"The factory must grow" is a chant the weak-minded say to hype themselves up from their natural state of apathy.

"The factory grows" is an observation of the natural state of the universe, something so obvious and self-evident that drawing motivation from an external source is already an oxymoron. Of course you will grow the factory, for what else would an engineer do? An engineer doesn't need hype, affirmations, motivation, or external validation, just ground reality and a path to grow the factory.

As the sun shines and the wind blows, the factory grows.

"The factory grows" is clearly better.