DTIC ADA429294: Real-Time Robotic Control System for Titanium Gas Metal Arc Welding

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by  Defense Technical Information Center

Geare

ReAL-Teee Roporic CoNrRo. SysteM FOR TITANIUM
(GasMersL ARC WELDING

Final Report
Option Phase
January 13, 2004-Decembsr 1, 2004
Unclassified
CDRLData Item No, 4002

APhase I SBIR Project for US. ARMY TACOM-ARDIIC

Contract Na WESQKN-14-C-1082
‘Creare Projact 744

Robert Kline-Schoder Wroject Dizoctor
‘Nabil Elkoub. -Projcct Engineer

Diseahmer

“This rezort wns propored by Caesre Inc for US: Army TACOM ARDECicaony Arsral. Neither ieare 20r
‘ny pet avtne omit bch als any waaay Ge fereastaron, express or ple we avuie> any Joga
Tiebity ne reponstliy er tke acces, wanglteaes, or yeas of Ms infarction, apps, eu OF
‘ieee med in Ci open. Nor ix any reprcenttion coe ot ewe of he Interac, appara, method
‘proses nlosd inthis report my mt binge pre-owned ih,

‘esate ansumes mii with respect Lo tbe ave ul ur Fur Uaages vosulng tom te use of ay inkoemaion,
ppt tor poe dlcaed iis repo.

Disrbation Si lerent A: Agqwnyed fe public reas: dsb is uniui

SIR DATA KIGLIS

(Conia Nos WISQION-O4-C-1082
(Contactor Nar” Core Enceepimtel

‘ule 16 Great Hillow Road, P.O. Box TL, Hanover, KIL O31SS
Bepiraton of SBIR Data Rights Period: 12 July 2008

‘The Govermentsrighs to me, modi, oproducs. eens, prfonn, splay, wr Uelne technical deta or compute
sifhwats eared ita Gi legend ae estite donng Ihe pied choo as provided in pargpaph (KS) oF Be
igh tn Noncoouoeciil Tec! Dats ae Comper Sefeware— Smal Tsiness Innovate Research (SBI)
Praga cane consi the above dein! cre. Ne tesbctons apply ale te expan Oats eho
hove. Any repoicion of nal dia, couptcersohwze, o prs (heat mavksd wth tis legend cust
alas rooducs De mgs

‘Creare Invorporuted Fanuary 14, 2005

“20050119 048
Geare

Finl Repwut
Oplian Phase

‘Beat -Tiont Rozos1e CONTROL S¥STEM
vow THANIEM Gas Mirra, ARC WELDING

TM-24074—Deceanber 2004
Greare seats

TABLE OF CONTENTS.

SIGNIFICANCE OF THE PRORIL
PITASE.F PROJECT RESULT:
4.1 Ovmesitanpwane Desien,
4.2. WELD FOOL TEMPERATURE SENSOR,
43. WELD POWER SUPELY vn annnsni
5 CONCLUSIONS.

LIST OF FIGURES

Figure |. Conceptual Implementation of Creare's Reat-Time Roboue Control System for

Titanium Gas Metal Are Welding, a
Figure 2. Drawing of Overall GMAW System Hardware “6
Figure 3. Picture of Infrared Temperature Senso. 4
Five 4. 10 Ti Meesutement of Lamp Bulb Temperature, ‘emprave Variations Are
Likely Due oo Lamp Metioa, . 8
Figure 5. Block Diagrara of Real-Time Fl 2
Figure 6. a) Photo of Pulsed GMAW Power Supply. (2) Wavelurm Tsed to Affect
. 10

Prper Transfer During the Pulsed GMAW,
REPORT DOCUMENTATION PAGE Tam Raed
OMB No, C7018

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1 AGENT OBER oben) ERERORTRTE REPORT TY 0 On eS COVERED

OIbECO OFR 13TAN04-01DEC4
1 TE MOSETTTE 7 © FURR HOES
Real-Time Robotic Control System for Titanium Ges Metal Are Welding

WISQRN-04.

