a portable integrated servo lab for cnc training

A Portable Integrated Servo Lab for CNC Training

Roberto S. Apóstoli Laboratorio Elinon Cordoba, Argentina

[email protected]

Abstract—a wholly designed and built portable lab is described. The task is to bring an integrated training facility concerning with the computer numerical control (CNC) instruction. Main objectives are to: (1) Offer one axis CNC machine tool, resembling a real one (2) Make an interactive training lab, mostly with mechanical components. (3) Follow the correlation between theory and practice about open and closed controls. (4) Install and test the up to date Linux O.S., like Ubuntu and Debian. (5) Pour these practical experiences into a low cost DVD Multimedia course. (6) Bring a “hands on” basic learning on manufacturing subjects involved informatics, digital controls and machine tools, especially to those Industrial Technical Schools which have not a CNC mill. The blackboard, photos, films and PC simulations are good education tools. But it's necessary to acquire a deep knowledge involved by the complex multidisciplinary Mechatronics engineering.

Keywords—cnc training; manufacturing control; multimedia course instruction; mechatronics

I. INTRODUCTION

To face the manufacturing technology challenges today it is mandatory to train skill people such as operators, technicians and engineers. This workforce includes not only scientists and engineers with advanced degrees, but also factory-floor engineers able to oversee, fix and improve complex manufacturing processes. It also needs workers able to use sophisticated machinery and tools in factories. Machine tools and robotics with Computer Numerical Control (CNC) are the main important applications in the competitive production. An integrated project on manufacturing automation started with an IDB (BID)-Argentine National Research and Technological Council (CONICET) contest in 1991: its purpose was to bring a wholly designed and developed manufacturing cell. The main task is to incorporate the most added local knowledge value, in order to get a CNC and robotics innovative integrated project. The first step was to obtain the Manufacturing Module Cell #1. “Fig.1”. It shows a 3-4 axes CNC mill (Elinon1), a 5 axes Robot (RSA1) and an 8 pieces rotational storage magazine. The environment simulation and control was implemented with real time Petri-Nets and later with Turbo Prolog. [1], [2], [15].The second step deals with the design, develop and build a 4 axes CNC mill machine (Elinon 0). “Fig. 2”. This experimental-test machine was controlled by several Operational Systems (O. S.): MS-DOS 6.22; Caldera DR- DOS 7.03, Ubuntu 8.04 and CNC programs: TurboCNC 4.01, Zeus 1.89 and Linuxcnc 2.4.6 [1].

Fig. 1 ELINON 1 3-4 CNC axes with robot RSA1 and an 8 pieces magazine

The third step concerns with learning on a Flexible Manufacturing Cell, named “Cellflex”, integrated with a mill CNC Elinon II 5 axes and the RSA2 robot 5 axes. The whole system is simulated on a Real Time Expert System G2 Gensym-USA. “Fig. 11” [15]. Then, the author came to this conclusion: the need of a portable basic CNC training equipment for beginners’ students and workers. “Fig. 3”.

Fig. 2 ELINON 0. Three and four CNC axes with two spindles

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DOI 10.14684/EDUNINE.1.Vol.2.2017.26-30

Fig.3. The portable CNC-LAB-1 bench

II. THE CNC PORTABLE LAB

The lab-project embraces the following components:

• A step motor kit for axis rotation demonstration only.It has the power supply and a micro-stepping driver, soit can bring the current to this motor and, optionally, tothe CNC bench two motors.

• The demonstration CNC-LAB-1 bench whichresembles the Elinon 0 CNC Y axis. It has two motioncontrol systems: a step motor and a servo closed directcurrent (DC) motor with one digital encoder.

• A PC #1 AMD-Sempron 3000 + for CNC control.

• A PC # 2 Intel Atom 525D for Computer AidedDesign (CAD) and multimedia CNC courses on O. S.Windows 7 Ultimate.

• A Sony CX220 high definition (HD: 1920+1080pixels) digital video camera.

• The Ouku FB5800 HD resolution LED projector.3500 lumens.

• One HD-250 MHz VGS video splitter with two portsand 10 meters of video HDMI and PC VGA cables.

