3. Machine-controlled Cutting

This week we were introduced to our first 2 fabrication methods; the Laser cutter and Vinyl cutter.

We learnt the key considerations for laser-cutting safely and successfully. We also learnt how to create “Press-Fit Construction kits”, which are repetitive cut-out pieces that could be assembled and constructed into 3D objects. In the process, we learnt about how to account for the “kerf” to ensure precision in cutting, which is especially important when producing pieces that need to fit tightly.

Assignments for this week (Feb 5 - Feb 11):
Group assignment:
- Receive the safety training for the lab’s lasercutter
- Characterise lab’s lasercutter’s focus, power, speed, rate, kerf, joint clearance and types
- Document work

Individual assignments:
- Create a “Press-fit construction kit”, which can be assembled in multiple ways
* Account for the lasercutter kerf
* For extra credit, include something that’s not flat
- Cut something on the vinyl cutter

Group Assignment:

We went over the Laser-cutting process step-by-step, and in the process learnt the dangers of Laser-cutting and how to ensure safety. We also learnt the optimal Power/speed settings for the machine at FabLab Kamakura, and measured its “Kerf” and “joint clearance”.

About the Laser Cutter at FabLab Kamakura

- Model: Trotec Speedy 300, CO2 laser cutter (30-120W Laser Power)
- Work area: 610 x 305 mm (24 x 12 inch)
- Maximum material thickness: 200 mm (7.8 inch) with 1.5 inch lens - 149 mm (5.8 inch) with 4.0 inch lens

👉How does FabLab Kamakura's Laser-cutter work?
It's a type of cutter that utilizes a CO2 tube, which generates a laser beam through the electrical stimulation of a gas mixture predominantly composed of carbon dioxide.
A series of mirrors and a focusing lens precisely guide and focus this beam onto the material's surface, which melts/burns/vaporizes the material, enabling intricate cutting, engraving, or marking.
https://fabacademy.org/2024/labs/puebla/students/ximena-mendieta/assignments/week03.html

👉What materials can be cut using CO2 laser-cutters?
Typically, they cut Wood, acrylic, fabric, paper, leather, glass, certain plastics, rubber, etc.
CO2 lasers cannot cut metals as their lasers operate at 10 micron but recently some more sophisticated machines such as Plasma and water-jet cutters are becoming more accessible.

Group documentation here

Some of my personal learnings:

⚠️Important Safety Precautions for the Laser Cutter:
※ Laser-cutting involves risks of fire; so never leave the laser-cutter machine unattended during the printing process!!
※ If a fire starts, be careful when opening the lid as adding oxygen can add fuel to the fire.
・If it’s only a little fire, you can open the lid and extinguish it appropriately, such as blowing it out or covering it with non-flammable material.
・To prepare for the worst case scenario, be aware of where the fire extinguisher is stored (in FabLab Kamakura, it's stored next to the machine) so that larger fires can be put out immediately.

※ In case of emergency, press the red Stop button.
※ While printing, don’t look directly at the laser light, it can damage your eyesight.
※ Keep the room well-ventilated (keep all windows wide open) while printing, as the fumes produced from cutting materials can produce harmful gases.

Then, I learnt 2 important concepts for Laser Cutters; “Kerf” and “Parametric Design”, which helps us achieve precision when cutting.

👉What is a kerf?
- It's the small width of the material removed by the laser beam during the cutting process. They are typically around 0.3-0.5 mm
- Some of the factors that can affect kerf width are Laser type, the material, cutting settings, etc. If precision is important for your project, it's a good idea to figure out the Kerf beforehand by test-cutting with your machine.
- In FabLab Kamakura, since a joint width of 2.55-2.65mm produced 3.00mm width, the laser width can be calculated as 0.35-0.45mm, which makes the kerf work out to be 0.17-0.22mm.

👉What's a Parameric Design?
It's a design method that uses an algorithmic approach to modeling structures (a little like Functions in Excel). Adopting parametric design enables the designer to quickly and accurately make design updates. This is especially helpful when we need to tweak the design iteratively, such as when the kerf and joint-clearance is yet unknown.
https://www.sciencedirect.com/topics/engineering/

Making a Press-fit construction kit:

For this week’s individual assignment, I designed and laser-cut 2D designed shapes that can be assembled and constructed into 3D shapes. They are called “Press-fit Construction kits”, and the key is to create a tight fit that creates enough friction to hold the 3D structure together, achieving very stable joints (without needing additional fasteners).

My Design Concept

Since the concept of Press-fit construction reminded me of a Japanese traditional woodworking concept called “Kumiki (組木)”, I was initially interested in experimenting with Kumiki design in this week’s personal assignment.

