Design of CNC system scheme on laser processing machine based on motion controller

Hong-yan SHI，Xiao-qiang WU，Chun-you ZHANG

(College of Mechanical Engineering，Inner Mongolia University for the Nationalities，Tongliao 028000，China)

Design of CNC system scheme on laser processing machine based on motion controller

Hong-yan SHI，Xiao-qiang WU，Chun-you ZHANG*

(College of Mechanical Engineering，Inner Mongolia University for the Nationalities，Tongliao 028000，China)

Since there exist some shortcomings for the present laser processing machine CNC system，the design scheme of laser machining open CNC system was proposed in this paper based on multi-axis motion controller.The multi-axis motion controller is the core of the system，and the PC is served as the support unit.The hardware selection and design of software were introduced in this paper and it provides a new way for the study of laser machining CNC system.

Motion controller，Laser processing machine，CNC system

1 Introduction

The main application fields of laser processing technology are the material cutting and welding，cladding，heat treatment，etc.It is a kind of advanced technology that concentrates light，machine，electricity into one product.CNC laser processing technology can also realize automation of production，it has broad prospects in the industrial applications［1-2］.Laser processing adopts non-contact processing，since there is almost no cutting force，it cannot be matched by the other processing methods［3-4］.The CNC systems of general CNC laser processing machine are always the special CNC systems，the special CNC systems are closed structure，and lack of flexibility and extensibility［5-6］.Users are unable to use experience and new technology on the machine tools，and lots of features of them will never be used，resulting in a waste of resources.The cost of the special CNC system isrelatively high［7-8］.The concept of open architecture CNC system makes up for the lack of special NC system，open CNC system has good opening，wide universality，and it has advantages of transplantation and interchangeability，so it is widely adopted in the real industrial applications［9-11］.In order to improve the current situation of closed CNC system of laser processing machine，the motion controller is used as the core to build the open CNC system for laser processing machine in this paper.

2 System control requirements and the overall design scheme

2.1 System control requirements

The working principle of laser processing machine is that the laser beam with certain energy gather together，then the gathered laser beam irradiate the metal powder which was supplied by powder feeding device，the metal powder will be melt in a very short period of time，the internal microstructure of metal will be changed，so as to achieve the purpose of molding［12］.

Laser processing machine has four axes in total，they are the main feeder axis and X，Y，Z three motion axes，respectively.The machine table position is determined by the motion of X，Y，Z three axis during the working procedure.Through the linkage of the three axes，the process of drawings is completed，in the process，powder feeding device spindle is uniformly rotating.X，Y，Z three axes are driven by three servo motor through the ball screw，respectively，feeder axis is driven by the servo motor which is connected with a speed reducer.The coordinate of laser processing machine tool is defined as shown in Fig.1.Laser processing machine system control requirements are that servo motors are controlled by system，and so does the association.According to the association of three axes，the machine will complete the workpiece machining.

Fig 1.Coordinate definition of laser processing machine

2.2 The overall design scheme

According to the control requirements of the system，the open CNC system was established by multi axis motion controller.The PC is the upper computer and the multi axis motion controller is the lower computer in the system.The function of the system is realized by the connection of upper and lower computer.The system parameters are inputted and monitored through the HMI.The PC will communicate with multi axis motion controller through the Ethernet，HMI carried out communication with multi axis motion controller through RS232/485 interface.The overall design of the system is shown in Fig.2.The system has the advantages of fast response，good reliability，and good portability.It could satisfy the control requirements of laser processing machine and achieve the specified function.

3 The system hardware design

3.1 Multi axis motion controller

Multi axis motion controller based on digital signal processing is the best choice for the open structure of CNC system，it is the core of the control system.In this paper，multi axis motion controller is required to make accurate and fast communication with upper computer and servo drivers，and it requires short response time.Real-time data transmission and realtime measurement feedback should be guaranteed，multi axis linkage and accurate control of machine tool should be realized.In this paper，the motion controller is the Trio MC405 multi axis motion controller，Trio MC405 is a multi-axis motion controller based on DSP of Trio Corporation，the controller could control up to 5 axes，which can not only control the servo motor，but also control the stepper motor.And it could also receive the signal input of the encoder.It is equipped with the Ethernet，USB，RS232/485 standard interface.It could directly communicate with other hardware.Programming software-Motion Perfect V3 is provided by Trio company，and the programming language-Trio Basic is also developed by Trio company，the language is similar to Basic，and it is easy for programming.