Tarr -
Robert Kline-Schoder
1 EN ORAS AND REESE 7 ERRNO ORT
Creare Ineosporated ePoRr waveen
P.O. Bor 71, 16 Great Hollow Road TA-2OTA
Hanover, NH 03755
TSR STRTOONTORNG AGENCY WINE HOOPER E ERRSANSNOMTOT
U.S, Army TACOM-ARDEC EADY REPORT HOMBER

AMSTA-CM-CPB, Bldg. 9
Picatiany Arsenal, NJ 07806

1. SUPPLENERTARY ROTES

Te, SU VALABTY STEEN DETROUTION OE
Approved for public release; distibucion is unlimited, a

TE ABSTRACT wT
“Titanium addresses the Aumy's need for high sttength-Wo-veighl characteristics amd can mect the

perfornunce and transpovtability eequitements of future lightweight systems. ‘There arc initiatives to develop

To-coit titacium materials supplies; however, low-covt and high-rate abrication processes are sovely lacking.

‘Welding and joining technologies enable improved mannfuctored components hy reducing the weight,
production time, and cost of joining pans. Improved welding technology increases product lifetimes and makes
possible the fabrication of large souctures, Gas Motal Are Welding (GMAW) has the potential to significantly
Smprove the quality, speed, anc penctration depth of fuaniuen welds, while reducing the cost per part. However,
this eesult can only be achieved if proper weld perumeters ae selected and dynamicully maintained during the
welding process dic to the nature of uitanium.

‘During this Phase I SBIR project, we have sucorssfully demonstrated the feasibility of our innovation
hy determining the eequitemonts for tho system for bolh Army and commercial applications, designing,
Fabricating, and testing one of the key tensors used in the adaptive control system; determining the hardware
necessary to-adoquetely meusure the weld temperature for cantral usc; and designing a prototype contol system
for Ti GMA Who be fabrivaled and tested duting the Pase I project.

TREES TS NET OFFS
i)
‘Titanium, welding, control, FCS, robot
‘RPE CODE
SECURITY CCRSEEATON | 18 SEELATTY CESIONTN RECUR CI ASSENTON |B LATTA GF ASTRA
‘OF REPCAT OPTS PASE oe AESTRACT
Unclassified Unclassified Unclassified

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1 TYTRODUCTION

‘This is the final \echnical vepoa for che Option Phase of Phase 1 SBIR projoct that is
being pertormed hy Creare Inc. for the (LS, Army TACOM-ARDEC. It covers ti time perind
between August 1, 2004 and Decombsr J, 2004. The specific aim of this overall project is ro
develop a Real-Tim Robotie Congo! Syster for ‘Disnium (Ti) Gax Metal Ate Welding
(GMAW) for current and falure Army and ecmmercial applications. GMAW is a paniculesly
anractive welding process for Ti becansc of its potential for high deposition rate, deejy
penetration, and low cost, We are working t» uchieve aur objective by developing an integrated
system thot will measure characterislicx of The weld, the are, and the metal transfer mechanism
‘and use these data to ajos! the weld curcent, voliaze, aud speed, Our system will make uss of
both oxisting well hardware, new instrumentation, «nd computational algorithms to enable a
significnn. improvement inthe ability ro wotd Ti

2 PROJECT SUMMARY

‘The Need. Joint Vision 2020 advocates for the develupment of flexible, effoative, and
efficient malti-dimensivnal forces capable of rapidly projecting overwhelming military eambat
over anywhere in the world. AS part of this vision, the largest vehicles must be lighter than
‘surrent mechanized systems with cach ayslem possessing common or multi-fonctions!
characteristics and capabilities, Thus, weight reduction is of primary importance to moe! the
operational objcatives, Low-cuil sourees of titanium (15) are becoming availible and as a
‘result, iis boing employed in these and otter systems to reduce weight signifivanily and enhanoe
convsion resistance. However, low~or! manufacturing technologies for Ti have wot kept pice
wilh Ihe demand for high produciien vale und low cost. Most Ti alloys can be welded with
Iypieat ete welding processes. Hhnvever, io eousisceutly achieve high weld quality requires a
proper gas mixturashield, adjument of che weld parumeters, and, potentially, guidance for the
wold are that wan wander substantially during the weldiag of tinium. Without substantial
improvements to achieve a viable high-rate welding process, de henefits of itanium structures,
companents, and weapons will no be realized.

