Wire Feed Rate Vs Voltage Chart

Wire Feed Rate

The wire feed rate of the filler metal is practically independent of the welding current, thus it permits the variation in the elative amount of the fusion of the parent metal and filler metal.

From: Advanced Welding and Deforming , 2021

HOW PULSING IS OF BENEFIT

Eur IngJ A Street BA, CEng, SenMWeldI , in Pulsed Arc Welding, 1990

3.4.5 Advantages of synergic pulsing

In operation the synergic system provides high arc stability even when wire feed rate fluctuates because of slipping drive rolls, variations in mains supply voltage or poor motor speed regulation. Almost instantaneous readjustment of the pulse parameters ensures that no arc instabilities result and consequently no defects occur in the weld. Because the synergic system accommodates fluctuations in wire feed rate, it is possible to modulate wire delivery intentionally for weld profile control. At the end of a run wire feed rate can be progressively reduced from the normal welding level for crater filling. At the start, wire feed rate can be progressively increased to avoid build up which normally occurs in MIG welding.

This feature is useful in pipework where normal circumferential seams with cold starts are subsequently overlapped. A tapered start is a more satisfactory profile for overlapping, readily obtainable with synergic pulsing. If changing parameters are required for joint filling, for example, to accommodate a changing gap in a root run, average current can be reduced to avoid burnthrough by reducing current alone. Similarly, in subsequent and capping passes, wire feed rate may be adjusted to maintain the required joint geometry. Fume evolution is lower for single droplet transfer compared with identical volume multiple transfer because surface area from which evaporated metal ultimately becomes particulate is also lower.

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Developments in hybridisation and combined laser beam welding technologies*

D. Petring , in Handbook of Laser Welding Technologies, 2013

18.2.2 Physical model of the root formation

The appropriate amount of filler wire deposition depends on groove and gap volume as well as on welding speed and can easily be estimated and adjusted. The amount and the distribution of the energy input due to the laser beam power and the focal position influence the root formation and is handled experimentally. A remaining important question is: Which gap width can maximally be bridged and what are the determining factors for existing limits especially in thick-section welding?

As mass and energy balance have already been treated above, a momentum or pressure balance, respectively, shall give the answer (see Fig. 18.5). The pressure balance determines, for example, whether the root becomes concave with perhaps even incomplete penetration, whether it becomes convex and sound with regular appearance, or whether excessive penetration with drop through and sagging melt occurs. With a simple physical model the pressure balance at the root can be calculated [13]. The outcome will reveal suitable measures to improve gap bridging capabilities.

Fig 18.5. The pressure balance at the root [13].

The model illustrated in Fig. 18.5 considers the gravitational force (gravitational constant g) due to the mass of the melt column (density ρ and height t) above the root with width w_m , the dynamic pressure of a 'downward' melt flow component with a velocity v_m and the supporting capillary forces due to the surface tension σ of the root melt. The arc pressure could also be included in the balance equation, but during thick-section welding of steels its contribution can be neglected compared to the other terms. The gap width w determines the minimum possible root width. On the other hand, the root width determines the minimum possible root radius w _m/2, which occurs at a contact angle α = 90° (see Fig. 18.5).

By setting gap and root width identical, the balance equation can be resolved for the maximum gap width w _max [13]:

[18.1] $w_{max}=2\sigma {\left[\mathrm{\rho }\left(gt\mathit{+}{v}_{\mathrm{m}}^2/2\right)\right]}^{-1}$

To adjust the process, first of all an appropriate wire feed rate has to be set for properly filling the missing volume. It is also clear, that in order to fulfil the above condition of minimising the root width w _m to the gap width w, the laser beam power has to be adapted, namely minimised, accordingly:

•

Adapted laser power reduces root width w_m to gap width w.

This is of course a somewhat idealised condition, but as the absolutely limiting case it perfectly leads to the maximum allowable gap.

Equation18.1 presents three possibilities to maximise the allowable gap width w_max, which can be implemented by corresponding measures:

•

increasing surface tension σ by root protection with inert gas (if two-sided access is accepted)

•

reducing downward melt velocity v _m by ensuring a stable process with low melt dynamics, mainly achieved by a proper basic parameter configuration

•

avoiding gravitational effects by using horizontal position PC.

