
Inspect and clean your protective gear thoroughly after each use.

Our Lab Safety Guidelines for Resine Printing (Photon Mono X)

Photon Mono X

The Photo Mono X is a fairly big size resin printer from Anycubic

Some of the printer characteristics:

Build Volume: 192mm(L）x 120mm(W）x 245mm（H）
Light-source: high-quality filament（wavelength 405nm）
XY Res.: 0.050mm 3840*2400（4K）
Z Axis Res.: 0.01mm
Layer Res.: 0.01-0.15mm
Printing Speed: MAX 60mm/h

Resin Printer Configuration

For the resin printer we had two settings as for the first print (in grey) we observed an elephant foot. For the second the exposure time for the bottom layer was reduced from 28 to 18. We also changed the resin (white.)

Test design Rules

1. Negative Tolerance Test

We found that 0.05 and 0.10 millimeter would lock in the two pieces. The former is too tight and might not be the most appropiate size difference between the two pieces.

2. Thickness Test

Overall, for the thickness test we found the thickness decrease from left to right for the Prusa printer(white). However, it would seem that given the diameter of the nozzle is 0.4, some of the smaller width repeated. This was not the case for the resin printer(grey) which printed one additional thickness, and were you can see that all the thickness decrease from left to right.

3. Bridging Tests

The bridging test was successful for the Prusa printer. For most bridges length there were some lines of filament that hanged from the bridges bottoms. The maximum bridge length attained was 8 cm.

4. Angle Test

The angle test was a bit redundant as we had already seen that “parallel to the ground” bridge construction was possible. However it was interesting to see that there were some residual filaments only on 0 and 10 degrees from the ground plane.

5. Overall test resin

We could observe that in resin we were capable of building very fine structures….

Bambu A1 Mini - Testing Results

Below are the results of various print tests conducted using the Bambu A1 Mini.

1. Wall Thickness Test

Print Time: 23 min 38 s
Observations: The print quality was excellent. Thin walls were well-defined, but the first three layers (0.1, 0.2, 0.3 mm) did not print due to slicer limitations. Most slicers establish a minimum threshold based on the nozzle diameter. If a feature is thinner than this threshold, it may be automatically omitted to prevent printing errors. Adjusting the extrusion width settings in Bambu Studio could help resolve this.

2. Bridging Test

Print Time: 28 min 38 sec
Observations: Bridges up to 5 mm were good, but at 9 mm and 10 mm, there was noticeable stringing and sagging.

3. Angle Test

Print Time: 49 min
Observations: Overhangs remained stable up to 30°. At 10° and 0°, noticeable imperfections appeared.

4. Tolerance Test

Print Time: 54 min
Observations: 0.1 mm tolerance fits well with a firm grip, similar to laser-cut fits.

Tested Infill Patterns

Honeycomb: Excellent strength-to-weight ratio, ideal for structural parts but increases print time.
Cross Hatch: Balanced strength and speed, useful for general-purpose prints.
Adaptive Cubic: Optimized for strength while using minimal material, dynamically adjusts density.
Cubic: Strong and efficient for load-bearing parts, faster than honeycomb.
Octagram Spiral: Visually unique, flexible but weaker than the other patterns, suitable for aesthetic prints.

Files

Bridge Overhang String Test (thingiverse)

Printer Tolerance Test (thingiverse)

Resin printer test (thingiverse)

Negative Tolerance Test(Printable)

Angle test (Fab Academy site)

Overhang Test(Fab Academy site)

Thickness Test (Fab Academy site)

Fabruary 26, 2025

Week 6
Electronics Design

use the test equipment in your lab to observe the operation of a microcontroller circuit board.

Understanding Electronic Testing & Measurement

Before diving into hands-on testing, it’s important to understand the essential concepts behind electronic diagnostics. Electronic circuits are built upon voltage, current, and resistance, and each component behaves differently under these conditions. Testing tools allow us to measure, visualize, and troubleshoot these properties effectively.

Voltage (V)The potential difference between two points in a circuit, measured in volts (V). Essential for checking if a circuit is powered correctly.
Current (A)The flow of electric charge, measured in amperes (A). It determines how much power is moving through a circuit.
Resistance (Ω)Opposition to the flow of current, measured in ohms (Ω). Helps diagnose faulty components or incorrect wiring.
Digital vs. Analog SignalsDigital signals - switch between HIGH (1) and LOW (0), while, Analog signals - vary continuously. Understanding this distinction is key when using logic analyzers and oscilloscopes.

Group Task Distribution

Task	Person Responsible
Multimeter	Camila
Power Supply	Alfredo
Logic Analizer	Camila
Oscilloscope	Alfredo

Exploring Test Equipment for Electronics Design

Power Suppy

The Hanmatek 305 is a power suppy with knobs to control the voltage and the amperage in a range of 0-30 Volts and 0-5 Amperes respectively. In addition, there is a safety button to stage the changes made in these knobs. We used the device to to run different sizes motor to guess what were the operating ranges by varying the voltage and amperage.

Oscilloscope

While the multimeter takes an average of the signal at point in time giving a single value, the oscilloscope is used to measure an electrical signal dynamically throughout time.

In this video you can see the electricall signals as we change from DC to AC.

For this purpose we ran a micro python program where we turn on and off a pin in the Xiao ESP32S3 micro controller.

from machine import Pin
from time import sleep
on_pin = 4
pin = Pin(lon_pin, Pin.OUT)
for i in range(1200):
  pin.on()
  sleep(1)
  pin.off()
  sleep(1)
  print("on",i+1)

In the video above the bottom labels indicate:

the vertical separation on the vertical axis (in this case 2 volts)
the attenuation of the probe,
the horizontal separation of the measurements in the horizontal axis (in this case 5\(\mu\)S)
and the type of current being measured (AC/DC)

Multimeter: The Go-To Debugging Tool

A multimeter (Measures electrical properties such as voltage, current, and resistance) is the first tool you reach for when something in a circuit isn’t working. We used it to:

Check LED polarity (because putting them in backward is a classic mistake).
Test continuity in cables—some of the wires in the Fab Lab were unreliable, so we had to confirm which ones were actually conducting.
Measure voltage levels to ensure our power lines were supplying the right amount to the microcontroller and components.

