Introduction: From Sketch to CAD to 3D Print
Seventh Prize in the
Makerspace Contest 2017
When I'm staffing at the Invention Studio, I like to teach skills that aren't typically practiced among engineering students - particularly sketching. While teaching a colleague to do quick sketching by using helicopters as an example, I accidentally came up with a cool-looking concept.
Concept drawings make for great 3D printable models, but they are often perceived as impossible to translate into a 3D medium. With a little time and some basic knowledge of Fusion 360, anyone can take concept drawings into CAD - where you can use them for 3D printing cute models, decorative electronics housings, or whatever remixes that you dream of.
Camera or (2D) Scanner
Step 1: Ideate Until You Draw Something Worth CADing.
I was doodling a bunch of weird alternative helicopter forms, to illustrate a point about creativity driving innovation. Most of them looked really, really dumb (as they do when you are being silly), but I created one with a sweeping, streamlined appearance.
When you find something that you like, you should run through a few iterations of the design, so that you can refine the features to make it even cooler.
Step 2: Draw the Orthographic Views.
Once you're satisfied that your design is awesome enough to spend time CADing, you're going to need to draw all 3 orthographic views (top, front, and side). If you've been ideating in side views, as I was, that's great! You only need to draw 2 more views.
While drawing your orthographic views, you're continuing trends in features that you identified in your first drawings. Try to not invent random extra features on your design - or if you do, go back and add them to your other drawings.
Keeping things proportional is important here, so if you can't guesstimate proportions very well you should draw all of your views on the same page, using rulers to align the key features and edges.
Step 3: Place Canvases in Fusion 360 on Appropriate Planes.
Use your camera or scanner, digitize your orthographic drawings onto your computer. Crop the drawings down until the edges of the crop touch the widest and tallest points of your drawings. Now, we'll import them into Fusion 360. The whole point of this step is to make sure that every one of your drawings is aligned to a single origin. Once you have a new document in Fusion 360, do the following steps:
- Insert Canvas and select your Side view drawing as your image. Select the YZ plane as your target.
- Manually align the image so that the bottom corner on the "front" side of that drawing is touching the origin.
- Insert Canvas and select the Front view drawing as your image. Select the XY plane as your target.
- Manually align the image so that the bottom edge of the drawing is in line with the XZ plane.
- Move your drawing until the YZ plane bisects it down the center.
- Scale the drawing until the height of the Front view drawing matches the height of the Side view.
- Insert Canvas and select the Top view drawing. Select the XZ plane.
- Align the drawing so that the front of the drawing is in line with XY plane.
- Center the drawing over the YZ plane.
- Scale the drawing until the length of the Top view matches the length of the Side view AND the width of the Top view matches the width of the front view.
This is the time to make sure that your drawings are whatever size you want. However big your drawings are will dictate the size of your model. Changing the size of the drawings later will make everything weird. It is also optional that you scale the size of the final model, which is what I did.
If you ever want to lower the opacity of the drawings, you can change the transparency settings by editing the feature.
Step 4: Make a CAD Strategy.
You're almost ready to start CADing!
But before you do, you should think about what types of shapes you're going to have to make for your design. Identify key features of your design I split mine into two categories: organic and geometric*, and I do that based on major break lines in my drawings.
Organic components are those that have a complex curvature. In other CAD programs, you would attempt to make those features with surface modeling and hope, but, with Fusion 360, we'll be tackling them with the sculpt tool.
Geometric components are simpler objects that can be made with traditional solid body modeling techniques, like extrusions, lofts, and sweeps. These will be handled without sculpting.
Keep in mind that some geometric features may be used to modify organic features later. My general strategy is to make all segments of the drawing as separate bodies and then combine them later. I usually take a copy of my original drawing and mark up the different features, and writing which techniques I'll be using and in what order. Taking a few minutes to do this BEFORE you start modeling is a great way to save you time, panic, and rework later.
The order of these next few steps will change based on your own CAD strategy, but this is what I did for the helicopter.
*Disclaimer: I'm using my own terminology here, and there's probably a different way to think about it.
Step 5: CAD Base Geometric Bodies.
My geometric components happened to be 3 modified extrusions.
For my extrusions, I created a sketch on the side plane, and I outlined those features. I extruded each sketch of those features symmetrically across the YZ plane. I matched/cross referenced the width of those features against the front and side drawings that I imported earlier.
My truss was a bit unusual, because I hadn't referenced it in any of the other drawings, so I had to make it up as I went.
If I was given the option to join the features together, I purposefully made a separate body, so that I could combine them later.
Step 6: In Sculpt Mode, Create Blobs Where Organic Bodies Should Be.
Open Sculpt mode, and create a new body on the YZ plane. Make sure it is roughly the same size, shape, and location of the part you are trying to make.
In my case, I made a sphere for the top of the main body, a box for the bottom of the main body, and boxes for the original rotors.
Step 7: Modify to Shape the Existing Body to Match the Profiles on Different Planes.
- Symmetry - Put your line of symmetry on the YZ plane. Any actions you do to one side will also happen to the other side of that object.
- Modify - Creates a cursor that allows you to pull, scale, and rotate your selection.
- Crease - Allows you to make sharp corners on your bubbly parts.
- Subdivide - Divides up a face to give you more intricate/controlled interactions.
Basically, looking at each imported image, select parts of the body and move/modify them to closely match the sketched profile. Then, once you're satisfied with how the body looks in that view, change to reference another imported image on a different plane. Repeat until you get a good approximation of the organic body that you drew originally. Not going to lie, this can take some time.
Step 8: Fix Errors (probably)
Sometimes, when working with the sculpt tool, Fusion 360 will allow to make things that are impossible. Instead of letting you leave the sculpt mode, it'll direct you to fix the model errors. There's no one way to fix your errors.
I got rid of the message above by deleting more and more of the side panels and then using the Fill Hole feature to replace them.
Step 9: Modify Base Bodies.
- Circular Pattern - Use this to copy and place things you don't want to model again. I used this to make the rotors.
- Extrude Cut - Add some sharp edges to more organic bodies.
- Chamfers - Creates interesting corner elements.
Step 10: Don't Discount Pre-Made Shapes.
Fusion 360 can just make random cylinders and spheres. If you need those shapes, don't bother CADing them.
Step 11: Combine Bodies Into Printable Chunks
3D printers are marvelous, but they have their limits. When making printable models, I realize that some assembly may be required. In this case, I split off the tail and the rotor because I knew that these would be really fragile and hard to remove support from.
Step 12: Print!
Send it to the printer, clean your part up, and you've done it!
You can now sketch and CAD anything!
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