Mobile Navigation

Benefits of Laser Welding

‘Big’ means ships. This is an aspect of automation that isn’t obvious, unless you weld really big stuff. If you do, here’s a rundown. If you don’t, here’s automation for welding ships.

The KAT carriage is supplied with a sophisticated control which maintains the speed of the carriage regardless of the carrying load, up ro 100 lb. capacity.

These are the welding carriages being utilized by shipyards throughout the world to improve productivity and increase weld quality — both competitive issues in an industry which has seen increased quality standards, increased costs and a reduced skilled workforce over the past decade.

Trackless Fillet, Lap and Butt Welding Carriage
Welding carriages have become increasingly easy to operate and have become one of the most cost-effective ways to improve a shipyard’s efficiency in a multitude of common shipbuilding processes. One such carriage is the trackless fillet welding carriage supplied by various equipment manufacturers including Gullco Internationals MOGGY®. Instead of being mounted to track, these carriages are guided by adjustable wheels which track the vertical member of the fillet or lap to be welded. These carriages can be equipped with two torches to allow for simultaneous welds to be produced. This not only doubles the productivity of the operator but also reduces heat input and distortion.

Multiple carriages, each fitted with twin torches can be automated with a PLC unit and controlled by one operator. Up to 16 arcs have been controlled by a single control. The 16 arcs are capable of depositing at a cumulative rate of over 80 kgs per hour of weld metal.
These portable fillet welding carriages give accurate leg lengths at high quality, avoiding over welding — which is expensive (example — if 6mm is welded instead of the desired 5mm the extra weld metal used is in excess of 78% when combined). Over welding not only increases the heat affected zone and causes distortion, but also slows down the overall speed of the welding operation.

A two-torch version, shown in the photo, is a great example of automation, which increases arc-time and weld deposition tremendously. A single operator controlling a dual-torch carriage can easily deposit 11kg/hr of weld metal. The skill of the welder has been transferred to the equipment. The operator experiences less fatigue and at the same time can use the equipment to maintain high arc-times. This equipment is typically used in the fillet and lap welds on the deck as well as the stiffeners and bulbs. An example of the increased productivity which is achieved through the use of the dual torch carriage is below:
Taking productivity for a 5mm fillet weld in an 8 hour shift
Manual welder = 40m
MIG Welder = 60-65m
Dual Torch Carriage (one operator) = 220m @ 50% arc time
308m @ 70% arc time

The benefits which can be realized while using a trackless fillet welding carriage such as the MOGGY:
– Minimal welder skill is necessary to produce high quality welds.
– Minimum set up time required
– Faster weld deposition and higher arc times up to 80%
– Welder environment improves as they are further away from the fumes and the heat of the arc
– One operator can operate dual torches
– High quality, consistent and accurate fillet welds, leading to savings on consumables
– Precise control of the weld parameters eliminating over welding
– Minimum heat input and controlled heat affected zone
– Less distortion, faster heat dissipation, and less induced stress due to stop/start
– Eliminates the implementation and removal of “stays” (very costly)
– Higher output with lower manpower, hence a direct contribution to lower hours per ton
– One operator can control 2 carriages within a reasonable distance
– Several carriages can be connected with one another and controlled through a single PLC
– Carriages can be used for fillet, lap and butt welding in the 1G and 2G positions
– Magnetic versions of the carriages can be used for out-of-position welding

Gullco’s MOGGY tracks the weld itself, rather than a separate guiding track.

Programmable All Position Welding Carriage
This type of welding carriage runs on aluminum or flexible spring steel track, which is mounted with the use of magnets to the weldment. The flexible track provides the added advantage of being able to contour to the workpiece, allowing the travel carriage to follow the profile of the weld seam accurately. It has quickly become one of the most popular ways to automate the current welding processes being performed manually. This type of carriage is especially ideal for long continuous seams.

One of the most important features of modern welding systems like the Gullco KAT® carriage is that it is supplied with a sophisticated control which maintains the speed of the carriage regardless of the carrying load (within the 100lbs capacity). This means that the carriage can pull wire feeder and cables at the time of operation keeping critical equipment close to the point of work.

