You are correct here, but that view is only one application of the technology (much like prototyping is only one application of FDM).
The general flow (for engineering design) starts with FDM printing, which is used to print as many iterations as is necessary to reach a final design. The FDM prints are used to help gauge how the final product will “feel” and behave so the design can be improved upon as needed. This is why it’s not uncommon to have multiple prints which demonstrate multiple changes to each part at this phase (the prototyping phase).
SLA is used once the design is refined and finalized for injection molding because, as you mentioned, it’s surface finish mimics that of an injection molded part well (when it’s properly post-processed) and it gives a really good representation of what the final, market product will look like. This print will include all the injection molded pieces components (gussets, coring, ribs, draft, etc.), which are not necessarily included in the initial FDM prints. Generally, the final design is printed once in SLA but can be printed again if major design changes occur.
To be honest, I think labeling each technology by it’s name from the get go is a better approach. Yes, customers may not know what it means initially, but it’s a more holistic approach to doing this (in my opinion). Not only does it eliminate almost all the issues being addressed in this thread, but it helps the customers better understand the process if they want to. FDM has a much wider range of materials than PLA and ABS (which is what people think of when you say just plastic), and customers may not even know TPU, Nylon, wood based, metal infused, etc. are options. Breaking it down by process, then material is much better for everyone as each process has a lot of materials at this point. For SLA, you can choose casting, dental, flexible, standard, etc. all of which have drastically different properties, but none of that is well explained by the default selection process. The same goes for FDM; PLA is nothing like Nylon, TPU, or WoodFill (or any of the exotics), and that really should be better presented to the customer. It’s more work on your end, but we are rapidly approaching the point where the choice of material/desired end properties supersede the choice of print technology. Gone are the days where SLA was just for visual models and delicate prints, and when FDM was just for ABS. Material variety is growing more and more diverse by the month, and that’s not represented here.
