LIBRARY ı6ıul 0) - Cranfield University

More documents

Recommendations

Info

5. Experimental Equipment, Materials and Procedure This chapter gives a description of the equipment and materials used in the experimental trials. The calibration curves and the experimental procedure äre also presented. 5.1 Welding robot A Panasonic AW7000 robot was used. It is a six axis articulated welding robot which can be interfaced with external equipment via digital inputs and outputs. Although analog outputs are also supplied for interfacing with a welding power source, these were not used due to the fact that they could not be freely adjusted on- line. They can only be pre-programmed. The main draw back with the use of this robot in this work is that it was not equipped with a communications port for off-line programming. Positioning errors could, however, be simulated by intentionally on-line programming a known wrong path. 5.2 Welding power source A Migatronic BDH-550 welding power source was utilised. This is a 100 kHz inverter-based microprocessor controlled power source with 80 volts nominal open- circuit voltage and current range from 5A to 550 A. It works as a constant voltage power source in conventional GMAW mode and uses integral control to maintain the set up parameters constant throughout a welding operation. The power source operates in two modes, namely manual and synergic. In manual mode both the welding voltage and the wire feed speed are directly set by the operator. In synergic mode, a welding current value is specified and the power source selects the appropriate wire feed speed and voltage according to a pre-programmed synergic curve. The power source was used in manual mode for this work. The BDH-550 can be driven externally by using a module called Robot Interface supplied by the power source manufacturer, Migatronic. The Robot Interface is controlled by a single microprocessor (SIEMENS 80C515A) which includes, in the same chip, a 10-bit analogue-to-digital (A/D) converter, random access memory (RAM), digital inputs and outputs (110), serial communications and watchdog. The analogue inputs can be connected to analogue outputs from a welding robot or from a computer, allowing on-line external control of welding parameters (voltage and wire feed speed, in manual mode conventional GMAW). It interfaces with the power source control unit via a RS-232 serial communications port. It is also possible to directly communicate with the power source control unit via RS-232 serial communications. However this is only possible if a special control program, stored in erasable programmable read only memory (EPROM) modules, is used in the power source. This program, although available, was still in the development phase. The program in its present form does not have a function for setting wire-feed-speed. This limitation led the present author to opt for the Robot Interface alternative. 115
5.3 Monitoring system The monitoring system consisted of a VME/STE bus industrial computer equipped with an ARCOM VME/STE VSCIM 486 DX2 50 MHz main board, 4 megabytes of random access memory (RAM), 100 megabyte fixed disk, two 12-bit 2- channel simultaneous sampling analogue-to-digital (A/D) converter boards (ARCOM SAD-2X250) and an 8-bit 2-channel digital-to-analogue (D/A) converter board (ARCOM SADA-8). Both A/D and D/A converter boards are STE bus based. The STE bus uses 8 bits to transfer data from the peripheral boards to the main board. Each SAD2X250 board has 64 kilobytes of memory, which allows data aquisition to be carried out in blocks, independently from the main board microprocessor. A signal conditioning board was used to adjust the sensor signals to the voltage range required by the A/D converter boards (-10V to +10V). The voltage and current signals were filtered with a 1.0 kHz cut-off frequency eighth-order analogue Butterworth filter, before being digitised. During initial welding trials, a monitoring software (CranMon), developed at <strong>Cranfield</strong> <strong>University</strong>, was used. This software has limited memory, which prevents it from acquiring welding data for long duration welds. Also, no facilities are provided for implementing the control algorithms. In order to overcome these problems a dedicated monitoring and control software, written in C programming language, was specially designed and developed by the author. It consists of two main parts, namely monitoring and control. The monitoring part was developed to make use of the windowing technique developed by Chawla [ref. 161], which permits