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Lean manufacturing enhances welding operations |
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Applying the principles of lean manufacturing to welding can yield significant benefits including increased welding quality, reduced waste, and cost savings.
Designed to eliminate waste at every production stage, lean
manufacturing streamlines a company’s processes to offer greater value
to customers. This Japanese management philosophy has become
increasingly well known in the West as companies such as Toyota have
used it to make astonishing gains.
With the globalization of markets, the need to optimize processes has
become urgent, with companies finding themselves compelled to improve
their manufacturing methods to remain competitive. This is particularly
true in Canada, where the dollar’s recent rise has threatened the
profitability of many facilities. Under these economic conditions, lean
manufacturing can be a strategic choice.
To illustrate the potential benefits in terms of welding, this paper
will look at a case study carried out in a plant producing front-end
loaders with the help of 35 arc welding specialists. A systematic
approach was used to measure welding process parameters and skills.
Welding processes were then monitored to measure their deviation from
optimal parameters. This made it possible to diagnose the specific
areas where Kaizen management methods could deliver continuous
improvement.
The five basic principles of lean manufacturing were applied to the
plant’s welding operations. The first of these consists in achieving
perfect first-time quality. Attempts to achieve this objective focused
on fillet welds. Fillet welds are often ignored by engineers, who take
for granted that welders are sufficiently skilled to make them
correctly, yet fillet welds are the source of many fatigue failures. It
was subsequently decided that producing perfect fillet welds, every
time, would be the initial point of introducing the lean process. The
study initially measured the in-process parameters among a sample of
welders and discovered that 37% of the sample group failed to make
good-quality welds the first time. Kaizen events for improving fillet
weld quality were initiated.
The second major principle of lean manufacturing is waste reduction
through the elimination of all non-value added activities. The excess
weld metal used along with the resulting wasted effort during the
welding operations offered another excellent opportunity for
improvement. During the case study, it was discovered that weld sizes
exceeded the design requirement of 1/4 in. by 33% to 206%, with an
average of 107%.
Other adjustments were also required to minimize waste: the use of
simple lap fillets instead of flare groove welds in the design of
certain parts; reducing the dimensions of certain fillet welds and the
standardizing to one filler metal wire size; and optimizing gas welding
parameters. Various measuring devices and instruments were used to
efficiently implement these measures.
Once optimal welding parameters had been established, the third basic
principle of lean manufacturing, continuous improvement, could begin.
Every week, the Kaizen team recorded production welding parameters of
wire feed speed, welding speed, quality of welding, and extent of
overwelding. Throughout the plant, on-the-job training was provided to
welders not performing to the new standard.
The results were impressive. After eight months, the average welding
speed increased by 6.4 in./min. (from 17.6 in./min. to 24 in./min.)-a
36% improvement. In addition, the average cost per foot of perfect
first-time fillet welds shrunk by $0.44 (from $1.57 to $1.13). This
improvement represents potential annual savings of $526,772. In fact,
in the first year alone, the company saved $400,000. By decreasing
waste and increasing welding speed, the company thus achieved
significant savings and throughput.
The last two major principles of lean manufacturing are flexibility in
production and long-term relationships with suppliers. It was observed
that, despite marked improvement in welding productivity, bottlenecks
were frequent at the final assembly of the machines. For this reason,
the Kaizen method needed to be focused on the next electrical,
mechanical, and hydraulic systems. Management wished to use robotics to
increase the flexibility of production, including welding, but it was
decided to defer the automation projects until improvement could be
observed in the other components of the manufacturing process.
To initiate and continue the lean effort, the company secured a four-
year contract with their supplier of welding consumables and gases.
This supplier had on board a team of welding engineering experts who
provided this value added service, from the start of the lean journey.
In summary two Kaizen events were organized: the first focused on wire
feed speeds and reducing undercuts, and the second focused on welding
speeds and fillet weld sizes. During the first eight months, the plant
inspectors learned to measure and report the parameters targeted by the
events to ensure that the new productivity standards would be
maintained over the four-year contractual period.
The principles of lean manufacturing resulted in continuous improvement
to every aspect of the welding operations. After just 12 months,
productivity had increased significantly and major savings had been
achieved.
Lean is a long term commitment and requires dedication to achieve the
desired results. The methodology described in this paer can be applied
to any job shop using semi automatic welding to initiate a fully lean
operation in the plant. The common denominator of every such success
story is the commitment of upper management to the continuous
improvement process. Indeed, no initiative of this type has yielded
equivalent results without the active participation of top management.
Equally vital to the project’s success is effective communication with
employees to ensure they understand what is being done and participate
fully in the process. Many managers believe that the key to the success
of their lean manufacturing project is the positive attitude of their
employees.
This article was written by Viwek Vaidya, director, welding technology
and business development, Air Liquide Canada Inc., Montreal, QC.
airliquide.com
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