Computer Aided Design

Concept: Laser Cutter.

The requirement for this assignment was to learn to work with laser cutter as well as produce an object by using the technique of cutting, engraving as well as implement joints between parts.

Initial idea was to build a regular dodecahedron (DOD) - a polyhedron with pentagon shaped faces, that would be displayed on the desktop as a nice accessory.

In contrast to cube, one of the most ubiquitous shapes, polyhedron takes a step further by extending the number of it's face to 12. With the goal in mind to learn better the Model environment of Autocad Fusion 360, this seemed like a perfect project to implement.

Since DOD has 12 sides available, it could easily be used for displaying some meaningful information or instructions. After a short brainstorm, the final concept evolved in producing an instructable of how to use the 30W Epilog laser cutter available in the Fablab HSRW. By using the dodecahedron as a case scenario, I intended to place the instructions on each side, along with examples of settings. Since I was anyways intending to learn how to operate the machine, it could be helpful to pass the information further.

The vision is to have the polyhedron attached to the laser cutter with magnets placed inside. Available at all times, anyone that would like to operate the machine, could simply grab the object, flip it around and follow the instructions. Once finished, the polyhedron is placed back to its place, on the laser cutter.

Parametric Sketch.

My intention with the model of DOD was to allow to ease the modification process, in case resizing was necessary or/and to allow anyone to replicate the object using his/her own dimensions. For that I decided to tap into Parametric Values which basically makes the object programmable and responsive depending on the initial constraints and sizes given.

Breaking down the DOD to it's base shape, we arrive to the shape of the pentagon - 5 edges polygon.

To create a polygon in fusion, we first enter into the Model environment. After which we go to Sketch, followed by > Polygon and >> Circumscribed Polygon.

We draw a polygon by clicking using Left Click on to the origin point and extending our mouse outwards. By stopping at an arbitrary size, we proceed by entering Tab key on the keyboard, which firstly allows us to modify the diameter of the object and by clicking the Tab button again, we are able to modify the amount of edges desired. For this instance the first value is arbitrary, since it will depend on the parametric value later given, while the second value is 5, since a pentagon has only 5 edges.

To enter our first parametric value, we go to Modify, followed by > Change Parameters.

We would like to enter the value for the edge length of our DOD. We create a new User Parameter by clicking on the Green +. Our first user parameter is called dodecLength for the length of the DOD edge. We give it a value of 100 and hit OK.

If we were to simply create a pentagon shaped face, we will lose the ability to connect each face to another. For this, we will want to use joint connections, which basically allows connecting side edges of each pentagon one to another, without using any external material, other that the absence of the material itself. The edges become more like lego blocks, while fitting one into another gives a mechanical grip and stability.

Having each face of the DOD connected to other 5 faces for each edge, limits us to which joints we could use. Also the laser cutter itself, cutting only in the X and Y directions, allows use to produce limited joint types. Considering also the fact that each edge of the DOD is connected to the other using an angle of 116.56 degrees, I decide to use the commonly used joint that looks like a square wave.

Sketch Constraints.

We won't be using the edge of the pentagon as an edge itself, however we will turn it into a guideline to see if by recreating the joints we are following the direction, length and angle of the pentagon's edge. For that we Left Click on the top edge and in the Sketch Palette on the right we choose Construction. This turns the rigid line into dashed line for our construction reference.

By Right Clicking on our new construction, we select Sketch Dimension to attribute our previous defined parameter as a length.

Instead of typing an integer digit for the dimension, we type in the name of the previous defined parameter, or dodecLength. An automatic suggestion will appear, so we can go ahead and select it.

Once we do it, we observe the change of dimension of the edge to 100 mm as previously defined.

However we also notice that our shape has rotated. As we would like to keep the top edge parallel to the X axis, we go ahead and select our construction and in the Sketch Palette we choose <>Horizontal/Vertical/>.

This aligns our construction according to our contraint.