An example is calculated in Table 18.1, where three different theoretical cases for laser-arc hybrid butt welding of structural steel plates at a thickness of 15   mm in flat position PA are compared. A corresponding experimental value for the maximum allowable gap size with properly adapted wire feed rate and laser power has also been determined. The first case in Table 18.1 implies a clean root, free of oxides and with correspondingly high surface tension. Furthermore, an ideal situation with no downward melt flow is assumed. In the second case, an oxidised steel melt surface reduces the surface tension at the root, and in the third case additionally a significant melt flow velocity typical for high dynamics is indicated. Following these steps, the maximum gap width which can be bridged is decreasing from 1.7   mm to 0.5   mm. An experimental value of 0.7   mm has been achieved without root protection, which means with an oxidised root. The process was adjusted quite stable, which should result in a moderate downward melt velocity component. This condition meets the situation between the second and third case and corresponds very well with the average of these two theoretical values. This rather simple model provides a surprisingly accurate description of the gap bridging capability and allows a well-defined course of action to optimise the process.

Table 18.1. Three different cases for the gap bridging capability w_max during welding steel in flat position PA, calculated according to Eq. [18.1] with ρ(steel) = 7,800 kg/m³ and thickness t = 15   mm

	Clean root	Oxidised root	Oxidised root and melt dynamics
σ [N/m]	1.0	0.5	0.5
V m [m/s]	0	0	0.5
W max [mm]	1.7	0.9	0.5

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Gas Metal Arc Welding: Automatic Control

Desineni Subbaram Naidu , ... Kevin L. Moore , in Modeling, Sensing and Control of Gas Metal Arc Welding, 2003

4.9.4 Other Works on Control

On-line control of arc welding processes by obtaining a relation in equation form between the inputs (such as arc applied voltage, current, wire feed rate, welding gun position and speed) and outputs (such as weld bead dimensions) of the welding process was performed in [712]. Automatic precision TIG welding techniques were developed in [713] for welding all types of joints required on nuclear fuel elements by the Springfield Nuclear Power Development Laboratories (SNPDL), Salwich, Preston, UK.

Cook, in [714], gives a distributed microcomputer control system used in the programming, sensing, and feedback control of the welding process parameters. An interesting general discussion on the need for automation in welding processes aiming towards flexible manufacturing facilities is given in [715]. An automatic weld-line tracking system was developed in [716] by employing a light scanning technique using a laser and an image sensor for the sectional pattern of the joint groove.

A real-time machine vision-based feedback control system was designed in [717] to compensate for static and dynamic geometry variations as well as control of welding process parameters. A general-purpose, real-time seam tracking algorithm was developed in [529] for implementation on any six-degree-of-freedom robot, where the algorithm requires knowledge of only one point ahead to track a seam.

A process control system for arc welding applications was designed in [718] to provide advanced capabilities for tracking and analysis of welding variables. The requirements for second generation automatic welding systems capable of multipass welding, such as the machine intelligence capable of image perception with the ability to think strategically, were investigated in [719]. A process controller for vertical strip cladding using melt level sensing methods and a guide shoe design for the GMAW process were presented in [720].

An excellent tutorial and review type of discussion on modeling, sensing and control of welding processes were given in [469]. In [721, 722] it was pointed out that a simple automatic voltage control system, obtained by using gain scheduling technique, may be unstable over a wide range of current settings due to variations in arc sensitivity with current. A wire feed control system using a DC motor is given in [479].

The use of an infrared feedback signal for the automatic tracking of single V-groove prepared butt joints was discussed in [723]. In [722], a simple automatic voltage control (AVC) system that was unstable over a wide range of welding currents because of the arc sensitivity with current was designed. Digital feedback control of weld penetration of a GTAW using ANN for modeling was proposed in [724].

An automated robotic variable-polarity plasma arc welding (VPPAW) for the Space Station Freedom Project (SSFP) is presented in [725]. The SSFP requires approximately 1.3 miles of aluminum welding for the final assembly. The VPPAW was chosen because of its ability to make defect-free welds in aluminum and the robotic VPPAW system was built by ABB Robotics, Inc., of Greenwood, SC, and installed at NASA's Marshall Space Flight Center.