the analysis of the welding data in independent blocks. An attempt was made to keep the interval between windows to a minimum. This interval depends on the speed of data transfer from the acquisition boards' memory space to the program data memory and also on the time required for processing the window of data that was collected before. Due to the on-board memory available in the SAD2X250 data acquisition boards, it was possible to use some parallelism: while the main processor was calculating the statistics and performing other tasks, a new window was already being collected. Established numerical and statistical methods were implemented for extracting the statistics of each signal. The welding models developed by Ogunbiyi [ref. 51] were built-in to provide the information about mode of metal transfer and stability characteristics of the process. In the control part, functions were implemented to provide communication capabilities with the table controller and the power source controller. The control commands could be sent to the power source (via analogue outputs) and to the part- positioner (via RS232 serial communications) whenever required, according to the control rules developed. Further details of the software can be found in the Appendix E. 5.4 Welding voltage and current sensors Voltage sensor The voltage was sensed by directly connecting sensing leads (maximum continuous voltage 100 V) to the back of the welding torch and to the workpiece 116
Page 1 and 2:
CRANFIELD UNIVERSITY GC CARVALHO AN
Page 3 and 4:
ABSTRACT The aim of this work was t
Page 5 and 6:
I dedicate this work to the memory
Page 7 and 8:
FIGURES TABLES APPENDICES NOTATION
Page 9 and 10:
3.3.2.1 Welding parameters generato
Page 11 and 12:
References Further reading Appendic
Page 13 and 14:
Figure 3.12 Offsets for weld start
Page 15 and 16:
Figure 6.31 Voltage step input test
Page 17 and 18:
Figure J. 2 Plot of stand-off varia
Page 19 and 20:
Table A. 1 Welding extended entity
Page 22 and 23:
NOTATION A, Electrode sectional are
Page 24 and 25:
Pr(ign) Possibility measure of proc
Page 26 and 27:
1. Introduction Welding is the thir
Page 28:
Chapter 4 describes the on-line pos
Page 31 and 32:
In pulse transfer, the welding curr
Page 33 and 34:
Pd = Pv - pzh-s (2.1) where Pd is t
Page 35 and 36:
the bridge. Another factor that ind
Page 37 and 38:
establish the stable conditions for
Page 39 and 40:
Philpott [ref. 21] developed an on-
Page 41 and 42:
current peak at the moment the tip
Page 43 and 44:
obot on the line must be individual
Page 45 and 46:
collision detection capabilities wh
Page 47 and 48:
cause dynamic variation in the seam
Page 49 and 50:
Another type of robot static calibr
Page 51 and 52:
spatter the gas nozzle is particula
Page 53 and 54:
Table 2.1: Joint positioning tolera
Page 55 and 56:
In order to minimise the undesirabl
Page 57 and 58:
c) Ultrasonic sensors; d) Through-t
Page 59 and 60:
where K,, K2, K3 and K4 are constan
Page 61 and 62:
Philpott [refs. 21,131], based on t
Page 63 and 64:
centre. This is attributed to the m
Page 65 and 66:
technique must be employed to preve
Page 67 and 68:
" digital hardware, which is basica
Page 69 and 70:
" Maximum value, W.: Wmý = max(W )
Page 71 and 72:
process studied over a small range.
Page 73 and 74:
In-process welding control is a muc
Page 75 and 76:
volume caused by the presence of a
Page 77 and 78:
SHIELDING GAS IN CONSUMABLE ELECTRO
Page 79 and 80:
Arc voltage Anode Arc length I Anod
Page 81 and 82:
computed ideal procedure optimisnti
Page 83 and 84:
CONSTANT CURRENT POWER SOURCE `j' O
Page 85 and 86:
Original Surface New Surface Electr
Page 87 and 88:
otating welding wire direction weld
Page 89 and 90: 3.1.1.1 Robot errors A robot arm is
Page 91 and 92: 3.2.2 Programming error correction
Page 93 and 94: 3.3.2 Off-line programming module I
Page 95 and 96: Pen is the weld penetration (side p
Page 97 and 98: a. 2) Geometrical constraints from
Page 99 and 100: Step 11 Step 12 Step 13 Step 14 Ste
Page 101 and 102: Step 21 Step 22 If the wire feed sp
Page 103 and 104: the Y'-axis results in a positive "
Page 105 and 106: _ p1e0a - pORoba m31 Ilp! - poll (3
Page 107 and 108: of a robot in its zero position12 w
Page 109 and 110: frame points to the front of the ro
Page 111 and 112: CAD Off-line (AutoCAD) programming
Page 113 and 114: Z Surface 4 A Y 7 M2 Open Edge Join
Page 115 and 116: WCF World Co-ordinates Frame 2a = J
Page 117 and 118: x Torch Co-ordinates Frame o Indica
Page 119 and 120: vo Ö 't7 Y7 't O m O 'S O O S O S
Page 121 and 122: ýý aý 0 oA aW ö A O Zt A OO 't
