The Importance of Adjustable Designs

One of the key advantages of 3D printing is rapid prototyping. This is due to the low switching costs in 3D printing – you can print a hundred different models as easily as you can print a hundred of the same. In order to unlock the full potential of rapid prototyping, we need to reduce the cost of varying our designs.

However, this ignores another cost in switching designs – the CAD work. The cost of printing a variety of parts is low but designing them could be expensive. The cost of printing a design variant could be expressed as CAD Time + Slicing Time + Machine Setup Time.

Parametric modelling software allows us to use variables to define the dimensions of our part. By using variables and constraints rather than punching in numbers, we can make a design which can be modified in seconds.

My most recent project allows me to easily adjust the shape and all key dimensions of the part. With a printing time of less than 6 hours, this means I can easily produce 4 prototypes per day. With each prototype, I can easily modify the shape without needing to re-draw or redefine the geometry. It has made me realise the importance of adjustability and how I need to focus on it.

From today, I’ll be starting all my designs by defining all known key variables. In Fusion 360, this can be found in the ‘change parameters’ menu.

First I’ll be defining my intended printing parameters: line width, layer height and overhang angle. I believe it’s best to decide these things before you design your part, because they influence the choices you make in design. For example, convex fillets can never be smaller than the nozzle size and features should ideally be multiple of the line width and/or layer height. The material you choose and the cooling capabilities of your machine will influence your maximum overhang angle, which in turn influences the shapes that you can print without support structures.

Another way I prepare is by deciding on the best print orientation before I start designing my part. When I start to make sketches for it, I ensure that the match the orientation of the CAD program. This lets me easily identify where I need to avoid overhangs and which planes will be restricted by my nozzle width.

e.g. a fillet on the XY plane cant be smaller than my nozzle radius, while a fillet on the Z-axis would cause an unwanted overhang.

Note: The default settings of your slicer may have a line width which is larger than your nozzle width. Make sure you check your intended LINE WIDTH not your NOZZLE WIDTH – they are not necessarily the same.

If you’re doing CAD work for 3D printing, I strongly recommend focusing on adjustability. This will unlock the full potential of rapid prototyping and let you iterate extremely quickly.

Thanks for reading,

Simon