Ordinary Lathe Digital Control Transformation

At present,the ordinary machine tools of many mechanical product production enterprises are generally long.Due to long-term wear and tear,the machining accuracy of the machine tools has declined dramatically.In addition,this type of machine tools can not realize mass production and the production efficiency is low,so it can not meet the normal production demand.However,the structure of the machine bed,guide rail and other parts of the extension machine bed are still well preserved,so as to save cost and maximize the degree Based on the principle of making full use of the existing resources,the corresponding equipment can be upgraded by digital control;the transformed CNC machine tool has higher processing precision and efficiency,can realize batch automatic production,reduce the dependence on manual operation and other characteristics;in addition,the enterprise's goal is to pursue maximum benefits,and the cost of transforming the existing ordinary lathe is far lower than that New equipment with same performance will be purchased,and if the transformed equipment can meet the production demand,it will definitely give priority to the selection.This paper introduces the significance of the digital control transformation of the common lathe and the determination of the transformation scheme.Through a large number of enterprise field investigation and data search method in the early stage,and the introduction of theoretical basis method to demonstrate the feasibility of the digital control transformation scheme of the ordinary lathe(1)Transformation of spindle motion controlThe spindle movement of lathe mainly includes the forward and reverse rotation of the spindle and the speed regulation of the spindle.The spindle speed of the ordinary lathe adopts the ordinary three-phase asynchronous motor to realize the speed change through the headstock.After the transformation,the frequency converter is used to control the forward and reverse motion of the spindle and the frequency conversion speed regulation,so as to realize a more flexible adjusting movement mode.(2)Improvement of feed systemThe feed motion includes transverse motion and longitudinal feed motion.In the transformation,the original sliding lead screw is removed and replaced with rolling lead screw to realize the transmission of feed motion;the feed box,change gear mechanism,smooth screw and slide box of the original machine tool are removed;the original feed control motor is disassembled,and the stepper motor is used as the driving element in the transverse and longitudinal feed directions respectively,and the first gear is passed through After deceleration,the CNC device sends instructions to the stepper motor driver,and then the driver controls the forward and reverse motion of the two stepper motors;the limit switch and accessories are installed at the horizontal(x-axis direction)and longitudinal(Z-axis direction)axis ends.The original turret is removed and converted into a four station electric turret.A stepping motor is installed on the turret to realize the automatic tool change operation function.(3)Design of numerical control systemNumerical control system is the core of machine tool transformation.Combined with the research and the starting point of cost saving,this paper uses PLC as the core control part of CNC system.The control circuit is mainly composed of PLC,crystal oscillator circuit,address latch,decoder,EEPROM memory and programmable keyboard / display controller.The stepper motor is selected as the bidirectional feed driving motor.The improved equipment is mainly used for training teaching,and its machining accuracy only needs to reach the intermediate accuracy level,so the control mode of semi open-loop servo system can be selected.(4)Internal circuit designThe main circuit,control circuit and other auxiliary circuits are redesigned at the original circuit position according to the control of different function modules of the machine tool after modification,and then they are uniformly installed in the electrical box of the machine tool after the single function debugging is successful.(5)Design of other partsAccording to the characteristics of the machine tool,the structure of over range limit switch device,cooling and lubrication system,machine failure alarm device and other structures are added to realize the effective control of the machine tool.This design difficulty is based on PLC numerical control system design,which mainly realizes the automatic control movement of the machine tool,including the realization of X,Z axis return to zero and feed operation command,automatic tool change command,coolant on or off command,control of spindle forward and reverse,feed rate control,selection of machining mode and other functions;finally,the paper is the machine tool detection feedback and function verification,which is used in the detection device The measurement of the runout tolerance of the machine tool guide rail by the dial indicator can detect whether the reformed machine tool guide rail can meet the accuracy requirements,and feed back the displacement error or feed error by installing the photoelectric encoder at the shaft end,and the actual error is fed back to the position unit.The position unit takes the input feedback error as the input signal again to execute the processing part program again,so as to realize the automatic control of the parts Re adjustment of machining accuracy.In this paper,on the basis of fully studying the mechanical structure,performance and function of the original machine tool,PLC + HMI(Human-Computer Interaction Technology)is used to realize numerical control,which improves the cutting process of the original system and improves the cutting accuracy and efficiency.