An introduction to CAD modelling with 123D Design
27 November 2018

Hello everyone.

As one of the contributors to techopsy.org’s 3D Design section, I will be endeavouring to share some of the experience and know-how I’ve accrued over the years with one of the best free CAD modelling software currently available to hobbyists who would like to start dipping their toe in the field of CAD modelling. The software in question being 123D Design, from Autodesk. The software, while free and free to use and continue to use for non-commercial purposes, has (to the best of my knowledge) unfortunately been discontinued by Autodesk, with Autodesk no longer offering it for download on their website(s) and it no longer being developed or updated by Autodesk. Indeed, the 123D Design website itself was taken down some time ago. If I remember correctly, Autodesk pulled the plug on 123D Design in 2016. Anyone who already had the software installed (or installs it afterwards using the installer downloaded from the Autodesk 123D Design website prior to the discontinuation of 123D Design) can certainly still use the software. Hopefully Autodesk will one day reconsider and revise their decision to discontinue developing and maintaining this software.

Lacking a hugely extensive panoply of tools and variations or customisations or options for those tools, the software really puts the onus on the user’s skill, mastery, imagination and visualisation skills to be used to its fullest and give all it’s capable of. This is a tool for the craftsman and requires a craftsman’s technique to reach its full potential. You will be doing a lot of planning in your mind when using this tool effectively. But don’t be mislead, the software is very powerful and very capable provided you don’t need software which holds your hand and helps you cross the street.

Although no longer offered on any of Autodesk’s own websites, the software can be downloaded from the Softpedia website at the following link : softpedia.com . I personally downloaded the software from the Autodesk website shortly before the 123D Design website got taken down so I can testify that the version available for download on the Softpedia website (2.2.14) is indeed the latest available.

The software is available in both a 32 bit and 64 bit version but the 64 bit version is highly advisable to use unless you are running on a 32 bit operating system. The 64 bit version will not run into memory limits the way the 32 bit version can with some of the more complex models you might get up to designing with it and is also less likely to crash or corrupt saves or exports. Not that that is a common occurrence at all with the 64 bit version but it can happen on occasion, with very complex design operations or strings of complex design operations. So make sure to safe often, even though the 64 bit version is generally quite stable.

Assuming you’ve downloaded and installed the 123D Design software, let us begin by talking about the interface of this  software :

123D Design interface.

123D Design interface.

Please excuse the tiny menus and icons as this is what 123D Design looks like on a 3840×1600 display.

In the top, left hand corner of the interface we have what would be analogous to the ‘File’ menu in an office work type application :

File Menu.

File Menu.

This menu gives the options to start a new model (if we choose to) discarding our progress on our current work since our last save, open a previously saved model, overwrite the last save file with the current status of our work, import into our work a CAD model file of a different format than the one native to 123D Design itself (which has the file extension of .123dx ), export our work as a CAD model of a different format than the one native to 123D Design itself, 3D Print (for sending the model to an on-line 3D printing service or to our own 3D printer), send the model to other free apps put out by Autodesk (Meshmixer and 123D Make) and exit.

Near the top you’ll notice the undo and redo buttons along with the tool menus pallet :

Tools Pallet at the top of the 123D Design interface.

Tools Pallet at the top of the 123D Design interface.

Most of the widgets / icons will display a drop-down menu when you hover your cursor over them. This is useful as it groups tools similar in scope and application in the same dropdown menu, keeping the interface nice and tidy and avoiding clutter. The various menus at the top is where you’ll find the tools you’ll be doing the actual modelling work with.

