Analysis And Control Of Cutting Force With Reciprocating Cutting Of Hard And Brittle Materials

Hard and brittle materials have become increasingly popular in various modern and equipment fields due to high hardness,low friction,high wear resistance,and good chemical stability,like silicon carbide,monocrystalline silicon,sapphire,and optical glass.However,because of its high hardness and brittleness,hard and brittle materials are very difficult to process.At present,hard and brittle materials are sliced using the fixed diamond abrasive wire saw technology,which have the advantages of narrow incision,high material removal rate and low reject rate.In the cutting process,in order to effectively using the wire,the wire saw performs a reciprocating motion.In this case,even if the process parameters(such as the contact arc length of between the workpiece and the wire saw,the tension of the wire saw,etc.)are constant,the cutting force keep continuing to change.The result is in high surface roughness and low surface flatness.Therefore,it is imperative to study the control methods of the cutting force to improve the quality of the slicing surface.During the cutting of the reciprocating fixed diamond abrasive wire saw,the main factors influencing the cutting force are the wire saw velocity and the feed rate.Domestic and foreign scholars have studied how to keep the cutting force constant by adjusting the feed rate.At present,there is a lack of methods for maintaining a constant cutting force by adjusting the wire saw velocity.Therefore,the paper focuses on the wire saw velocity and studies control methods of the cutting force in the reciprocating cutting process.Based on the original open reciprocating fixed diamond abrasive wire saw cutting machine,the system is composed of PC,dynamometer sensor,multi-function data acquisition card,DC motor and velocity control module.The cutting process motion control platform is supplemented with Lab VIEW software development and embedded motion control algorithm.It provides the basis for the experimental verification and application of follow-up cutting force control methods.In order to control the cutting force by adjusting the wire saw velocity,a cutting force control model based on PI controller is proposed.The PI control strategy is introduced into the reciprocating diamond wire saw cutting system,and the transfer function of the wire saw velocity and cutting force is constructed.The method of Ziegler-Nichols is used to determine the processing parameters of the PI control system.The model is embedded in the built software platform for experimental verification.Comparing the constant process parameters with the cutting force and surface roughness under PI control,the results show that the controlled workpieces are subjected to a more stable cutting force and a smaller surface roughness.In order to improve the accuracy of cutting force control,a cutting force control model based on adaptive control is proposed.We design a minimum variance self-correction control system for wire saw velocity and cutting force.The system identification method is used to identify the order of the structure of the reciprocating fixed diamond abrasive wire saw cutting system,and to design the self-correcting control rate for the controller's performance target by outputting the minimum variance.The recursive least squares algorithm is used to estimate the object parameters of the wire saw system in real time.An adaptive control model of the diamond wire saw cutting system is established.The model is embedded into the built software platform to verify the experiment.The results show that compared with the PI controller,the minimum variance self-correction can apply the online real-time identification system parameters to the actual cutting process,which can well solve the time-varying problem of the system under working conditions,and the controller effect is better.