A very good general presentation on the need for modeling and control of manufacturing processes in general and welding in particular is given in [726]. The author reviewed two decades of manufacturing control research in the ASME Journal of Dynamic Systems, Measurement and Control and found that there are only 25 articles published in the Journal on the whole of manufacturing, and out of them, there were only 6 papers on arc welding.

The work reported in [727] is an edited collection on sensors and control systems in arc welding, and, although a very good presentation of various topics, almost all the literature is limited to works in Japan. Control systems in general and welding process control in particular are discussed in [728] and [624], respectively.

A process control system for the arcing and short-circuiting phases and a study of its effect on spatter is presented in [729]. Future trends on control systems for arc welding processes, with an overwhelming response towards adaptive control, are discussed in [730]. Holm, in [731], develops a method for state space modeling of the whole manufacturing control system, including welding, and presents the use of state space models for improving processing control by articulating issues such as stability, disturbance compensation, hierarchical control, state estimators, and plant parameter estimation.

An arc welding penetration control system using quantitative feedback theory (QFT) is given in [732]. QFT is a unified theory that emphasizes the use of feedback for achieving desired robust system performance tolerances despite structured plant uncertainty and plant disturbances [733]. Other works in these areas can be found in the section on sensing, control and automation in [734]. A computer simulation of GMAW start-up was developed in [735] that accounts for the voltage-current characteristics of the welding arc, the welding power supply, and the interaction between the moving anode wire and the welding arc.

In [736], it was shown that an arc discharge in a GMAW welding process with fusible electrodes starts before a short-circuit bridge, made by a metal drop between the electrodes, is broken. The possibility of this premature ignition is proved by voltage and current measurements, by analysis of the electrical field near the neck of the drop, and also by simulation of the increase in current in an electrical discharge.

A unique excitation, sensing, and control system was developed in [737] to predict and control the state of penetration during the GTAW process. Excitation of the molten pool is accomplished by synchronously modulating the arc force in phase with the weld pool's own natural frequency using a phase-locked loop (PLL) technique. Regulation of GMA welding thermal characteristics via a hierarchical MIMO predictive control scheme that assures stability has been presented in [738]. The work proposes a hierarchical predictive control scheme for the metallurgical characteristics of GMAW.

Numerical analysis of the dynamics of droplet growth in GMAW was studied by Zhang in [739]. Feedback of droplet transfer is pursued as a solution to produce sound GMAW welds. Zhang has also developed a robust control algorithm to control the pulsed gas metal arc welding process [740]. In a recent study [741], Zhang also proposed a modified active control to ensure a specific type of desirable repeatable metal transfer modes.

Other results that have been reported at various experimental facilities for implementing automatic controllers for the GMAW process include [526, 501], [478], [489], [603, 579], [742, 561, 560], [633, 637], [626, 743, 744, 745, 627].

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Machining processes utilizing thermal energy

Bijoy Bhattacharyya , Biswanath Doloi , in Modern Machining Technology, 2020

4.1.7.3 Influence of WEDM process parameters

Emphasize on realization of higher machining productivity with desired accuracy and surface finish is becoming a major issue in Wire electrical discharge machining. Though, even a highly skilled operator with a state-of the art WEDM is rarely able to achieve the optimal performance because of involvement of a large number of variable parameters as well as other controllable factors in WEDM. The optimum utilization of the WEDM process needs appropriate selection of machining parameters. WEDM is complex in nature and can be controlled by large number of parameters and other factors as shown in Fig. 4.1.33.

Fig. 4.1.33. Factors influencing the wire EDM process.

Major variable parameters of WEDM can be identified as pulse peak current, voltage, pulse on time, pulse off time, duty factor, flushing pressure of dielectric, types of wire electrodes, wire feed rate and wire tension etc. Other major factors of WEDM which are indirectly influencing the machining responses are properties and thickness of job materials, types of dielectric, construction and controlled features of the machine tools. Research is going on to investigate the effect of various process parameters on desirable outputs. Major outputs which play a crucial role in modern manufacturing applications are cutting speed (MRR), accuracy, overcut and surface integrity etc. However, the different parameters controlling the machining performance can be described here-in-under:

(i)

Pulse-on time: During this period the voltage is applied across the wire electrode and job. The discharge energy contains in a single pulse, increases with the increase of T_on, resulting in a higher cutting rate.