Several variations in the programs are available in order to add flexibility to the automation process. Some carriages have programs for stitch welding using a simple but affective series of operations. (i.e Full Speed Start, Park, Arc Start, Weld, Carriage Stop, Repeat) This simple program can automate this repetitive production process with more accuracy and at higher deposition rates than manual welding. Similarly, this same carriage can be equipped with an oscillation head which allows for various weld patterns to be completed and is an essential element in the affective automation of various shipbuilding processes. Controls are provided which allow the operator to preset the weave width, oscillation speed, side and center dwells, and wire feed delay. Some carriages are supplied with an L.E.D screen, which gives the operator of the welding parameters during welding. This type of oscillation system is supplied in both linear and radial oscillation and either head can be mounted to the same welding carriage with minimal effort.

One of the key advantages to a system such as the one described above is that welder skill becomes much less critical and the maintenance of the torch position becomes the key operation concern. A series of operators with predetermined welding procedure specifications (WPS) managed by a skilled welding supervisor can do the work of a team of highly skilled welding professionals, all at a higher efficiency. 

This type of carriage can be fitted with a variety of different functions, including oscillation. Oscillation is used in automatic mechanized operations for minimizing defects, such as poor penetration, incomplete fusion, and undercut. These carriages can be upgraded by retrofitting electronic seam trackers and laser seam trackers for following the welding seams automatically. They can also be upgraded for cladding operations with the addition of an indexing unit. All the carriages have input ports for receiving commands from PLCs for automation applications and are compatible with all existing power sources and wire feeders. Typical applications include butt welding of the blocks, horizontal welds on the hull, out-of-position welds on the stern, butt welding on the decks and all types of fillet and lap welds.

Due to the versatile nature of the travel carriage, the same unit can also be equipped with a gas cutting setup. One very important application is “in situ” cutting and bevelling the green on the blocks. The flexible track can be followed, followed in turn by a bevel. This reduces the amount of grinding required when gas cutting is carried out manually. The joints on the blocks are consistent as a result of automated cutting, which helps in the welding process through more accurate fit-up and helps to reduce over-welding and distortion.

Comparison Between MMAW and MIG Welding with and without Oscillation
Vertical Welding (3G) – Without Automation Weld Deposition Rates:
MMAW- Average 60 electrodes per 8 hours shift= 2 kg/8 hr shift
MIG – 1.2 dia FCAW wire deposition rate at 180-200 amps = 2.8 kg/hr
1.2 dia FCAW deposition (at 23% – arc-time) = 5.15 kg/shift
Average arc time for MMAW is 18-19%
Average arc time for manual MIG/FCAW is 23% (without automation)
Vertical Welding (3G) – With Automation, Weld Deposition Rates:
MMAW welder deposition rate per shift @ 18% arc-time = 2 kg/8 hr shift
MIG welder deposition rate per shift @ 23% arc-time = 5.15 kg/8 hr shift
Automated MIG welder deposition rate per shift @ 50-60% arc-time with oscillation = 11.2 – 13.5 kg/8 hr shift

With the increased arc on-time achieved through the use of welding automation, deposition rates of nearly 50% or greater can be achieved. Arc times of 70% or more can easily be achieved on longer welding joints.
When examining the deposition rates using the MMAW, MIG & MIG automatic process, without oscillation.

Butt Welding (1G) Position – Without Automation Weld Deposition Rates MMAW 5mm electrodes, average weld deposition, 8 hr/shift = 3.2 kg/8 hr shift
MIG – 1.6mm dia. FCAW weld deposition @ 300 amps = 5.2 kg/hr
MIG – 1.6mm dia FCAW weld deposition, 8 hr/shift (23% arc-time) = 9.6 kg/8 hr shift
Butt Welding (1G) Position – with automation 1G (oscillation) weld deposition rates MIG – 1.6mm dia, FCAW, 8 hr/shift (50-60% arc-time) = 21-25 kg/shift

For shipbuilding, heavy-wall oil storage tanks, hortonspheres, penstocks, girders, etc., all are being welded at construction sites around the world using technologies like the all-position welding carriage and oscillation head combination. These carriages, with their high weld deposition rates and high arc times are very effective in out-of-position welding applications. An example of the automated welding carriages effectiveness is the 11 runs required to complete a 3G 30mm V joint in combination with the appropriate weld backing. As mentioned earlier 70-80% arc times can be achieved on seams such as this.

KAT carriage with oscillation.

A gas cutting setup for the carriage.