Week 03: Computer-controlled Cutting

A new exciting week! This week will be my first time trying computer-controlled cutting. I was so excited for it during the session that I just started jotting down what I wanted to do during the session.

We will be learning to operate vinyl and laser-cutters to create our own construction kit, a set of pre-made parts to be assembled in to a final shape; and cut our own “stickers!”

Here is a quick sneak peak for both my neuron construction kit and some of vinyl cutting creations:

Jump to this week's checklist

Group Assignment: Operation, Safety, and Testing of the Trotec Speedy 400 Laser Cutter

This week, we got our first group assignment, where Carlos and I, alongside our instructors, learned about the laser cutter we’ll be using and testing it to determine the right settings for our materials and projects for this week.

Since our FabLab’s laser cutter was under maintenance, we needed to visited another FabLab. Thus, we went to Evora and spent a day with Marius of FabLab Arteria!

Group assignment at FabLab Arteria

Link to the full documentation of our laser cutter testings and safety training.

I learned a lot about this VERY powerful tool.

First off, YOU NEVER LEAVE IT ALONE. This came as a surprise to be since I thought that usually a laser cutter would take long to complete a cut (coming from my past experience with 3D printers).

However, the story is completely different here since a lot of thing s could go wrong, and if they do, they can cause a lot of damage not only to your material nor the cutter itself, rather to the whole place. It could catch on fire, so you need to always be attentive, stay close to it, and have methods to extinguish fires (if they happen)!

Second, I loved seeing all the physics in action. I learned in school about how lasers work, but it was incredible to see how it translated to the real world, and how there are variable we usually didn’t think about when learning about it in school.

The star of the show is the a concept called kerf. It is defined as the width of material vaporized or melted away by the laser beam during a cut. How does this come in play?

Kerf leads to parts not fitting right together, so if you were just cutting an individual shape you wouldn’t think about it, but as our instructors mentioned, at Fab Academy we are pursuing high standard in our work and what the “real-world” would expect.

Thus, to account for it, we should include it as a parameter, or account for it, in our parametric designs. I will demonstrate that below!

There are a lot of learnings, so you can find the full documentation of the safety training, characterization of the laser cutter, and how we tested it here in this link on FabLab Benfica’s website. I wrote it in collaboration with Carlos!

Learnings from the Global Session

This week we had an incredibly informative global session on computer-controlled cutting led by two amazing global instructors:

Debabrata Goswami is a professor from the Indian Institute of Technology Kanpur. He's a currently on sabbatical leave with a Fulbright-Nehru Academic and Professional Excellence Fellowship. His work focuses on ultrashort laser pulses with a passion for precision and innovation, having worked extensively on light-matter interactions, femtosecond laser machining, and nonlinear optics. He focuses on hands-on practicalities reflecting the very essence of Fab Academy to blend theory, prototyping, innovation, and connecting academia + industry.

Daniele Ingrassia has taught Fab Academy for 7 consecutive years. He is the founder of InMachines, an open-hardware company based in Hamburg, Germany. He has developed several open-source projects, including SafariMirk, LaserWeb, and Big FABULOUS. In recent years, he created the Open Lab Starter Kit, a complete Fab Lab inventory of open-source machines, and is currently developing a metal 3D printer. His projects have been replicated worldwide, and the laser cutter we have at FabLab Benfica is from him!

Software Tools Overview

Daniele and Debo walked us through an extensive list of software tools for computer-controlled cutting.

CAM (Computer-Aided Manufacturing) software is what bridges the gap between our designs and what the machines actually understand. The workflow is pretty straightforward: CAD Modeling → CAM Programming → Post Processing.

