Attaining Ultraprecision Machining by Feed Drive System Stability Control with Piezoelectric Preloading Actuators

In this paper, a variable preload force control structure utilizing piezoelectric actuators (PEAs) is proposed for the stability control of the feed drive system. Three PEAs are installed between the two nuts to exert preload force on the ball screw, leading to an elimination or substantial reduction of the backlash, which is the main cause of instability of feed drives. This results in better machining precision throughout the operation process. In addition, the force analysis of the whole preload feed drive system is established. Moreover, the hysteresis of the PEAs is determined with reference to the Prandtl–Ishlinskii (P-I) model. Lastly, the P-I model-based feedforward controller is applied to the feed drive system to improve the resultant machining precision. Based on the modeling and experiments, to demonstrate the efficacy and high-performance of the proposed P-I model-based control algorithm against conventional PID control system, comparative experiments are conducted, showing satisfactory results.

Recent Patents on Tension Control Device of Wire Electrode in WEDM

Background: WEDM (Wire Electrical Discharge Machining) is widely used to machine difficult-to-machine materials, such as high-strength and high-brittle materials. The research on tension control device of the wire electrode is mainly to improve the machining precision and surface quality of WEDM. Objective: To meet the growing demand for processing of difficult-to-machine materials, such as highstrength and high-brittle materials, the machining precision and surface quality of WEDM are improved continuously. Methods: This paper reviews various representative patents related to the tension control device of wire electrode in WEDM. Results: Through retracing the characteristics of different types of the tension control device of wire electrode in WEDM, the main problems existing in the current development are concluded and analyzed. The development trend of patents on the tension control device of wire electrode in WEDM is discussed. Conclusion: The optimization and development of the tension control device of wire electrode in WEDM are beneficial to improve the machining precision and surface quality of WEDM. More related patents on the tension control device of wire electrode in WEDM will be invented.

The average effect of multi-divisions cutting method on thermal error in cutting horizontal grooves array on roller mold

Microstrutured surfaces can be manufactured by roll-to-roll process with roller mold in a high precision and high efficient way. The roller mold machined by drum roll lathe has a large cutting area and takes long time, and thus, the machining precision of roller mold is very sensitive to the thermal error of machine tool. This study analyzes the influence of thermal error on the machining horizontal grooves array on roller mold and proposed a processing method to improve the machining precision. First, the thermal error of hydrostatic guideways system in drum roll lathe was analyzed by simulation and measured through experiments, respectively. Given the diamond tool position offset caused by thermal error, the pitch error of horizontal grooves array with sequential cutting method was discussed. And then, multi-divisions cutting method is proposed to average the pitch error to multiple horizontal grooves instead of cumulative error in the seam position of horizontal grooves array, compared with sequential cutting method. Finally, the experiments with Four Divisions Method were carried out to verify the validity of multi-divisions cutting method. The experimental results demonstrate that multi-divisions cutting method can considerably improve the machining precision of horizontal grooves array.