Logic Analyzer: Seeing Data in Action

While a multimeter is great for checking voltages, when it comes to digital signals and communication protocols, we needed something more advanced—a logic analyzer(Captures and visualizes digital signals to analyze communication protocols.). We worked with a Saleae Logic Analyzer, which is essentially a device that "listens" to data traveling between components and helps us visualize what’s happening, We saw a video to guide us: Decoding UART, I2C and a non-standard signal

We clipped it onto an Arduino’s TX and RX pins to monitor serial communication.
The "Logic" software let us capture and analyze the data being sent and received.

We could see real-time data packets moving across the screen, confirming that our Arduino was actually transmitting information correctly.

void setup () {
	Serial.begin(9600);
	delay(1000);
}
																	
void loop() {
	Serial.println("hello camila and alfredo!!!");
	delay(2000);
}

Why These Tools Matter in PCB Design

This assignment wasn’t just about using test equipment—it was about developing a debugging mindset. It’s easy to assume a circuit will work just because the schematic is correct, but real-world electronics always have surprises.

Key takeaways:

A multimeter is your best friend for checking power, connections, and basic functionality.
A logic analyzer is a game-changer when working with communication protocols—it helps you actually see what's happening in your circuit.
Always test your components before soldering them—bad wires or incorrect polarity can cause hours of frustration later.

Marcg 05, 2025

Week 7
Computer-controlled machining

This week at Fab Academy, we focused on CNC machine safety, setup, and calibration to ensure proper operation before cutting. The session covered lab safety training, machine controls, tool selection, and materials.

🔧 Lab Safety Training

Before operating the CNC machine, it was crucial to complete a safety training session. The CNC milling machine is a powerful tool, and improper use can lead to injuries, tool breakage, or material damage.

Key Safety Considerations

Personal Protective Equipment (PPE)

Safety glasses: Protect against flying debris.
Hearing protection: CNC machines can be loud.
No loose clothing, jewelry, or gloves: These can get caught in moving parts.
Closed-toe shoes: Protect feet from falling tools or materials.

⚠️ Emergency Stop and Safety Protocols

The Emergency Stop (E-Stop) button immediately halts all operations.
Power failures or sudden machine malfunctions require a manual reset before resuming operations.
Fire hazards exist when cutting flammable materials, so a fire extinguisher must always be within reach
A first aid kit should be easily accessible in case of minor injuries.

CNC Machine Overview & Controls

For this assignment, we used the Fresadora CNC 1325, a mid-size CNC router equipped with an air-cooled 4.5 kW spindle, a vacuum bed.
Machine Components The main components of the CNC router include:

Spindle: The motorized cutting tool, capable of reaching 18,000 RPM.
Worktable: The machine features a vacuum table that helps secure materials during cutting.
Linear Motion System: The X and Y axes move using a rack-and-pinion system, while the Z-axis is controlled via a ball screw drive.
Control System: The DSP handheld controller allows the operator to move the spindle and set the zero position manually.

Setting the Home Position we must set the home position (machine zero):

Move the spindle to the desired origin point (X, Y, Z).
Use the DSP controller’s movement keys to fine-tune the positioning
Set this point as the zero reference by pressing "XYZ Zero".
Control System: The DSP handheld controller allows the operator to move the spindle and set the zero position manually.

Router bit

The choice of router bit determines the cutting efficiency and final surface quality. We tested several types of bits: Common Router Bits & Their Applications

Spiral Upcut BitThis bit is great for removing material quickly and keeping the cut cool. It pulls the chips upward, which helps clear debris but can also cause rough edges on the top surface. It works best for plastics, soft metals, and deep cuts, where chip evacuation is important.
Spiral Downcut Bit Unlike the upcut bit, the downcut bit pushes chips downward, leaving a cleaner top surface. This is ideal for wood, plywood, and laminates, where you want smooth edges on the visible side. However, it can trap chips in deeper cuts, which might generate heat and affect performance.
Straight BitA straight bit cuts evenly in all directions, making it perfect for pocketing and simple profile cuts. It doesn’t create a pulling effect like spiral bits, which helps prevent material tear-out. This bit works well for MDF, softwood, and plastics when a clean and stable cut is needed.
Compression BitA combination of upcut and downcut geometry, this bit is ideal for plywood and veneered materials. It pulls up from the bottom and pushes down from the top, leaving both surfaces clean and smooth. This makes it perfect for materials that tend to chip or splinter. Each of these bits has its own strengths, and selecting the right one depends on the material, the type of cut, and the final finish you want. By understanding their behavior, we can achieve cleaner cuts, faster production, and better overall results in our CNC projects.
End Mill Designed for precision and high accuracy, end mills are commonly used in metal, acrylic, and composite materials. They provide smooth, controlled cuts and are great for detailed profiles and deep slots. Unlike typical wood-cutting bits, end mills have sharper edges and can handle harder materials.

Source: ToolsToday Learning Desk

Ensuring CNC Precisiong

Runout: Checking Tool & Spindle Accuracy

Before diving into machining, we performed a runout test directly on the CNC router to check if the spindle and tool were properly aligned. Runout happens when the cutting tool doesn’t rotate perfectly centered, causing wobbling. This can lead to inconsistent cuts, uneven slot widths, rough edges, and faster tool wear.
We ran a test by cutting parallel slots into the material at different feed rates and speeds to observe any variations in cut accuracy and edge finish. The image below shows the results, where we measured slot widths and noted speed settings. Our findings confirmed that runout on this CNC machine was minimal, meaning the spindle and collet were well-calibrated.

Dial Indicator Test

Why Did We Also Use a Dial Indicator?

Even though the CNC’s runout was minimal, we wanted to better understand how misalignment impacts precision, so we performed a secondary test using a dial indicator on a smaller milling machine. This allowed us to visualize how small tool or spindle misalignments affect precision.
By rotating the spindle manually and observing the needle movement on the dial, we saw how even slight shifts in alignment could impact cut quality. This reinforced the importance of checking tool seating and spindle calibration before machining.

Speeds and Feeds

Understanding Feeds, Speeds, and Chip Load

One of the most crucial aspects of CNC machining is setting the correct feed rate, spindle speed, and chip load to achieve clean, efficient cuts while preventing tool damage. These parameters determine how fast the tool moves through the material, how deep each pass should be, and how much material is removed per revolution. We used the spreadsheet calculator from “Calculating Feeds and Speeds – A Practical Guide | Wood CNC Router” by Cutting It Close to determine the optimal settings for our tool and material.

