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PTC CAD

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randej edited this page Dec 31, 2014 · 27 revisions

Designing the mechanical systems for the robot can be done in several Computer-Aided Design (CAD) programs, such as SketchUp, AutoDesk Inventor, PTC, etc. PTC is a very common CAD package used throughout industry, and extensively at the FIRST Tech Challenge (FTC) level. Like with many CAD programs, PTC files can be exported to be used for 3D printing, other CAD programs, machine shop tooling, etc.

Advantages

There are several advantages to using PTC CAD for robot design:

  • A CAD model allows the designers to see clearances & how well parts fit (or don't) BEFORE items are purchased or material is cut.
  • The team can get a Bill-of-Materials (BOM) automatically from the program. This makes it easy to place orders and report to the hardware inspectors at competition.
  • Mass properties of the robot can be calculated, things like weight, inertia, etc., before the robot is built. If the robot is heavy for example, the designers will know earlier - allowing them to refine the design (and avoid wasted parts & materials).
  • Multiple developers can collaborate on a single robot, especially when the code is stored on WindChill. This is standard practice for the CAD industry. Anyone can see who changed what parts, see the entire history of all part updates, and keep library parts in a central location.

Tools

  • PTC Creo - Creo Parametric is the program necessary to create 3D CAD files while Creo Direct is the 2D version. We will primarily use Creo Parametric for its 3D modeling and visualization capabilities.
  • PTC Simulate - PTC Creo Simulate provides structural and thermal simulation capabilities. This app gives users early insight into how their design will perform and can reduce the time and cost associated with physical prototyping. We will use it to look for high load/stress forces, robot appendage travels during motion, etc.
  • PTC MathCAD - Mathcad is a visual "notebook" for solving, analyzing, and sharing engineering calculations.
  • PTC WindChill - Windchill helps teams manage their products through all phases of its lifecycle. It will be the central repository for all of our CAD information - allowing multiple users to share, view, and edit CAD files with or without having the CAD tools installed.

Educational licenses for ALL these products are available to FIRST teams.

Install the tools

There are several things that must be done one time before you can start CAD'ing on your own Windows computer. You will likely need to install all of these. NOTE: If you are using Mac OS or Linux, you'll have to run this in a Windows emulator as these are Windows only tools right now.

  1. Install PTC Creo - Start by going to http://www.ptc.com/communities/academic-program/products/free-software. Select the right option (mentors should use "I am a K-12 Educator"), then register or sign in and you should get an email from PTC with the location of the installation files. Follow those instructions to download PTC and create an install DVD (you can also borrow one of the team DVD's).
  2. Install WindChill - There is no installation for WindChill as it is simply a browser & Creo plug-in. You will first need access to our team project, so you will need to contact a team mentor for an invitation. Once you get that, you simply "Join" the project (you will have to create a PTC.com account if you haven't already).
  3. Install MathCAD - MathCAD is part of the Creo 3.0 installation image, so you can install it at the same time as Creo by checking the box during the installation process.

Set up Creo

First, determine where you are going to keep your library parts and robot designs. Library parts are usually stored separately from the robot design since they are common, stock parts we buy directly from vendors like McMaster Carr or AndyMark. The robot design is where you assemble custom parts and library parts into a "assembly" that represents some or all parts of the robot.

Let's say you store your CAD work in a directory called "C:\CAD". You would probably keep library files in something like "C:\CAD\Library" and C:\CAD\201x Robot" for the robot files. Right now we're storing our part Libraries on DropBox at \FRC4931-2014\2015\CAD. Pull the zip file down and put the contents in your Library folder.

Now, look in the Library directory for a file named "search.pro". Open that file with a basic text editor (like Notepad) and change all of the "S:\Creo" portions of the paths to whatever path you used for your "Library". All the rest of each line should stay the same -- this file tells Creo how to find common library parts used on multiple projects. Example: "S:\Creo\Library\MiscHW" becomes "C:\CAD\Library\MiscHW" or similar.

Launch Creo, but don't load any files yet. Instead select File->Options->Configuration Editor. Press the Add button and type "search_path_file" in the Option Name box. Select Browse and navigate to the search.pro file you edited. Select Ok to close the browse window, then Ok again to close the Add dialog. When you hit Ok in the Configuration Editor, it'll ask if you want to save the current configuration. Say yes. You can store it in your main CAD folder or project file. Later we may have to tweak this, but this works for now.

Creo Training

PTC has very good self-paced training materials located online at: http://www.ptc.com/communities/academic-program/k12/tech-support/training

There are two links we've used: How to Model Almost Anything (HTMAA), and the Primer. We recommend starting out with Exercise 1 of HTMAA to learn the basics, then jump around in the Exercises to cover material you want to learn. Exercise 6 is a very good one as it shows how to build a working FTC drive train -- useful technique for FRC too! Again, the Primer teaches you how to build and assemble some custom parts, but unless you're doing 3D printing you will not do too much of that. HTMAA covers using existing parts to make things, which is directly applicable to FRC and FTC once you get the KOP.

Set up WindChill

WindChill makes it possible for every developer on the project to have a complete copy of the CAD files and part libraries (including their revision history). WindChill makes it easy for these developers to share their changes and to merge all those changes into the shared Libary repository on WindChill.

There are then two ways to access WindChill:

  • For Creo users, WindChill is integrated right in to Creo Parametric. Start Creo Parametric and:
    • select File -> Manage Session -> Server Management
    • select Server -> Register New Server in the dialog box that appears
    • Type "Team Project" for Name and https://academic.ptc.com/Windchill for the Location.

Hit the "Check..." button. If all is good, you'll be asked for your PTC.com login. Do that, hit ok, and then wait for "Team Project" to appear in the Server List. Click on it and you'll see a list of workspaces show below (most folks will just have one). Right-click on the one you want and select "Activate & Set Primary". This will make the workspace active and show it in your Creo folders list. You're set! For non-Creo users (or quick browsing of parts), simply type https://academic.ptc.com/Windchill in your web browswer. You will be asked for your password and then will see the team workspace. TBS - WindChill setup.

Develop the CAD projects

Once all of this setup work has been done, it should not have to be done again. That means that from now on, you can edit and design the team's CAD files on your computer.

At any given time, you should only be working on a single project. All the CAD projects are independent of each other, and represent different designs. Current projects are often prototypes, and we'll probably create a single project for each specific robot that Team 4931 builds. That project can evolve as the robot evolves. We can even take completed, working designs and turn them into "libraries" for use on later robots!

Create new parts and assemblies in your project folder and use common parts from the Library folder as much as possible.

Remember that we can always "go back in time" (verify - true with WindChill?).

Let's look at the DriveTrain project. This prototype project...

Making changes

See the WindChill? page for step-by-step instructions to modify the parts/drawings and publish your changes.

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