Creme's Innovation. The averall abjestive of dvs project is tw develop 2 Real-Time
Robotic Control Syslem far Titanium Ges Moul Auc Welding (GMAW) (also known as Metal
Inori Grs, of MIG Welding), for current and future Army und commercial applications. Palsed
GMAW. in particular, is an wlractive welding process for Ti because ofits potential for high
depesition rate, deep peretraion, and better control of droplet formation, transfer, and doposition
renting in low fabrication cost, Pulsed CMANW welding of titanium is nor cunently a stondord
Drictice, but hes been shown ua have great promise by Ihe Army. Hor example, ARDEC hus
Successtlly fabticated titanium prototype reccivers im support of the M240 Machine Gun
Ligtivcight Initiwsive, the uppor hull for 4 Composite Armored Vehicle (CAV) Integrated
Hybrid Structare (LHS), and un all Gtonium martar baseplate for che U.S. Murine Corps using
rubetic pulsed GMAW: however, before the proves can be considered for production. reu-time
contra af the process is mandatory

‘We will achieve our objective hy developing aa integrated system that will coutinuously
mesure characteristics ofthe weld, the are andl the metal transfor mechumism and use these det
to adjust the weld current, voliage, speed, and sar concentration. Our syslem, shown
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achemalically in Figute 1, will make uso of both oxisling robotic weld hardware and new
‘nstramentation and computational algorithms (o enable a significant improvement inthe ability
toweld Ti. ‘The Crearo roal-time weld vontroleystem wil integrate: (1) feedback senso sch 0s
weld width, weld tompsrature, draplet formation, detachment, and transfer, (2) adjustment of
‘weld parameters svch a eurrea, arc Tength, and tarch speed; and (3) reu-time udaptive contro!
algorithms Ural are used to make ctitical changes to the weld parameters duriug welding co
achieve high-quality welds,

Phase | Results Prove Eeanbility, During Phase f of this SBIR development project,
‘Create nas clearly demonsiited the ality of cur innovative Real-Time Rubie Control System
for Titmium GMAW. During the Phase 1 base period, we: (1) determined the requirements for
the syatern uo be of use to bork Aumy and commercial applications: (2) designod and fabricated a
resatype af one of the scusors that will be used in che adaptive contol systimm (2) used che
protatype sensor to measure the druple ormation and wansior during pulsed GMAW of steel
‘and titankum; (4) dotormined the hardware necessary to adequately meubure the weld temperate
for control uso; und (S) designed a prototype contrl system for Ti CMANW that can be fabricuted
and tested daring the Phase I projoct. During ihe Phase I option petiod, we: (1) prepared to
‘wansition the conceptual dasign inly a full edged desiga: (2) sclocteal anil ondered a weld pool
temperature sensor, (3) performed dhe layout design of the overall system: (4) selected tho
‘welding power supply uhut would meet the necds af the Phase I system; and (3) determined the
available high-meedl cameras that would be appropriate for the droplet tansfer metwurement.
During the Phase I effort, we expcet fo achiove all aif the specitications to meet the Phase lt
applications by optimizing the hirdwure design, implementing the optimized hardware design,
pevfomting open loop tosis lo verify accursey and dynamic range of the sensors, und
flemonstrating the wie of our Real-Time Robotic Control System for Titanium GMAW using a
lve pawee supply to control dropict formation on applications of interest al ARDEC.

