Marco Boccadoro GFMS Head of EDM Research & Innovation. WEDM technology : is a quantum leap in the process performance still possible?

Transcription

1 Marco Boccadoro GFMS Head of EDM Research & Innovation WEDM technology : is a quantum leap in the process performance still possible?

2 Table of Contents Introduction WEDM: state of the art The progress of WEDM The latest innovations 2

3 Introduction 3

4 Georg Fischer Corporation Founded in 1802 and headquartered in Switzerland 125 companies, 48 of them production facilities 13,500 employees worldwide (32 countries) Generated sales of 3.6 billion Swiss francs in 2012 Three divisions: GF Piping Systems GF Automotive GF Machining Solutions 4

5 GF Machining Solutions A complete solution provider GF Machining Solutions is a leading provider to the tool and mold making industry and to manufacturers of precision components. Based in Switzerland, globally active with 50 sites worldwide At your service with 2,798 employees We are a premium brand in these core businesses: EDM Milling, Spindles Laser Automation Customer Services 5

6 Market segments Customers worldwide depend on our technologies, application knowhow and process expertise in our five key market segments. Aerospace and Aeronautics Automotive Medical and Dental ICT Electronic components 6

7 ELECTRICAL DISCHARGE MACHINING (EDM) Wire-cutting EDM Die-sinking EDM Hole-drilling EDM Machine conductive materials of any hardness like steel or titanium to an accuracy of up to one-thousandths of a millimeter. 7

8 WEDM: state of the art 8

9 The state of the art in WEDM The productivity of WEDM has been increased by a factor of 100 between 1972 and The overall accuracy of WEDM was brought from several tenths of mm to better than 1um (CUT 1000) WEDM machining in oil achieves best results in terms of accuracy, without any corrosion The surface quality of WEDM is now better than Ra 0.05um The surface integrity of WEDM is now better than that of grinding (White Layer less than 1um)

10 Performance increase of WEDM Most of the performance increases that EDM generators have seen are a direct result of the electronics industry advancing at a furious pace! 10 From 1970 to Number of transistors in a PC processor has multiplied X 1,000,000 Times

11 Technological boundaries Factor WEDM Improvement possible Speed(DS) / WEDM speed Achievable roughness Ra 500 mm2/min (0.3 mm wire) 0.03 um Electrode wear 115% - 170% Precision on finished wkpc 1 um Minimal radii 10 um (with 20 um wire) H max Energy consumption 800 mm 0.8 KW (stand by) - 10 KW Surface integrity ~0 um white layer - no cracks Material resistivity 100W-cm

12 The progress of WEDM 12

13 The EDM improvement imperative: Improve operating efficiency Improve surface integrity Improve erosion speed

14 The Early Years: Wire EDM V to 350V R NPN Silicion linear C Imeas. Regulation Idc 20A Metal removal rate is at approx. 8mm²/min Energy efficiency is at 7%. 1μs V to 350V R NPN Silicon Ipulse Metal removal is increased to 12mm²/min. Energy efficiency still 7% C 50A 1μs V R NPN Silicon Ipuls The last version reached 227mm ² / min in Efficiency was still poor at 8%. 200A μs

15 WEDM surface integrity The Early Years: Wire EDM Microstructures following WEDM of Ti-6Al-4V Case Study: Univ. of Birmingham

16 Present + C 700A + C 1200A Improving Performance - 75V L NPN Silicon Metal removal in the range of 300mm²/min Efficiency increases from 7% to 33% 1-3 μs - 85V L IGBT Metal Removal in the range of 500mm ² / min Efficiency increases to 80% Key technology improvements: μs MOSFET and FPGA (programmable logic) allow the integration of large discrete logic boards in a single module.

