WPE 3 Robot Welding of an Excavator Boom Valeriy Gornyakov c111434

UNIVERSITY

Cranfield

MSc in Welding Engineering 2008-9 WPE3

Robot Welding of an Excavator Boom

Valeriy Gornyakov c111434 2/6/2009

Valeriy Gornyakov c111434 Assignment: “Robot Welding of an Excavator Boom”

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Table of Contents 1 Introduction and objectives .................................................................................................................. 3

2 Literature review ................................................................................................................................... 3

2.1 Robotic Systems ............................................................................................................................ 3

2.2 Seam tracking sensors ................................................................................................................... 5

2.3 MAG Fillet Welding ....................................................................................................................... 5

2.4 Costing of robots welding ............................................................................................................. 6

3 Welding Trials ........................................................................................................................................ 7

3.1 Equipment and experimental method of welding trials ............................................................... 7

3.2 Results of welding trials ................................................................................................................ 8

4 Design of robot welding system ............................................................................................................ 8

5 Time Cycles .......................................................................................................................................... 10

5.1 Loading/Offloading and Tacking /Welding of Excavator Boom .................................................. 10

5.2 Repairs and data acquisition. ...................................................................................................... 11

6 Cost Justification. ................................................................................................................................ 11

7 Conclusions ......................................................................................................................................... 12

8 References ........................................................................................................................................... 13


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1 Introduction and objectives Robotic systems take one of the leading roles in modern automate industry. Robots make all routine work which human made in past, job which human cannot performs cause of harmful environment or lack of accessibility. Introduction of robots is cost effective way to improve productivity. Large amount of robotic systems use for welding applications in modern automate industry. Arc welding robots utilized in branches of industry which require high speed of welding, repeatability and low cost of welding operations. Objectives of this work are to design complete robot welding system for production of excavator booms, determine manufacturing cost per part (include labor, facility, overhead costs, consumables cost and etc).

2 Literature review

2.1 Robotic systems First time word robot was used by Czech author Karel Capek in his play Rossum’s Universal Robots at 1920. The word “robota” in Czech has simple meaning “work”. Instead of such practical beginnings, science fiction writers and early movies have given us a romantic and unrealistic impression of robots. Consequently, in the 60s of last century robots had fantastic promises for improbable change industry in short period. In fact, many of the more unrealistic anticipation from robots have failed to realize. But, through good design practices and endeavour attention to detail, engineers have successfully applied robotic systems to different industrial branches, where the work environment is predetermined or predictable. In present moment, by developments in computer’s technologies and artificial intelligence techniques we are ready to achieve scientific breakthrough in robotics, which will allow some levels of autonomy in unpredictable environments (Lewis and Fitzgerald, 1999). In a practice, robots are outstanding from other electromechanical motion equipment by their dexterous manipulation capability. Robots can work, reposition, and move tools and other items with far greater dexterity than other equipment found in industry (Lewis and Fitzgerald, 1999). Robotic manipulators can be divided in categories by kinematic configuration. Most of the commercial industrial robots are serial link manipulators with maximum six kinematically coupled axes of motion (Lewis and Fitzgerald, 1999). Common types of commercial robots configuration are: Articulated, Type 1 SCARA, Type 2 SCARA and Cartesian Figure 1.

Figure 1 (Fitzgerald, 1999)

Articulated robots. Many commercial types of articulated robots are available in market. Most of them have six axes, all axes are revolute. Firs axe is base, the second and third axes are parallel and work together to produce motion in a vertical plane. This type of robot is flexible, dexterous. Applications for


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articulated robots are work in spot welding, spray painting, material handling, and arc welding. It is most widely used type of robot in industry (Fitzgerald, 1999).

Type I SCARA robots. The Type I SCARA (selectively compliant assembly robot arm) has two resolute joints to provide motion in horizontal plane. Seldom found with number of axis more than four. This type of robots widely use for work which requires quick and precise motions, such as electronic parts assemblies (Fitzgerald, 1999).