Chip Load Calculation Formula

The chip load is the thickness of the material removed by each cutting edge of the tool. Proper chip load values help ensure that the tool doesn’t overheat or wear out too quickly. We calculated our feed rate using the following formulas:

Feed Rate Formula:

Tool Diameter	Hardwood (Chip Load)	Softwood/Plywood	MDF/Particle Wood	Soft Plastic	Hard Plastic
3mm	0.08 - 0.13	0.10 - 0.15	0.10 - 0.18	0.08 - 0.15	0.05 - 0.10
6mm	0.23 - 0.28	0.28 - 0.33	0.33 - 0.41	0.18 - 0.26	0.15 - 0.23
10mm	0.41 - 0.46	0.43 - 0.51	0.51 - 0.59	0.26 - 0.31	0.20 - 0.26
13mm & up	0.48 - 0.54	0.54 - 0.59	0.64 - 0.69	0.31 - 0.41	0.26 - 0.31

Using these formulas, we adjusted our settings to maintain a balance—avoiding a feed rate that’s too slow (which could cause burning) or too fast (which could break the tool or create rough edges).

Feed Rate Table

Below is the feed rate table we used to determine the correct cutting parameters based on tool size and material.

If you’d like to reference or modify the calculations, you can download the feed rate spreadsheet here:

Vacuum Table & Sacrificial Board

Why Material Holding Matters? Before any CNC machining operation, one of the most critical steps is securing the material. If the workpiece moves, even slightly, during the cutting process, it can cause misalignment, rough edges, tool breakage, or even machine damage. To ensure stability, two common methods are used: vacuum hold-down systems and sacrificial boards.

How the Vacuum Table Works

A vacuum table uses negative pressure to hold down the material during machining. The principle behind it is simple: atmospheric pressure pushes down on the material while the vacuum pump removes air from beneath it, creating a pressure difference that keeps the workpiece firmly in place.

How Strong is the Hold?
The force holding the material depends on the vacuum pressure and the surface area of the material. A larger material has more surface area in contact with the vacuum, increasing the holding force.

See the diagram below for a visual explanation of how vacuum tables generate hold-down force
See the diagram below for an illustration of cutting forces acting on the material

Source: Mekanika.io

The CNC router we worked with has a vacuum table divided into six independent sections, controlled by valves. Each section can be activated or deactivated depending on the size and position of the material being cut. By closing certain valves and keeping only the necessary sections open, we could optimize the suction force applied to the board, making sure it stayed completely flat against the sacrificial board.

Factors Affecting Vacuum Strength:

Material surface area Larger pieces experience stronger suction.
Leaks or gaps in material Air leaks reduce the vacuum’s effectiveness, so materials with holes or rough surfaces may need additional sealing
Vacuum pump power A higher-pressure vacuum pump creates a stronger hold.

Sacrificial Board

The Role of the Sacrificial Board A sacrificial board is a layer of material placed between the CNC machine’s bed and the workpiece. Its main purpose is to protect the CNC table from tool damage while also improving vacuum performance.

Protecting the CNC Table: Since CNC operations often involve cutting all the way through the material, the bit can cut slightly into the machine’s surface. A sacrificial board absorbs these cuts, preventing permanent damage to the actual bed.
Enhancing Vacuum Hold Some materials, like plywood, have tiny air gaps that weaken the vacuum suction. A sacrificial board—typically MDF—creates a better seal between the vacuum table and the material, preventing air leaks and ensuring a stronger hold.
Allowing Full-Depth Cuts Without Worry With a sacrificial board in place, users can confidently set their toolpaths to cut slightly beyond the actual material thickness, ensuring clean cuts without worrying about damaging the machine

Source: Cutting It Close "Calculating Feeds and Speeds A Practical Guide | Wood CNC Router"

---

File Preparation

Here I describe how to prepare the Aspire file for the CNC machine.

We set up .SVG file or .DXF with the vectors to be cutted.

Note: We want to arrange the files that we have exported with the sharper tool(Fusion) one by one in a svg file. In our lab workflow we import this as DXF into Aspire rather than an svg as the latter produces the following Aspire warning:
Then in Aspire we set the dimensions of the board and the origin point.
We go to file and import a vector file with the tracing of the object(see above).
We can observe the imported trajectories where the CNC machine will cut.
We set the cut depth and the number of passes.
Then we set the tool characteristics.
Subsequently we set taps/bridges.
We can edit the taps displayed produced by the program.
And finally, the software allows to do a simulation of the cutting.

Pre-programation of spindle and feed speeds

Below you can find a image of the of the CNC control where you can see the different keys needed to operate the machine:

The control will allow us to set up preconfigured spindle and feeds speeds. Below you can find the sequence of commands to program these parameters as to have a set of options

Press Menu → Auto Pro Setup → OK.
Scroll to G-code setup→ OK
Navigate to Read →press Run→ select ReadS→ press OK
Press Menu→ Enter Machine Setup → OK
Select Spindle Setup → OK
Select Spindle State→ OK
OK x2 to get to the speed set up menu
Set the spindle speeds as needed:
Level 8: 18,000 RPM
Level 7: 17,000 RPM
Level 6: 16,000 RPM
Level 5: 15,000 RPM (for acrylic work)
Level 4: 14,000 RPM

NOTE: Ensure that Aspire uses only these preset values (e.g., 18,000, 17,000, 16,000, etc.). Intermediate values like 16,500 will not be recognised by the controller.

Configuring Feed Rate Recognition
On the Rich Auto controller:
Go to Menu → Auto Pro Setup
Scroll down to Gcode setup → OK
Choose F Read→ press Run
Select Read F → press OK
And stop/cancel to go back to main menu
After completing these steps, the Rich Auto controller should correctly interpret both the
spindle speed and feed rate as defined in Aspire.

Actions prior to cutting

Decide on the the type of cutting needed and change the bit for one that is appropriate. For this, the case that holds the collet will need to be loosened with a couple of wrenches. Depending on the width of the shaft of the bit a different collet could be needed.

First snap the collet into the collet nut and then insert the bit. The shaft of the bit should not stick beyond the collet it should stay 3mm away from the end of the collet in case the bit is long otherwise it will not clamp well. Also, make sure that the flutes are not inside the collet.

source: cutting it close

Thereafter inspect the board to check that the board is even and flat. Otherwise correct for this with clamps or screws.