  1. From left to to right, the first two icons are the undo and redo buttons. These are pretty self-explanatory.
  2. Next up is the Transform menu (which contains tools for moving or rotating solids (closed hull / watertight 3D shapes with internal volumes hermetically sealed from the outside) and sketches, aligning solids, scaling solids and measuring distances).
  3. Then follows the Primitives menu, symbolised by an icon depicting a cube and a 2D circle behind it. This menu is where you can find tools for creating various basic 3D and 2D geometrical shapes. The 2D shapes are created as sketches. To be honest, I personally hardly ever use the tools in this menu but your work flow may differ if you’re still learning this software.
  4. Further on, we have the Sketch menu, symbolised by a pencil tracing a Bezier spline showing two control points. If your modelling work flow is anything similar to mine, you’ll be using the tools in this menu a lot and you’ll always start your modelling using the various tools in this menu, which are all quite powerful. They are too many and varied in application to do justice here, we’ll get to talk about each of the tools in this menu in a later instalment to this series.
  5. The next menu is the Construct menu. It’s another menu you’ll be picking a lot of tools from as you model, as it contains the very powerful tools : Extrude, Sweep, Revolve and Loft.
    • Extrude is used to create 3D shapes from 2D sketches. But the extrusion doesn’t need to result in a straight prism / parallelogram. When we extrude, we have the option of extruding straight up (up being relative to and from the surface we can imagine the sketch which we are extruding is residing on) or as a frustum, by angling the walls of the extrusion either inwards or outwards as we extrude it, by an angle of our choice (the angle being the one between the wall of the extrusion, at any point along its perimeter, and the flat surface the sketch we are extruding is residing on). You can only extrude from flat surfaces, not curved ones. This is your go to tool for creating three dimensional solids from 2D sketches so you’ll be using this one a lot, especially at the beginning of the process of modelling something.
    • Sweep is used to create a solid which can be described by translating a chosen 2D profile a long a chosen 2D or 3D path. You can choose whether the orientation of the profile changes to keep in accordance with the changing orientation of the path the profile is swept along or whether you want the original orientation of the profile being swept along a given path to be preserved along the path. If you want to keep your modelling neat, tidy and as accurate and precise as possible you may want to be very discriminating and conservative in the use of this tool.
    • Revolve is used to create circular shapes (or sectors thereof) from 2D shapes or sketches which describe and define the profile of the circular shape and using an axis of rotation of the user’s choice. This is your go to tool for anything round or that’s a cut-out of something round.
    • Loft is an extremely powerful tool which can be used to create smooth, organic 3D shapes by inference or interpolation from sets of 2D sketches provided and specified by the user and which define profiles of sections of the 3D shape to be generated by the Loft tool. This is a very powerful tool if you’re going for organic shapes but it’s not something you want to loosely use when there are more rudimentary tools that can get the job done. Or else the complexity of your model will be greater than it absolutely needs to be and the accuracy / precision of your modelling might not be the absolute best it can be. Remember : the tool interpolates a 3D shape from sets of two or more 2D profiles you provide it as input. So anything between any two profiles might not necessarily be exactly what you had in mind or expected. For example, if you have 4 2D sketches you use as input for the loft tool, the outermost sketches will partially affect what the interpolated tridimensional shape will be like between the innermost two profiles.
  6. We’ve reached the Modify menu. The tools in this menu will see moderate to high use, especially as your model matures, growing in complexity and beginning to approach it’s final state. If your modelling technique is similar to mine, the tools you’ll mainly use from this menu are :
    • Fillet. Smooths sharp edges between adjacent surfaces of a 3D solid.
    • Chamfer. Chamfers edges between adjacent surfaces of a 3D solid.
    • Split solid. Use a 2D sketch, a surface of a 3D solid or all surfaces of a 3D solid as planes or curves to cut another solid along, into separated constituent pieces.
    • Shell. Use this to hollow-out a 3D solid to a desired wall thickness (walls can be on the inside of the original 3D solid, on the outside or half of their thickness on the outside and half of their thickness on the inside of the original tridimensional shape you apply this tool to, according to your preference). If you apply this tool to a particular surface of a 3D solid, the solid would be hollowed-out just as it would be if you applied the tool to the entire object itself, but the wall of the hollowed-out object which would correspond to the facet or surface you opted to discriminatingly apply the Hollow tool to would be missing and allow what would otherwise have been the airtight inside of the hollowed-out object to communicate with the outside of the object.
  7. The Pattern menu can be used to create circular arrays, straight or curvy path arrays or rectangular arrays of 3D solids of our choice (and even selections of surfaces of those solids, on those same solids). This menu also houses the Mirror tool, which can be used to create mirror halves of objects given a 3D solid to start with and a flat surface as reference or mirror surface relative to which a mirrored half of the 3D solid selected as input should be created.
  8. The Group menu. I hardly ever, at all use the tools in this menu and it’s not something I would recommend others do either. The tools in this menu aren’t useful to modelling itself. In fact, apart from clicking a single 3D solid selecting all 3D solids it is grouped together with and preventing one shape in the group from being inadvertently displaced from its original position relative to the other shapes in the same group, I’m struggling to find a use for the grouping function.
  9. The Combine menu is another powerhouse of modelling tools. This is where the tools for performing Boolean operations with 3D solids reside. These are incredibly powerful tools indispensable to any respectable CAD modelling software. This menu contains the Merge, Subtract, Intersect and Separate tools. The latter one which I basically never use.
  10. We’re done with modelling tool menus and reached the Text tool. Use this tool to create 2D sketches of characters, to then extrude or do whatever else you’d like to with, on flat surfaces of your choice.
  11. Oh Snap! The Snap tool can be used to relocate parts of a model so that they are in contact with one another. You can use it to select a flat mating surface on one object and a corresponding flat mating surface on another object and the first object will be repositioned so that the centre of its chosen mating surface is in direct contact with the centre of the chosen mating surface of the second object. You then have the option of rotating the re-positioned object around the normal to the mating surface of the second object or pushing or pulling the relocated objected nearer or farther from the second object selected. If you chose curved mating surfaces then no centring (of the relocated object) on said curved mating surfaces will occur.The centring is only applied to flat mating surfaces you choose, not curved ones you choose. If you choose curved mating surfaces, the snapped object will be aligned along the normal of the curved mating surface at the specific point you clicked on that curved surface at. If you choose curved mating surfaces on both of the two objects the tool takes as input, it will snap the the relocated object to the second object such that the respective normals of the two respective curved mating surfaces of the two objects (at the specific points on those curved surfaces you clicked on) are collinear. You really want to refrain from using this tool if you’re after top notch precision and accuracy in your modelling.
  12. The button for opening the Material options window, where from you can choose the material applied to a given selected shape. There are enough materials available here to get you by and the visual appearance and verisimilitude of most materials is decent to pretty good but you certainly won’t be using 123D Design as a replacement for Keyshot or 3D Coat.

