direct access of cnc data for vibration control
Contents
1. 3 CNC TOOL MACHINE The CNC tool machine of this work manufactured by Hermle and model C600U is placed in laboratory CCM Center of Competence of Manufacturing do ITA Aeronautics Institute of Technology This machine work with HSM High Speed Machining technology The Hermle machine has five movement axes X Y Z A e C The machine and movement ax s are showed in Fig Figure 3 CNC tool machine Hermle and movement axes ABCM Symposium Series in Mechatronics Vol 4 pp 553 558 Copyright 2010 by ABCM To control the axes motion the tool machine uses a CNC controller made by Siemens model Sinumerik 840D This system has besides high capacity of information processing it has a mixed architecture that integrates a CNC Computerized Numerical Controller to a PLC Programmable Logic Controller of Simatic 7 300 family The Hermle machine uses a serial communication protocol the MPI Multiple Protocol Interface a simple version of Profibus to connect in a single network the processing components such as the HMI Human Machine Interface the PLC Programmable Logic Controller control panel and others SIEMENS 2006 4 RESEARCH ABOUT DIRECT ACCESS OF CNC DATA The focus of this paper is vibration control and it must guide all over the research of direct access of CNC data As showed in section 2 in order to control the vibration in CNC machine it is possible to guarantee the stability process with correct selection of s2. reached cut speed it suggests to work in cut speed significantly higher than typical had been worked in a specific material ABCM Symposium Series in Mechatronics Vol 4 pp 553 558 Copyright 2010 by ABCM 2 2 Machining Vibration Machining of the materials is invariably followed by vibrations between part and tool however due to intermittent character of machining process The tolerable maximum vibration level that 1s the maximum vibration amplitude in a machining process depends on your aplication In roughing stage what determine the tolerable vibration is mainly the effect that vibration exerts on tool In finishing stage superficial quality and dimensional precision are parameters that determine the maximum vibration level ALTINTAS 2000 The appearance of vibration durring process is a function of chip thickness variation that occurs due to tool or part vibration or both This form vibrations can have origin in different sources e external vibrations to machine tool e vibrations caused by machine tool e vibrations caused by interrupted cut e vibrations due to lack of part homogeneousness e regenerative vibrations chatter vibrations Some strategies can be used to aviod vibration during the milling process e Special tools e Process Planning using stabiliy letter e Cyclic variation of cutting speed e Vibration detect and control during the process 2 3 Stability of milling process To verify the stability of mi
3. ABCM Symposium Series in Mechatronics Vol 4 pp 553 558 Copyright 2010 by ABCM DIRECT ACCESS OF CNC DATA FOR VIBRATION CONTROL Carlos Eduardo Oliveira da Silva csilva ita br Emilia Villani evillani ita br Jefferson de Oliveira Gomes gomes ita br ITA Aeronautics Institute of Technology Square Marechal Eduardo Gomes 50 Vila das Acacias 12228 900 Sao Jos dos Campos SP Brazil Abstract This paper discusses the direct access to CNC data in order to control in real time the CNC parameters and avoid the vibration problems The purpose of the direct data access is to integrate an external system with the CNC controller This external system must be able to monitor the level of noise and change in real time the parameters of the CNC process in order to avoid excessive vibration Many of the controllers available in the market for CNC machine have a number of functions that are usually not used by the CNC manufacturer In this sense this work explores the use of these functions for implementing direct access to CNC data The direct access is tested in both ways read and write The purpose is to map what are the monitoring parameter that can be directly accessed and what are the control parameters that can be changed in real time Keywords direct access CNC machine CNC controller manufacturing process numeric control 1 INTRODUCTION The shortest deadline to introduce in market reduced life cycle and high multiplic
4. Milling In Proceedings of ASME International Mechanical Engineering Congress and Exposition New Orleans LA 2002 Cabral G F Determination of Machining Requirements for Alumium Components Manufacturing Dissertation Master in Aeronautics and Mechanical Engineering Aeronautics Institute of Technology Sao Jos dos Campos 2007 Del Conte E G Schutzer K Data Acquisition Strategy for Open CNC Monitoring in HSM Process In International Congrees of Mechanical Engineering COBEM 19 2007 Brasilia DF Proceedings Rio de Janeiro ABCM 2007 Ferraz Jr F Development of Monitoring and Supervisory System for Turning Process Dissertation Master in Mechanical Engineering Engineering School of Sao Carlos of the University of S o Paulo S o Paulo 2002 Polli M P Analisys of Dynamic Stability of Milling Process High Speed Cutting Thesis Doctor in Mechanical Engineering University of Santa Catarina Florian polis 2005 Schmitz T What is chatter lt http highspeedmachining mae ufl edu htmlsite fag html gt 2006 SIEMENS Sinumerik 840D 810D FN NC OEM package MMC User s Manual 12 ed 1997 SIEMENS Automation Systems for Machine Tools Catalog NC 60 2006 Silva C E O da Remote Monitoring System of Manufacturing Process Dissertation Master in Aeronautics and Mechanical Engineering Aeronautics Institute of Technology Sao Jos dos Campos 2008 Souza A F Interpolation Analisys of Tool Path in HSC High S