17 Wire EDM surface integrity Improving Surface Integrity Inconel 718, trim 4 Image taken on a Leica microscope 500x magnification No measurable recast Case Study: Univ. of Birmingham

18 Best Surface quality with oil dielectric Progressive tool Hard metal 30mm Surface quality in oil Wire AH 0.10mm Main cut Ra 1.25µm feedrate 0.45mm Segment 1 1 HS + 1 NS Ra 0.56 Segment 2 1 HS + 2 NS Ra 0.48 Segment 3 1 HS + 3 NS Ra 0.24 Segment 4 1 HS + 4 NS Ra 0.18 Segment 5 1 HS + 5 NS Ra 0.06 Segment 6 1 HS + 6 NS Ra 0.05 Segment 7 1 HS + 7 NS Ra 0.04 Segment 8 1 HS + 8 NS Ra 0.03 VSM mm/min VSM mm/min VSM mm/min VSM mm/min VSM mm/min VSM mm/min VSM mm/min VSM mm/min

19 Trends in WEDM Increase of cutting speed Accuracy increase Ultra-fine cutting (wire Ø<0.01) Surface quality and homogeneity Machining of ceramics, exotic materials and alloys Higher degree of freedom Duotec / Twin Wire Automation issues (Handling, automatic cycles) Multiwire machines for production applications Economical & ecological issues (consumables, energy) EDM coating

20 WEDM: the latest innovations 20

21 Back to the basics of wire EDM: shortest current pulses! Negative particles(electrons) are released faster from the wire surface than positive particles from the workpiece 2. Positive particles (ions) from the workpiece have a bigger mass and are slower A very strong erosion takes place at first at the positive electrode. If too many ions reach the wire, the risk of wire breakage increases, wire material is deposed on the workpiece, the white layer and HAZ increase. The pulse must be turned off before the ions reach the wire! 21

22 Erosion performances improved, why? Removal of both gap- box (upper and lower) Repositioning of PCB power modules (from cabinet close to work area, worktank rear) Removal of electrode cables Generator located as close as possible of the sparking area (better control of the spark) 22

23 Advantages of short cables Short cables = short pulses! Smaller impedance Better gap acquisition Better gap control Better geometry and surface Indipendency from the machine size V L C IGBT No wire breakage Smallest heat affected zone No brass deposit on the workpiece Higher machining speed Higher cutting rate 23

24 A better control of the sparking Creating the most effective spark

25 New speed performances Machining time CUT 2000 /CUT 2000 S 180 Steel Machining time (mn) Machining time CUT Gain in % 40 Machining time CUT 2000 S Gain in % Thickness of the work-piece (mm) 25

26 Machining comparison example Customer P. (Germany) Customer S. (Germany) Material : steel Contour : 148 mmm Machining time on CUT 2000 : 3H 52 min Machining time on CUT 2000 S : 2H 23min Gain : 89 min (38 %) Result : Ra 0.2µm / accuracy : ± 2µm Customer G.P. (Taiwan) Material: Steel Wire : Ø0.20mm Machining time on CUT 2000 : 75 min Die B01 Punch B02 CUT H 01 mn 3 H 02 mn CUT 2000S 39 mn 53 2 H 10 mn Gain (mn) Gain % 34% 28% Result : Ra 0.2 µm / accuracy : ± 2µm Machining time on CUT 2000 S : 46min Result : Ra 0.2µm 26

27 Integrated Vision Unit Advance CCD camera embedded on the machine with backlight for measurement 27

28 Integrated Vision Unit Advance Detection of the exact position of the cut edge by analysis of the light intensity variation Accuracy: ± 1μm with a magnification of 150X and ± 1.5μm with a magnification of 50X Without contact to the workpiece : fully automatic measuring cycles and automatic integration in the program measuring piece contour Examples : radius, distance between lines, or the positioning of a special location on the workpiece Automated proposal of a correction of the programmed contour 28

29 Integrated Vision Unit Advance: Closed Loop Graphic Check.dxf generation Erosion Contour Scan Erosion results Form error Average error Standard deviation Contour Presenter CONOPTICA Definition of the new contour geometry Contour Modifier New erosion 29

30 Analysis and correction of the cut contour Close loop means the correction of the programmed geometry by the scanned measure after the machining, and comparison against the DXF Data (Sollwert ) Die ISO Data are not modified!

31 IVU Advance Close loop: Example mm Without Close Loop correction With Close Loop correction

32 Conclusions WEDM generator technology has been improving for many years. WEDM has been advancing and will advance as fast as electronics innovation will allow it to. There is still a big potential for innovation in this fascinating technology!

33 33