PS1: Intro to 2D CAD — Britton Builds

Creating a Ground-Up Introduction to 2D CAD Class for the Community Makerspace

Pumping Station: One is Chicago’s oldest and largest hackerspace. From late 2019 to Spring 2022 I was the Industrial CNC Area Host. This meant that I was in charge of education and maintenance on our most advanced machines and workflows. The educational backing for this was insufficient, and one of my major projects for the space was to navigate the shifting landscape of CAD and CAM and to bring that knowledge to our members. This page is an adaptation of the information and lesson plans from that course.

Introduction: Course Page

What is CAD?

2D CAD in the context of manufacturing focuses on generating vectors for output to a machine. Whether you are using a laser engraver (Boss or Universal lasers) or a CNC machine like the Shapeoko, X-Carve, or ShopBot.

To generate vectors, this means that you need to use a vector design program. For the purposes of this course, I will be using Inkscape as the software of choice. Inkscape is free to use and available on MacOS, Windows, and Linux operating systems.

What do I Need?

A computer running Mac, Windows, or Linux (including Chromebooks)
Inkscape software if you wish to follow along with this guide.

Other applicable programs are Adobe Illustrator, AutoCAD, DraftSight, CorelDraw, and more.

We'll also want to use a mouse that has a left click, right click, and scroll wheel to follow along exactly. Doing CAD with a touchpad is a terrible experience.

Part 1: What Are Vectors?

When thinking of a usual picture file like a .jpg, .png, or even Photoshop file (.psd), you are looking at what is called a "bitmap." This simply means that a pixel of a certain color is at a certain location in the file. If you expand or shrink the picture, it gets blurry and artifacted.

Vector programs, in contrast, use mathematically defined paths to generate a picture. This means that if you need to expand the work, it scales perfectly without artifacting. In the context of manufacturing, this means it gives your tools paths and bounding regions to do its work in.

If we look at this example, we have two pictures of the same thing. One of these is a vector file, the other is a standard bitmap. Zooming in on the bitmap, no matter how high the resolution, it becomes grainy.

Contrast with the vector, where no matter how far we zoom in it stays smooth. It is not just a fidelity difference, though, it is that the vector’s use of directions can be translated much easier to our devices like the Shapeoko, ShopBot, or lasers.

Part 2: How Does This Work?

First, we're going to open up Inkscape. Unlike Adobe Illustrator, Inkscape is free. Inkscape is highly customizable, and we'll cover how to do these customizations ourselves later on.

Now, when we open up a new document, we are looking at the file's "canvas." This canvas simply gives the borders we'll be working in. We'll start putting some art in the next video.

First, to move around the software we can hold the Control key and scroll up or down to zoom in or out. We can also press down on our middle mouse button to drag our view around the canvas.

Very quickly, to look at the menus, we're going to go up and down on the left hand side. If you choose a tool there, you'll see that the top toolbar's options change as well. It gives you powerful additional options and controls to really get the most out of the tools..

Lastly, I want to highlight three of the most useful toolbars on the right hand side: stroke & fill, layers, and alignment.

When drawing a shape, the stroke & fill toolbar controls the outline of your path and the infill, if it is a "closed contour." A closed contour is simply a fully enclosed shape. For example, a triangle is the most basic closed contour because it has only three sides. The "stroke" settings give you your line weight & color and the "fill" settings determine the color within the shape.

Layers are the next tool and they are great! I like to dedicate a single layer to the outline of my stock material I'm going to cut from. On another layer, I keep the cut out profile of my work. Layers on top of that are going to be engravings (e.g. letters), or pockets (cleared out sections that don't go all the way through).

The last part is alignment. Alignment features give you precise control over how different elements relate to each other. Our demo project is going to be a name tag, and we want to be able to keep your name nice and centered with respect to the outline of the tag. We can also align things to the left, right, top or bottom! We'll talk about grouping as well, which combined with alignment give you powerful ways to lay out your project.

Next up, we're going to make a simple nametag!

Part 3: Follow Along Project — Name Tag

Sharp edges are not very fun to deal with, so we always want to make edges filleted. We'll apply a 5mm fillet to each corner.

Using the “Select” tool (regular arrow) we’re going to click on our nametag outline. We will then go to the top menu bar and choose “Path” > “Path Effects”

This opens a new toolbar on the right hand side. We’ll hit the “+” sign to add an effect. The top-right option for “Corners” will give us the effects that we want. Click it and then the check icon.

Set our units to “mm” and radius to 5. We can hit the “Chamfer” button to change to a chamfer as well as inverse fillets and inverse chamfers.

We can come back to these menus any time to add, remove, or edit these values.

Now we're really cooking with gas. Let's align this outline by Shift+Selecting the stock shape and nametag outline. We'll choose these two options so it's centered horizontally and vertically with respect to the stock outline. Lock the layer.

We're going to go ahead and open a new layer. This is our last one and where we're going to put our engraving, so let's call it "Engraving."

