The predictability of a ball machine is both an advantage and a potential disadvantage. If you need to groove a stroke, the repetition of a consistent feed is just the ticket, but you have to be careful to avoid the lazy footwork that can easily result from knowing where the ball will be.
Ball machines range from inexpensive, tiny, battery-powered units that pop out a short, soft feed to near cyborgs that can generate almost any speed, spin, and placement pattern you could want.

