The use of high frequency DC welding guns in robotic cells

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ISSN 1018-5593 EU RO PEAN COMMISSION SCIENCE RESEARCH DEVELOPMENT technical steel research Properties and ¡η-service performance ' The use of high frequency DC welding guns in robotic cells Report hi EUR 18000 EN STEEL RESEARCH EUROPEAN COMMISSION Edith CRESSON, Member of the Commission responsible for research, innovation, education, training and youth DG XII/C.2 — RTD actions: Industrial and materials technologies — Materials and steel Contact: MrJ.-L Martin Address: European Commission, rue de la Loi 200 (MO 75 1/10), B-1049 Brussels — Tel. (32-2) 29-53453; fax (32-2) 29-65987 European Commission technical steel research Properties and in-service performance The use of high frequency DC welding guns in robotic cells N. T. Williams, C. Lewis, S. A. Westgate British Steel pic 9 Albert Embankment London SE1 7SN United Kingdom Contract No 7210-KA/815 1 July 1989 to 30 September 1992 Final report Directorate-General Science, Research and Development 1998 EUR 18000 EN LEGAL NOTICE Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of the following information. A great deal of additional information on the European Union is available on the Internet. It can be accessed through the Europa server (http://europa.eu.int). Cataloguing data can be found at the end of this publication.

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ISSN 1018-5593
EU RO PEAN
COMMISSION
SCIENCE
RESEARCH
DEVELOPMENT
technical steel research
Properties and ¡η-service performance
'
The use of high
frequency DC welding
guns in robotic cells
Report hi
EUR 18000 EN
STEEL RESEARCH EUROPEAN COMMISSION
Edith CRESSON, Member of the Commission
responsible for research, innovation, education, training and youth
DG XII/C.2 — RTD actions: Industrial and materials technologies —
Materials and steel
Contact: MrJ.-L Martin
Address: European Commission, rue de la Loi 200 (MO 75 1/10),
B-1049 Brussels — Tel. (32-2) 29-53453; fax (32-2) 29-65987 European Commission
technical steel research
Properties and in-service performance
The use of high frequency DC welding
guns in robotic cells
N. T. Williams, C. Lewis, S. A. Westgate
British Steel pic
9 Albert Embankment
London SE1 7SN
United Kingdom
Contract No 7210-KA/815
1 July 1989 to 30 September 1992
Final report
Directorate-General
Science, Research and Development
1998 EUR 18000 EN LEGAL NOTICE
Neither the European Commission nor any person acting on behalf of the Commission
is responsible for the use which might be made of the following information.
A great deal of additional information on the European Union is available on the Internet.
It can be accessed through the Europa server (http://europa.eu.int).
Cataloguing data can be found at the end of this publication.
Luxembourg: Office for Official Publications of the European Communities, 1998
ISBN 92-828-3499-9
© European Communities, 1998
Reproduction is authorised provided the source is acknowledged.
Printed in Luxembourg
PRINTED ON WHITE CHLORINE-FREE PAPER CONTENTS
Page
1. INTRODUCTION Π
2. DEVELOPMENTS IN RESISTANCE WELDING POWER SOURCES 12
2.1 DC Welding 12
2.2 High Frequency Welding Transformers 1
3. EXPERIMENTAL PROCEDURE4
3.1 Material Used
3.2 Instrumentation5
3.3 Characteristics of Welding Equipment Used 17
3.4 Weldability Tests8
4. ANALYSIS OF WAVEFORMS9
4.1 Influence of Power Source Type on the Basic
Waveforms Developed 1
4.2 Assessment of Power Efficiencies 21
4.3 Analysis of Power Losses in the System
4.4 Influence of Operating Parameters on Output3
5. WELDABILITY OF STRIP PRODUCTS4
5.1 Weldability Lobes 2
5.2 Electrode Life Tests6
5.3 Weld Growth Studies
5.4 Welding Under Non-Optimum Conditions 29
6. PRODUCTION TRIALS 32
6.1 General Description of Production Cell
6.2 Assessment Techniques4
6.3 Tagu chi Trials5
7. GENERAL DISCUSSION7
8. CONCLUSIONS 39
9. REFERENCES 40
TABLES1
FIGURES 73 LIST OF TABLES
1. Chemical analysis of steels
2. Electrical specification of equipments at The Welding Institute and British Steel Technical
- Welsh Laboratories
3. Basic characteristics of 'J' and 'S' type welding guns
4. Primary current demand with HF-DC and 50Hz AC welding systems
5. Electrical measurements on the single phase AC machine with hanging transformer
6.ls on the single phase AC machine with an integralr
7. Electrical measurements on the three phase secondary rectified DC machine
8.ls on the HF-DC machine
9. Energy losses within the system
10. Results for the variation of inductance and resistance (single phase AC)
11 ·s of the variation of gun impedance
12. Results of the variation of secondary inductance and resistance on the HF-DC supply
13. Electrode life obtained with 800Hz HF-DC, 1000Hz HF-DC and 50Hz AC welding currents
using a 'J' type welding gun
14. Nugget aspect ratios - height/width
15. Effect of electrode approach angle on weld splash and electrode sticking
16. Assessment of part fit-up in robotic cell (OP30)
17. Measurements of electrode approach angles in robotic cell (OP30)
18.s of flange widths in robotic cell (OP30)
19. Weld size measurements in robotic cell (OP30)
20. Measurements of the positional accuracy of the weld spot in robotic cell (OP30)
21. Experimental array for Taguchi trial at Jaguar cars
22. Welding parameters for confirmation run
23. Measurement of weld nugget size from confirmation runs
24. Effect of inductance on nugget diameter IJST OF FIGURES
1. Schematic of HF-DC system
2.c of electrical systems
3. Typical waveforms from single phase AC supply, current and voltage plus their product
IV, power
4. Typical waveforms from three phase secondary rectified DC machine
5. Schematic of three phase primary waveforms showing the voltage between phases and the
current flowing in each phase for full conduction and low heat conditions DC
6. Characteristics of the lOüOHz HF-DC current waveform
7. Waveforms showing current voltage and power on the mains supply of the single phase AC
equipment (hanging transformer).