5. NC controller receives a command to start spindle internally the controller create a desired spindle speed command and control the actual spindle speed variable In tests it was discovered that the desired spindle speed command created by CNC controller cannot be changed before neither after this one It is a command for restrict use of CNC controller SIEMENS 1997 And from this way it is not possible to change the spindle speed ABCM Symposium Series in Mechatronics Vol 4 pp 553 558 Copyright 2010 by ABCM CP 5611 Machine NCDDE DDE Programming data MPI net NC converter variables software variables Figure 5 Data exchanging between machine and programing software DDE variables Channel Spindle cmdSpeed 1 only read Channel S pindle actSpeed 1 only read According Silva 2008 the PLC variables and R parameters from Siemens CNC controller can be changed from outside of controller Then another way was tested but this one needs an advanced command of CNC programming The main idea is to use a R parameter to select the spindle speed before to start the CNC program It can be done by inserting one programming line in the CNC program AT point of CNC program the programmer must set the spindle speed before to start the milling process In this way this line must be changed as following M3 S5000 start the spindle speed with 5000 rpm M3 S R10 start the spindle speed with rpm recorded
6. cutting depth cutting speed tool advance number of tool teeth ABCM Symposium Series in Mechatronics Vol 4 pp 553 558 Copyright 2010 by ABCM 2 4 Vibration control To control the vibration during milling process the user had to collect many data from it Starting with the impact test when the user needs a frequency response hammer and an acceleromether The output this is FRF Frequency Response Function in form by chart The FRF shows which frequencies are more flexible to system After obtain the FRF the user note how many cutting edges the tool has in it body and starts the exhaustive tests to obtain the limts of ap for each rotation value A spindle speed and ap are selected and this last is increased up to system of sound pressure acquisition inform what the sound level is to high This ap is taked as higher value before vibration And the user repeats this process for each spindle speed until to conclude the stability letter The whole vibration control process is showed in form of blocks diagram in Fig 2 Genetate Select spindle Search ap Find best FRF speed limit spindle speed Augment spindle speed Figure 2 Blocks Diagram to obtain best spindle speed After this process the user inform to programmer of CNC machine the best spindle speed for specifc tool and machine It would be a ideal situation if had a automatic process to obtain the best spindle speed to milling a part And it lead this work
7. g Polli 2005 and Cabral 2007 the vibration control also called chatter control aims to remove the vibration during milling process It brings reduced time in milling better surface finishing and longer tool life In the context the purpose of this paper is to present the data what can be remotely changed in a CNC machine towards to vibration control and test a solution that makes remotely speed selection of spindle of CNC machine The paper is organized as follow Section 2 describes the vibration control in milling process Section 3 desribes the CNC tool machine used in this work Section 4 presents the research about direct access of CNC data Secction 5 shows the results of work Finally Section 6 presents some conclusions and discusses about work 2 VIBRATION CONTROL IN MILLING PROCESS In order to perform the vibration control it is necessary to understand how and where it occured in process 2 1 High Speed Machining Milling is a cutting process in which the removal of material of the part is made in intermittent mode by tool rotary moviment generally multi cutting denominated mill The part moves with advance speed among mill A process characteristic is that each edge cut of mill removes material portion of part in form of small chips It is widely process applied in the aeronautical automobilistic and moulds and dies manufacturing POLLI 2005 High Speed Machining HSM or High Speed Cutting HSC can be defined considering
8. in R10 parameter In any way if the R10 parameter was not recorded before the start CNC program the CNC controller will use the last recorded value And it does not cause any problem to CNC controller only can set an wrong spindle speed to process depending of selected tool DDE variables Channel Parameter R 10 R10 parameter Plc Input Bit 2 1 set start CNC program Plc Input Bit 3 7 set stop CNC program Then this form the user or some software can select the correct spindle speed before the start CNC program besides starts and stop CNC program all it remotely If someone success to develop some software to obtain e calculate the optimum spindle speed it can access CNC data from the same way of this work And it 1s a desired solution by many enterprises 5 RESULTS After to change the CNC programming line as suggered it was developed an application in Visual Basic 6 software due facility to handle DDE variables in this environment In this application was inserted a command to select spindle speed a function to monitoring spindle speed a command to start CNC program and a command to stop the CNC program For run the developed application previously it was run the NCDDE server Siemens software The application is showed in Fig 6 and it was called Spindle Control Software The example shows a situation when it was selected the spindle speed 1000 rpm and give the start CNC program start As result