Type II SCARA robots. Type II SCARA robots have same four axes design as SCARA I, but first axis is a long, vertical, prismatic Z movement which lifts the two parallel rotatable axes and their links. Compare to SCARA I this type of robots have higher lifting capacity and over longer distances. Application for these robots is large mechanical assembly, palletizing packaging, and other heavy material handling (Fitzgerald, 1999).

Cartesian robots. Cartesian coordinate robots rectangular prismatic axes, referred to as X, Y, and Z, to move their tool or payload through their rectangular workspace. Commercially available different sizes cartesian robots, from few cubic centimeters to thousands of cubic meters. Payload can exceed several hundred kilos. Gantry robots are most common type of Cartesian robots. Gantry robots have huge capacity and high accuracy (Fitzgerald, 1999).

Programming of robots can be performed with 3 ways.

1. Offline programming. 2. Teaching mode. 3. Combined mode.

Most productive way is offline programming. Programs are prepared without delays of robot operation, reduction of robot system down time, increase in productivity, and flexibility (Carvalho and Siqueira, 1998).

Some of the main characteristic of robots listed below.

Reach can be determine by measuring the radius of the space described by the robot motion and dexterity by the angular displacement of the individual joints. Horizontal reach, measured radially out from the center of rotation of the base axis to the furthest point of reach in the horizontal plane, is usually specified in robot technical descriptions (Fitzgerald, 1999). Payload weight is specified value by the manufacturer for all industrial robots. Some manufacturers also specify inertial loading for rotational wrist axes. It is common for the value of payload to be established for high speed and reach conditions. Limits of Load have to be examined for each single application, if the robot will lift and move payload larger-than-specified then reach and speed are reduced. Total payload should be calculated as weight of inertia, of all tooling, work pieces, cables, and hoses (Fitzgerald, 1999). Quickness is difficult to identify by using manufacturers specifications. Manufacturers will specify a maximum speed one of single joints or for a specific kinematic tool point (Fitzgerald, 1999). Precision can be defined by measuring repeatability. Theoretically all robot manufacturers specify static position repeatability. On practice, tool point repeatability is given, but in some cases repeatability will be provided for each individual axis. (Fitzgerald, 1999) Accuracy assessment of the modern industrial robot has been performed by Ken Young and Craig G. Pickin. They have made experimental measurements repeatability of Cloos Romat 310, The ABB IRB 6400S, and the KUKA KR125 robots. For Cloos Romat 310 robot errors for X,Y axes are within an error band of 1.7mm, but for one side of the measured envelope this error is within a 0.5mm error band. Most accurate is ABB IRB 6400 robot, which showed accuracy in the X,Y axes locates within an error band of 0.5mm. KUKA KR125 robot has accuracy in the Y axes is within an error band of 1.8mm, for X axes a bit smaller and lies within a band of 0.8mm


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(Young and Pickin 2000). For some precise applications such as, resistance and arc welding, such low values of accuracy will be insufficient. To compensate motion errors of welding robots it is necessary to use seam tracking sensors. Other reason of using seam tacking sensors in MIG/MAG welding is distortion of the welded part from high heat (Ryuh and Pennock 2006).