Page 123 and 124: Ti 9ý-! i4 *Tx t ap31 jx ý- ymin
Page 125 and 126: errors', (i. e. joint positioning,
Page 127 and 128: was considered to be outside the sc
Page 129 and 130: Table 4.3 - Linguistic representati
Page 131 and 132: The introduction of such a reduced
Page 133 and 134: Table 4.8 - Final welding process c
Page 135 and 136: the collection of welding data corr
Page 137 and 138: Step 4- Calculate the confidence of
Page 139: Z Table Co-ordinates Frame Y X Robo
Page 143 and 144: the torch end. Only one degree of f
Page 145 and 146: Current: 500 Position: 234.5 5.7.3
Page 147 and 148: I" va JI ºr ö C 3 r" r" rl f_ £-
Page 149 and 150: IgurC a. H -I UI qur vCiSUJ JpCCU C
Page 151 and 152: 126
Page 153 and 154: Table 6.1 - Welding trials carried
Page 155 and 156: Table 6.3 - Coefficients of Ogunbiy
Page 157 and 158: Note that the calibration model sho
Page 159 and 160: Table 6.6 - Welding parameters used
Page 161 and 162: constant set-up welding parameters
Page 163 and 164: stickout lengths and the temperatur
Page 165 and 166: of the dip mode of metal transfer.
Page 167 and 168: which would become active by settin
Page 169 and 170: In section 4.2.5 it has been mentio
Page 171 and 172: 300 280 260 240 rd 35- 3D 25 20 15
Page 173 and 174: Figure 6.5 - Measured "versus" Pred
Page 175 and 176: i S 0 -0.1 -0.2 -0.3 -0.7- 68 10 12
Page 177 and 178: 32.0 E 31.5 y 31.0 30.5 30.0 j 29.5
Page 179 and 180: 35 - 30 p 15 10 0.00 2.60 5.42 8.23
Page 181 and 182: 40 35 30 25 20 15 10 A+iIII+F0.17 2
Page 183 and 184: 30 28 26 24 22 SO_act [mm] DipR [mo
Page 185 and 186: 22 20 18 SO_act [mm] DipR [ohm/100]
Page 187 and 188: !: 30 25 20t 10 5-- 0 Dip Transfer
Page 189 and 190: 0.430- - 0.380- - :r 0.330 fPR L- 0
Page 191 and 192:
7.2 Tests with varying stand-off an
Page 193 and 194:
Table 7.3 - Bead geometry along the
Page 195 and 196:
ö a2 ., u" u,.., g .,. aucyuaac VI
Page 197 and 198:
0 24-- 22-- 18 210 1 90 0 v 170 mm
Page 199 and 200:
Q 34 32 3o mIm Viewing direction Fl
Page 201 and 202:
ýa 34 mm JO a .. ý nn ýr "u 00 M
Page 203 and 204:
22 20 18 Viewing direction Flange W
Page 205 and 206:
36 33 31 o 29 t 350 310 o 290 U due
Page 207 and 208:
I C, x -i 23 21 j 19 Q 240c WFS =10
Page 209 and 210:
en 34 32 - vsec 30- 26- 24 + .. ++
Page 211 and 212:
186
Page 213 and 214:
" to design and build the hardware
Page 215 and 216:
Although only linear joints were im
Page 217 and 218:
for predicting possibility of bad a
Page 219 and 220:
8.4 Process monitoring and control
Page 221 and 222:
satisfy the required quality criter
Page 223 and 224:
198
Page 225 and 226:
types of joints and multi-pass weld
Page 227 and 228:
[14] NEMCHINSKY, V. A. The effect o
Page 229 and 230:
[38] D1LTHEY, U. , REICHELL, T. , S
Page 231 and 232:
[64] KING, F-J. and HIRSCH, P. Seam
Page 233 and 234:
[86] CARGNELLI, M. and ROGOWSKI, A.
Page 235 and 236:
[109] KURKIN, N. S. and DRIKKER, V.
Page 237 and 238:
[130] USHIO, M. , LIU, W. , MAO, W.
Page 239 and 240:
[151] DAVIS, A. R. Orr-line gap det
Page 241 and 242:
[177] COOK, G. E. Feedback and adap
Page 243 and 244:
[201] WON, Y. J. and CHO, H. S. A f
Page 245 and 246:
220
Page 247 and 248:
222
Page 249 and 250:
wnum: local variable which defines
Page 251 and 252:
Table A. 1 - continuation List item
Page 253 and 254:
Imean = a2 + b2*WFS + c2*SO + d2*SO
Page 255 and 256:
TCP2 number are also defined. The o
Page 257 and 258:
f ROBSET. DAT: This file is created
Page 259 and 260:
Figure C. 3 - Main dialogue box of
Page 261 and 262:
Choose the set of welding parameter
Page 263 and 264:
Water Cooling optic fibre bundle 0
Page 265 and 266:
Figure E. 1 - Main graphical screen
Page 267 and 268:
242
Page 269 and 270:
Table G. 2 - Interface box external
Page 271 and 272:
Robot ii Controller +24W CO . +24Vd
Page 273 and 274:
248
Page 275 and 276:
Table 1.1 - continuation Run Vpk M
Page 277 and 278:
10- y =0.001ac 0 r. dSO [mm] $0 '10
Page 279 and 280:
5.00- 0.00 y=0.0019x 1000 1500 2000
Page 281 and 282:
Table J. 7 - Welding data collected
Page 283 and 284:
Table J. 10 - Welding data collecte
Page 285 and 286:
Page 287 and 288:
20.00- 15. M y=0.0047x - 1.7922 10.
Page 289 and 290:
Page 291 and 292:
266
Page 293 and 294:
Table K. 1- continuation Set-up par
Page 295 and 296:
Table K. 1 - continuation Set-up pa
Page 297 and 298:
Table K. 2 - continuation Set up pa
Page 299 and 300:
Table K. 2 - Continuation Set-up pa
Page 301 and 302:
Table K. 3 - Continuation Set-up pa
Page 303:
Table K. 3 - Continuation Setup par
show all

LIBRARY ı6ıul 0) - Cranfield University

Create successful ePaper yourself

Delete template?

Save as template?