👉What is “Kumiki” (組木)?
It’s a carpentry technique used in traditional Japanese buildings such as temples and houses. The wood planks were joined together purely by interlocking joineries, without needing nails or fasteners.

But unfortunately I decided there was simply not enough time this time.
Instead I decided to keep my goal simpler, which was to try create a rack that can adjust its size to accomodate to wide variety of scenes.

Design (Version 1)

Initially, while scanning for design ideas, I found this simple shelf that I thought I can adapt into a modular design.
(Source: Creema)
Starting with this as my initial inspiration, I started by cutting out cardboard to test out a simple structure, and then sketched out some rough measurements.

To model the Press-fit kits, I decided to use Fusion 360. It was quite a challenge to figure out the appropriate parameters based on my requirements, but I eventually completed it.

CAD Modelling Process:

1. I started by setting up some basic parameters.
   
   The parameters I set were based on these requirements;
   ・Cardboard thickness: 3mm
   ・Kerf (laser diameter/2): 0.225 cm
   ・Maximum material size: 30 x 60 cm
   ・Shelf needs to fit inside 7.7cm width space
   
   
2. Then I drew a rectangle, defining the dimensions according to above parameters.
   
   
   
3. I drew in one slot and then made multiples of it using the “multiply” function.
   
   
4. Then I mirrored it on the other side, across a central horizontal Construction line.
   

Below you can see the benefit of Parametric design;
Because I set the slot width to be Material thickness - kerf, if I change the dimensions such as the material’s thickness, Fusion 360 will automatically reflect the measurements without me having to manually change them.

To make the structure more stable, I initially thought of making snap-fit joints, but my instructor Rico told me it wouldn’t work on cardboard. I tested-cut it anyway and he was right.

Design (Version 2)

After showing the above prototype to my Instructor Rico, he told me it reminded me of Chinese display cabinets.

This inspired me to make another design, which is essentially a series of boxes that can be stacked together.

This is my very simple side-view sketch which I made on Excel.

The base box design was inspired by Lucas Lim’s box, but I adapted it a little by making the joints resemble plum flowers.
I tried to design this parametrically, but because of the limited window of time to use the Laser Cutter, I drew it manually.

I also started trying to incorporate a Kumiki design, but eventually I had to give this up. This is a very quick preliminary prototype I tried, which is a back-flap design inspired by kumiki grid, controlled by a living hinge, with lots of room for improvement.

Laser-Cutting and Assembly

I exported the final Press-fit designs into .DXF files for laser-cutting.
The steps for operating the laser-cutter are documented in the groupwork page.

📝Troubleshooting
For some reason, my parametric parts designed on Fusion 360 had 2 overlapping lines. We had to stop the printer mid-way as the machine was going over lines which were already cut. I could not figure out when or how they were made, but I hope to be more careful next time.

Here is the final result!

I was expecting the cardboard structure to be more flimsy, but it was surprisingly quite sturdy.
Maybe one day it might come in handy as a prototyping technique.

Vinyl cutting:

There are 2 models of vinyl cutters at FabLab Kamakura.
- Silhouette Cameo
- Brother ScanNCutDX

I used the Brother vinyl cutter to cut out a cute duck sticker for my coffee mug. I simply loaded a standard duck shape image that was already included in the Brother machine, set the sticker sheet on the base sheet, and cut it.

My instructor Nagano showed me an example of Vinyl cutting copper sheets to make flexible circuits. I am interested in trying this out when I have the chance.

Design files:

• Final Design (Shelves)
  
• Final Design (Corners)
  
• Draft design of kumiki flap

Links

• Tutorials
  
• On Safety
  
• Vinyl Cutting Tutorial

Reflections:

This week’s exercise introduced a very important concept in CAD modelling; Parametric Design.
I personally found parametric modeling and thinking in 3D objects to be very challenging, especially as my design had quite a few specific requirements (such as overall depth and height, material width, etc). But my instructors taught me that generally with parametric design, it’s important to 1. keep the parameters as simple as possible (which is often the tricky part!), and 2. Plan out the model with pen and paper first, with the exact measurements, before starting work on CAD.

Further Questions:
I am curious to explore more into what kind of designs/functions Parametric design can enable, especially around architecture and furniture design.
I am also interested in exploring more about the living hinge and how it can be applied to woodcrafts.

Assignment Checklist:

• [x] Linked to the group assignment page
• [x] Explained how I created my parametric design
• [x] Documented how I made my press-fit construction kit
• [x] Documented how I made something with the vinyl cutter
• [x] Included my original design files
• [x] Included hero shots of my results