We encourage all customers of the mechanical workshop to generate their designs with such software. Here is why, and how.
Why use CAD programs?
By using computer aided design (CAD) software, mechanical designs can be significantly improved, because informative drawings for manufacturing can be generated that make communication and documentation much more efficient. This is because this software makes it easy to give all specifications necessary to make the parts.
It also helps you as the designer a lot to find out if a part fits, and has the exact shape you wanted. You can e.g. simulate if a part fits into a given geometry, and thus reduces a costly and time-consuming reworking of your parts.
For certain geometries, it also makes it a lot easier for the workshop to convert a drawing into something the manufacturing machines like the CNC mill and the wirecutter understand. This reduces the waiting time, and possible errors in data transfer.
Modern CAD systems are relatively easy to use, and can probably be considered as an element of technical literacy for experimental researchers in physical sciences. If you are likely to require a number of mechanical designs, it is almost certainly worth the effort learning how to use such software.
Several companies provide free or very reasonably priced licenses to students and researchers; see below of a few options you have.
2D vs. 3D
Traditionally, technical drawings were generated as projections and cuts of the object you want, with a standardized way to generate such drawings to avoid misunderstandings, and to simplify reading and interpreting them. An important aspect is that drawings almost always to scale, so you get a good impression how the part looks like. Most Drawing programs can be used for that purpose, but dedicated CAD software allows a relatively simple labeling with the correct dimensions once you designed your part. This is the an important piece of information the workshop needs to make something.
Some of the machines (e.g. the wirecutter) understand directly the file formats used to save 2D drawings, so you can efficiently translate your drawing in the mechanical piece you want, cutting down the waiting time.
With more powerful computers and graphics systems, several 3D construction programs became widely popular that allow you to generate drawings not as projections, but as complete 3D models. Most often, you start with simple geometrical shapes, and modify them in the CAD program until you have a complete model of the part you want. This has the big advantage that you don't need to worry about making the right projections, and allows you also to better check if the part looks like you really want. A 3D model also helps the workshop to extract the dimensions you may not have specified explicitly, because you perhaps don't care too much about a particular dimension. But because the workshop needs to know what to make, a 3D model helps them to get an idea what would work for you.
Another big advantage for generating 3D models is that the workshop can translate sometimes directly the 3D model into commands for the CNC machines. This significantly speeds up the manufacturing process, and reduces the number of mistakes when transferring data. Therefore, the workshop is equipped with software that can directly interpret the 3D models you generate.
CAD software packages
Several companies provide user-friendly and CAD software to NUS staff and students. If you know another provider, please let us know so we can add this information. Below a short overview:
There are several CAD products from Autodesk, namely Autocad for 2D drawings, and Autodesk inventor for 3D designs. As of 2013, Autodesk provides a free educational license to NUS. For this, you need to register at http://www.autodesk.com/academic. More details can be found on this flyer.
The software is available for Windows OS, and supports commonly used file formats.
There are a large number of licenses of this 3D CAD software used in several research groups, and NUS has bought some licenses as well. Licensing is a bit complicated, so if you don't have access to it via your research group, you can contact the Computer centre or visit their web site at http://www.solidworks.com.
The physics workshop can accept the native solid files generated with this software.
Requirements: Windows OS
This is another 3D cad software that can generate standard 3D solid files, and also a range of 2D files. Details and a trial version can be found at their web site (http://www.varicad.com), and we get free access to NUS physics students/staff for educational purposes. For this, please fill out this form and send it to the address indicated on the form.
This package runs both on under Windows and Linux OS, and can export to IGES, STEP and some other formats.
Any other suggestions what we should include?
Formats of designs
This format was the original document standard for the early Autocad versions, and started as a closed proprietary standard. It eventually became opened, and now can be imported by many CAD and other programs. The DXF standard is most useful for 2D structures, and can be understood by some manufacturing devices, e.g. the wire cutter in the Physics Workshop.
These are very common file formats for 3D models of mechanical parts. Since at some point the US navy made it compulsory to prepare all mechanical part documentation in this formats, just about every 3D design program can handle these files, which made the initial IGES and its successor STEP a de-facto standard for 3D manufacturing.
If you are able to prepare model files in these formats, the workshop and any manufacturing company will be able to make a part. You still may need to clarify a few things such as the Tap standards etc on a separate drawing.
There is a wide number of proprietary file formats around, and various companies were/are happily suing each other for copyright infringements and all of that. The target for the mechanics workshop is to be able to process Solid works, Autocad and STEP files. Future will show what the best format is for communication with the workshop.
An incomplete list of some formats (characterized by their file name extensions):
- .dwg: Native format used by Autocad (can someone please verify this?)