Introduction to CAD & 3D Printing

Computer Aided Design (CAD)

Many professionals use CAD in a wide variety of industries, from product design/engineering to architecture. Many tools and softwares exist to help us CAD, most of which cost money to use. Here are a few free tools by Autodesk you can use to start designing your own CAD models. Autodesk offers educational licenses to students, and that allows you to use most of their products for free as long as you are in school.

Out of the three tools, TinkerCAD is the easiest and fastest way to get started with CAD, as the design features are not as comprehensive as the other two and there are many pre-made models in TinkerCAD that you can use for your own designs. There are many free YouTube tutorials for all tools. For TinkerCAD, this short video covers all of the features you need to know and will be sufficient for making custom parts for the class. But if you start feeling like TinkerCAD is too restrictive, it may be time for you to move to Fusion or AutoCAD!

Printing your model

Once you have a 3D model you’re satisfied with, the next step is to export the model so you can 3D-print it. For FDM printers, the model needs to be sliced into very thin horizontal slices so that the printer can print each layer at a time, from bottom up. There are tools called “slicers” that will read a 3D model, slice it into layers, and translate that into a language called “g-code” that printers can read.

First, you’ll want to export your 3D model into either an .stl or .obj file. You’ll need to know in advance what printer you will work with. At TechLab (first floor of Caltech Hall), they have CraftUnique Craftbot Plus printers.

Next, we bring the .stl or .obj file into a slicer software like these:

When you use a slicer, you will need to state what printer you will use. You may be able to find presets for the printer, or set up a custom profile for the printer. For Ultimaker Cura, watch this video to set up a custom profile for the TechLab CraftBot printers.

Almost all FDM printers will have these parameters, which will most likely be included in the printer profile:

  • Bed temperature: the printer bed is usually heated (so don’t touch it with your hands, obviously) to make sure your print doesn’t move around as the printer nozzle moves over it to deposit more material. If your bed temperature is too low, the print won’t adhere to the bed very easily and you can end up with a spaghetti-monster-looking blob instead of your print, or get bad warping on your prints. If your bed temperature is too high, then you can end up with an elephant’s foot, which refers to when your lower print layers spread outwards.

  • Nozzle/Extruder temperature: the nozzle (a.k.a extruder) is made of metal that can heat up to temperatures that can melt the print material. Needless to say, nozzle temperature depends on the material you’re printing with. For PLA, it’s 180-220 celsius, and for ABS, it’s 240-290 celsius. You can adjust the nozzle temperature within a narrow range around the optimal temperature for a material, as higher temperatures usually give a glossy finish and lower temperatures a more matte finish to your prints. Printing outside the optimal temperature range can lead to print quality issues.

  • Nozzle size: the most standard size for nozzles is 0.4 mm. Smaller nozzles are better for fine details, while larger nozzles can deposit more material at once, which makes printing faster. Some materials, like carbon or metals, will need larger nozzles than plastics like PLA and ABS.

Load your model into the slicer. You can rotate or translate the model to wherever on the print bed. You can even print multiple models at the same time. There are a few parameters you can tweak on the slicer. Some of them are:

  • Dimensions of the model: will your model fit on the printer bed?

  • Supports: for any part of your model that is floating (not attached to the printer bed) there will need to be supports from the printer bed to that part of your model (essentially extra plastic that will hold up your model). Supports add material and time to your print, so make sure you design your model with minimal floating structures, and orient your model such that most of your model is laying on the print bed to minimize the need for supports.

  • Infill: how solid do you want your prints to be? A good place to start is 20%, meaning that inside the walls of your model, the object will be 20% full with material.

Save the .gcode output to a USB drive, and you’re ready to print!

Additionally, here are slides I put together a couple of years ago for 3D printing. Please feel free to take a look!

(contributed by Anne Kil, October 2024)