Week 3: Computer-Controlled Cutting

Our job this week is to design and create a parametric construction kit with the laser cutter.

Group Work: Understanding KERF

Kerf is a new and important concept - it refers to the laser beam width.

Generally speaking it is the width of material that is destroyed by the cutting instrument.

When we are cutting something with the laser, it is burning material.

So if we cut out a square from a shape, and try to fit it back in, it will not fit tightly.

Of course! because the material around the square has been burned.

Here is the square which I cut with instructor Saheen:

Using calipers, measure both the inside and the outside of the square.

In our case the kerf is (20.05-19.56)/2=0.49/2=0.245

Here we divide by 2 to find the kerf since there are 2 cuts.

Hence when we print we will offset by kerf/2=0.12mm

Then the square will fit securely.

This is essentially the same result found by the group.

The group measured the kerf for various materials as can be found in the following table.

More details at the group page on Kerala Fab Lab site

here

Individual work: Triangular-based Platonic Solids:

In the Kochi lab is a parametric construction kit for a dodecahedron, the best of all the platonic solids.

However, 3 of the 5 platonic solids are made from equilateral triangles,

so obviously a good option will be to make a construction kit for the triangular faced platonic solids.

Using Fusion 360 to make the Design

After using FreeCAD and enjoying it, I was peer-pressured into using Fusion 360. Sad.

So the first part of making the parametric kit was in Fusion 360. It involved:

• Sketching the entire triangle and connectors with constraints
• Extruding and adding the chamfer
• Added the parameters
• Projecting the sketch onto a face, and exporting the sketch as a .dxf file

Creating a parametric design is very important. Here we have the designs for triangle and connectors:

For context, the values for material thickness, kerf and compression were found by testing on the cardbaord using caliper.

The following parameters were used: (parameters can be found from the modify section of sketch menu.)

We printed a test and it was good, but needed to be adjusted for the kerf and cardboard compression.

However, it was very helpful to have parameters, and we could quickly change the appropriate values;

the changes were automatically implemented both on the triangle and the connectors.

.........

The final step is to print the whole kit! For this we need to make copies and arrange them:

Fortunately there is an arrange function in Fusion 360. Actually it didn't work perfectly but Saheen helped...

Using Inkscape to prepare the design for laser cutter

We cannot immediately send the file from Fusion to the laser cutter, we need to put the design in a simple format to give to the laser cutter

For this we use inkscape. Basically we just need the outline, in a red colour, with thickness (stroke) of .1 mm

This is for the test:

Here is for the whole construction kit:

Using the Laser Cutter to make the Parametric Kit:

In the lab there is a nice laser-cutter we gonna you use it:

The power and controls are there. Important is to calibrate each time by pressing the two buttons on the right.

Also there is a software on the computer to adjust settings like power and speed:

When we put the cardboard in, we must calibrate to the edges and hold it down with tape.

Here it is starting to cut the final project:

Now it's nearly done. Just took about 3 minutes:

Now we took the lid off after the toxic air removed!!

Note that the pieces have been cut cleanly and fallen out.

Here is the kit of construction pieces:

And here is the assembled triangular faced platonic solids

NB: Considering this photo the "Hero" shot.

The design files for this week's assignment here:

SVG File Fusion 360 File

Thanks Saheen and Kerala team for their patience and support!!

Using Vinyl Cutter:

Last part of this week's assignment is to use the vinyl cutter.

I have a file. It's a logo. I want it on my laptop. Let's go!!!

Here's the machine we gonna use:

This is the software interface:

There were some issues with processing.. 1. had to remove stroke 2. had to make it black

Then we gonna watch it cut!! Very nice, very smooth:

Now after it was printed, I just took it off and stuck it on my laptop.

Apparently that was not how professionals like Saheen do it.. Instead this process:

Now I installed the vinyl cutouts professionally. My laptop increased in value.