Here's what I learned about the main options that are dependent on the laser cutter you’re using:

For Laser Cutting:

Visicut: Open source (URL: 3.0), works with Epilog Zing, GRBL, and others - operates inside to outside for cutting
LaserGRBL: Open source (GRBL), great for GRBL-based laser engravers
LaserWEB4: Open source (MKI AFFERO GENERAL PUBLIC LICENSE), supports G-code based laser cutters
MDos: Open source for Roland SRM/MDX/GSX Vinyl, Cameo, S-Gofix, others
LightBurn: Commercial (paid) tool for GRBL, Ruida, TopWisdom, and more
RDWorks/PhotonPro: Proprietary (free with hardware) for Ruida controller CO₂ lasers
Trotec JobControl: Proprietary (free with hardware) for Trotec laser systems (we used this)
Epilog Control Panel: Proprietary (free with hardware) for Epilog laser systems
Autodesk Fusion 360: Commercial (subscription, limited free tier) with CAD + CAM + control for many lasers

For Vinyl Cutting:

Several tool options including cutting (blade), writing (pen), foil transfer (tips), scoring (wheel), and debossing (tips)

Important resources for parametric box designs:

Vinyl Cutter Settings Deep Dive

I learned about three critical parameters for vinyl cutting:

Speed: How fast the machine moves. Use slow speed for small text, complex logos, or thick materials.

Force: The downward weight applied to the blade. Low force works for light and delicate materials, while high force is needed for "heavy" or dense materials.

Depth: This controls the "stick out" - how much blade is exposed to cut through the vinyl. The adhesive should be left intact on the back paper (you don't want to cut all the way through!).

Weeding Tips: The process of removing excess vinyl is called weeding. Here are some pro tips:

Box it: Always put a rectangle around your design or add weeding lines
Peeling angle: Peel the waste vinyl at an angle
Lighting: Use low angle lighting to see the cuts better
Apply masking/transfer tape carefully - cut a piece slightly larger than your design, place it gently over the weeded vinyl, use a squeegee or credit card to press firmly so the tape sticks to the vinyl, then slowly lift it up at 180 degrees (or flat out)
For the vinyl to peel (lift) off easily, it should feel like peeling, not tearing. Revin settings and blade set up if needed.

Understanding The Physics of Lasers

The session included a deep dive into how lasers actually work! Here's how I understand it:

A laser is a medium that stores energy, surrounded by two mirrors. A partially reflecting output mirror lets some light out. A laser will lase if the beam increases in intensity during a round trip: this happens when Gain > Loss.

This threshold concept is crucial. The laser medium has gain (G), and there are various external energy sources. The system requires:

Population inversion (more atoms in excited state than ground state), and that cannot be achieved in a 2-level system (you need at least 3 levels) So we need either a:

Three-Level Laser: Pump → ULL (Upper Laser Level) → Excitation → Ground (intrinsically pulsed laser - Ruby) or

Four-Level Laser: Pump → ULL → Excitation → LLL (Lower Laser Level) → Ground (can act intrinsically as a continuous wave laser)

This is the physics I learned in school coming to life in the fablab :0

Some other notes:

We shouldn’t neglect the vinyl cutter! It's incredibly versatile. We can even combine laser cutting with vinyl - cut something with the laser and then apply vinyl details to it. The possibilities are really exciting.

Cardboard is often underrated, but it's actually really easy to cut! In the US, it's rated by where it kinks or folds (you can check this with an edge cut test.) However, PVC is bad to use unless you really know what you're doing (toxic fumes!). Also, kW lasers are specifically for cutting metal.

This can't be stressed enough: never leave the laser alone! Laser cutters can catch on fire. Between the laser cutter head and the material, all the combustion outputs are produced, and they need to be exhausted properly.

Some cool fun facts:

UV lasers can now engrave glass from the inside! This is a relatively new technique.
Back in the day, 3D printers used to play music from how loud they were (thankfully technology has improved!).

Vinyl Cutting: I had a bit too much fun

As we were getting introduced to the vinyl cutting during the session, I immediately started noting down things I wanted to make stickers for and add to my laptop! I made a small list of them:

Syria’s Emblem
My Logo
UNC’s Logo (my university)
Morehead-Cain Foundation (scholarship funding my gap year and university)
FabAcademy Logo
My FabAcademy Project’s Logo

First thing I wanted to get a sticker for is Syria’s new emblem, which is a golden eagle (we don’t have the specific golden color in the lab, but will try with either green or yellowish white/cream) inspired by Palmyra, with three stars from the flag above it.

First, getting an SVG of the emblem, here’s a link to where I got it from, and you’ll find the file at the end of this documentation similarly with all my other files.

Second, importing it to Inkscape and having a general guide for its size since importing it to the vinyl cutter software might mess up the dimensions, so i created a 55 * 50 mm box around it.

