How to Avoid Sizing Mistakes in 3D Design: Model Accessories First

In this post, I'll show you how I designed and printed a coffee bean grinder, brush, and measuring spoon holder. See Fig. 1.

Fig. 1

I've seen too many instances where a student's completed 3D design turned out to be the wrong size despite looking proportionately correct.

This happens because students often start by 3D modeling their design as the first step. But what's the problem?

The moment I sketch the accessories (items or objects to be held or stored) into their design, the holder almost always ends up looking tiny compared with the accessories. What happens next usually requires extensive modification, sometimes even re-modeling the entire 3D design.

This is how to avoid making the same mistake ever again:

• Always model the items to be held or stored first.
• Then model the design that will hold or store those items.

Here are the steps:

• Firstly, make a list of the items you want to hold or store.
• Secondly, make notes about their dimensions. I call these the "Critical Dimensions".
• Next, before modeling your design, model all the accessories first (see Fig. 2).
• You don't have to model them exactly as they look.
• Use basic geometric forms to represent each item.
• Finally, model the design. Then place the items into the model and see if they fit (see Fig. 3).

Fig. 2: Modeling the accessories first (see the three items on the right hand side)

Fig. 3 shows the coffee grinder (round cylinder), the brush (narrow cylinder), and the scoop, all positioned on the holder. These are their final positions after a few rounds of adjustment. You can see that all the items fit nicely on the holder. The holder not only looks proportionate, but it is also the correct size.

The image on the right shows the actual 3D-printed holder with the accessories in place. They all fit nicely.

Fig. 3: 

Left: The Tinkercad Model. 

Right: The actual printed design.

Conclusion

It is not necessary to model all the items or accessories before modeling your design. In fact, if you model your design using actual dimensions during the development phase, you may be able to get it right on the first attempt.

However, in my experience, many students either miss the instruction that their design must be modeled according to its actual proposed size, or they are simply too excited to see their design in 3D and forget about the dimensions altogether.

Whatever the case, I believe it is good practice to model the accessories first. This gives the designer another opportunity to evaluate whether the placement of the accessories is final or requires further adjustment.

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