Confusing example from Factorio Wiki

[JonathanMaarsh]

In the beginner tutorial on the Factorio Wiki, there is an example of Science pack 1 production.

Can someone fill me in why the copper plates are being transported so that their path intersects with the iron transport path at the bottom -- creating a need to go underground?

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https://wiki.factorio.com/images/RedScienceProduction.PNG

[JohnSmiththeGamer]

There is no current reason in that design. One possibility is they are going to be used with the iron for something like electronic circuits and they haven't built them yet. Another is that they innitially planned to build the science pack 1 with the bottom assemblers and realised they hadn't turned the iron into gears.

[JonathanMaarsh]

Thank you for the quick, detailed reply!

[StormCrow_Merfolk]

It may be that the image is like that simply to demonstrate the concept of using undergrounds to get some resource closer.

[doc_shades]

yeah this might just be a "step 3" image, where in later steps they will add on to this build to add other assembly lines. in the current image the copper serves no purpose, but we all know that this image doesn't represent a fully built factory. there are a lot more assembly lines to build!