Autodesk Autocad (2D) and Inventor (3D) and are good quality design/modeling tools that are free for academics.
Onshape is a Cloud-Based (3D) system that works with any modern web browser irrespective of computer OS. (Requires internet connection)
3D Modeling a design is always better than designing something on the fly. Not only is it cheaper, but it’s also faster to have a complete design ready before you start building. Additionally, if you have a model of your design I can better assist you in building in.
A few tips for 3D modeling
- A paper sketch or something to work off can be useful
- Understand your scale, try to understand the size of what you’re modeling. 1 Inch may look big on the screen, but it reality it can be small.
- Understand and use fillets to avoid stress concentrations.
- Filet and champers can add curves and edges to sharp corners
- The loft tool can be used to stitch two or more non co-planer surfaces
- Take into account machineing tolerance when designing
- Slots can help with alignment
- Understand the difference between clearance and tapped holes
- These tools can find all the mass properties of your object (moments of inertia, center of gravity, area, volume)
- Design for manufacturability