Parametric modeling in Fusion360

If you’re modeling something in Fusion360, you’re probably used to defining dimensions by directly inputting values in sketches or when using tools like extrude, or chamfer. This works fine when you’re designing something from scratch and the part doesn’t really have to fit with any existing objects.

But that’s very often not the case, right? Mechanical parts usually need to fit perfectly with other parts. And sometimes you might even want the part to fit various different sizes or types of objects. Say, a wall-mounted holder for an aluminum LED profile. You don’t want to re-draw it from scratch every time you buy a slightly different one.

Or a self-watering insert for a flower pot. Ideally, you’d like to be able to quickly resize it to whatever size your pot is. This is where parametric modeling excels. In short, if you go to Modify – Change parameters, you can define dimensions and name them. If you have experience with any kind of programming, these are basically variables.

You can then use these variables whenever you’re defining dimensions. And you can even do basic math with them. For example, you can define that an edge should be “thickness*2” long.

If you then, later on, want to resize your model, instead of painfully changing the dimensions everywhere manually, you can simply open the parameters window, change the values here and see the model updating in real-time. It’s really cool and if you’re not using this feature, you’re missing out a lot!

Let’s take a look at two examples and actually try to modify them to fit a different sized object.

Example 1 – Self-watering flower pot insert

First, we’ve modeled this without the use of parameters, just like you’re probably used to modeling. So how can we change the size in this case?

Parametric modeling in Fusion360 - 3pots

3 different self-watering plant pot inserts generated from the same Fusion360 design

Scaling the model (STL) in the slicer

Your first option is to simply re-scale the exported STL in the slicer. This will work if the size difference is fairly small. Because you’ll also be scaling all tolerances, the wall thickness. So at some point, parts of the model will be either too small to be printable, or if you scale it up, unnecessarily thick and tolerances too loose. There is only so much you can do with simple scaling, What if the pot has a bigger difference between the top and bottom diameter? Scaling is not flexible enough for such a case.

Changing the dimensions manually

The second option is editing the dimensions manually in Fusion360. This sounds easy, but even this shape-wise relatively simple model has 18 sketches and dozens of steps in the Design history timeline.

If you, for example, change the height of the pot in the very first design step, it will most likely create errors in the following operations. E.g. if you decrease the height from 140 mm to 120 mm, but later on you do a full height chamfer, it’s still set to chamfer the old value of 140 mm, which is invalid.

You will most likely have to go through the individual design steps one by one and re-write the value everywhere. Again,

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