(ii)

Pulse-off time: During this period the voltage across the electrodes is absent. With a lower value of T_off for a particular pulse period increases pulse on time, results in more number of discharges which increases sparking efficiency and cutting rate. However, very low value of T_off causes wire breakage and an unstable discharge condition. When sparking becomes unstable, it is better to increase T_off which allows lower pulse duty factor thereby reduces the average gap current.

(iii)

Peak current: The increase in the peak current, I_p increases the pulse discharge energy. At higher value of I_p, the gap condition may become unstable with improper combination of T_on, T_off, voltage and servo feed settings. Reducing the I_p value helps to attain an unstable discharge condition into a stable condition.

(iv)

Flushing pressure of dielectric: Generally, a high flushing pressure of dielectric is necessary for cutting with higher values of pulse power and, especially, while cutting the jobs of higher thickness. However, low input pressure should be used for thin jobs and precise cutting.

(v)

Wire feed rate: This is a feed rate at which the fresh wire is fed continuously into the sparking zone during machining. For working with higher pulse power, higher values of wire feed rate are required.

(vi)

Wire tension: This is a gram equivalent load with which the wire being continuously fed to the system such that wire can be kept under tension and it remains straight between the wire guides. Due to spark induced reactive forces and flow of water dielectric in the machining zone, the wire vibration and deflection occur which deteriorate the machining accuracies. The wire tension makes the wire straight between the wire guides during machining.

(vii)

Servo feed setting: The parameter decides the servo speed of the worktable, which can vary in proportion with the gap voltage or can be held constant during machining.

(viii)

Threshold setting voltage: This is threshold setting for corrective action in abnormal discharge condition. At gap short or short circuit condition, the controller will reduce the current drastically and will retrace the sparking path in backward direction so as to overcome the short circuit condition.

Pulse on time, pulse off time and peak current are most influencing parameters for cutting speed during rough cutting. Pulse on time is the most significant parameter during finish cutting with constant cutting speed. The surface roughness is influenced mostly by peak current during rough cutting. During finish cutting, most influencing parameters for surface roughness are pulse on time, peak voltage, gap voltage, dielectric flow rate, wire tool offset and constant cutting speed. Highest productivity with best surface finish and least geometrical inaccuracy can never be achieved by a single set of parametric combination. A proper trade-off is essential during selection of parameter setting to satisfy all the above-mentioned three machining responses simultaneously.

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Commonly Used Resins and Substrates in Flexible Packaging

Barry A. Morris , in The Science and Technology of Flexible Packaging, 2017

4.3.4 Metallized Film

Metallized film is used to provide moisture, oxygen and light barrier, and for aesthetics. A variety of substrate films for metallization are used in flexible packaging, including PET, PP, PA, and PE. Of these, oriented PET and PP are most common.

Metallized film is produced on a metallizing machine, which vacuum deposits a thin layer of aluminum (or other metals, but aluminum is the most common) onto the film substrate. The aluminum is melted, vaporized, and condensed onto the film surface. High vacuum is required to vaporize the aluminum [137].

As described by Mount [138], there are a number of manufacturing variables that affect film performance, including the following:

•

vacuum level;

•

conditions of the "boat" that holds the aluminum (temperature, wire feed rate);

•

film formulation;

•

treatment level (surface energy),

•

presence of adhesion layer,

•

COF technology used (some technologies bloom to the surface and interfere with adhesion),

•

film dimensional stability (oriented films are typically used).

•

web cooling conditions;

•

tension levels;

•

mechanical condition and cleanliness of the rolls.

These variables in turn influence the appearance, optical density, metal adhesion, and barrier properties of the metallized film.

The thickness of the metallization layer ranges from about 3 to 40   nm. As the thickness increases, the optical density (opacity) increases, as does the gas barrier performance. For oxygen and moisture barrier applications, typically around 30   nm are needed.

Metallized films are used in many packaging applications, including the following:

•

bags for snack foods such as potato chips (met-BOPP for light barrier);

•

coffee pouches (met-OPET or BON);

•

candy wrappers (met-OPP or met-OPET);

•

stand-up pouches (met-OPP or met-OPET);

•

meat or cheese packages (met-OPET).

