Both are grammatically correct. However, "on a large scale" (and "on a scale" in general) is a set phrase. There may be variations in local ... ... <看更多>

The expressions 'on a small/large scale' are common and use a different preposition. I'm guessing that 'at' is chosen in 'at the production ... ... <看更多>

This video covers how to the scales on maps and scale diagrams to find distances. This video is suitable for maths courses around the world. ... <看更多>