It is important to make sure that when setting the cutting area to take into account for this, in order to avoid that the milling over this metal pieces as it is very dangerous!

It is a good idea to test the table vacuum in order to see if the wood will move by pulling sideways.

Use the controller xy + and - buttons to re position the CNC head to the start point or origin. Remember that x increases from left to right, z from bottom to top and y increases from the control station to the back of the room. In order to set up the z origin it is necessary to take small steps to touch the board lightly with the bit. In order to do this it is a good idea to activate the table vacuum as this will change the z position of the board.

Cutting

Connect the usb drive to the controller.
Set up origin point: Then press XY->0 and Z->0.
Thereafter, select the Run/Pause key to call the file menu and select UDisk using the x+ and x- keys + OK.

After, you can select the Aspire file you created using the X+ and X- keys + OK

Note: The controller will use the parameters specified in the G-code as long as their values have been preset in the controller previously.

Prior to sending the job if you haven’t already turn on the table vacuum sections that you need and the extractor.

You may want to do a test run i.e. without cutting i.e. to see the trace. Make sure the you lift the CNC head in Z position to avoid cutting.
Send the job and stand in next to the control center always with a finger positioned in the stop key.

Tests

Press Fit Test

We created some cuts files for different path widths in order to evaluate fit of two pieces. Given that the regular dimensions of the board were 10mm we set up a range of slit widths from 10-10.8 with a step separation of 0.2 mm. We found that the 10mm cut provided a good fit but still could use some width reduction for better grip. We realized that the finger piece was actually 9.8mm in width. Then we cut an additional slit piece with 9.8 mm and this provided a good fit with good grip but was not excessively tight allowing still to separate them. Possible a 9.7mm slit would be great if we lookfor a permanent lock.

Dog Bones Test

We wanted to see if different dogbones shapes had an impact on the fit so we tested 3 different dogbone shapes with slit widths of 9.8mm. We were not able to identify any differences in fit. We used the Nifty Dogbone extension for Fusion 360 that can be found:

https://apps.autodesk.com/FUSION/en/Detail/Index?id=3534533763590670806&appLang=en&os=Win64

Files

Download Computer-controlled machining- Lab Safety Training

March 12, 2025

Week 8
Electronic Production

Group Task Distribution

Task	Person Responsible
Infromation and details of the machines we used	Alfredo
Preparation of the files	Camila
Design rules and results	Camila
Sending a PCB to a boardhouse	Alfredo

1. Group Assingment

For this week assignment we looked at two processes:

1. Milling a board and cutting it with the CNC machine.
1. Engraving the board copper paths with a Llaser machine and then cutting it with the CNC machine.

For the milling process we used the:

LUNYEE All-Metal 500W CNC Router Machine

Specifications:

Working area: 300x180x80mm
Machine size: 485x415x374mm
Spindle: stnd configuration: 500W 10000 r/min
Machine accuracy: +/- 0.1mm
Max speed 5000mm/min
Max cutting speed 2000mm/min
Power supply 48V 500W

This machine is suitable for milling: wood,bamboo,acrylic,plastic, PVC, ABS, PCB, brass and resin.

In general terms, the machine consists of three axes that allow the milling bit to move in three directions. It features two pole terminals (positive and negative) used to determine the probing depth. One terminal is connected to the milling head, while the other is attached to the board. When the tip of the bit touches the metal plate, it completes an electrical circuit, allowing the machine to record the exact depth of the board surface.

Below we can find some safety guidelines:

Be aware where the stop button is.
Use appropriate goggles when operating the machine.
Use appropriate breathing protection given the material you are cutting.
If you have long hair tied it back.
Do not use gloves as they can get caught in the spindle.
Ensure proper ventilation
When changing bits disconnect the machine.
Make sure clamps are well fastened.
Make sure there is no wiring in the cutting area for example remove the probes terminal before cutting.
Double check that you have the right cutting area.
Stay close by the machine while there is a ongoing cut job.

For engraving in the second process we explored we used the following laser engraver.

ComMarker B4 MOPA 60

An additional but important accessory of the laser is a safety enclosure that is made of an anti laser coating light absorbing material.

Please note that once the engraver is enclosed, the emergency stop button (highlighted in yellow) will not be accessible from the outside. Ideally, an additional emergency stop button should be installed on the exterior of the enclosure for safety and easy access.

Specifications:

Laser Source: MOPA-JPT
Laser Power: 60W
Laser Wavelength: 1064nm
Engraving Accuracy: 0.01mm
Engraving Speed: 0-15,000 mm/s
Frequency 1-4000 KHz
Pulse Width: 2-500ns
Work Area: 110mm x 200mm dual lenses
Primarily designed for engraving metals and plastics
Can cut Stainless Steel, Aluminum, Brass, Copper, Silver and Gold.

In this page you can find a blog that describes the advantages that a fiber laser engraver have for PCB engraving. Below you canfind a short summary of this article.

The high precision laser technology of a fiber laser engraver allows to etch, cut and mark the different layers of a printed circuit board. Some specific advantages are:

High Precision and Accuracy to achieve fine detail.
Efficiency and Speed resulting in faster processing than traditional methods thanks to high speed galvo technology.
Versatility: that allows processing several types materials.
Auto Focus Technology: Allows adjustments based on material thickness and variations in the material surface.

This is a laser cutter that uses the MOPA technology i.e Master Oscillator Power Amplifier. This technology has a much wider frequency range than q-switch machines and it can also control the pulse width parameter enabling the control of the individual laser pulses.

In the fields of Electronics, Semiconductors, and ITO Precision Machining achieving precise lining is often essential. However, a Q-switched fiber laser struggles with this task due to its fixed pulse width. In contrast, a MOPA fiber laser, with its adjustable pulse width and frequency, effectively delivers smooth edges and precise results. Mopa Fiber laser has a tunable width which facilitates small laser spot and tunable energy (source: link)

Steps for engraving a PCB:

1. Design Circuit Diagram
1. Input the Circuit Diagram into EZCAD in our case we have a version of Lightburn.
1. Set Parameters power, speed, and frequency
1. Preview and adjust position and size
1. Initiate the laser engraving process.
1. Check the result.