2.2 Seam tracking sensors Sensors can be categorized by principles of sensing. Most of seam tracking sensors mounted close to welding torch and detecting position of robot arm relative to seam location. Most of seam tracking sensors can be subdivided on electromagnetic, arc sensors, mechanical and optical devices. Electromagnetic sensors based on principles of high frequency transformer. Electromagnetic sensors useful for butt welds, lap welds and T joints, but this type of sensors large, not flexible, sensitive to magnetic interference with arc and assembly accuracy. Arc tracking sensors were used in industry last 30 years. They have some advantages compare with mentioned attached sensors: Detection point at the end welding wire (no distance between sensor and torch), good accessibility, low cost, durable system. Principals of operation based on variation of welding current during arc oscillation across the groove. The probe of mechanical seam tracking sensor slips in grove and detects deviation of torch from proper position in groove. Micro switch detects direction of deviation. Advantages of mechanical contact sensors are simplicity and low cost, that’s why they are so widely use in industry at present moment. Disadvantages are that sensors are only employed to welds which have grooves, strait first root pass welds or T joints. As well mechanical contact sensors require different probes for different grove shapes, probes deform, wear. Tack welds in joint makes impossible to use mechanical contact sensors. Mechanical sensors are not applicable for high speed welding. Optical sensors have been intensive developed in last decade. Many different mode of operation can be obtained by using optical sensors. For example relative position of torch, shape of groove, arc molten pool penetration etc. Optical sensors can be subdivided to several categories: Single spot light sensor, linear light sensor, scanning light sensor, CCD image sensor. Photo electronic sensor used in single spot light sensor for groove detection, laser spot source can be used as well. Linear light sensor. Light line projected to work piece, CCD camera receive reflected light and processed by controller to locate center and width of groove. Scanning light sensor. Laser beam scans over groove, CCD camera receive reflected light and processed by controller to locate center and width of the groove. CCD image sensor observes tip to work distance, center of groove, and molten pool. Image processed by modern sophisticated software to locate center, width of groove and other parameters. Optical sensors have high precision and repeatability. Disadvantages are high capital cost, sophisticated and expensive software, distance between torch and sensor creates extra errors, limited accessibility of torch sensor system. Due to disadvantages they are not highly utilized in industry (Pan 2000).

Development of Ultrasonic seam tracking sensor was reported by Ajay Mahajan and Fernando Figueroa ( Mahajan and Figueroa 1997).

2.3 MAG fillet welding Gas metal arc welding was first time developed in 20th for welding aluminium parts of planes.

Equipment is either automatic or semiautomatic. Variations of process are MIG and MAG. MAG

characterize by addition active gases, such as oxygen in shielding gas. Equipment requirements are wire

feed unit, torch assembly, CV power supply, cylinder of shielding gas. Process can be utilized for welding

majority of metals (MIG/MAG Welding Guide, 1997).

Development work was conducted by Karadeniz, Ozsarac, and Yildiz to determine influence of welding

parameters (voltage, current, travel speed) on depth of penetration (wire electrode 1.0 mm). Was

reported that depth of penetration increases linearly with increasing welding current between 95 and

115 A and the average penetration increase was measured 0.0225 mm for each 1 A current growth.


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Voltage as well increases penetration by 0.02–0.12 mm for 22–26 V accordingly. Deepest penetration

was achieved when travel speed was 0.6 meters per minute. Optimum welding parameters to get

appropriate penetration and weld joint 105 A–24 V 80 cm/min (Karadeniz and Ozsarac, 2005).

High speed MAG welding of fillet welds was reported by Seigo Nishikawa. Maximum speed achieved

during experiments was 4 meters per minute. Such high results were achieved cause use 1,2 mm wire

electrode, high values of current 500A and voltage 34V, shortened arc, high speed robot’s control

system and high accuracy stick out control (Nishikawa, 1999).

2.4 Costing of robots welding Cost of robot welding includes (Weston, 2008):

1. Labor cost

2. Cost of facility rent

3. Amortized capital cost (Calculate annually as 20% of equipment capital cost)

4. Cost of welding consumables (shielding gas, wire electrode, other equipment consumables)

5. Service cost

6. Overhead cost.

Development work of robots welding cost estimation was performed by Verhaeghe and Weston. Report

includes cost comparison manual welding operation with robotic welding operations. (Verhaeghe and

Weston 2001) Figure 2

Figure 2 (Verhaeghe and Weston 2001)


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3 Welding trials

3.1 Equipment and experimental method of welding trials Objective of welding trials is to achieve maximum possible travel speed during welding of T joint (parts

of excavator boom). Quality requirements are 4 mm leg length fillet weld, concavity less than 1.6 mm

profile without undercut, lack of fusion, cracks, skips or humping (single poses less than 2mm

acceptable). GMAW process was used. For experiments,

as base metal, been used 6mm mild steel plates. Plates

been positioned in T joint. Filler wire was used 1.0 mm

EN 440G3SI1 AUTAL GOLDMATIC. GMAW welding were

performed with ESAB Aristo LUD 450 automatic wire

feeder and inverter with current capacity 0-450A and

voltage capacity 036.5V, OCV voltage is 65-80V. For

movement of welding torch seamer device was used.

