A type of mixer used for mixing powders. Powder blenders are broadly classified as vertical or horizontal mixers depending on whether the mixing impeller rotates on a vertical or horizontal axis. Vertical mixers have a movable bowl in which the contents are mixed by mechanical agitation. Paddle agitators are commonly used and the shape of the impeller frequently conforms to the vessel walls. Planetary motion devices are commonly used in vertical mixers in which the agitator revolves in a circle in addition to rotating on its own axis. This ensures that the entire mixer volume receives a beating action and that there are no dead spaces.