Safety

These are additional safety guidelines that complement those outlined in Week 3, as this is a powerful and potentially dangerous machine. The following points are excerpted from the manual:

Laser Safety
- The machines use Class IV lasers. The lasers are very powerful and can cause eye injuries and burnt kin. It is recommended to wear laser goggles when using the laser engraver.
- Avoid exposing your skin to Class IV laser beams, especially at close range.
- Do not touch the laser engraving beam while it is switched on.
Material Safety
- Do not engrave materials with unknown properties.
User Safety
- Use this laser engraving device only in accordance with all applicable local and national laws and regulations.
- Use this device only in accordance with this instruction manual and engraving software manual.
- DO NOT leave this device unattended during operation.
- Cut off all power to the machine and contact either our customer service or repair service if anything seems to be working abnormally.
- Be aware that where the
- Any untrained personnel who might be near the device must be informed the danger of the machine before operation

Milling/Cutting Materials for Electronics

Finally, it is important to metion some characteristics of the material we used (FR1) and the FR4 another commonly used material. Below you can find a summary from link by ChatGPT on the advantages and disadvantages of these materials (prompt: please summarise this in 2 paragraphs )

FR1 and FR4 are two commonly used materials in PCB (Printed Circuit Board) manufacturing, each with distinct compositions and properties that suit different electronic applications. FR1 is a paper-based material impregnated with phenolic resin, known for its low cost and ease of machining, but it offers lower mechanical strength, thermal resistance, and electrical insulation. In contrast, FR4 is made from woven fiberglass cloth and epoxy resin, providing superior strength, higher heat tolerance, and better electrical properties, making it more suitable for demanding electronic environments.

The choice between FR1 and FR4 depends on the specific requirements of the application. FR1 is typically used for low-cost, single or double-layer PCBs where performance demands are modest. On the other hand, FR4 is favored for multilayer PCBs and high-performance electronics due to its robustness and reliability under stress and heat. Understanding these differences allows engineers and designers to select the right material for optimal functionality and cost-efficiency in their electronic projects.

Finally, it is important to emphasize that FR4 can be a much more dangerous material to work with especially if aspired as it is fiber glass based.

PCB Milling and Laser Engraving: Workflow and Results

For our PCB fabrication process, we used a CNC milling machine to remove copper and create circuit traces. This involved several key steps, from preparing the files to sending them to the milling machine. Additionally, we explored laser engraving as an alternative method. Below is a breakdown of our process.

Preparing the File
To generate the milling paths, we used mods project, an online tool that allows customization for different bit sizes and milling parameters. For this we use the test file that they shared in the global class.

Loading the File: We imported the test PNG file into Mods. This file contained small trace patterns to evaluate how well different bit sizes could mill fine details.

Configuring Milling Parameters: In PCB Default Settings, we adjusted the trace width and tool diameter to match our selected bits. Using the Bit Calculator, we determined the cut depth and offset for each milling pass. In the Mill Raster 2D module, we configured the feed rate, cut depth, and number of offsets to define how much copper should be removed.
Generating the Toolpath: Mods processed the data and provided a preview of the offset path, showing how many passes would be made around each trace.

Exporting the G-Code: Once satisfied with the settings, we exported the G-code file to be used in Candle, the CNC control software.

When setting up the exterior cut in Mods, we explored the use of tabs, small uncut sections that keep the PCB attached to the base material during milling. This prevents the board from shifting or coming loose, ensuring a clean and precise cut while making it easier to remove afterward.

Sending the File to the CNC: Candle Software

With the G-code file ready, the next step was to send it to the milling machine using Candle, a G-code sender software, to control the CNC. The first step was to connect the machine and set the origin point for the milling process. This involved manually adjusting the bit’s height and using the jog controls in Candle to position the tool at the correct starting location.

Before starting the milling process, we performed a Height Map calibration. This step is crucial because even slight surface irregularities on the PCB material can affect the milling depth. The Height Map compensates for these variations, ensuring the milling bit follows the correct depth across the entire surface.
To create the Height Map, we first opened a valid G-code file—this step is required, as the software needs the defined area to place the probe points.
Then, in "Edit Mode", we used the Height Map tool to set up a "Probe Grid", which defines where the surface will be measured. More points mean better accuracy. Once the probing was done, we saved and applied the map before running the job.

After verifying all settings, we loaded the G-code file and initiated the milling process. The machine started by cutting the traces with the selected bit size, followed by the outline cut using the configured tabs to keep the board in place. Throughout the process, we monitored the cut.

Finally, once the milling was completed, we carefully removed the PCB, checked the trace quality, and cleaned the board to remove excess material. The result was a precise, well-milled PCB, ready for further processing.

In the image, we tested three different milling bit sizes:
The 0.1mm bit, located at the bottom , provided the sharpest detail, making it ideal for intricate traces and high-density PCB designs. However, due to its thin structure, it is also the most fragile and prone to breakage if not handled carefully. The 0.2mm bit, in the middle, offered a good balance between precision and durability, making it suitable for general PCB engraving while still maintaining fine details. The 0.4mm bit, at the top, was the most robust but resulted in wider traces, which may not be ideal for compact circuits but is useful for faster milling and larger traces. This test helped us determine the appropriate bit size based on the required level of detail and durability considerations for milling PCBs effectively.

Exploring: PCB Laser Engraving

For this test, we used a ComMarker B4 60W MOPA Fiber Laser to engrave a PCB instead of milling. We opted for engraving only since laser cutting the board leaves undesirable burns and discoloration. The goal was to test how different power settings and number of passes affected the engraving quality and depth.

Preparing the File:We converted the PCB design into an SVG file for compatibility with the laser software. This with Inkscape using the option trace.
Laser Parameters: Engraving Speed to adjusted to prevent overburning. The number of passes, we tested multi-pass engraving to determine the ideal depth. As well the engraving direction, the machine performed horizontal and vertical passes for even copper removal.

Top sample (2 passes, 90% power): Produced a dark, well-defined engraving, with strong contrast against the copper surface. However, the material removal was limited, leaving a slight texture.
Middle sample (4 passes, 90% power): Increased the engraving depth while keeping clear and legible details. The copper was effectively removed, revealing a more uniform and matte finish.
Bottom sample (6 passes, 30% power): Despite more passes, the lower power setting removed less copper, resulting in a subtle and less contrasting engraving. The details are still visible but not as deep or pronounced as the 90% power tests.

For the laser parameters we chose: Speed of 1500 mm/sec, a Maximum Power 90%, a Pulse width of 250ns, and a frequency of 30Khz

Generating files in Kicad

This week, our goal was to simulate the process of sending a printed circuit board (PCB) design to a manufacturer. To achieve this, we needed to generate Gerber files—essential documents used in PCB production.