‘The Benetits. ‘The primary boncils of Creare’s Real ‘Time Rubotic Control System for
‘Tiiasiam Gas Metal Arc Welding include: (1) high quality titniam welds tor usc in critical
Tabrication and mannfastoring processes; @) high-speed welding chat will reduce revuring
‘mannfactoring costs for ighuweight stectures; and (3) Tower fixed costs because ofthe minimal
capital equipment investment required for GMAW systems. ‘This combination of benefits will
tenuble the labseation of very lighweighl, very capable systams for use in future army systema
Commercial applications are equally mumcrous in the verospace, automotive, and eonstruction
industries. Our system lor pultod GMAW welding of Gtaoium is an cnsbling technology that
could substantially expand the demand for flanium leading to the proliferstion of titanium
swelded steactues, which will correspoad with the advent of lower eost titanium.

Commercial Potsmtal. Gur Real-Time Robulic Cantal Systema for Titanium Gas Metal
Ac Welding has tremendous commercial potential. While the cost of titenium is dropping andl
‘now tow-vost pradkction processes arc poised Lo drop the price furher, there is no vishle
high-rate joining process that will eaahle the cost-cffoctive fabrication of titanium structures,
‘Our system wil ill chat void allowing titanium to reach its marketplace potential. As such, the
proposed work is critical and has substantial eeommeccial upside,
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‘Cocaine

Figure 1. Conceptual implamantztor of Crsare's Resl-Time Robuie Control Syaters for Titanlun Gas
Hata’ aro Watding. “Our robetle GMAW contol system uses advanced instrumentation sensors (aos
backlight system for montaring crapet charactarlce and Infared terperstura eancr for neitring
weld charastelatos) 10 inploment a real-time, aceptve conlol sysiam. We wil uso these senso"
Tmeasurenents to determine optimizad welding parameters, The development of an advanced pulsed
lar lo guide the aro slee so are placement i predctable and repeatable Is to be funded under &
separate non-SEIR effort along wih a intogyation wth the congo system.

3 SIGNIFICANCE OF THE PROBLEM

Poure Army Forges Need Ta Be Lightweight, A sccemt Defense Planning Guidance
document states that the Army needs to develop an Objective Forve that is capable of operations!
rmancuvers from strategic distances; can penetrate and sustain operations in environments where
socess is denied; and he less dependent on tational vir and sea ports of entry and host nation
suppor, eeception, and infrastructure, The Army's tesponsibility to satisfy Uhis requirement
demands the development of a Future Fall spectrum forco thut will be organized, manned,
equipped, anc) injne! us he stiategically responsive, deployable, agile, versatile, lethal,
sutyivable, and sustainable accoss the cutie apcctrum of military operations.

‘Titanium Js an Iaportont Enabling Sursctural Material, ‘Ditanium and its alloys have
proven to be teclulcally suporior and cost-effective matcrials for a wide variecy of axtospece,
industial, marine, and commercial applications. ‘Titanium whireswes che Anny’s need for high
strength-to-weight characlefistics ad can mcct the performance and raneporability
requirerenta of Highoveight syerans, Tho woe of titanitin has the potential to achieve significant
reductions in the mass of systems ax compared to steel analogs. Tor example, the XM777
Lightweight Howitzcr weigh wos reduced from 17,000 Ibs uo 9,(KH) bs with design Unat was
betod on using titanium siruetuisl components foe approximatcty 80% of the vehicle,
Forthermene, Tos-cost sources of bulk vteniu we being developed to supply the materia
needed ta employ Ti in furace Army ar commercial sructurs,

Welding Is a Critica] Munufaconsing Process. The need for highor quality, less
expeasive, and more robws! produets fas helped to spur the development of welding processes,
All manofsctured products have joints thst join different pieces of motal together. More often.
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‘han nat, the joins are the weakest part af the structure and the joint quiliy determines Une
‘quality of the end product, Welding and joining technologies endble impraved manufactured
camponcnts by reducing the weight, produclion Time, and eost of fabricating quality joints.
Improvements in welding huve resulted in ineceased product lifetimes snd cnubled the
fubricalion of large seructures.