Stick out was fixed to 14 mm. Constant parameters

during experiments was base metal thickness 6mm, filler

wire diameter 1.0 mm, shielding gas composition 2% O2,

8% CO2, 90% Argon, stick out 14 mm. Variable

parameters was voltage in volts, current in amperes,

travel speed in meters per minute, wire feed speed in meters per minute, torch angle in degrees.

Welding current was read from ESAB inverter’s pendant. 10 welds were produced. Weld were visually

inspected, throat thickness of fillet welds were measured by gauge. See Figure 3. All variable

parameters were combined in Table 1. After completion 6 welds were cut perpendicular by saw. Cut

surfaces were polished by sand paper grades 240, 320, 600, and 1200. Degreased and etched in 2% Nitol

solution till development of microstructure. Macros were observed and pictured by zoom optical

microscope. Penetration, horizontal leg length, vertical leg length, throat thickness, convexity/concavity,

undercut was measured from pictures by specialized software.

Sample Number

Voltage Volt

Amperage Amp

Travel Speed m/min

Wire feed speed m/min

Torch Angle Deg

Leg Length mm

Profile Undercut Appearance

1 20.8 175 0.4* 6.4 0 4.1 Slight convex

No Good

2 21,7 225 0.6* 9.6 0 4.24 Slight convex

No Good

3 23 290 0.9* 14.4 0 4.38 Slight convex

No Good

4 24 337 1.2* 19.2 0 4.1 Highly convex

No Bad

5 25.5 344 1.2* 19.2 0 4.38 Highly convex

No Bad

6 23 285 0.9* 14.4 8 Lead 4.38 Highly convex

No Bad

7 23 234 0.9* 12.4 8 Lead 4.24 Convex No Good

8 23 244 1.0* 12.4 8 Lead 3.95 Flat No Good

9 23 247 1.0* 12.4 8 Lead 3.95 Flat No Good

10 23 245 1.0* 12.4 8 Lead 3.95 Flat No Good

Table 1

*Seamer device was not calibrated during welding trials. Values of travel speed could be lower than

showed in Table 1.

Figure 3


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3.2 Results of welding trials Totally 10 weld were produced with different parameters, throat thickness, leg length, convexity and

undercut of 6 welds were measured. All measured values presented in Table 2. Highest speed (1.2

meters per minute) was achieved during welding of Sample 5, but appearance of weld was bad, profile

convex. Best ratio between quality of weld and travel speed was achieved during welding of Sample 8,

good appearance, flat profile, no undercut and relatively high travel speed (1.0 meters per minute).

Samples 9 and 10 were welded to proof repeatability of achieved results.

Sample number Horizontal Leg Length mm

Vertical Leg Length mm

Throat Thickness mm

Convexity Undercut

1 4,64 5,75 3,64 0,40 None

2 4,69 5,21 3,76 0,69 None

3 4,14 4,47 5,15 1,16 None

4 3,86 3,12 4,28 2,46 None

5 3,54 5,06 6,08 1.80 None

6 5,66 2,15 4,19 1,85 None

Table 2

Figure 4 Figure 5

Highest penetration (throat thickness 6,08mm) was archived during welding of Sample 5

Figure 5.Highest voltage (25, 5 volts), wire speed (19, 2 meters per minute) and highest current as well

(current function of wire speed in GMAW) was used to produce sample 5.

4 Design of robot welding system Reputable companies have sizeable experience in designing of robot cells. This is allowing them to use

full performance capabilities of equipment. (Verhaeghe and Weston, 2001).For this assignment Flex

Arc® 250K Robot Cell of ABB Company was selected

Figure 6. A FlexArc robotic welding cell contains

complete robot systems, which can have several

flexible and versatile, standard modular packages.