To create the Gerber files, we followed these steps:

Navigate to the File menu and select Plots.
Configure the production settings according to the specifications of our chosen manufacturer.

For a concise demonstration of how to format Gerber files specifically for NextPCB, refer to the video linked below.

Generating Gerber Files in KiCad

KiCad 9 has introduced several interface changes, which might make it tricky to locate certain options. If you’re starting with the default settings for generating Gerber files, you can navigate to File → Fabrication Outputs → Gerbers.

From there, you can use the default layer selections and settings provided by KiCad or you may want to modify if you know the correct settings.

As per the video above we use the defaults and select use protel file name extension. In addition, create a dedicated directory to store your output files, as they can quickly become disorganized. Once the directory is set, press “Plot” and your files will be generated in the specified location.

Next, press “Generate Drill Files.” This step is useful if your PCB requires holes to be drilled—for example, for mounting purposes.

Thereafter, you will need to generate the zip file with all the files created in order to upload them to NextPCB page that you can see below.

Here you can see the different options chosen and the price of the boards and shipping resulting from the uploaded files.

Alternatively, using a plugin can streamline the process. For example, plugins tailored for specific manufacturers, like NextPCB, can automatically configure the settings to match their requirements

Once the plugin is installed, it can be accessed directly from the menu to review the configuration options provided by the company. This ensures that all necessary parameters for production are properly set. After verifying the options, you can click “Update Price” to receive an instant quotation for the board. If you’re satisfied with the setup and pricing, you can proceed by selecting “Add to Cart”, which will redirect you to the company’s website to finalize your order, just as before.

Happy ordering!

Key Learnings

This week’s exploration of PCB manufacturing techniques gave a better understanding of the trade-offs between milling and laser engraving. The milling tests showed how bit size affects precision, and the importance of settings like depth, feed rate, and toolpath optimization. Using Mods for file preparation allowed us to refine the process for different bit sizes, ensuring better control over the cut. The height map calibration in Candle also proved essential for maintaining accuracy, especially when switching between tools.

March 19, 2025

Week 9
Input Devices

Group Task Distribution

Task	Person Responsible
Analog	Camila
Digital	Alfredo

For this week’s Input Devices assignment, we explored both analog and digital input signals through simulation and real-world testing. We began by simulating a potentiometer in Tinkercad.

Analog Input - Accelerometer / Potentiometer

To explore input devices, we worked with both analog and digital sensors using simulation tools and real hardware. I started with an analog input test using Tinkercad, where I connected a potentiometer to an Arduino UNO. In the simulation, the potentiometer was wired with one side to 5V, the other to GND, and the center pin connected to analog input A0. I used a simple Arduino sketch to read and display the analog values via the Serial Monitor, which helped visualize the range of values as I turned the knob. The code used for this simulation is shown below:

int sensorValue = 0;

void setup()
{
  pinMode(A0, INPUT);
  Serial.begin(9600);
}

void loop()
{
  sensorValue = analogRead(A0);
  Serial.println(sensorValue);
  delay(10);
}

This program prints the analog signal from the potentiometer every 10 milliseconds, allowing me to see a smooth transition of values on the Serial Plotter. It helped me understand how analog signals behave and how sensors can reflect continuous variation based on physical input. You can view and interact with the simulation here by opening the shared project.
Later, I recreated this analog test physically by connecting a real potentiometer to an Arduino UNO, then used a multimeter and an oscilloscope to observe the voltage changes on the analog output pin.

For the multimeter test, I didn’t need to connect the Arduino to read values. Instead, I connected one outer leg of the potentiometer to GND, the other outer leg to 5V, and then placed the positive (red) probe of the multimeter on the middle pin of the potentiometer (the wiper), and the negative (black) probe on GND. As I turned the knob, I observed a smooth change in voltage from 0V up to nearly 5V, confirming how the potentiometer acts as a voltage divider. This method provided a quick and direct way to verify that the component was working correctly without involving any programming or microcontroller.

Next, I tested the same potentiometer using an oscilloscope. Similar to the multimeter, I connected one probe tip to the center pin (wiper) and the ground clip to GND. The oscilloscope allowed me to see a real-time waveform that changed dynamically as I rotated the knob. This gave me a visual representation of how the voltage responded over time

Key learning

Although both tools measured the same voltage range, the multimeter showed stable, precise values, while the oscilloscope provided a detailed, time-based view of the signal. These two tools together gave me a deeper understanding of how analog signals behave and how input devices like potentiometers can be tested from both static and dynamic perspectives.

Digital input - button

To explore digital input behavior, I created a simple simulation in Tinkercad using an Arduino Uno and a push button connected to digital pin 2. In the circuit, I connected one side of the button to 5V, and the other side to digital pin 2, with a 10kΩ pull-down resistor connected from pin 2 to GND. This resistor ensures that the signal reads LOW (0) when the button is not pressed, avoiding floating values. I uploaded the following code to read the state of the button

int buttonState = 0;

void setup()
{
  pinMode(2, INPUT);
  Serial.begin(9600);
}

void loop()
{
  buttonState = digitalRead(2);
  Serial.println(buttonState);
}

Once the simulation was running, I opened the Serial Monitor and observed the output values. When the button was not pressed, the serial output printed 0, and when I pressed the button, it changed to 1. This binary behavior clearly demonstrates the concept of digital input: it only has two states — HIGH and LOW. This activity helped reinforce how buttons can be used as inputs to trigger events or control behavior in physical computing projects.
You can view and interact with the simulation here by opening the shared project.

Below is an illustration of the digital signals generated when a button is pressed. For this demonstration, I used a button board designed during the electronics production week. The digital analyzer was connected to the board's ground and to pin number 8, which is linked to the button circuit. When the button was pressed, the signal read as a logical high (1); when it was not pressed, the signal remained low (0). The high signal persisted for the duration of the button press.
The setup includes a pull-down resistor connected between the microcontroller's input pin and ground. The button itself is connected between the same input pin and the positive power supply. When the button is not pressed, the resistor pulls the pin voltage low (logic '0'). When the button is pressed, it connects the pin to the positive supply, pulling the voltage high (logic '1').