Fig.2 System design schematics

3.2 Servo system

Servo system is the drive device of machine tool，the motion controller will send command to the servo driver，and servo drivers can transform command into pulses to drive servo motors.Worktable is driven by servo motor through ball screw，the machining is realized by the motion of X，Y，Z three axes.The option of servo control system should consider motor load characteristics and system characteristics.Based on the calculation and comparison，the delta ASDA-AB series servo system is chosen in this paper，the servo system could realize the accurate position control.The connection between servo system and the Trio controller is shown in Fig.3.

3.3 HMI

The HMI is the window for users to interact with the system，the system requires that the HMI could real-time display the operation condition of the system，and input the data.It should have good interactivity，quick processing speed，and large storage capacity.After comprehensive consideration，Panel-Master PV084-TNT is selected，which is equipped with a 8.4 inches(800 x 600)65536 color TFT LCD screen，the largest program memory is 16 MB and the working memory is up to 84 MB.It has three standard serial interfaces，in which COM1/COM2 could not only support for RS232，but also support for RS442/ 485.It also has two USB interfaces.The HMI can be programmed through the“PM Designer”software which is provided by the PanelMaster company.The program could generate the package which could be directly transmitted to the HMI through the USB interface.The connection between HMI and Trio controller is shown in Fig.4.

Fig.3 Delta ASDA-AB series servo system connected with the Trio controller

Fig.4 PV084-TNT connected with the Trio controller

4 The system software design

4.1 Motion management module

Motion management module is the core of system software.Motion management module is divided into several parts as follows:data acquisition and processing，motion control，parameter setting，program explanation，PLC function and manual function.The software structutre of motion management module is shown in Fig.5.

Fig.5 Sports management module software architecture

As shown in this figure，the data acquisition and processing is used to detect and receive real-time external data，and then the data will be processed by internal unit.Data sending and receiving is realized based on I/O interface controller;motion control is mainly responsible for the analysis of external feedback data，to make corresponding instructions according to the prepared program，and execute the interpolation of straight line，arc or other curve;parameter setting is mainly to set the parameters of machining operation，ensure the machining accuracy of machine tools，and improve the machining efficiency;the program explanation will explain the program through the internal mechanism of the controller;the PLC function is used to input/output the logic control，and ensure the accuracy of motion;manual function will conduct the manual operation of machine tools by Manual Pulse Generator.The programming interface is shown in Fig.6.The program statements are shown in this figure，for lack of space，only one portion of the code is given in this paper.

Fig.6 Programming Interface

Program code:

4.2 The human-computer interaction module

The human-computer interaction module is the interactive window for operator and the CNC system，the operator will input parameters，send control command，and monitor the running status through the user interface.The design of man-machine interaction module should be people-oriented，it will reduce operator’s physical and psychological burden in the actual operation［13-14］.In this paper，man-machine interaction module is designed according to the actual need of laser processing machine.As shown in Fig.7，the interface is mainly to conduct the parameter settings，monitoring and debugging.

Fig.7 HMI module

5 Conclusions

This paper gave a brief analysis of the current situation of the CNC system of laser processing machine.It is concluded that the open CNC system is the future development direction of CNC system of laser cutting machine.Based on the scheme structure of“PC+ motion controller”，the CNC system was established，and the hardware selection and software design were introduced as well.Multi-axis motion controller could flexibly match the hardware according to the requirement of system.Therefore，this paper could have a certain reference significance for the future development of laser machining CNC system.

Acknowledgements

This paper is supported by National Natural Science Foundation of China(No.11202078).

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基于運動控制器的激光加工機床數(shù)控系統(tǒng)研究

侍紅巖，吳曉強，張春友*
內(nèi)蒙古民族大學(xué)機械工程學(xué)院，內(nèi)蒙古通遼 028000

針對現(xiàn)有激光加工機床數(shù)控系統(tǒng)的不足，提出了以多軸運動控制器為核心的激光加工機床開放式數(shù)控系統(tǒng)設(shè)計方案，該方案以運動控制器為CNC控制核心，PC機為支撐單元，對硬件選型和軟件設(shè)計進(jìn)行了說明，為激光加工機床數(shù)控系統(tǒng)的研究提供了新的思路。

運動控制器;激光加工機床;數(shù)控系統(tǒng)

10.3969/j.issn.1001－3881.2015.06.017 Document code:A

TH215

Hydromechatronics Engineering

http://jdy.qks.cqut.edu.cn

E-mail:jdygcyw@126.com

2 September 2014;revised 7 November 2014;

20 December 2014.

Hong-yan SHI，Lecture.E-mail:187145524@qq.com *Corresponding author:Chun-you ZHANG，Ph.D.，

E-mail:wangzai8402@163.com