Then, I exported it as DXF, since that compatible with our vinyl cutter:

Then, I imported it to the Silhouette Studio, the software used to operate our vinyl cutter:

For context, we have the silhouette cameo vinyl cutter, which is a desktop vinyl cutting machine. We have another, more professional Roland cutting machine, but currently it has some issues.

I turned it on and loaded the vinyl I am using.

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Then, removed the bounding box from around the emblem, and connected the cutter to my device via USB and sent the print from the app (Spoiler alert: I made a mistake).

When it finished, there was nothing on my vinyl, so I wasn’t sure what the issue was, so I went through the process again.

After 2 tries, turns out it was first cutting with the unloaded blade (this cutter has a spot for 2 blades) because of the settings I chose, and I needed to make it cut a bit stronger, by increasing the force and the blade depth.

After that fix, it became ready to be moved from the vinyl to my laptop:

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Here, I felt like a surgeon since I needed to do very precise cuts to the vinyl, so I could extract the sticker easily with the transfer material:

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Then, I cut a piece of the transfer material and remove all the air from its connection with the sticker so it could be removed easily:

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After place it on my laptop, the process was done!!

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Then, I did the same process again but for UNC’s logo. Again, we didn’t have the exact color but the color we have would work will replace it with the actual stickers from them when I go in the fall (or on second thought, I might just stick with this)

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Then, it was time to create a sticker for my Fab Academy project. That’d be more complex since it involves layering multiple colors and shapes (Disclaimer: it was a bit painful).

First, I placed the logo in a bounding box to make it easier to get the same size when moving it to the software:

Then, I added a marker that would be cut with each layer so I’d be able to align everything appropriately after everything is cut separately:

Then, I export each layer separately to be cut on its respective vinyl sheet. Here is an example, but all the files are below. Additionally, in some of those layers, I added a small offset to their design so layering them would be cleaner at the end:

I put the design on the cutter’s software and removed the bounding box:

Here are all the elements after printing them in their colors, some errors definitely happened through printing like having too small of a vinyl piece, and some very tiny details like the waves on the glasses didn’t make it.

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Note

For the finer details of the logo (i.e. the brain), I needed to lower the force and speed of the blade. I still lost some details, though.

After an excruciating 1.5 hours to remove the fine details of the brain, I was done, and it was time to start layering:

The layering processing is exactly the same of the transfer process, but instead of putting one layer at the final destination, I’d just use the same (or different transfer material piece if it wasn’t sticky enough) to move other layers on top of it using the marker I added as a way to ensure alignment.

Here’s the final result:

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I did the same process to cut the FabAcademy, my logo, and Morehead-Cain’s stickers:

Laser Cutting: quite the process!

As I mentioned previously, we needed go to FabLab Arteria since our laser cutter was under maintenance. We had a few days to think about what we wanted to create and create our designs before going to cut on Monday, remember, out Fab Academy week start on Wednesday!

To be honest, during the session, I knew what I wanted to create for this week’s assignment: a neuron model press-fit construction kit that could be assembled in different ways!

Check out our group assignment for more on the cutting process itself.

I started by thinking through different ideas and different parts of the neuron to include in my model, and wanted to visualize it, so I described what I wanted to ChatGPT and got an image of the potential model.

The process of deciding how exactly I want the model to be like and getting the right visualization went through a couple of iterations, but finally I was happy with something that would look something like this:

Note

This model generated by ChatGPT wasn't very biologically accurate, but still was a helpful inspiration.

Let me walk you through what neurons are, how they work , and what elements I am including in my design.

Neuron anatomy diagram - Source: SimplyPsychology

Source: SimplyPsychology

Neurons are specialized cells found in the brain, spinal cord, and peripheral nerves. They form vast networks that allow us to think, move, sense, and respond to the world. Each neuron is built to receive information, process it, and pass it on.