Task	Person Responsible
Measurments and introduction write up	Camila
Measurements and measurment write up	Alfredo

April 02, 2025

Week 11
Networking and communications

Group Task Distribution

Task	Person Responsible
Common types of serial communications	Alfredo
Document test (RT/TX)	Camila

Serial Communication

Serial communication involves sending data sequentially, one bit at a time, over a single channel or bus (Wikipedia). This differs from parallel communication, where multiple bits are transmitted simultaneously across several channels. The summary below is based on information from Wikipedia, Circuit Basics, and these YouTube videos (Electronoobs,Rhode & Schwarz).

One of the key advantages of serial communication is its wiring simplicity, as it requires fewer channels. However, since data is transmitted one bit at a time, synchronous protocols need a clock pulse for each bit, which may reduce data throughput compared to parallel methods. Serial communication is categorized as either synchronous or asynchronous depending on whether a shared clock signal is used to synchronize data transfer.

Some Key Characteristics of Serial Communications:

Levels: Voltage levels represent binary values — 0 (low) and 1 (high).
Timing: Defines how often and how quickly bits are transmitted.
Framing: Organizes bits into message units.
Protocol: Specifies what data is sent and under which conditions.

UART (Universal Asynchronous Receiver/Transmitter)

UART is an asynchronous serial protocol that enables communication between devices using two elements:

Tx (Transmit) – Sends data
Rx (Receive) – Receives data

It is important to ensure that Rx and Tx work with the same settings/parameters including:

Baud Rate: Sets the speed of data transmission.
Start Bit: Signals the start of transmission with a low signal after an idle high state.
Data Bits: Indicates how many bits make up each data unit (typically 5 to 9).
Stop Bits: Signals the stop of the transmission with a high signal to return to an idle state.

Below you can find a schematic of a UART transmission packet.

source: circuit basics

Advantages:

Uses only two wires (one for sending the data + ground reference).
No clock signal required.
Widely used in embedded systems.

Disadvantages:

Limited to 5-9 bit dataframes.
Doesn’t support communication with multiple controllers or receivers natively.

I2C (Inter-Integrated Circuit)

I2C is a synchronous protocol that allows multiple controllers and receivers to share a two-wire communication bus (+ ground) which includes:

SDA (Serial Data) – Carries the data
SCL (Serial Clock) – Synchronizes the data transfer

Messages are broken into frames, each containing the receiver’s address, and are framed by start and stop conditions. Both the transmitter and receiver need to know the number of bits that will be sent and the clock frequency. Each receiver has specific receive address and hence is a one to one communication. In the transmission packets there might be some parts dedicated to acknowledge (see below) the correct reception of data.

source: circuit basics

Advantages:

Only three wires required (SDA,SCL and ground)
Can achieve speeds of 400kb/s-3.5Mb/s (depending on the mode)
Supports multiple controllers and receivers
Popular and well-supported protocol

Disadvantages:

Slower than SPI
8-bit data frame limit.

SPI (Serial Peripheral Interface)

SPI is a synchronous communication protocol that enables continuous and simultaneous data transfer between a controller and receiver. Unlike I2C and UART, SPI doesn’t rely on predefined start/stop bits and can transmit any number of bits without interruption.

SPI Lines:

MOSI (Controller Out, Receiver In) – Transfers data from the controller to the receiver
MISO (Controller In, Receiver Out) – Transfers data from the receiver back to the controller
SCLK (Serial Clock) – Provides the timing signal from the controller
SS/CS (Receiver Select/Chip Select) – Used by the controller to choose the receiver device

To send new data the controller will set the Chip select low and then send the MOSI clock and MOSI information. For each device connected a CS connection is needed. This type of communication is full duplex meaning that both transmitter and receiver can send data at the same time.

Advantages:

No start/stop bits; enables continuous data flow
Simpler than I2C—no addressing mechanism
Higher data rates—typically nearly twice as fast as I2C
Full-duplex communication (send and receive at the same time)

Disadvantages:

Requires four wires + ground.
No acknowledgment to confirm data receipt.
Lacks built-in error detection like UART’s parity bit.

Below is a summary of the characteristics of each communication system and hierarchies.

Key characteristics, source: Electronoobs

Hierarchies, source: Electronoobs

Arduino Serial Communication (RT/TX)

For the group assignment, we explored the basics of serial communication using several Arduino Uno boards. The goal was to simulate a basic network where one Arduino acts as the transmitter and the others act as receivers. We used Serial communication (RT/TX) and tested this through the Arduino IDE and a breadboard setup. We first connected two receivers and then added a third one to test multiple nodes reacting independently to a single transmitter.

Wiring and Connections

We used the following color-coded jumper wires to make our setup easy to understand and debug:

Red: RX (Receiver)
Blue: TX (Transmitter)
Black: GND (Ground)
Yellow: 3.3V Power

All the Arduinos shared the same ground (GND) and were connected via the TX pin of the transmitter to the RX pins of the receivers through a breadboard.

Code (Transmitter)

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.write('a');
  delay(100);
  Serial.write('b');
  delay(100);
  Serial.write('c');
  delay(100);
}

The transmitter sends a sequence of characters via Serial.write():
Each character corresponds to a specific node that listens for it. The delay(100) helps give time between messages so that each receiver can read and respond without conflict.

Code – Receiver (Node)

void setup() {
	Serial.begin(9600);
	pinMode(13, OUTPUT);
}
	  
	void loop() {
	if (Serial.read() == nodo) {
		digitalWrite(13, HIGH);
		delay(50);
		Serial.println("in loop");
	} else {
		digitalWrite(13, LOW);
	}
}

Each receiver is programmed to listen for a specific letter. When the correct letter is received, it turns on the built-in LED:
The variable nodo defines the unique address of each node. By changing this letter, each receiver only responds to its assigned message.

What We Observed

When we ran the code, each receiver board successfully detected its assigned character and responded by turning on its LED. For example, the board listening for 'a' only activated its LED when that specific character was sent by the transmitter.
The LEDs would flash in a pattern based on the order and delay of the characters being transmitted, giving us visible confirmation that the communication was working correctly.
Our basic multi-node serial communication system was functioning as intended!!

Adding a third receiver was quite straightforward, showing how this method can scale easily. This experience gave us a better understanding of how microcontrollers can communicate with each other in a simple but structured network.

April 23, 2025

Week 13
Molding and casting

Group Task Distribution

Task	Person Responsible
Document test	Alfredo
	Camila

Group Assignment

This week, we delve into molding and casting using a range of materials, each with its own unique properties—from varying hardening times to specific safety considerations. For our assignment, we used plastic water cups as molds to cast the following materials:

Alginate
Silicone
Plaster and
Resine.