8. Primary current and voltage waveforms measured under secondary load conditions
indicating schematically the influence of the magnetising current on the normal load
current
9. Waveforms taken from the mains of the 50Hz supply with the integral transformer,
showing current (I), voltage (V) and power (P)
10.s taken from the front of the gun with the 50Hz AC supply with the integral
transformer, showing current
11. Waveforms taken from the rear of the gun with the 50Hz AC supply with integral
transformer, showing current (1), voltage (V) and power(P).
12. Typical waveform from the three phase rectified DC machine
13. Schematic of three phase primary waveforms showing the voltage between phases and the
current flowing in each phase for full conduction and low heat conditions DC
14. Simulated H F-DC current waveforms
15. Current and voltage records from the Bosch high frequency DC supply
16. Schematic of HF- DC supply waveforms using a low heat setting
17. Primary mains current recorded for one phase in the Bosch high frequency-DC supply, low
heat setting
18. Simulated outputs from HF-DC current, generated by calculation
19. Typical monitor trace for a weld made using the Miyachi 1000 Hz HF-DC supply
20. Phase currents and interphase voltages on the mains supply to the HF-DC equipment
21. Waveforms taken from the transistor switched high frequency supply of the HF-DC
equipment showing 1 cycle of the 1000 Hz
22. Waveforms taken from the secondary circuit of the HF-DC supply showing short circuit
current(l), voltage(V) and power(P) 23 Schematic secondary current and voltage waveforms for the 1 IK-DC supply showing the
source of resulting measured voltage
24. Influence of variation of secondary impedance on secondary current
25. Variation of control level (equivalent to heat setting) with current setting on the Miyachi
H K-DC supply
26 Influence of welding rate on available current under short circuit conditions
27 Voidability lobes for AC and HF-DC welding' of 0.9mm mild steel (1.6 kN electrode force,
'S' type welding gun)
28. Weldability lobes for AC and HF-DC welding of 0.9mm hot-dip zinc coated steel (1.6 kN
electrode force, 'S' type welding gun)
29. Weldability lobes for AC and HF-DC welding of hot-dip zinc coated steel (2.2kN electrode
force, 'J' welding gun)
30. Weldability lobes for AC and HF-DC welding of 0.8mm iron-zinc coated steel (2.2kN
electrode force, 'J' type welding gun)
31. Weldability lobes for AC and HF-DC welding of 0.7mm nickel-zinc coated steel (2.2kN
electrode force, 'J' type welding gun)
32. Weldability lobes for AC and HF-DC welding of 0.7mm electrolytically deposited zinc
coated steel (2.2kN electrode force, 'J' type welding gun)
33. Weldability lobes for low frequency-DC welding of a 0.7mm electrolytically deposited
coated steel and 800Hz HK-DC welding of a 0.8mm iron-zinc coated steel (2.2kN electrode
force, 'J' type welding gun)
34. Difference in current level observed for a 1000Hz HK-DC current relative to AC
35.e in welding range 3.5>/t to splash observed when welding various zinc coaled
stools using 1000Hz HK-DC or 50Hz AC current
36. Influence of current waveform on welding range, 5\/t to splash
37. Comparison of electrode life obtained with AC and HK-DC welding currents for a 0.9mm
hot dip zinc coated steel
'M. Influence of electrode material on electrode life
39. Cross sections through spot welded joints in 0.8mm mild steel indicating the influence of
weld time on weld growth for both 50Hz AC and 1000Hz HK-DC welding currents
4Ü. Cross sections through spot welded joints in 0.7mm electrolytically deposited zinc coated
steel indicating the influence of weld time on weld growth for both 50Hz AC and 1000Hz
HF-DC welding currents
41. Cross section through spot welded joints in a 0.8mm iron-zinc alloy coated steel indicating
the influence of weld time on weld growth for both 50Hz AC and 1000Hz HK-DC welding
currents
42. Comparison of weld nugget growth for 800Hz HK-DC and 50Hz AC welding of 0.7mm
electrolytically deposited zinc coated steel (0.08s weld (4cycles))