This CNC-LAB-1 is an Open Source Educational Project. The operation manual and the complete technical description can be requested to the author’s e-mail at no charge: he suggests to trainers encourage a similar copy. Special consideration should be taken about the Real Time Application Interface (RTAI) CNC control. The main drawback is the system core latency. This delay can reduce the step pulse bandwidth. A good performance can be reached with a 10000 nanoseconds jitter latency.

A low cost PC Sempron 3000+ and O.S. Ubuntu 10.04.4 LTS together with Linuxcnc 2.5.5 brings the better answers. Talking about the step motor control, linuxcnc presents a configuration wizard. “Fig. 4.” The trainer can set all the motor, driver, screw, pulley and mechanical parameters. He can also modifies the table velocity and acceleration. Finally, he can set the home physical position switch. The operator can change the acceleration and later on he can check the dynamic system response. The trainers can also draw the velocity profile, show the acceleration ramps and calculate the maximum velocity. This lab equipment can demonstrate the basic kinematics and dynamics movement laws applied to the computer numerical control CNC concepts. Trainers and students can be motivated by the real action: they can see and hear the slide movement and check with a precision dial indicator the final micro-position. Trainers and students have to be in control of what they are doing. This also builds enormous amounts of self-esteem.

Fig. 4 Linuxcnc 2.5.5 configuration wizard


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III. DESIGN AND MANUFACTURING INTEGRATION

The CNC experimental lab bench belongs to the first basic training stage. A second training stage starts with some basic drawing by means of computer programs. This is called Computer Aided Design (CAD). Among different open and commercial programs, Freecad, Librecad and QCad are the proper start. The screen in “Fig. 5” shows a “Pica” 2D logo design made on the QCad/Cam last version 3.15.5 (August, 19, 2016).This QCad is running on O. S. Linux Mint 12 and Linux Ubuntu 16.0.4 LTS with motherboard AMD Phenom II six cores. The drawing is saved on .dxf extension code. The same program has a Computer Aided Manufacturing (CAM) plug in order to generate a program written for the CNC standard G language (.ngc for linuxcnc). Another G code program is PYCAM release V0.5.1.1 (2014) which convert the .dxf into a Cam (.nc and .ngc) operative list. “Fig.6” presents the 3D tool-path simulation on a CNC machine.

Fig.5 Pica logo design on Q Cad V 3.15.5

Fig.6 CNC path visualization on PYCAM V 0.5.1.1

“Fig.7” is a capture of linuxcnc 2.7.8 last release (November, 9, 2016) screen on Debian Wheezy 7.11 LTS (delivery June, 4, 2016) O. S. running on an Intel Atom 525. It shows the 3D tool-path representation movement around lines generated with the PYCAM program. This is the same screen of linuxcnc for the training bench. The first step is to set the home axes positions. In the bench case there is only one axis: X. By hand, the trainer calls Machine, then Homing X axis andthe inner algorithm moves the table up to touch the homeswitch wheel. Then it slides the table three times until stop tothe exactly Home Position.

The CNC bench has an average home position error of 3.8 micrometer (measured with a Mitutoyo dial 21095-10). This is the most important open step CNC control action, because all the movements are refereed to this point. “Fig.8” presents a photo of the “Pica” Cad design manufactured on the ELINON 1 3-4 axes CNC machine, also wholly designed and built at Elinon Laboratory. “Fig.1” and “Fig.9”. The material is Aluminum 7074, the tool is a carbide 1 mm. diameter. The spindle speed is 3500 revolutions per minute.

Fig. 7 CNC tool path representation on Debian 7.11 plus Linuxcnc 2.7.8

Fig. 8 “Pica” logo manufactured on ELINON 1 CNC mill

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IV. MULTIMEDIA COURSE

All these experiences are poured into a CNC multimedia course. There are many commercial courses on this subject, especially on Internet, books with CD and simulation. This Lab is developing another course on CNC, but based on the own acquired experiences on three CNC machines: Elinon 0 (4 axes); Elinon 1 (3-4 axes), Elinon 2 (5 axis), two robots: RSA-I (5 axes, step), RSA-II (5 axes, servo), and three benches: one digital servo, one analog servo, and the present CNC bench. The idea started several years ago with multimedia projects and the proper program: Multimedia Toolbook 4. The program can run on Windows 7 Ultimate, XP, and even on Windows 98. A sample of the course is presented in “Fig. 9”. It is the first page at the student mode. It is interactive: he can receive the answers to special questions. “Fig.10” shows another page with some helps: the program can present sound and shows videos, photos and hypertexts.