Below, we review each material in detail:

Alginate

Alginate is a naturally derived material, typically extracted from brown seaweed, and is widely used for making molds, especially for body parts like hands, faces, and feet. It is known for being safe for skin contact, easy to mix with water, and capable of capturing fine surface details quickly. Alginate molds set rapidly at room temperature and are usually used for one-time casts because they are flexible but not very durable over time (summarized from Wikipedia).

Characteristics:

Brand name: Feroca
Product Name: ALGA-CAST FAST
Mixing Ratio: 1 part of alginate powder 3 of water
Curing time: 3-3.5 minutes
Shelf life: 24 months
Toxicity: non-toxic.
Data sheet: link

Test results: The casted material was easy to remove, as there was a slight gap between the mold (cup) and the alginate. The material was elastic; however, it does not seem durable enough for repeated use.

Silicone

Silicone for molds, often called mold-making silicone, is a flexible, durable material used to create detailed molds for casting various objects. It is typically made from silicone rubber, a polymer known for its elasticity, chemical resistance, and ability to capture fine details (summarized from Wikipedia).

Characteristics:

Brand name: Reschimica
Product Name: Silicone RPRO 30
Mixing Ratio: 1 to 1.
Curing time: 3 hours
Shelf life: 6 months
Toxicity: non-toxic.
Data sheet:link

Test results

The silicone maintained its shape and dimensions, and we had to cut the plastic cup to remove the casted material. This was easily done, as the silicone did not adhere much to the walls of the cup. The material was elastic, with good structural properties.

Epoxy Resine

Epoxy resin is a class of reactive prepolymers and polymers containing epoxide groups, commonly known as polyepoxides. These resins are typically cured (hardened) by reaction with hardeners such as polyfunctional amines, acids, phenols, alcohols, or thiols, forming a thermosetting polymer with favorable mechanical properties and high thermal and chemical resistance (summarized from Wikipedia).

Brand name: Resin-pro
Product Name: Resin-pro
Mixing Ratio: 100(B):60(A)
Curing time: 24-36hrs
Pot life: 50 minutes
Shelf life: 12 months
Toxicity: This is a toxic compound; it is recommended to use safety gloves, goggles, and a filter mask.

Please follow the safety data sheets provided below:

safety compound A, safety compound B, general instructions,

Test results

After waiting 24 hours, the resin still had not cured. However, the material was hard and retained its shape and dimensions, following the contours of the recipient.

Plaster

Plaster is a versatile material used in molding and casting, typically composed of gypsum, lime, or cement. When mixed with water, it forms a workable paste that hardens through crystallization, making it suitable for creating detailed molds and sculptures (summarized from Wikipedia).

Brand name: NA
Product Name: Plaster
Mixing Ratio: 28-30 grams of material for 100 grams of water.
Curing time: 30-60 minutes, complete drying 24-48 hrs.
Shelf life: 3 years
Toxicity: Not toxic, however powder inhalation can cause irritation of breathing pathways.

Test results

The plaster dried swiftly, though it proved a bit tricky to remove from the plastic cup. Despite the challenge, it held its intended shape perfectly. There were a small amount of bubbles.

Conclusion

In conclusion, both alginate and silicone produced flexible molds that accurately captured the intended shapes. However, alginate showed some reduction in size and had weaker cohesion compared to silicone, which maintained both its scale and structural integrity. Additionally, bubble formation was observed in the alginat. Both materials cured quickly. Regarding the other casted materials, plaster cured rapidly and preserved both the shape and size of the molds effectively. Resin, on the other hand, maintained shape and size very well but required significantly longer curing times.

Text

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Dolor pulvinar etiam.
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Dolor pulvinar etiam.

Buttons

Preformatted

i = 0;

while (!deck.isInOrder()) {
print 'Iteration ' + i;
deck.shuffle();
i++;
}

print 'It took ' + i + ' iterations to sort the deck.';

April 02, 2025

Week 0
Networking and communications

Group Task Distribution

Task	Person Responsible
	Alfredo
	Camila

Text

List Unordered

Dolor pulvinar etiam.
Sagittis lorem eleifend.
Felis feugiat dolore viverra.
Dolor pulvinar etiam.

Buttons

Preformatted

i = 0;

while (!deck.isInOrder()) {
print 'Iteration ' + i;
deck.shuffle();
i++;
}

print 'It took ' + i + ' iterations to sort the deck.';

April 02, 2025

Week 0
Networking and communications

Group Task Distribution

Task	Person Responsible
	Alfredo
	Camila

Text

List Unordered

Dolor pulvinar etiam.
Sagittis lorem eleifend.
Felis feugiat dolore viverra.
Dolor pulvinar etiam.

Buttons

Preformatted

i = 0;

while (!deck.isInOrder()) {
print 'Iteration ' + i;
deck.shuffle();
i++;
}

print 'It took ' + i + ' iterations to sort the deck.';

April 02, 2025

Week 0
Networking and communications

Group Task Distribution

Task	Person Responsible
	Alfredo
	Camila

Text

List Unordered

Dolor pulvinar etiam.
Sagittis lorem eleifend.
Felis feugiat dolore viverra.
Dolor pulvinar etiam.

Buttons

Preformatted

i = 0;

while (!deck.isInOrder()) {
print 'Iteration ' + i;
deck.shuffle();
i++;
}

print 'It took ' + i + ' iterations to sort the deck.';

Group Task Distribution

🔧 Lab Safety Training

Fire Safety & Emergency Procedures

Laser Cutter Safety Guide

⚠️ General Safety Precautions

🔧 Operating the Laser Cutter

Before Starting a Job

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🚫 Prohibited Actions

Emergency Procedures‼️

Fire Occurs

Machine Gets Stuck or Malfunctions

Long Running Time

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Laser Cutting Tests

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📂 Download Files

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Comparison Insight:

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Velostat Pressure Sensor

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Xiao ESP32 S3

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Safety Guidelines for Resine Printing [in our lab]

Photon Mono X

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Test design Rules

1. Negative Tolerance Test

2. Thickness Test

3. Bridging Tests

4. Angle Test

5. Overall test resin

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Tested Infill Patterns

Files

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Chip Load Calculation Formula

Feed Rate Table