Now that we’ve gone through the tools palette to some degree, we can go over the controls on the right edge of the interface.

Side Menu buttons and options.

Side Menu buttons and options.

You can ignore the ‘Go Premium’ button. It’s simply a leftover from before Autodesk discontinued the software. As is the ‘Sign In’ button. The question mark button displays a dropdown menu of which the only useful or interesting entries at this point in time are Help, Preferences and About.

Lower down we have a cube we can left-click and hold down as we drag the mouse to swivel the entire scene around a pivot point. We can also click and release on centres of faces of the cube, corners of the cube or edge sections of the cube to swivel the entire scene until it’s reached a specific pre-set orientation corresponding to the clicked on region of the cube. The orientation of the cube corresponds to the orientation the scene has relative to the viewpoint of the user. If we hover the mouse cursor over the cube we’ll see that right below and to the right of it is a drop-down menu button which allows us to toggle between Orthographic and Perspective projection rendering modes for viewing the scene.

  • Lower down we have three Camera Control buttons (Pan, Orbit and Zoom).
  • Then a Fit button, which will try to set the camera position and orientation such that all shapes and sketches in the scene are visible in the view frustum of the camera. The results produced vary according to whether we are in the Orthographic view or the Perspective view.
  • Then we have a menu for choosing how we’d like to have solids in the scene rendered. We can choose between an Outlines Only rendering of solids, where only their edges are displayed, a Materials Only rendering of solids where edges / outlines are not highlighted or a Materials and Outlines rendering mode where solids in the scene are not invisible except for their edges or seams but also have their edges highlighted.
  • Next down we have a menu which allows us to toggle between having solids visible or not and having sketches visible or not.
  • A button for toggling the visibility of the reference grid.
  • A button for taking a snapshot of the scene as currently viewed by the camera. The resulting image file will be saved in the same folder as the currently open model file was last saved in.
  • A button for choosing whether solids we used the Snap tool on are also grouped together after being snapped together or not. I would recommend keeping this set to off.
  • A button for toggling snapping on or off. I would recommend keeping this set to off.

On to the bottom menu :

Bottom menu.

Bottom menu.

This one shows up when you select a shape / 3D solid in the scene. It gives the user the option to Move the solid, Smart Scale, Scale or Hide the solid, launch the Material options window for the selected solid or solids specifically, Export the selected objects specifically, Send to MeshMixer the selected objects specifically, Send to 3D Print the selected objects specifically and finally send to 123D Make the selected objects specifically.

There are more menus in 123D Design to discuss but we’ll go through them in due time and as we find we need to touch on them as this is article is only meant to be but a first acquaintance with 123D Design and its interface. As closing notes, I would like to list the following which, in my opinion, are good or best practices and which I abide by in my use of this software:

  • You simply must read the Help document of the software, accessible from the drop-down menu under the question mark button.
  • I would recommend getting accustomed to using the Orthographic rendering mode and only using the Perspective projection rendering mode to admire your work from time to time or review your progress before switching back to Orthographic rendering mode if further work is required.
  • Especially in Orthographic rendering mode, once you get accustomed to it, the quickest most easiest way to move around the scene is simply through various combinations of :
    • Holding down the right mouse button and moving your mouse to swivel the camera around the scene then releasing when you’ve reached the desired new orientation.
    • Using the mouse’s scroll wheel to zoom in and zoom out. The camera always zooms in to or out of where the region in the scene which corresponds to the place on your screen you have your mouse cursor located at the viewport so you can use this to zoom out from areas of the model or scene you’ll no longer be working on for the time being and zoom in to areas which you’d like to start working on next.
  • Do as much of your design work a the sketch phase and only start extruding, revolving or otherwise converting your 2D Sketches to 3D solids when you’re absolutely ready and there’s simply nothing more you can do on just the initial sketch. You’ll have an easier, more productive modelling experience this way.
  • Delete or at least hide sketches you no longer need. Having a lot of sketches on screen at once, especially if they are large, can (also depending on the specifications of your machine) reduce your frames per second and the overall responsiveness of the program. If the software becomes sluggish and hiding or deleting sketches doesn’t seem to help, simply export the model as an .stp file, start a new scene and import it back in to that new, blank scene. That will get rid of any lingering sketches or ghosts of deleted sketches which might have been causing the sluggishness. I’ve only ever had to do this when using the 32 bit version of the software.

Please be sure to check back in from time to time as we’ll try and add additional instalments to this series, with practical walkthroughs and step-by-step tutorials on how you can model all sorts of things using this wonderful free CAD software!

For an idea of what can be done using 123D Design check out this awesome featured image showing a rendering of a model made almost entirely using 123D Design :

Piston and Connecting Rod model on spiralled cylindrical support.

Piston and Connecting Rod model on spiralled cylindrical support.

So please stay tuned as it will be worth your while!

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