The metallized layer is typically turned inward in a laminate structure to protect the thin metal layer. Some example structures include OPP/print/adhesive/met-OPP and print/OPET-met/adhesive/PE sealant film.

Metallized film has replaced aluminum foil in some barrier packaging applications. While in theory foil has superior barrier properties, handling and flex cracking can reduce its performance. An economic analysis by Lush and Ferrari shows that metallized films may provide a lower total cost in many applications when taking into account price per square meter, handling and processing [139].

Transparent barrier coatings of SiO_x and AlO_x onto film substrates are also available. These provide moisture and oxygen barrier but not opacity. They are useful for applications not requiring light barrier, where the product is meant to be seen, or when aluminum coatings interfere with online packaging metal detectors used to detect possible contamination in the product. Electron beam deposition or plasma-enhanced chemical vapor deposition processes are typically used to apply these coatings. At present these coatings are about two to three times more expensive than aluminum metallization [140].

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Thermal Evaporation

Charles A. Bishop , in Vacuum Deposition Onto Webs, Films and Foils (Third Edition), 2015

16.1 Introduction

The bulk of aluminum evaporation is done by passing an electric current through an intermetallic boat thus heating it up and simultaneously feeding a wire of aluminum against the hot surface of the boat. The aluminum, on touching the surface, melts and, if the wire feed rate is high enough, forms a pool of molten aluminum that steadily evaporates. A series of these boats is arranged in a line across the width of the web that results in a coating of somewhere between ±5% to ±20% uniformity depending upon geometry.

The same basic technology is used for the evaporation of aluminum at narrow web widths onto polymer film as thin as 0.6 micron used for capacitors and through to very wide systems as shown in Figure 16.1 that would be used on 12 micron thick polymer films for packaging applications. For the wider machines there are more boats at the same spacing to cover the wider film and each with their own wire reel and feed system and thickness monitoring head.

Figure 16.1. The photograph courtesy of Applied Materials is of one of their largest aluminum metallizers at 4.45   m wide and capable of running at 1250   m/min.

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Modern optimization techniques for performance enhancement in welding

Bappa Acherjee , in Advanced Welding and Deforming, 2021

3.5 Arc stability and process monitoring

The stability of the arc also impacts the weld quality, and an unstable arc produces a massive spatter of metal [82]. Soft computing techniques are used to monitor and control the stability of the arc. Conventional controllers such as constant voltage type with constant wire feed rate cannot maintain a steady arc length during processes of short-circuit welding transfer. Hu and coworkers [101] implemented a fuzzy controller applying Mamdani fuzzy inference system for stabilizing the arc in GMAW, where the arc voltage deviation and its transition rate acts as inputs and the welding current is the output. The test result indicates that under all conditions, the proposed fuzzy controller has a good dynamic response and high stability. Wu and coworkers [102] developed a fuzzy logic system for process monitoring and quality control in automated GMAW. Using measured welding voltage and current signals, the fuzzy logic system identifies typical disturbances during welding. The system can identify and classifying GMAW experiments that are disturbed and undisturbed. The entire assessment process can be automatically carried out by analyzing only calculated welding voltage and current. Naso and coworkers [103] suggested an approach focused on the application of optical sensors and fuzzy logic classification algorithms for the real-time weld quality monitoring. Fuzzy logic allows a robust classification scheme to be built using expert information on the relational interactions between weld quality and observed signals. The accessibility in real-time error information including current or voltage anomalies, holes or contaminations, enables the creation of a closed-loop network to perform corrective measures during the welding cycle, if necessary.

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Gas-tungsten arc welding of magnesium alloys

L. Liu , in Welding and Joining of Magnesium Alloys, 2010

11.3.2 The effect of welding parameters on weld shape

Initially, bead-on-plate GTAF welds were made on 5 mm thick AZ31 magnesium alloy to study the effect of welding parameters on depth of penetration and width of weld. Because current, welding speed and arc length in GTAFW act in the same way as GTAW, only the effect of wire feed rate on the appearance of weld was noted as shown in Fig. 11.11. It was found that depth of penetration decreased with the increase of wire feed rate, which is caused by the energy consumption of filler wire. At the same time, the width of the welded joint showed little variation or reduction (Liu and Dong 2006). Then the welding process was investigated by optimizing specific experiments on butted 2.5   mm thick plates. Macro sections are also presented in the figure at three feed rates of 11, 18 and 22   mm/s.

