Design Basics

Overview

Note

I do not intend to cover all of design, as it is a complicated art.

This document is intended to get you started on what things to research.

In Fusion 360 Design, there are 4 types of design. (Here listed in terms of usability)

1. Solid / Sheet Metal (covers about 99.999999% of design we need to do)
2. Form (creates a body using geometries instead of computations)
3. Mesh (useful for editing STL or other non-computable geometries)
4. Surface (use faces or something idk dont use this)

In robotics, we basically only use solids, and sheet metal sometimes (but we dont have fabrication capability so typical nah). In design, we want to use as many COTS (Commercial Off-The-Shelf) parts as possible. Our vendor is Gobilda. For custom parts, we have capability to print plastic parts (Contact Han for more information). However, these plastic parts are limited by their properties, such as the fact that plastic is less strong than metal. We would like to minimize using these parts and utilize 3D printed parts as mere modifications to already available parts.

Note

If you do own a 3D-printer but don't know how to use it, contact Antonio.

Back to designing!

Below is the typical workflow for creating a design.

1. Importing COTS (if applicable)
2. Creating a sketch
3. Creating a body
4. Modifying a body
5. Joints and assemblies

Note

In Fusion, we utilize things called "parameters" to be able to change different lengths / distances quickly. This is good for making edits later on in the project. Basically, when you are creating a feature, there is a dialogue box, in which you can enter things in the format of 'variable'=int, with the variable being any string, and integer being any integer corresponding to the type of parameter (i.e. mm/in/m, etc. for LWH, and deg/rad for angles.). EX: "length=50", "angle=30deg"

When designing, it is important to keep in mind the material you are working with. For 3D printed parts, please think about what orientation you plan on printing it in, remembering to minize overhangs (3d printers cant print on air!). Small holes are fine. Again, this is a complicated point, so feel free to contact Han if you are unsure.

Importing COTS

Our COTS are from Gobilda. Click on the STEP link, and you should download a file called "RANDOMNUMBER.step". Please rename that RANDOMNUMBER to something intellegible. Or else (I will find you).

Note

If you are interested, I have created a program that does this automatically (Contact Han for usage details):

https://gist.github.com/arihant2math/27add2d4db741b0528053e892cbb299d

These COTS are what we primarily use on our robot, so it is good to get used to using them.

Start Designing: Sketch

A sketch is the foundation of our design and the basis on which bodies are created. After pressing "Create Sketch" (at the top left of the toolbar), you can see the following categories:

1. Create
2. Modify
3. Constraints

When using Create, you can choose from the following:

1. Line
2. Rectangle
3. Circle
4. Splines/Arcs
5. Polygon
6. Slots
7. Patterns
8. Mirrors
9. Dimensions
10. 3D Sketch
11. Project

For 1–6, they basically just create different shapes, each taking different parameters and integers. For patterns, it takes a sketch and creates a pattern either in a circular form or a rectangular one (dual axis). For mirrors, it reflects a sketch object (created in 1-7) across an axis or another line. For dimensions, this is useful for changing the distance between sketch lines or sketch objects. For 3D sketches, please do not use these. They are very imprecise and are typically only used for single lines to connect objects.

The next step for sketches is constraints. I will not list the constraints (see documentation here.) They are mainly used for making sketches behave as you would like when changing parameters. When a sketch line turns black, it means it is fully constrained. Additionally, sometimes constraints are automatically generated (such as parallel constraints when creating a rectangle), which could be useful.

My favorite feature is project. As the name implies, it projects a sketch from another surface onto the current sketch plane. This is useful for referencing things such as holes on COTS or need to align something to another feature.

Finally, the "modify" feature is similar to modifying a body, except it does it to the sketch.

Note

When you are trying to make a sketch on a presently non-existent plane, it might be useful to use a construction plane (under construction tab).

Creating a Body

To create a body, you can choose from the following:

1. Extrude (makes your sketch 3d by going up!!)
2. Revolve (makes your sketch 3d by going around a center axis)
3. Sweep (makes your sketch 3d by going along a path)
4. Loft (connects two faces, with optional sketched rails to contain it)
5. Rib (connects two faces that are 90 degrees in relation to one another under a sketch, with a specified thickness)
6. Mirror (creates a body by reflecting an existing body across an axis)
7. Pattern (creates a pattern like in the sketch pattern but this time with body)

Note

The default setting is always join, but when please change that to "New Body" for easier usability. After completing your model, please combine all your bodies and create a component.

Modifying a Body

There are dozens of different things you can do to your new body. Here are some I like to use:

1. Chamfer: good for making your model look a little bit better, with increased printability.
2. Fillet: makes your model look good as well, but sacrifices good quality when printing (think about steps)
3. Combine body: after making all the bodies you want, press this to combine all your bodies and create a new component!
4. Split body: the opposite of combine body, splits a body according to a construction plane.
5. Shell: empties out the middle of your solid, generating new faces (esp useful for steel bars)
6. Move: it moves things
7. Press-pull: extrudes but doesn't require a flat plane, but instead requires the face to be part of a body.

The parameters mentioned above are able to be changed at the bottom of the "modify" drop-down.

Finally, appearance changes how the material looks like. Good for renders.

Joints and Assemblies

There are two types of joints: joints and as-built joints. Joints are good for connecting things, such as a shaft to a bearing. There are many options to do so, but all of them involve a snap point, which is the center of where the joint will be counted. There are different types of joints, such as revolutes, rigids, and sliders, each with different types of interactions. An as-built joint is basically this but without the snap point, keeping everything at the same place.

Note

Everything mentioned above (except joints) are usually applied in "parts," and we use joints to connect them in "assemblies." Although in Fusion, there are no hard rules for these; it is a good practice to keep.

Closing Thoughts

I hope this short tutorial was helpful. Feel free to contact me (Han) on slack if you run into any problems. Fusion 360 is professional-grade software, so there are bound to be difficulties. Happy designing, and thank you for your contribution to the team.