Fig. 9 CNC Course on Windows 7 Ultimate and Atom 525

Fig. 10 CNC Course: Interactive video, sound and hypertext

V. CONCLUSIONS

• This portable lab helps young students and workers tounderstand the basics of CNC machine tools [1], [2].The core idea is: First to show a workingdemonstration, and second to make all the physical-mathematical correlations. These practicaldemonstrations embraced mechanical, electronics,informatics and control subjects. This adopted mindsetof “learning by doing” brings interested and engagedstudents. For trainers, the best way to truly learn aboutCNC is to design and build by themselves the project.There are commercial turnkey portable units for controland CNC training, for example: China [3], [4]; U. S. A.[5]; UK. [6], [7]. The O. S. Linux Ubuntu and Debianare reliable, affordable, open systems and up to date [8].

• This portable lab can exhibit three important basicsubjects related to advance manufacturing: 1) the CNC,2) the design Cad and 3) the multimedia course.

• The next demonstration stage will be a feedback closedloop servo. The Elinon Lab already designed and builttwo projects: with Hewlett-Packard HTLC-1100 [9] andDSP Motorola 56F805 [10] chips. The Gecko servodrive G320X is a very simple start for this educationalpurpose. The PID servo tuning follows the Ziegler &Nichols experimental cut and try methodology. Theacademic analysis by the complex Evans Root Lociplane, Laplace Transform (poles & zeros) and ZTransform are not applied at this training stage.

• All these engineering CAD-CAM experiences arebeing transferred into a DVD interactive course runningon a low cost PC. [11].At no charge, and under a properagreement, the author can delivery experimental copiesto technical schools and engineering colleges.

• The project was exhibited at the 2016 Expotrónicameeting in Cordoba City [12]. It also had a TVinterview [13].

• The Industrial Technical School IPET 77 brings theeducational-trainers to build up a pilot-team whichevaluates and points out the project advantages anddrawbacks [14].

• This basic educational project is linked to someinternational advices and recommendations subjectsrelated to science, technology, engineering and math(STEM). In U. S. A. There was a special report namedPCAST [23]. Another sources can be found in: theMillennium Project 2015-2016 “State of the future“[20], United Nations UNCTAD Policy Brief Nº 50[18], “Impact of Future Technology”. OxfordUniversity [19]. ”How artificial intelligence and robotswill radically transform the economy?” Newsweek.[21]. “The second machine age” MIT Research. [22].President’s Council of Advisors on Science andTechnology (PCAST) U .S. A. [23], [24].


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Fig.11 “Cellflex” manufacturing cell with robot RSAII and ELINON II-5 axes

ACKNOWLEDGMENT

The author wishes to express gratitude to the following institutions who contributed to develop the project and made a broad diffusion into the educational and industrial environments.

• CONICET. Argentine National Scientific andTechnological Research Council.

• National Universities of Córdoba, San Luis, Cuyo andTechnological of Córdoba and Buenos Aires.

• Cordoba Provincial Government. IPET 77 TechnicalHigh School.

• Technological Center De Arteaga|.FIDEIAR. Cordoba.

• Metallurgical Industrial Chamber. CIMCC. Cordoba.

• Electronics, Informatics and CommunicationsIndustries Chamber. Córdoba. CIIECCA.

• Technological Education Federation. FOPET.Cordoba.

• The National Polytechnics Institute. InstitutoPolitécnico Nacional (IPN). Querétaro. Mexico.

• West Virginia University. Mechanical and AerospaceEngineering College. U. S. A.

• Argentine Automatic Control Association. AADECA.

• Argentine Small and Medium Sized Manufacturers.

REFERENCES

[1] Apóstoli Roberto S. “Mechatronics developments applied to CNC training”. ACCA Congress. Chile. Pp 265-270. 2012. (Original: written in Spanish).