We would like to give some parameters for our tabs. A tab represents one of the tooth that together create the side joint of the edge. The length ,depth as well as the number of the tabs will influence how well the faces will hold one to another. Thus, we would like to define these parameters so we could later also modify them with ease. We access again the Change Parameters section and introduce new parameters.

tabCount for the number of tabs. This time we give realistic value of 3, since having a large integer number will result in too many tabs per edge, thus minimizing the rigidity of the material. We also make sure to change the property of Unit from mm to No Units to be considered as an independent integer number and not a metric value.

tabHeight for the height that will be later cut out from the pentagon shape, also considered as a negative tab property. Since for a tab to fit inside the other, a lack of material is needed, empty space so to speak.

tabLength for the length of each tab. This time, we use a formula to express the length of each tab, since we want all the tabs to be evenly spaced and fit in each other accordingly. Thus we say (dodecLength/tabCount)/2, meaning each length of the tab is equal to the total length of the edge, divided by the number of tabs defined and again divided by two - to create value for both the negative tab, as if empty space and positive tab, that will be inserted in the negative space. Speaking of engineering terms, negative tab is the female component and positive tab - male component.

Now we go ahead and draw our side joint. In the Sketch sub-menu we select > Line to draw our first tab of the joint.

A line is drawn to our top edge/construction, of arbitrary length but with 0 degrees as if parallel. For the length, we indicate the previously stated parameter tabLength.

We draw a second line, coincident to the right extreme of the first line but perpendicular at the same time. Thus an 90 degree angle results. For the length we indicate the tabHeight parameter.

For the length of the negative tab, we use the same attributes as for the positive one tabLength and 0 degrees, parallel to the edge.

We also draw a line that completes the negative tab, again perpendicular to the edge and symmetrical to the second drawn line. For parameters we use tabHeight and 90 degrees as if perpendicular.

Patterns.

At this moment of time, we have created a nice square wave-like construction, which will serve as the base for our tabs. By having this square wave construction, we can use it as a base for creating a pattern that will continue along our edge. To create a pattern, we first go to Sketch then Rectangular Pattern.

An Edit window will pop. Now using the pressed Ctrl key on the keyboard, we select our previously created lines. In the Quantity section we indicate the tabCount parameter. As for the Distance, instead of indicating that we use the entire distance of the edge, we type the equation dodecLength - dodecLength/tabCount. The rationale behind this is that we already use 1 tab length to create the rest 5 tabs, however for the Quantity we say that currently we want 6 tabs to be copied. This results in an overload of tabs. To get rid of that, we simply indicate that we reduce the Distance by the length of one tab, the one used for creating the pattern. Then click OK

In the next example we see how the pattern is created by using a number of 5 tabs for the tabCount. The tabs perfectly stretch along the length of the edge and become coincident with the edge on the right.

At this moment we successfully were able to create a pattern for one edge. We would however want to repeat the same operation for all other 4 edges. To accomplish that, the tool >Circular Pattern located under Sketch comes really handy.

In a similar fashion we select our initial lines and as for the Center Point we indicate the center point of our pentagon.

To space the objects according to each edge, we enter 5 for the Quantity. This results in perfect align of each pattern tangent to each edge.

Before proceeding, we make sure to attribute to each newly created pattern at each edge, the same parametric values as we did for the first sketched lines. Because the newly created patterns do not hold metadata about the original pattern they originate from, so specifying tabLength and tabHeight to each of the lines is critical.

We continue by again using >Rectangular Pattern for each edge. Before that we highlight all other edges and turn them into Constructions. This time, we make sure to specify the Direction to be the newly created Construction so that the pattern will align along it. We also modify the formula for the Distance by adding a - (minus) sign in front, for negative direction of the pattern. We make sure to do that for all edges.

As a result, we created a pentagon shape with tabs for each edge, that is parametrically adjustable according to our need, material etc.

To test the responsiveness of our coded shaped, we can go to Change Parameters and try to vary any of our numerical values. Here are some exaomples:

Now we can easily create our own desired dimensions to fit any design. That's the beauty of parametric values.

Testing the Laser Cutter.

Having my shape ready for laser cut(LC), I decided to experiment at first to understand the behaviour pf the LC and the change of it's printing parameters.

For this specific project, I focused my efforts on learning the Epilog 30W laser cutter. Here is a demonstration of couple of experiments I did to understand the settings of the LC and how it affected the 3 mm ply wood.

I made sure to note the settings I used for each operation, to get a perspective of how each setting affects the process.By experimenting with different patterns and text writing, I could clearly get an idea how the Vector mode is influenced according to Power and Speed.

