Coal pressure ball machine working principle: ¡¡Electromagnetic adjustable speed motor driving spiral feeding device, via belt wheel, worm speed reducer rotating, the material is forcibly pressed into the feed inlet. As a result of electromagnetic speed regulating motor constant torque characteristic, when pressure feeding quantity by screw feeder and materials quantity host needed is equal amounts, can maintain a constant feed pressure to guarantee the pellet quality. If the feeding quantity is too large, then feeding device will electrical overload, on the other hand, if the feeding quantity is too small, materials may not into a ball.