11.11. Effect of wire feed rate on depth of penetration and width of weld. Macro sections are also presented in the figure at three wire feed rates of 11, 18 and 22   mm/s (AZ31, t  =   5   mm).

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Multiresponse optimization in wire electric discharge machining (WEDM) of HCHCr steel by integrating response surface methodology (RSM) with differential evolution (DE)

V.N. Gaitonde , ... J. Paulo Davim , in Computational Methods and Production Engineering, 2017

7.4.3 Analysis of tool wear rate (TWR)

Fig. 7.10 illustrates the effect of pulse on time and pulse off time on TWR. TWR increases with the increase in pulse on time, which is due to high intense spark producing from the wire. The high electric discharge energy during longer pulse on time causes more heat dissipation and hence the wire rupture will be more due to excess thermal and increased discharge energy. As noticed in this figure, at lower pulse on and pulse off time, the TWR is found to be negligible. This is because the dissipated heat will vanish due to less sparking energy and less duration. Fig. 7.10 also reveals that the TWR decreased with increased pulse off time. The increased pulse off time allows a longer time to maintain the dissipated heat by sparking. The melted material flushed away from the machined surface also helps for the reduction in the heat.

Fig. 7.10. The effect of pulse off time and wire feed against TWR.

Fig. 7.11 shows the influence of pulse off time and wire feed on TWR. It is observed that the TWR is higher at 6 m/min of wire feed rate for varying pulse off time. Also, TWR is greater at longer pulse off time (60  μs) and wire feed (8   m/min). Increased cutting speed forms larger crater on the wire surface caused by erosion of wire material. The dissipated heat is not dispersed sufficiently around the wire and work surface. The higher wire feed (8   m/min) with lower pulse off time (20   μs) combination has resulted in the lowest TWR. Because of higher cutting speed, continuous spark was generated at each interval of time and further the generated heat was nullified by the dielectric fluid for higher feed and lower pulse off time.

Fig. 7.11. The effect of pulse off time and wire feed against TWR.

Fig. 7.12 presents the variations due to the interaction of pulse on time and pulse off time on tool wear rate for different wire feed rates. It is very interesting to note that for lower pulse on time of 110   μs, the tool wear rate linearly increases with the increase in pulse off time for any given wire feed rate; with further increase in wire feed from 4 to 6   m/min, the tool wear rate increases. However, with the increase in wire feed rate from 6 to 8   m/min, the tool wear rate decreases. On the contrary, for medium and higher values of pulse on time, tool wear rate linearly decreases with pulse off time, irrespective of the feed rate and exhibiting more or less similar behavior. Simultaneous increase in pulse on time along with wire feed rate provides the higher tool wear rate. Lower tool wear rate is observed for a combination of lower pulse on time, lower pulse off time with higher wire feed rate.

Fig. 7.12. Interaction effects of process parameters on TWR.

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DISCUSSION

Eur IngJ A Street BA, CEng, SenMWeldI , in Pulsed Arc Welding, 1990

Summary of the benefits of current pulsing in MIG welding compared with continuous DC

1

Droplet detachment, metal transfer and arc behaviour are under complete control for a wider range of average welding currents than natural transfer permits;

2

Stable spray transfer can be used at average currents well below the natural thresholds at which globular and dip transfer occur;

3

By linking pulse frequency in direct proportion to wire feed rate at 'unit' droplet operation, synergic pulsing is obtained. This is tolerant to accidental or inherent wire feed variation and also accommodates deliberate modulation for thermally pulsed MIG welding;

4

Thermal pulsing is achieved in MIG welding by switching welding current and wire feed rate in unison or with controlled phase difference, permitting root, filler and capping passes all to be made with the one process;

5

Pulsed MIG is suitable for positional welding because droplet transfer is independent of gravity, and low average currents prevent formation of an uncontrollably large molten pool by keeping heat input low;

6

In AC pulsed MIG welding there is much better resistance to magnetic arc blow and up to 50% higher deposition rates are possible than for conventional DC electrode positive operation.

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