Titanium Welding Is Particularly Difficult and Expensive. One of the factors Hosting the
use of dtantom in military systems is tho lok of an asceplable Gas Metal Arc Welding, GMAW
(or MIG) welding proccss approved for milivry Tubricaviona. Almost all titanlum is welded
using a laborious and time-consuming Gus Tungslen Arc Welding, GITAW (or 1G) process. In
comparison, both slvel and alurnisu are eapable of employing GMAW systems wilh sigificant
prouuctivity impeovements af ten times the GTAW systems.

GMAW systems have not been cmployod successtully for titanium dae ta several
coastains, which mostly contribute to inlerliial contamination. Intetstidsd increases of
©>50D ppun. N'>50 ppm, and H>35 ppm are typical with GMAW systems curently available
from equipment devlers.” large portian of this contamination is derived from the typical spall
genera‘ed during the process. This spacer or spiting of molten thuniuin to the outside of the
Protective yes coverage envelope leads to a potential re-ingostinn of the conlaminated materiel
Also, the lurhulence of the protective gos sticara from a turbulent ar¢ leads in gas contamination.
Some invesdigatars havo attempted to solve, with yuestionable success, these problems with
extensive lesding and trailing shiclds, which limit visibility and mobility of the weld sorch, and
‘hus init the ability o weld serctutes of signitfeance,

‘The fuctors contralling the spattaring or spitting ore well understood and have been
largely addressed in the latest Gus Mistal Are Welding Pulsed (pulsed GMAW) cquipment
produocd from Linsoln Blevirie in their Power Wave 435 with compuler wave conteol. This
system, under che Atmay Titanium Mancfacturing Technology Objective (MTO), hats shown ua
have a Gramuatic veduction in sputtering by inecnparating « high-pulsed nite waveform, which alsa
Incorporates a pre-hea! in each pulse. This micro-adjastment in wave shape o Tam is possible
because the system is exquble of heing prugrammed (controlled) by a separate staadalone
computer.

Under the Titanium MYO, ARDRC is demonstrating the pulsod GMAW pravess on
several applications of imporiince. One such exareple is te fabrication via pulsed GMAW
process of an nll Gimium miontar baseplate for the U.S. Murine Corps (weight reduction from
138 hx to 65 Ths), The baseplate demonstration illustrates the promise of pulecd GMAW.
Tiowever, fabrication using pulsed GMAW sfill lakes coasidersble operator intervention ta adjust
‘weld paramncters dnc to the neture a lianiam and exe interactions. Thus, before the process cam
be transitioned to the Army's production base, rliable realtime sohatic coutrol 1s aceled) ky
adjust the weld pararaeters dynamically during the fahrication process based on mennured weld
‘quanti,

4 PHASE I PROJECT RESULTS

‘The mpevific abjective of the Phase T hare project was to develop and demonstrae
‘prototype instramaentation herdvare far enboccing the quality wnd speed of performing titanium
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gas metal are welding. During the Phase I Option project, we prepared wo ttansition the
conceptual design into a full-fledged design. During Phase ll, we will combine tho
instrumentstion, adaptive control algorifhs, anal veal-lime hardware in a complete control
system for pulsed titanium GMAW.

