It is in your best interest to publish your products to a category that describes it correctly. Ensure you are focused on a product’s application rather than the production method. Then, select a root category, then a subcategory in order to add a product to the correct section.
For example, let's say you are selling a 3D printed bottle stand,
The wrong category will be:
Additive Manufacturing Products > 3D Printers > Fused Deposition Modeling (FDM)
The category you should choose:
Consumer Electronics & Appliances > Domestic Appliances > Domestic kitchen appliances