[2] Apóstoli Roberto S. “Mechatronics developments applied to CNC” 24

AADECA Congress. October 27-29. 2014. Argentina. (Original: written inSpanish).

[3] Jinan Should Shine Engineering Educational Equipment. China.Educational kits: ZM3199 Motion Control Trainer, and Flexible ManufacturingSystem with CNC.

[4] Zhetang Yalong Educational Equipment. YL-338B Motion control trainingequipment. YL-550 Servo Motor load

[5] NextWave Automation. U.S.A. CNC educational equipment:

3 axes CNC mill Piranha XL,

[6] Feedback Instruments. U.K England.

Servo Fundamentals Trainer Model 33-033

[7] Denford Machines. U.K. England.

A compact 3 axes CNC educational milling machine:

Micromill CNC Milling Machine

[8] Linux Computer Numerical Control: Linuxcnc.

[9] Apóstoli Roberto S.; Mármol Alfio; Artola Gerardo. "Digital servo controlenvironment for experimental robotics". Original: written in Spanish. VIIArgentine Congress on Computer Sciences. October, 16-20. 2001. Argentina.

[10] Apóstoli Roberto S.; Tissera Hector; Sauchelli Victor. “CELFLEX: aproper platform for training undergraduate engineering students”. VIInternational Conference on Engineering and Computer Education. ICECE.Pages 120-123. March 08-11. 2009. Buenos Aires. Argentina.

[11] “CNC Interactive Multimedia Course”. “Curso Multimedia Interactivosobre Control Numérico Computarizado-CNC.” Written in Spanish andEnglish. Roberto S. Apóstoli. Author' copyright Nº 5150747. DirecciónNacional de Derecho de Autor. (Argentine Author Copyright National Agency)

[12] 2016 Electronics Exposition. Expotrónica 2016. CIIECCA . (Electronics,Informatics and Communications Industries Chamber). June, 2016. Cordoba.Argentina.

[13] Technological Education Federation. EDUTEC-FOPET. TV Channel 10.Edition: August 20, 2016. Argentina. You Tube.

[14] IPET 77 Technical High School. Instituto Provincial de EducaciónTécnica. ”Gobernador Dr. Santiago del Castillo”. Cordoba ProvincialGovernment. Argentina.

[15] Apóstoli Roberto S.; Conforto Antonio; Laffaille Alejandro. “Modelingand simulation of a manufacturing environment” IXX International Congress of Mechanical Engineering. ABCM-COBEM 2007. November 5-7. University ofBrasilia. Brazil.

[16] “The next manufacturing revolution: the future of CNC technology”

Institute of Technical Trades (ITT). May 20, 2016. Toronto. Ontario. Canada.

[17] “The benefits of getting an education on CNC” ITT. May 24, 2016.

[18] “Robots and industrialization in developing countries”. Policy Brief Nº50.October 2016. United Nations Conference on Trade and Development.UNCTAD.

[19] Frey Carl Benedict and Osborne Michael “The future of employment: how susceptible are jobs to computerization?” Oxford Engineering SciencesDepartment and Martin Program on the Impact of Future Technology. OxfordUniversity. United Kingdom. September17, 2013.

[20] Glenn Jerome; Florescu Elizabeth “2015-2016 State of the future”. TheMillennium Project Team. Book. Pages: 289. Library of Congress Control 98-646672.

[21] Maney Kevin “How artificial intelligence and robots will radicallytransform the economy?” Newsweek. December 9, 2016. Vol 167, Issue 21.

[22] McAfee Andrew and Brynjolfsson Erik “The second machine age: Work,Progress and Prosperity in a time of brilliant technologies”. MIT Research.Book. 320 pages. January 2014. ISBN 978-0-393-23935-5.W. W. Norton.

[23] Report to the President on “Ensuring American leadership in AdvancedManufacturing”. President’s Council of Advisers on Science and Technology(PCAST) Appendix A. Advanced Manufacturing provision in AmericaCompetes Act. Pages 33, 34. Appendix B. Pages 35, 36. June 2011. U. S.A.

[24] “Prepare and Inspire: k-12 Education in science, technology, engineeringand mathematics (STEM) for America’s future”. Report: PCAST. Sept. 2010.


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a portable integrated servo lab for cnc training

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