Jose Alegria - Fab Academy

Computer Controlled Cutting

ASsignment

wHAT iS THE ASSIGNMENT ABOUT?

The goal for this assignment is to develop a way to parametrically design a project to cut it with the laser-cutter, and finally to report the learning process.

Group Assignment:

Characterize your lasercutter’s focus, power, speed, rate, kerf, and joint clearance.

While doing the group assignment I learned:

· The machines have different functions we will not be using during our fabacademy projects, nevertheless we should at least know what they do and where we can find the information in the case we need to learn more about them later. For example, the engraving features of our laser cutter.

· The same will happen with some of the parameters that the machines allow us to change, even if we don’t inquire about them for now.

· While making the cardboard parameters, I found that different materials need to be treated differently because of special conditions, for example: if I tried to engrave over the cardboard a different letter font, what I would get was a few holes over the first layer of the cardboard.

1^st Step. Vinyl Cutting

For this week's assignment’s first part, I have decided to use the vinyl cutting machine.

I made a very simple drawing in Autocad, an international oval ID sign displaying MEX to make a sticker, I saved the drawing as a DXF file in order to be able to export it, and use it in the machine, as I was suggested, prior to get into the machine's software, I made a copy of my drawing in a different file format, so I've got a .eps file, as well as a .plt one using Corel to make this changes.

Then I have got into the vinyl cutting machine software. It's called GreatCut, and it's essentially a blank canvas where you can import the different files.

At first, I tried with the DXF file, but it was rather not compatible as it showed a distorted image of what I have

drawn, then I used the eps which changed the drawing by splitting the vectors into triangles, so at last I used the plt file which displayed the image as it was intended to be.

Then, you must set up the machine with the vinyl or the material you're going to use, setting the sheet dimensions, and finally you get to the tool's menu where you should specify the parameters you need the machine to use, as the speed and force, and for some reason, you must set again the material dimensions.

Once you're over that, you must get the material into the machine and click OK.

2^nd Step – Designing For Laser cutter

The assignment was to make our own construction kit with the laser cutter.

I designed a truss bridge that could be made as long or tall as wished. The first part was to design the pieces, so I used Fusion 360 to make a parametric design in which I could change the dimensions of the bridge pieces as I wanted and they should stay aligned in a way that made the construction possible.

I made a draft to try to design the main components of the bridge, the most difficult part was to design a joint that would keep the different components in their place.

I came up with an idea in which all elements should be compatible with the joint. Once I had the design made, I made a DWG file with the pieces I was going to cut.

3^rd Step – cutting with the laser-cutter

As we did the group assignment before the individual assignments, I already had the laser-cutting parameters needed to cut all the pieces I needed.

So, the task was half done, I only had to set the parameters and then I was able to cut.

4^th Step – Assembly

Having cut my construction kit, I started building the truss bridge. The cardboard wasn't as rigid as I thought so the small joints I cut weren't able to keep the structure up, I think the design could work if I repeat the assignment with a stiffer material, maybe I could use MDF for the next attempt. I'm posting here the structure as I was able to assemble it.

5^th Step – New Design for the final project

For the final project I tried a new approach to the parametric design. Using Autocad for parametric design proved difficult and slow, due to the constraints needed to be used, so I tried to design with Fusion 360.

First, as I explained in the last assignment, if designing in Fusion you should start by making 2D sketches of the bodies that you will be using. This sketches should be thought to be converted into bodies by extrusion, so when you cut certain material in the laser-cutter it will become the parts you want to assemble.

Fusion 360 file Sketches

These are the parametric sketches I made in Fusion 360, they have parametric measures that helped me to cut in different materials, mostly changing the size of the tabs accordingly with the material thickness, also to change the size of the container to make different tests and redesign the container as I discovered new needs to be considered.

Every part is constrained to change it size according to the new design considerations.

To accomplish this you should take kerf into account. The Kerf value is the width added to the cut by the laser during the cutting process. This value is characteristic of the material being used and the method of cutting.

To take that value into account you should add it to the parameters you are designing with. For example: in this case I parametrized the size of the notches in my container to be the result of the material width minus the kerf. If the adjustment is not tight enough you can add another adjustment setting.

Interfaz de usuario gráfica

Descripción generada automáticamente con confianza media

This will help for easier parameters change if you should modify your project.

Interfaz de usuario gráfica

Descripción generada automáticamente

After designing in Fusion, I exported the drawing to a dwg file to be used with the laser-cutter machine. It is not as straightforward as I thought it would be, but it is not as difficult to use as it was to design directly in Autocad.

Fusion 360 Export Screen

Autocad file exported from Fusion 360, already modified to be cut.

Laser-cutter in process.

Laser-cutter settings

First cut

The cutting parameters for the first material where as I stated them in the first part of the assignment, I cut the design in cardboard to test it and find any detail that could be missing from my original design. After a few revisions and a few new versions (exactly: 14) I finally got to my final design and cut it in acrylic (instead of cutting at a 3.6 in/sec 90% power setting, I used a 0.7 in/sec 70% power setting).

Material	Speed [in/sec]	Power [%]
3mm cardboard	3.6	90%
3 mm acrylic	0.7	70%

Here is a photograph of the different versions cut and assembled.

Different versions of the same parametric box.

After so many versions, I made extensive use of the timeline feature within Fusion 360. This feature helps to know when you started changing a certain part of your project and what were you doing with it.

Parametric box cut in acrylic.

Conclussions

This assignment importance was to design a webpage to keep track of our work, and to be able to demonstrate the steps we would have to follow to replicate each assignment.