The Makerspace @ Williams

Beginner 3D Modeling in Rhino

The Makerspace computer has a huge selection of sophisticated 3D modeling software available for student use. Although the programs are accessible, actually sitting down to use them can be daunting. Here is a short Q&A and beginner’s guide to Rhino help you get started in the world of 3D modeling.

What are the differences between the various 3D modeling software?

Some 3D modeling software are more suited to artists and animators. To create character rigs and models for a movie or video game, you would want to use Blender or Maya. Other software, like SolidWorks and Rhino, are better for engineers and scientists for product and tool design.

Some software also differ in modeling philosophy. Many modeling software allow you to create meshes, which are closed surfaces defined by a collection of polygons. Rhino, on the other hand, is a NURBS modeling software, which means the surfaces of models created in Rhino are infinitely smooth.

What should I keep in mind while designing my own model for printing?

  1. Think small. Objects larger than a teacup can take several hours or more to print. However, the square-cube law can work to your advantage: printing thimble-sized prototypes only takes a few minutes. As you increase the print speed, you lose printing accuracy and definition on your model.
  2. Consider the overhang on your model. The LulzBot and MakerGear print additively, from the bottom-up, so if you ask it to print a horizontal overhang, it will try to print on thin air. The Form 1+ has similar problems with underhang. Keep gaps between supports to a few millimeters or less, and try to keep outward slopes steeper than 45 degrees.
  3. Make sure your model consists of closed surfaces! The software that compiles your model to G-Code will ignore 2D shapes entirely.

Using Rhino

Below are notes taken from Dave Schultze’s Rhino 5 Essential Training class. The entire class can be accessed on Lynda. For instructions on how to set up a Lynda account through Williams, refer to the Williams OIT webpage.

Before Starting a Project

First, always check units and tolerance. Units are the units you are using to measure the size of your model. Tolerance is the accuracy of the model. A small absolute tolerance means high accuracy.

To switch units, navigate to Tools > Options > Units at the top menu. Since our 3D printers are calibrated for mm, you will probably want to use mm while modeling.

Rhino also provides default settings for units and tolerance based on the size of the object you are modeling. They are located in the Splash Screen, which can be reached by navigating to Help > About Rhino > New at the top menu. If in doubt, you should use Rhino’s default settings. It is important not to change the tolerance midway through your project. Then you will have different surfaces with different tolerances.

Basic Entities

There are four basic entities in Rhino. These are:

  1. Point (these are usually just used as a reference)
  2. Curve
  3. Surface
  4. Solid

A collection of surfaces joined by a common edge is called a polysurface.

The commands for creating 2D entities (points and curves) can be found in the Curve menu and the Curve Drawing tab.

An easy way to model a complex 3D shape is to draw its silhouette with curves and then use the extrude command, located in the Surface or Solid menus and the Surface or Solid Creation tabs.

Commands and Shortcuts

Commands can be executed in three ways: Locating them in the top menu, finding the corresponding button in one of the toolbars, or typing the name of the command in the command line.

To access the in-program documentation, navigate to Help > Help topics. If you are having trouble locating a command, you can search for it in the Help documentation and click “Where can I find this command?”

For real-time help, navigate to Help > Command Help. Drag the tab to the panel on the right to dock it. When you start a command, the tab will update to the command’s help page, giving you easy access to the software documentation and a guide to how to use the command.

Below are more tips and shortcuts to help you out.

  • Pressing spacebar repeats the last command
  • Right clicking on the command line lets you choose a command to repeat
  • Remember to look at the command line to adjust command options
  • Turning on Osnaps makes moving curves and solids precise. When you move them, they will snap to points
  • Dragging an object while holding the alt key makes a copy of it
  • Shift + click allows selecting multiple objects, and ctrl + click deselects an object. Many additional selection options are available under Select toolbar.
  • The lightbulb icon in Layers panel toggles layer visibility
  • To select all the objects on a layer, right click on the layer and pick “Select Objects”
  • To move an object to a different layer, select the object, right click on the layer you want to move it to, and select change object layer

Modeling tips

  1. Make a sketch of the object you’re modeling. It’s a good idea to determine one or two profiles of the object. Look for symmetry to reduce the amount of modeling you’ll have to do.
  2. Draw in curves on the plane first – don’t start with 3D primitives! If the object you’re modeling has fillets, pre-filletize the curves.
  3. Make the object bigger, then trim. The split, intersection, and solid difference tools will help you.
  4. Save details for last. Holes, fillets, and chamfers should all be saved for the last step.

To see these tips in practice, watch this enlightening 10-minute Lynda video that clearly demonstrates how beginners should approach 3D modeling. The class this video is taken from is very helpful for getting your bearings with Rhino and learning what commands are available in the software and where they are located.

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