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The tub was tested for a 50-L, 1400-rpm unit, and tested for 4700 cycles.
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Does a $2.50 saving on a washer tub really make a difference?
Saving
money was one of the goals when engineers from Italian engineering and
moldmaking company Meccanica Generale (MG) began a €1.8 million,
two-year project to develop a new generation of washer tub.
Already
a strong player in horizontal-drum washer tub engineering, the company
began with the notion that the current design leaves little room for
improvement in material use and production cycle time. MG came up with
the idea to separate the water-containing and the structural functions
of the tub, thus allowing for more accurate dimensioning.
Three-Section Design
Instead
of the main back section and the front section, the new design is
composed of three parts. In addition to the front and back tub is a
bottom plate, which carries the bearing support and the structure. By
switching the weight of the drum to the bottom plate, the weight of the
back and front drum can be reduced—which gives designers a great deal
of freedom to change the design.
There is also a new system for attaching the counterweights that is engineered to be safer and more cost-effective.
To
some, the concept might be counterintuitive: saving resources by
designing-in an extra part. But it begins to make sense when explained
by Stefano Mancini, MG’s director of R&D and inventor of the new
concept.
“We took an unusual step. One of
the changes is to use a glass fiber–filled material for the full range,
instead of calcium carbonate–filled PP (polypropylene),” Mancini says.
“Glass fiber might be more expensive, but measured in strength units,
it is more cost-effective. Second, the total tub weight is
approximately 40% lower.”
Creating a box
section between the tub and the back plate, Mancini says, results in a
design that resembles the iron cross construction used in
stainless-steel tubs. “The advantages are significant: on a typical
1200-rpm tub you normally need 6 kg of PP with calcium carbonate, but
our design only uses 3.5 kg of the 30% glass fiber PP.”
The
standard plastic is usually calcium carbonate PP that costs about €0.5
per kilo less than glass fiber PP. But measured in strength units,
glass fiber costs only 67% of the cost of calcium carbonate PP.
The
tubs also save 40% in material processing and 15% in molding time.
Looking at the savings on a mass-production scale, there are notable
environmental advantages: The energy saved to process 500,000 parts is
equivalent to 1261 barrels of crude oil; the reduction in material
weight for the same quantity of parts saves 39,000 tons of water and
reduces CO2 emissions by 1400 tons.
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 A bottom plate handles bearing support and allows more design flexibility for other tub sections.
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Joining Techniques Provide Speed and Savings
“The
structures are attached using vibration welding,” Mancini tells
APPLIANCE magazine. “Welding only takes 20 seconds. We also designed a
new method for attaching the counter weights, using special springs,
achieving a 50% reduction in fixing costs. Applied together, our ideas
can shave €2 to €3 off of the typical tub costs of around €10.”
It
only takes a little math to see how significant such savings can be.
“If you make 3 million to 5 million washers a year, and your net profit
is 100 million, the cost reduction is very interesting,” Mancini says.
Particularly, he adds, when one considers that the payback time is
about one year.
Advantages can extend to the
performance of the appliances itself. “A lighter tub also affects the
energy use of the actual wash cycle,” Mancini says. “There is less
material to be heated; the end user saves up to 8%.”
The
tub was tested for a 50-L, 1400-rpm unit, and tested for 4700 cycles.
Future development may include integrating components such as pump,
recirculation, or air trap.
Mr. Montevecchio,
MG’s director of business development, says the design project was
completely self-initiated. No specific customer was a partner in the
development of the new tub. However, the company already works with
most European appliance OEMs and several are evaluating the new tub.