9. ity of variants of the industrial products have been pressed the enterprises to search new technological and organizational solutions in order to maintain competitive The HSC High Speed Cutting arises as a considerable potencial for increasing the quality and productivity of enterprises of important industrial sector such as aeronautical automobilistic and moulds and dies manufacturing and others Polli 2005 Several aplications have been developed with intention to make data acquisition and remote monitoring of CNC Computerized Numerical Control machine Some aplications face production monitoring and others monitoring of milling process data Example of remote monitoring of production is presented in Ferraz 2002 This monitors the quantity of produced parts milling cycle time and speed of machine axis Other aplication is presented in Silva 2008 where the author proposes and aplies a method to develop software of production monitoring Example of remote monitoring of milling process is presented in Del Conte and Schutzer 2007 This work aims to determine optimum strategy to data acquisition from CNC machine Similar method is presented in Souza 2001 that makes an internal data processing obtaining higher precision and sample rate Instead of remote monitoring few aplications have been developed about remote control in CNC machine This data way is required in some aplications such as in vibration control in CNC machine Accordin
10. lling process in HSC frequently have been used stability letters SCHMITZ 2006 Figure 1 shows a stability letter ap lim Stable region ap crit rpm rotations per minute Figure 1 Stability Letter In these letters both regions stable and unstable show to be dependants of selected machining rotarion and depth This diagram can be analytical calculated or using techniques in time dominion BAYLY et al 2002 In any situation it is required knowledge of machine dunamics In many cases system dynamics can be obtained by impact test ou modal analysis The frequency response function FRF is mesured in tool end and nultiple modes adhere to results Other possibility is realization of milling assays to direct selection of stable speeds where tool rotarion is altered for various ap values The stability letter allows the user to select the preferential rotations and to avoid unstabilities For roughing operations where tool presents high radial cut depths the user must select rotation values defined by peaks of stability letter that means to excite the system with vibration modes more flexible For finishing operations where tool presents low radial cut depths the user must select rotaion values defined by valleys of stability letter that means to excite the systema with vibration modes less flexible Then the cutting parameters of milling process that influence the process stability are e axial cutting depth radial
11. peed Cutting Machining of Complex Surfaces Dissertation Master in Production Engineering University of Mechanical and Production Engineering of University Metodista de Piracicaba Sao Paulo 2001 9 RESPONSIBILITY NOTICE The authors are the only responsible for the printed material included in this paper
12. pindle speed And to make it an automatic process it is necessary to research how to input a comand to CNC machine from external side to select some spindle speed Silva 2008 showed a form to make data acquition from CNC machine using DDE variables This aplication used the same CNC controller of Hermle machine Then following the same form to acquire data from CNC controller this reaserch will try to make the same way for send controls to CNC controller Figure 4 shows the system architecture that will be used as programming tool for sending data to CNC controller Programming pm b S system Position Speed Power Machine Motors Hermle Siemens Machine Sinumerik 40D Acquisition a l l l l Ba l a Eas l 7 it wil I Ts 7 I B l l l l system L Amn 5 Siemens board p Seah Programming L tool Figure 4 System architecture The system architecture is composed by Hermle CNC machine Siemens PCI board CP 5611 and a PC Personal Computer In this case the acquisition system will be used as interface system to connect both side in bi directional way The programming tool can use the NC Numerical Control variables as DDE Dynamic Data Exchage variables It is possible due Siemens converter offered together CP 5611 board The converter called NCDDE Server converts NC variables in DDE variables and vice versa Figure 5 shows the way from CNC machine to programming tool When C
13. the machine spindle recept the command and it started to rotate It show that the application made can be used to spindle control of any Siemens CNC machine 6 CONCLUSIONS This paper presents and discuss an effort to make an automatic vibration control of CNC machine It also shows that mapping the CNC data which can be changed from outside of CNC controller only apper the PLC data input output flag data data block timer counter clock ans alarm mensages and R parameter and do not appear spindle speed data directly We can conclude through this paper that if someone success to develop some software to obtain e calculate the optimum spindle speed it is possible to access CNC data and to make the vibration control of CNC machine And it is a desired solution by many enterprises ABCM Symposium Series in Mechatronics Vol 4 pp 553 558 Copyright 2010 by ABCM w Spindle Control of x Software Spindle Control Monitoring Spindle Speed 1000 21 3623 rpm Spindle Speed 1000 fpr Set Stop Spindle Exit Figure 6 Spindle Control 7 ACKNOWLEDGEMENTS This research is supported by governmental agencies CAPES FAPESP CNPq and FINEP 8 REFERENCES Altintas Y Manufacturing Automation United States of America 1 Ed Cambridge University Press 288 pg 2000 Bayly P Schmitz T Peters D Mann B St pan G Insperger T Efects of Radial Immersion and Cuttong Direction on Chatter Instability in End
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