In adkhtion, during the Phone T pmiject under separate funding, we developed and
demonstrated tho ability to cvnirol a plasma asing a low-power pulsed laser. This innovation
was developed for a vepurate purpore, but has wide ranging application to Ti pulsed GMAW. As.
a result of this additional innovation, the Army Titaaiura MO plans 9 support inlcyravion of Tre
plasma eonlrol process withthe Yea-time eoatrol systom shat We vill develop under the Phase 1
SBIR,

Creue's solution, shown shemstivally in Figure 1, is based ou combining
state-of-the-art Yensor instrumentation, adeptive conteol slgoritoms, pulsed laser plasm
concentrtion, and real-time hardware to measure and monitor the weld shurwclerstion ond
modify the weld parameters in teal ime. Our Real Time Kobotie Contre) Syscem for Titania
COMAW ‘ill consist of sensors for measuring characterises of the weld, the are, and the droplet
fimation and transfer and use theso data 10 adjust the weld curtent, voltage, aud speed. We
expect chat by combining these components inly a complete robotic welding system that wo will
achicve higher quality, loner cost, and more robust dtanium welds than are currently possible
(ody, Belov iv description of the work perfocened using the Phase I eplion period related 10
the overall hardware design, selection af a weld poo! temperature senor, and selection of ths
power supply hardware.

4d Ovrau. HAwowane DEsten

‘A schematis of the hardware devign of ur Ti GMAW system is shown in Figure 2. This
figore shoves thatthe hardware consis af ibe Telowing:

1, Weld head, A commercial-off-he-shelf (COTS) systems that conluing the wire feed
mechanism, abield gos handling plumbing, wd the high power supply cloctronies.
‘The wire feed aud power supply en he cimirollad bg the control compute.

2. Weld motion system. The mation system is used to move Ihe wrk pieoe underneath
the weld bead, The motion system can be controlled hy the eonteot computer in order
lo sel the proper weld speed.

3. Temperature sensor. ‘The COTS temperaoine sensor is uscd 10 measure or eslimate
the weld temperature, Previous reseateh las shown thet this informacion can be used
to estimate wold penetration which has beon corrsluled with weld quality. This
sensor signs! will be input to the contol compuier and used to adjust the weld
‘Parameter

4, Laver backlight system, The laser, opties, and high-spoed camera are used co
determine the metal transfor meshaniam, This custom system ean raeasure the drop
formation and tramafer and the daca willbe uscd lo set. the proper weld parameter

During the Phase TI project, we will goncralc the drawings requiied to fabricate our TL
GMAW systern, assemble the hardware, write Ue soltware cequited to interface the hardware to
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the contol compoter, and perform open- and closed-loop experiments to quantify the advantages
of using ace GMAW contral syste.

‘pes for back
igh speed | Tigh. sensor

aaah
wer | Ny

emperatore

weld head

wel ee
a ayslem

Figure 2, Drawing of Overall GMAWE System Ha-dvare, The overall dosign of he GMAW hardare ie
‘amr at and taebi to alow reconfiguration and tanpor ofthe system

42 Wein Poot TereRaTURE SENSOR

‘The sensors make up some uf the most important components of the robotic titanium
wold control system, The sensors are used co observe and rmcwsure characteristics of the weld,
‘Those mensurements then serve ss the signal tht is used uo adjust the welding parameters
‘Several measurement techniques Rave boen developed in order to measure the peneization depdh
e.g. ultrasonic sensors, X rays, weld pool escilations, optical devices, ueoustic emissions, and
infrared senscrs) and the droplet formation and uansfer, We will employ a laser bucklizht
syvlem for monilocing the droplet formation andl transfer mechanisin (sorbed im the Phase 1
Tae geried final report) and infrared sonving ta manitor aspects of the weld formation. Below is
a description of cach af the weld pol temperatore sensors.

Tnfraret sensing has heen used to monitor various aspects of dhe welding pracess for
macy years, Tafcared cameras, thermocouples, and various cambinations of these devices have
‘een used to measure the tompzrature distribution avonnd the weld poo! in order to automatically
track seams, control the bead width, or regulate the weld penetration. ‘The temperature
disbibution near uke weld pool provides iraportant information on the statu» of the weldiag
process. The weld paramistors (voltaye, eurent, and speed) and ofher process variables (joint
‘istnatch, 100¢ gap, thicknes: of parls, and part coutposttion) effect the pool shape (determined