Laser Cutting

Lesson

For Week 2, we were introduced to the Laser Cutter. The laser cutter diagram that was shown in class  used a CO2 tube to produce a laser beam that is hot enough to cut through most materials. Inside the machine, 2 reflective mirrors would reflect the laser beams to a final mirror located in the Carriage. The laser is redirected through the focus lens to material to be cut. The carriage then moves around the material to cut the shapes/patterns that the user wants.

Suitable materials for laser cutting would include:

• Wood of up to 6mm thick
• Acrylic of up to 5 mm thick
• Cardboard and Paper

Unsuitable materials would be ones that had chlorine or PVC in them.

We were also to observe the material closely to see if it was getting cut through. If the material was not getting cut through, we would have to stop the cutting process and check on the focus lens to see if it was dirty. Continued usage of the dirty lens would result in a cracked lens.

After the Laser Cutter, we watched a video comparing Vector and Raster Graphics. Raster graphics are made out of millions of pixels to form an image, whereas Vector graphics are made out of points which are defined by coordinates and mathematical formulas. These points are then connected, rounded and coloured in to form an image. When the images are of the same scale, they are pretty much indistinguishable.

The main differences between these 2 graphics is seen when the image in scaled up. For the Raster graphic, the individual pixels can be seen, however, the image quality is severely decreased due to the quality of each individual pixel dropping and becoming blurry when increased in size. However, for the Vector graphic, the graphics are mathematically recalculated and scaling would not affect the image quality. There are also differences in file size. For the Raster graphic, when scaling the image up in size, the file of the raster graphic also increases in size proportional to the number of pixels present.

However, for the Vector graphic, the image size always stays the same regardless of the scaling.

Last but not least, we also watched a video on the importance on kerf. Basically, kerf adds an extra amount of space when cutting the material, an approximate of 0.1cm, which will cause pieces that are meant to interlock to fit very loosely.

Thus, by accounting for the kerf in the design before cutting, we can make it such that the pieces that are laser cut can fit tightly together.

Practical Session

On Friday, 5th November, we commenced with our laser cutting practical, with our main goal being to laser cut our construction kit. Firstly, we had to go through an individual competency test to deem ourselves fit to operate the laser cutting machine by ourselves. During this competency test, we would print out a test product as proof to start our practical.

We were allocated the Epilog Fusion M2 Laser Cutting Machine for our practical, and our SOP was listed as follows:

Laser Cutting Practical SOP

Before commencing the practical, we took note of some safety precautions: Refrain from staring at the  bright laser while cutting; wait for 30 seconds to 1 minute before lifting the glass cover of the laser cutting machine to retrieve our laser cut product, as the fumes are toxic when inhaled and the smell would stick to our clothing. We also learnt to import the file, and set the appropriate settings like air assist and material selection.

My Test Piece made during the Competency Test

For our design, we decided to laser cut many triangles that would press fit with one another. We chose 5mm thick plywood for our laser cut material.

Initial Design Piece

Laser Cutting Process

Importing Process

Using the CorelDraw Software for Engraving and Cutting

Laser Cutting Aftermath

When we cut our first triangles, I was surprised by the speed and accuracy of the laser cutter, and it was very satisfying to see the laser cutter dance around the sheet of plywood. The cuts it made were very clean, and our final product turned out pretty good. 

End Product Triangular Piece

However, due to issues in our thickness parameter, we could not fit the pieces together, which prompted us to use our backup plan that we had prepared.

Our backup test pieces consisted of circles that had 5 or 6 slots cut into them, and had links to join them together. We also chose to switch to 3mm plywood to see if that would help press fit the pieces in any way.

 

Backup Design: The 6 way hub connection circle

Laser Cut Product

Links

Links to connect the circles together

Fortunately for us, we managed to press fit the pieces together first try, unfortunately, that was where we ran into our second problem. We had initially wanted to use these pieces to form a radial dome, but however, our dome structure was very flimsy due to the differing angles between the links and circles, which cause our dome to fall apart easily. But Lionel came up with an idea on the spot, and used the pieces to form a dog and dog bowl. Here's how they turned out:

First Prototype of Dog and Dog Bowl

Final design of Dog and Dog Bowl (Test piece for food)

Our Hero Shot with the dog

Reflection

Overall, I felt that this Laser Cutting Practical was a success as we were able to come up with an end product with our press-fit construction kit pieces.

One learning point for myself, would be that I should pay attention to the position that we choose to laser cut our product. Due to my carelessness, I ended up spreading out my cutting area, which led to a lot of wasted material in between the spots. As my lecture told me, the usage of the material did not matter as much as the wastage of material. And for subsequent laser cutting exercises, I will pay more attention to the position the cut product.