Installation of robot welding system takes minimum

time and decrease installation cost. Layout of robot

cell showed on below. Major components of system is

robot- IRB 2400L, integrated IRBP 250K servo

positioner, jigs installed on IRB 250K servo positioner,

perimeter guarding which complies with ANSI/RIA

15.06/1999, man/machine (HMI) Interface,

Figure 6


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Figure 7

welding power supply, robotic welding torch, robotic torch cleaner/dresser, metal mounting base

(transportable with fork lift pockets), operator present sensing device, cables are completely integrated

into the base of the cell, cell door interlock device.

Industrial Robot IRB 2400 has 6 axes of freedom and optimized for arc welding. Robot’s characteristics-

7 kilos handling capacity and 1.8 meters reach, which enough to carry MIG torch and reach finite points

of excavator boom (1.4 meters).

IRB 250K positioner designed to work in two stations

loading/unloading and welding -and where the work piece has to

be rotated about one axis.

Dynamic control of the rotating work piece permits rapid

acceleration and high speed movements to reduce welding times

and to meet tough reorientation requirements. The arrangement

allows the operators to perform all loading and unloading

operations in ergonomic manner. As well the operator is shielded

from the welding process and robot’s motion.

Jigs designed to provide high accuracy clamping non welded components of excavator boom. Jigs have

pneumatic actuators to increase clamping strength and speed.

Man/machine (HMI) Interface provides programming of Flex Arc® 250K Robot Cell. System based on

modern IRC5 controller and robot teach pendant unit- FlexPendant®. Controller supports RAPID

programming language and can be off-line programmed by ABB Robot Studio software.

Advanced Weld Control AWC (seam tracking system). The system gives tracking functionality of the path

and adjusting the robot to the actual path location. The AWC measures current and voltage of the arc

and sends path corrections to the robot. Welding of excavator boom requires seam tracking system

cause: 1. to compensate motion errors of robot (repeatability) 2.to compensate distortion caused by

high heat from welding.

Figure 9

Figure 8


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Welding power supply is ABB RPB 420. Characteristics of power supply are voltage range 10 -41V,

current range 10 -420 Amperes, duty cycle 440 A / 37.6 V at 100 %, OCV 65 V. Power supply integrated

with robot cell control system. Programming of the welding parameters is performed from the robot

teach pendant unit. This includes all welding parameters such as voltage; wire feed speed and crater fill

data.

Robotic welding torch is ABB PKI. Current capacity is 400 A. Water-cooling system keeps low the

temperature of the gas nozzle, result is high duty cycle, less spatter collecting on the nozzle surface.

Wire feed system ABB A314E/324E-L integrated with robot, mounted on the upper arm of the robot,

which creates only a short distance between the wire feeder and the welding gun, a necessity for stable

wire feeding. Wire feed speed range 0.5 – 30 m/min, supported wire diameters (standard) 1.0, 1.2 mm.

Robotic torch cleaner/ dresser ABB TCS contains wire cutter, spray unit and air circuit for nozzle

cleaning, TCP gauging unit for automatic calibration of the robot.

Operator present sensing device stops movement of the robot and servo positioner, when operator’s

presence detected.

For offloading of welded parts overhead hoist installed over loading/unloading station of robot cell

(complete excavator boom weight approximately 60 kilograms and every part 15 kilograms)

5 Time cycles

5.1 Loading/offloading and tacking /welding of excavator boom

1. Parts for excavator boom cut with CNC plasma cutter. CNC plasma allows creating high accuracy

cuts with good appearance of the edges. (Background action)

2. Parts palletize and deliver to work cell. (Background action)

3. Two workers manually (every part 15 kilograms only) load 4 parts of excavator boom in jigs,

installed on positioner, activate pneumatic clamping actuators. Time to perform 7 minutes.

4. Positioner turns assembled and jigged excavator boom to robot side of robot work cell. Time to

perform 15 seconds.