Let's select the text tool and click and drag open a text box roughly inside of our Nametag Outline. We'll align the text later.

First, we're going to choose a font - the one we're going to use is called "Simplex". Simplex was designed with engraving in mind, and it will make our lives easier. It's easier to start with a small text size and make it larger, so let's set the font size to 10pt. To help keep things aligned, we're going to set the text box to center justified.

I'm going to write my name and hit Shift+Enter to insert a line break. I'll now write a subtitle. If things disappear or go haywire all we have to do is click and drag a corner of the text box to show everything we've typed.

We can now increase our font to fill up the space a little better. Always be sure to leave some good clearance between the profile and engraving so we don't lose any detail or get bad surface finish.

Once we're satisfied with the size and placement, we just need to swap back to the "Select" tool and click off the text box field. If we find that we need to edit the text box using that same "Select" tool to click into the box will let us edit the text.

Fonts can get funny between different computers, and vector software saves fonts as text, not as a picture of text, so we need to make sure that we convert the font to a vector like everything else.

Using the Select tool, we'll just click and drag to highlight all the text. Up in the very top toolbar, we need to choose "Path" > "Object to path." Now the text is treated the same as any other vector in the file. To double-check that this worked, when we use the "Select" tool on the text, it should no longer bring us into the text edit mode.

Now that the text is a path, if we aligned it to the Nametag Outline, it would just smoosh all our letters up into the chosen position.

Let's first use the "Select" tool to highlight all the converted text and hit Ctrl+G. This is the "group" command. This preserves the spacing and alignment of everything that is selected and tells the software to treat it all as a single entity. To ungroup, all we need to do is select the grouped objects and hit Shift+Ctrl+G.

Let's now select the grouped engraving and the Nametag Outline to align them in the center. We now have a file prepped and ready for our machines to turn into the final name tag!

The first step to making this name tag, and anything else, is to consider what materials and machines we want to make this with. Two materials come to mind:

* 2-layer plastic in the Shapeoko or

* Plywood in a laser engraver.

Luckily, both of these machines can utilize very similar files, so we can worry about the details of that later.

Now, just like the last video, we're going to open up Inkscape and take care of a few details. First, we're going to go to the document settings and set the following:

* Document Units: mm

* Canvas size: 250mm x 250mm.

What we have done is made sure that we have a consistent document unit that our output machines can work with. You may notice a few options for inches, point (pt), and percent when we get to choose units for different features. We're going to want to make sure we keep everything in millimeters.

The second thing that we have done is set the work canvas size. Since we are targeting two machines with different work areas, we should design around the smallest one, which in this case is the Shapeoko's work area of 250mm x 250mm.

Now, let's take a look at our layers. The first layer is called "Layer 1" and I want to rename it to "Stock Size". Let’s right click the layer, select “Rename Layer” and give it its new name.

“Stock” means the material you’re cutting, like plywood. We are almost always working on materials that are less than 2” thick. Using the piece of material I have on hand, it's 120mm x 120mm.

Now we know how big it is, so we need to put it on the document. I'm going to go to the rectangle tool on the left, and roughly draw out a square. Looking at the top bar, we have some options in there, namely the X and Y dimensions. I'll just type 120mm into each text field and we're good to go!

Because this is a stock outline, our stroke doesn't really matter. Just make sure you choose the "X" under fill to make sure we don't have any colors or anything in there.

Let's put our stock somewhere on the upper left hand corner of the document. It's an easy alignment point for all the machines we're planning on using for this project.

Now that our stock outline is drawn out and located, let's lock this layer by clicking the padlock icon next to "Stock Size" in the “Layers” menu

We're going to add a new layer, and this is going to be our outline, so let's name it "Nametag Outline." Hit the Plus sign on the “Layers” menu and drag it above the “Stock Size” layer if need be.

Roughly inside of the stock outline, we're going to make another rectangle. This time 100mm x 50mm. Inside of this menu, we also have some other boxes with the labels rX and rY - these allow us to make corner fillets.

Part 4: Customizing & Additional Tools

The last thing I want to cover for Inkscape is that it is a SUBSTANTIALLY more powerful tool than what is covered here.

First, I am a big fan of dark modes. If we go to the Edit > Preferences menu, we can see different theming options available for Inkscape. There are a lot of options in here to help with accessibility and just general preferences.

One of the big tools that I want to talk about as well are the path editing tools. Not every line needs to be straight or finely radiused - you can make all kinds of whacky curves by laying down Bezier curves and manipulating the “spline control handles” on them.

In addition to these, we can add or remove control nodes. Adding control nodes allows us to add more detail or curves to the path. Removing them gives us a smoother sweep for that segment. The less control nodes, the smoother the curve.

Lastly, Inkscape is extremely powerful as a file conversion tool as well. It can be difficult to get art programs to talk to CAD programs, and it can be very helpful.

Similarly, Inkscape can handle Adobe Illustrator .AI files for conversion for use in laser engravers or CNC machines.