Signals arrive at the dendrites, the branch-like structures that collect input from other neurons.
These signals move toward the soma (cell body), where they are combined.
1. If the overall input is strong enough, it reaches the axon hillock, the decision point of the neuron. When a threshold is crossed here, the neuron generates an electrical impulse called an action potential.
This impulse travels down the axon, a long extension that carries the signal away from the cell body.
1. Many axons are wrapped in a fatty insulating layer called the myelin sheath, which allows the signal to move much faster.
  1. In the peripheral nervous system, this myelin is produced by Schwann cells, which wrap around sections of the axon.
2. The small gaps between these insulated sections are called nodes of Ranvier, where the electrical signal is regenerated as it travels.
At the end of the axon, the signal reaches the axon terminal, where it triggers the release of neurotransmitters to communicate with the next neuron.
The junction where an axon terminal of one neuron communicates with the dendrite of another is called a synapse.

To design my press-fit kit, I chose to go with Fusion 360 for the design since it would be easier to visualize it in 3D and it has very good parameterization system.

I started with a design idea that had the axon as the primary piece of the design:

After building it, that wouldn’t make the design very modular and match my original vision, so I started by redesigning it, a good chunk of it happened on Monday actually since I needed do some redesigns (more on that below).

This was the design I came in with on Monday, but it had a bunch of design mistakes that Andre walked me through:

For example, I didn’t create a separate component for each of the sketches, which makes everything more modular and easy to control.

My sketches weren’t centered and it would be hard to make out how everything would fit together, and I cut holes for press fitting directly in the sketches rather than using a universal tool later on to do that which, again, makes things more universal, modular, and easy to follow.

While I had parameters, they were poorly defined and some were meaningless.

Thus, I got to redesigning everything. Acquiring a new skillset requires a lot of back-and-forth to master, and the second time was much faster (still though, I finished by the end of our day on Monday, meaning I barely got everything cut, but still had a nice result)

Learning from my first time, I started designing different elements by simple shapes and then adding more details to it through “universal components” that would enable me to repeat similar patterns on different parts of my design.

I started by centering my work around the soma:

Then , I designed all the other important elements: dendrites, axon hillock, myelin sheath, axon terminal, a stand (and its support), and a universal connector + a sketch for the “cut” or joint I’ll be using throughout the design (I added that part at the end based on an advice from Andre, my instructor).

During that process, I set a parameter named “thickness” that corresponded to the width of the cut, and I used that to adjust for the kerf.

Note

Kerf simply is the width of material removed by a cutting tool, so we need to adjust for that using a parameter in our CAD designs to ensure the press-fit kit fit properly.

The thickness, corresponded to the “thickness” of the cut for the joints across my design, where all the different elements will fit together, so once I update that parameter, all the cuts are automatically edited.

Then, I extrude all the surfaces to the thickness of our MDF, 3 mm:

This is an image of all the extruded surfaces after the cuts.

Since I created a “universal” cut tool, I’d just move it across my designs (using the right alignment methods by finding the exact positions I want those cuts to happen) and cut or use the pattern tool (for the soma) to get everything ready for the next step.

Then, I created a sketch and projected the surface of all the final designs for each piece:

I didn’t have time to do the arrange feature in Fusion so it is the most optimized way to cut my designs, so I exported them as DXF, and imported them to Inkscape to the template necessary for our laser cutter: 1000 * 600 mm with RGB color profile. You can read more about the laser cutter in our group assignment.

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I needed to prepare the right amount of pieces, arrange them, change the stroke to red hairline (the red is to tell the laser cutter to cut around that path and hairline is for the cutter to understand that this is a line to cut on and doesn’t have any width), and add my engraving (black filled). The engraving is mean to give more details to the soma, and showcase the myelin sheath:

Then, we put the designs on the computer connected to the laser cutter, and sent it to the Trotec Speedy 400 through JobControl, its software:

Before it started, we put our material and set the “home” of the laser cutter to the correct position on our material, a 3 mm MDF board:

Here's a video of how the laser cutter cuts, since I forgot to film mine:

After staying at the cutter for around 30 mins, we’ve got our final result:

Note

An important note, on Fusion, ensure all your sketches are fully connected since an error on that would lead to the parameters you set (like kerf) not changing appropriately.

Also, during the weekend, I watches those videos to prepare for using Trotec Speedy 400:

https://www.youtube.com/watch?v=5GTeIffOlzg

https://www.troteclaser.com/static/pdf/speedy-400/8086-operating-manual-speedy-400-C-EN.pdf