5. Welding robot performs tacking of assembled excavator boom. Tacking required for preventing

heat distortion during welding process. Robot’s arm reach is 1.8 meters. It is allows

tacking/welding of rear side excavator boom without turning part in rotating table of positioner.

After completion tacking of front and rear sides, positioned turns boom and tacking commence

on other side of boom. Tacking/welding sequence showed on Figure 10 (cross section of

excavator boom). Time to perform 1 minute.

4 3

Stage 1 Tacking/welding rear and front side

1 2

Stage 2 Turning in rotating table of positioner Stage 3 Tacking/welding rear and front side

Figure 10


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6. Welding robot performs welding of assembled excavator boom. Robot’s arm has reach 1.8

meters. It is allows welding of rear side excavator boom without turning part in rotating table of

positioner. After completion welding of front and rear sides, positioned turns boom and welding

commence on other side of boom. Tacking/welding sequence showed on Figure 10 (cross

section of excavator boom). 8 meters of weld seam perform with speed 1 meter per minute, so

complete welding time 8 minutes. Time to perform 10 minute (includes turning of rotating

table, robot movements, etc).

7. Positioner turns welded excavator boom to loading/unloading station of robot cell. At same

time assembled and jigged excavator boom turns to robot side of robot work cell and

tacking/welding commence. Time to perform 15 seconds.

8. Visual inspection by repair welder of welded excavator boom. Time to perform 1 minute. 9. Workers unclamp welded excavator boom and offload by using overhead hoist. Time to

perform 6 minutes. 10. Welded excavator boom stores in storing area. (Background action).

Complete welding cycle of excavator boom is 15 minutes (includes loading/offloading). Production of booms based on two 8 hours shifts, 6 days per week (7th day use for maintenance of robotic and welding equipment). Facility can produce 384 excavator booms per week.

5.2 Repairs and data acquisition. If repairing welder detects unacceptable imperfection (lack of fusion, undercut, convex profile,

undesirable leg length, porosity), imperfect part of seam manually grind off. Repair can be performed by

two ways.

1. Repairing by semiautomatic manual MIG welding process. Action performs away from robot

cell, which saves production time of robot cell.

2. After grinding positioner turns defected part to robot side, repair welder in manual mode

positions robotic torch on imperfect area, performs repairing weld. Action performs in robot

cell, which increase quality of repair. Repair by robot impossible in cases as undercut. Such cases

require experience and skill of repair welder.

Data acquisition for every single weld can be performed by robot’s cell controller. Data summarize and

collect by Client daily.

6 Cost justification. Cost of welding boom consists labor cost, cost of facility rent, amortized capital cost, cost of

consumables, service cost and other overhead cost.

Labor cost. Labor requirements (per 8 hours shift) for production of excavator booms are

1. Two workers for loading /offloading excavator boom in robot cell. Unqualified workforce £48

each person. (Weston, 2008)

2. Repair welder/inspector £56. (Weston, 2008)

3. Technician £64. (Weston, 2008)

4. Welding supervision £64. (Weston, 2008)


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Overall labor cost per 8 hours shift is £280. Robot work cell production rate per shift is 32 booms; labor

cost for production of 1 boom is £8, 75.

Cost of facility rent.

Amortized capital cost. Capital cost of equipment is cost of

1. Robot system £k 90. (Weston, 2008)

2. Welding equipment £k 18. (Weston, 2008)

3. Seam tracking system £k 18. (Weston, 2008)

4. Positioner £k 15. (Weston, 2008)

5. Safety guarding £k 8. (Weston, 2008)

6. Offline programming software/system £k 25. (Weston, 2008)

7. Jigs £k 15. (Weston, 2008)

Total capital cost of equipment is £k 189. Amortization is 20% annually or £k 37, 8 annually, £ 151 daily

(250 working days per year). Production rate per day is 64 booms; amortization per boom is £ 2, 35.

Cost of consumables. Consumables for MAG welding are

1. 1.0 mm EN 440G3SI1 wire electrode- £ 2, 5 per kilogram (Purchasing department of JRAY

McDermott company).