In order to better understand how the Raster mode is refined according to Power and Speed settings, I proceeded by changing each setting proportionally, with the scale of 10 %. Here I noticed that Power and Speed settings are linearly dependent, this can be noticed by taking a look the percentage settings that match, such as speed = 50%; power = 50%. The matching percentage settings will ultimately give the same result, while the one that vary in proportion, such as speed = 20%; power = 80% will give a contrasting result.

As a result I learned that LC operate in two different modes. Either Vector or Cutting Out mode, during which the laser tends to cut through the material and essentially cuts out a specific shape and Raster or Engraving mode, during which the laser would engrave text, image or shape, while leaving the material intact from cutting.

In order to operate in the Vector mode, one needs to adjust his vector lines to <0.01 pt/> of thickness. Anything else will be considered as Raster if otherwise not specified so. Each Vector as well as Raster mode can be adjusted using either Power or Speed percentile setting. This enables the cutter to refine the depth of cut for the Vector mode, depending how thick the material is and for the Raster mode, allows to specify the depth of engraving.

I finally arrived to the conclusion, that the most efficient way to cut out a shape using the Vector mode was to operate with the parameters of speed = 35%; power = 25%. As a result I proceeded by cutting out my first pentagon shapes to give it a try. Here is a demonstration of two parametrically shaped pentagons, with dimensions of dodLength = 30mm; tabCount = 3; tabHeight = 3mm; for smaller sized and dodLength = 50mm; tabCount = 3; tabHeight = 4mm; for bigger sized accordingly. For the material I used 3.5 mm plywood, which makes sense if to think that the average tabHeight for both shapes is 3.5 mm. This will be an initial test to later understand how it all assembles together.

The cuts were done without burning too much of the material, however I encountered a problem while assembling the pieces. The faces were not , meaning assembling them would not give a mechanical hold.

Experimenting with Joints.

Joints between the faces were loose. In order to avoid gluing them together, we would have to modify either the length of the positive tab or the length of the negative tab.

Before committing to any modification in the design, I decided to print out 12 faces, to see for myself whether assembling the entire polyhedron would give a mechanical stability. I used dodLength = 50mm; tabCount = 3; tabHeight = 4mm; pentagon faces for this experiment.

However I quickly realized that the stability will not exist without using a tape. Thereafter I removed the tap once it was fully assembled, to see how it looks in entirety, however the mechanical stability was yet not there.

However by holding the object in hands and passing it to colleagues, It was obvious the construction is not rigid and will not last for too long.

Adjusting the Kurf.

To improve the stability of the DOD, I experimented with reducing the joint's sizes. I decided to change the length of the negative tab. For that I had to firstly separate the two distinctive lengths of the tabs one for positive and one for negative. I then proceeded by adding 0.25 mm to the positive and remove the same amount of length for the negative accordingly.Some tweaking of the initial sketch was required to accomplish the result. Meaning the positive tab was attributed a parametric value of tabLengthPos and for the negative tabLengthNeg.

Then I printed two copies of each edge to test joint's press-fitness.

I then proceeded by printing a couple of 3 mm sized faces to see how they fit one into another.

As the writing states, I concluded that this change of parameters, with 0.5 mm as a total change, created a very tight press, which doesn't allow any place for the flexibility. As a result, I modified the difference of length to 0.125 , half the difference previously used.

As a result, I concluded that this provided a good hold of the faces as well as added some flexibility, which allows the faces to fit one into another.

At this moment I have successfully established the vector and raster settings for the laser cutter, created a parammetrical shape which is resizable, found the right approach for the joints. It was time to pick my size, choose the right material, design each face as an instruction for the Epilog 30W Laser Cutter and print it out.

Final Prototype.

For the material, I chose the 3mm white coated MDF(medium-density fibreboard) left as a spare material from the "Green FabLab" project. This material comes from the same family as plywood, so I expected to get similar results when working with the laser cutter. I chose particularly this material because I wanted to give the object a nice white color as well as more rigidity and a fine look. For the dimensions, I experimented by cutting out 3 mm and 5 mm edge-sized pentagons.

I realized that I needed a size in between to enlarge the object's surface for the text that will be printed on top, as well as not to over exceed it in size, in order to keep it comfortable when holding in hands. Ultimately my design characteristic shifted the dimensions to 4 mm.

