ANALYSIS OF METHOD FOR DETERMINING AZIMUTH OF PRINCIPAL AXIS OF INERTIA BASED ON DYNAMIC BALANCE MEASUREMENT

The dynamic balance quality of a rotating object is an important factor to maintain the stability and accuracy for motion. The azimuth of the principal axis of inertia is a major sign of dynamic balance. A usual method is measuring moment of inertia matrix relative to some base coordinates on a rotary inertia machine so as to calculate the azimuth of principal axis of inertia, By using the measured unbalance results on the two trimmed planes on a vertical hard bearing double-plane dynamic balancing machine, the dimension and direction of couple unbalance can be found. An azimuth angle formula for the principal axis of inertia is derived and is solved by using unbalance quantities. The experiments indicate that method based on dynamic balancing measurement is proved rational and effective and has a fine precision.

Rapid Evaluation for Feed-axis Lubrication Condition Based on Soft Sensor

Stribeck effect is regarded as the most important feed-axis friction characteristics. According to the relationship between friction and lubrication,a rapid technology for feed-axis lubrication condition evaluation of computer numerical control( CNC) machine tools based on soft sensor is proposed. To obtain its state information,the static friction force,Coulomb friction force,and viscous coefficient are used as the key parameters of the soft sensor for tread analysis. Then the various amplitude and velocity triangular wave test curve, and a precise nonlinear model identification method are presented. The results of the experiments analysis show that this method is feasible and reliable for evaluating feed-axis lubrication condition,which lays the foundation for on-line condition monitoring and reliability evaluation for feed-axis lubrication of machine tools.

DRIVE AND CONTROL OF VIRTUAL-AXIS NC MACHINE TOOLS

The structure features and driving modes of virtual axis NC machine tools are studied. Accor ding to different application requirements,the three axis control method,the five axis control method and the sixfreedom control method are put forward.These results lay a foundation for the product development of the virtual axis NC machine tools

Influence mechanism of machining angles on force induced error and their selection in five axis bullnose end milling

In the machining of complicated surfaces,the cutters with large length/diameter ratios are used widely and the deformation of the machining system is one of the principal error sources.During the process planning stage,the cutting direction angle,the cutter lead and tilt angles are usually optimized to minimize the force induced error.It may lead to a low machining efficiency for bullnose end mills,as the material removal rates are different largely for different machining angles.In this paper,the influence mechanism of the machining angles on the force induced error is studied based on the models of the instantaneous cutting force when the cutter flute traveling through the cutting contact point and the stiffness of the machining system.In order to evaluate the machining angles,the force induced error/efficiency indicator(FEI)is defined as the division of the force induced error and the equal volume sphere of the removed material.FEI is dimensionless,with the lower FEI,the lower force induced error and the higher machining efficiency.For optimal selection of the machining angles,the critical FEI is calculated with the constraint of force induced error and the desired material removal rate,and the critical FEI separate the set of the machining angles into two subsets.After the feed rate scheduling process,the machining angles in the optimal subset would have higher machining accuracy and efficiency,while the machining angles in the other subset have lower machining accuracy and efficiency.Through the machining experiment of five axis machining and freeform surface machining,the effectiveness and superiority of the proposed FEI method is verified with a bullnose end mill,which can improve the machining efficiency with the constraint of force induced error.