The dynamics of the librational mode of motion of the driving member of a nonideal system, a mixing-whipping device based on a simple slide-crank mechanism, is studied. The equations of motion are based on the Lagrange equations of the second kind, which are highly nonlinear and are solved numerically by the Runge-Kutta method. As a result, the dependences of the rotation angle of the driving member on time, the angular velocity of the actuating motor shaft on time and on its rotation angle, and the parameters of the nonideal mechanical system, such as the rotational torque of the motor, and the piston mass, were obtained. Analysis of these dependences shows that at reducing the rotational torque of the motor, increasing the mass of the piston, the rotational mode of motion of the device at certain levels of these values can switch to the libration mode of motion. The interaction of the mixing-whipping device with the nonideal excitation source causes the rotation angle of the driving member and the angular velocity of the motor shaft to fluctuate, accomplishing a damped process. The parameters of the device and the nonideal energy source have an effect on the kinematic and vibrational characteristics of the system. Thus, for example, a decreased value of the motor torque is accompanied by a decrease in the initial rotation angle of the crank and its limit value to pursue, a decrease in the range of fluctuations in the motor shaft speed. As the piston mass increases, the rotation angle oscillation range, the maximum magnitude and repeatability of the motor shaft speed oscillations decrease.