# Revolve Features
# Limits of extrudes
So far you've explored complex sketch relationships and extruded features. What happens when you want to make something like a flashlight? You could use a series of extrudes, like in the video below.
With some more work you might get to the right shape — you could add fillets and chamfers to smooth the transitions, and use a shell feature to create a part suitable for injection molding, as seen in this video.
But think about all the challenges that this process creates. What if you needed to design the opening at the top of the flashlight to match an existing lens? You could measure the opening, then keep adjusting the angle of the second extrude until the size was right — or close to it. Or you could do some trig and figure out what angle would give you the right dimension, but then you'd need to know trig. For shapes like this one, there is a much more intuitive and controllable way...REVOLVES!
# What are Revolves?
To make a revolve, you create a sketch that represents a side profile, then spin it around a central axis to create a complex form, like a flashlight or a wine glass. In general, the object you're making should be most easily defined by a cross section drawing. it's easier to show that explain. In the clip below, the same flashlight form is created using a revolve. Note that the whole form is created with one sketch, and critical dimensions are easily controlled.
In the example above the main form was revolved and then fillets and a shell feature were added later. These details can also be added to the sketch. In the video below, an open profile is created, including the fillets and wall thickness of the flashlight body.
This is not necessarily a better way to create such a form, but it is important to know that similar details can be created in either a sketch or in subsequent feature operations. The needs of the design should dictate which strategy makes the most sense.
# Other Examples
# Wine Glass
More complex and curvaceous forms can be created using revolves. In the example below, a wine glass is built from a single sketch and revolve. Take note of the relationships used in the sketch to create more complex curves.
# Doughnut
Imagine you needed to model a doughnut. Like the wine glass above, this would be impossible with just extrudes. But you can create a revolve around any axis, not just the center of your profile. This way, you can create forms with open centers, like a doughnut or an o-ring.
# Bearing Raceway
A more realistic example would something like a bearing raceway. In this video, a slightly more complex profile is created and then revolved around the world Y-axis.
# Arbitrary Axis
You do not need to revolve only around a world axis. Any linear element will work, including sketch geometry. If you do use a sketch line, It greatly helps to organize the design if you make the revolve axis dotted construction geometry
# Partial Revolves
Revolves do need to go all the way around their axis. Most CAD tools offer options for creating partial revolves that can be specified by angle or termination, and there typically options to revolve in both directions, singularly or symmetrically.
# Assignment
Create a set of tableware for your craftsman table using revolves. The actual design is up to you, but they should be a coherent set, with similar forms and proportions. Use one file and create each piece as its own component. Build the following:
- Dinner Plate
- Salad Plate
- Soup Bowl
- Water Glass
- White Wine Glass
- Red Wine Balloon