To test how many words would fit into one pentagon, I chose a font size of 10 pt that is small but still readable once printed, and try to fit as many characters into the 4 mm pentagon shape. As a result 297 characters would fit. This gave me a realistic understanding of how long can I write the actual instruction for the LC.

Some experiments on the white MDF gave me an idea of how the material behaves once exposed to the laser. To facilitate the printing process and create a neat look, I broke down the layers in Adobe Illustrator into 6 different layers. Each layer is either using the Vectormode or the Raster mode. I also specified which settings I will use for each layer accordingly. The specific layers needed a more detailed approach, having more settings per layer.

I wrote the instruction for the printer which I thought would be suitable, short and simple to comprehend.

My design is ready, final printing was left.

Once printing was finished, assembling the components together was a easy job. For the face that is the bottom side, I intended to to use glue to stick magnets. This would allow a better grip to the metallic shell of the LC.

Besides the link that is placed on the surface of the DOD, which leads to this tutorial page, I also made sure to include an Easter Egg. This one leads to my instagram feed. Ultimately the coolest part is that both links allow to track the click rate for the instructable and to the secret link accordingly.

Voila! Ready for user test!

Assembling in Different Ways.

To push it even further, I tried to reproduce one face on a smaller scale and assemble it in different ways. For that, first scaling was required.

I adjusted the size and kurf using the parametric design.

As a result I get the DXF which I replicate to have more building blocks.

The settings used for cutting using the laser are the following: SPEED:90% and POWER:100%.

Using the cut pieces, it is possible to assemble different shapes and achieve some variation in building.

Download Files:

40mm Length Pentagon Shape DXF file

Laser Cutter Instruction Faces AI file

Parametrical Dodecahedron Fusion 360 file

Concept: Vinyl Cutter.

For the vinyl cutter assignment I decided to vectorize an image retrieved from social media, after which to cut it on the stencil sheet in order to obtain a sticker.

The stencil sheet is made out of a layoer of the sticky vinyl and a the protection layer underneath. The goal is to cut out the vector on the sticky part, by leaving the protection layer untouched.

1. Preparing the Vector.

To accomplish the job, we will be operating the Silhouette Portrait 2 machine. The software can be downloaded here in order to get the environment running.

For the concept of the final sticker, I picked on of the images from my social media accounts. First we will download it as it is.

In order to vectorize the image, I am using Adobe Illustrator. After importing the image and choosing Image Trace, to get the desired look I chose the following settings of the trace tool.

These settings may vary according to the desired look and amoun of detail one wants to achieve. In my case I got the followings:

As a final step, in order to transform the current trace into vector lines, we go ahead and select the target object and click on Expand.

And voila, before, the original image and after, the vectorized image:

2. Working with Silhouette Printer.

I tried to find a good color that would match the back of my laptop, as the final target for sticking my sticker. The choice between black and red, ended up quite easy - red.

Knowing the size of the sticker we want to cut, a block of material is cut and positioned on the top-right corner of the sticky pad that is provided together with the printer.

In order to fixate the material inside the printer, the second button from the top is pressed and the material is slowly introduced to it's origin point.

3. Operating the Software.

Once the Silhouette Software is initialized, we can choose the printer as well as the settings we want to cut with. As a testing print, a tag shape was chosen. Also

Here are the crytical settings chosen to print the first shape.

As a result, our cut was too deep, and the protective layer was cut as well.

4. Changing the Blade.

To decrease the depth of the cut, the inside knife tool is removed and set from the value of 3 to 2, by rotating the knob clockwise.

Now we are ready to load our file, and to produce the final sticker.

The vector image is dragged and dropped inside the software, after which it is repositioned to match our material positioning.

Before sending the job to print, the settings of the blade are changed accordingly to match the number of the knife tool, which is 2.

We position the material accordingly.

5. Last Steps.

The vinyl is printed and the result is satisfying.

Last steps involve removing the excess material around the cut and inside, that we do not want to show on the final sticker.

In order to transfer the sticker from the protective layer to the final object, we use a layer of paper tape which is sticker on top of the sticker. This would grab the sticker and easily transfer it on the desired object.

Now we can trasnfer the sticker on the desired location, back lid of the laptop.

Download Files:

Adobe Illustrator File

Sticker Vector DXF File