2. Shielding gas 2% O2, 8% CO2, and 90% Argon -£ 4.8 per cubic meter (Purchasing department of

JRAY McDermott company).

8 meters of fillet welding seam (4mm leg length) requires 505 grams (steel density 7,9

gram/centimeters3 ) of wire electrode or £1,25 per boom. Let assume gas flow 45 liters per minute. 9

minutes of welding and tacking requires 405 liters of gas or £ 1, 92 per boom. Cost of welding

consumables per boom is £ 3, 17.

Annual service cost is £k 6 or per boom £ 0, 375 (250 working days per year). (Weston 2008, Verhaeghe

2001)

Annual variable overhead cost is £k 11, 5, per boom £0.718. (Weston 2008)

Based on aforesaid, production cost of one excavator boom is £15, 363.

7 Conclusions

1. 10 welding trials of performed. Maximum determined travel speed is 1, 0 meters per minute

Samples 8, 9 and 10 (soundness of welding seam meet quality requirements). Highest

penetration 6, 08 mm achieved on Sample 5.

2. Robot work cell was designed. Design of robot cell based on Flex Arc® 250K Robot Cell of ABB

Company. Welding equipment recommended inverter ABB RPB 420, welding torch is ABB PKI,

and wire feed system ABB A314E/324E-L. Necessity of using Seam tracking system was

determined.

3. Production time cycles, labor requirements was determined. Two 8 hours work shifts was

recommended.


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4. Final production cost was justified.

8 References

1. Frank L. Lewis, John M. Fitzgerald, Ian D. Walker, Mark R. Cutkosky and et. al. (1999),

Mechanical Engineering Handbook, CRC Press LLC, Boca Raton.

2. John M. Fitzgerald (1999), “Commercial Robot Manipulators”, in: Frank L. Lewis, John M.

Fitzgerald, Ian D. Walker, Mark R. Cutkosky and et. al. (1999), Mechanical Engineering

Handbook, CRC Press LLC, Boca Raton. p. 14-3 – 14-14

3. G.C. Carvalho, M.L. Siqueira, S.C. Absi-Alfaroet. et. al. (1998), “Off-line programming of flexible

welding manufacturing cells”, Journal of Materials Processing Technology, Vol. 78, p. 24–28

4. K.Young, C. G. Pickin (2000),” Accuracy assessment of the modern industrial robot”, Industrial

Robot: An International Journal, Vol 27, No.6, p. 427-436

5. B. Ryuh, G. R. Pennock (2006), “Arc Welding Robot Automation Systems”, in: Edited by: Low Kin

Huat (2006), Industrial Robotics - Programming, Simulation and Applications, ARS, Germany, p

596-603

6. J.Pan (2000), Arc Welding Control, Woodhead Publishing Ltd, Abington

7. A. Mahajan, F. Figueroa (1997), “Intelligent seam tracking using ultrasonic sensors for robotic

welding”, Robotica, Vol 15, p. 275 – 281

8. B. Alshuller, P. Pollak, P.B. Dickerson, F. Armao, E. R. Pickering (1997), MIG/MAG Welding

Guide,(3rd edition).

9. E. Karadeniz, U. Ozsarac, C. Yildiz (2007),” The effect of process parameters on penetration in gas metal arc welding processes”, Materials and Design, Vol. 28, p.649–656

10. S. Nishikawa (1999), “High speed arc welding”, Industrial Robot: An International Journal, Vol. 26, No. 5 , p. 371-376

11. J. Weston (2008), Robot welding systems-an approach to cost justification, TWI,UK. 12. G. Verhagae, J. Weston, N.G. Smith (2001), Consideration for robot welding cell- a guide

document, TWI, UK, Press release 12523.01/00/1074.3 13. ABB,() 14. Information received from Purchasing department of JRAY McDermott company (03/02/2009).

WPE 3 Robot Welding of an Excavator Boom Valeriy Gornyakov c111434

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