- Application of the right plastics
and production methods can cut costs and shorten development time.
The plastics industry has gone through
major changes since Dr. Leo Baekland introduced "Bakelite" in
1909. As recently as a decade ago there were perhaps 35,000 plastic
formulations. Now it seems that there are specific compounds for every
purpose. Today's design challenge is to build increasingly complex and
robust products faster, and at a lower overall production cost. Viable
solutions can be found with the use of plastics. With thousands of
possible choices, product developers need a solid knowledge of the
families of plastics, and be aware of the best candidates for specific
projects and applications.
The resins that account for 80% of those
used in the medical market are the commodity resins: PVC for tubing and
bags, polyethylene (medical
packaging), polystyrene (lab ware), and polypropylene for syringes. In the
remaining 20%, the so called engineering resins, we see uniqueness and
extensive cross-over from one category to another. Application requires a
specialized knowledge of the materials and processing requirements to make
the best use of their particular characteristics.
Most of the products Omnica develops
use plastics somewhere in the design.
In the last 30 years we have developed hundreds of molded parts. Before
designing a part, we need to make a decision on such factors as how it
will be produced, which performance characteristics are most important,
the cost and availability of the material, the required aesthetic values,
and if it will be exposed to sterilization. One example is how shrink rate
properties can affect material selection. A handle, for instance, could be
made of many materials including ABS or Delrin™. If injection molding
was chosen as the preferred manufacturing process, the designer/engineer
needs to be aware that the two plastics behave differently when heated.
ABS probably couldn't be used in a mold designed for Delrin™, because it
won't shrink to the same dimensions.
Andy March, a fixture at
Omnica for over 18 years ,
shows some of the rotationally-molded designs he has worked on.
Metal
replacement plastics
Plastics have often been used as
replacements for more traditional materials like metal and glass.
Performance plastics like Ryton™, Ultem™ and Valox™ weigh less than
metal, and some replacement parts can be less expensive to produce. We
recently designed eight plastic parts for Nellcor Puritan Bennett that
replaced the same number of metal parts in their conserver
valve. We shaved 60% from the total weight and reduced production
costs by more than 30%. The prototype tool was machined in-house, where we
injection molded and tested the first articles.
Rubber
replacement plastics
The Omnica team can
offer alternate choices that can save customers time and money. Thermoplastic
elastomers like Kraton™, Pebax™, and Santoprene™ are often good
rubber replacements. They can be used for over-molding buttons, keypads,
and handles to get just the right "feel". Engineering resins
like polycarbonate (Lexan™) and acrylic are aesthetic plastics that take
a high polish. They can be used in many applications that in the past
would have required glass. Substituting plastic (which can be hardcoated
for scratch resistance) for a glass lens can cut costs significantly,
reduce weight, and diminish the risk of breakage.
 Knowledge
of processes, not just the choice of materials can make huge contributions
to aesthetics and cost savings. Recently, a large California-based
ophthalmic supply and instrumentation firm hired us to redesign a
surgical-support cart. They came to Omnica, expecting us to simply offer
some innovative styling concepts. We suggested rotationally molded
polyethylene for their design, which ultimately saved hundreds of
thousands of dollars in production costs compared to what they had
budgeted. The new cart looks great, is easier to clean, and is more rugged
than the painted foam they had used in the past. The
cart won the American Rotational Molder Association achievement award.
Rotomolding offers many advantages
over other manufacturing methods.
1) The parts are rigid and light weight.
2) The integral color is scratch-resistant and easy to maintain. Designers
and clients can specify any of a variety of colors and finishes ranging
from smooth solid colors, to a heavily textured "granite" look
surfaces.
3) Post-finishing is usually not required.
4) Reduced assembly time is another important cost-saving factor. For this
project, structural foam components would have required joining many
individual pieces after molding. Instead, we were able to design the
surgical cart as a single finished part (minus the caster base - we
accommodated our client's insistence on that one structural foam part.)
with inserts, bosses, supports, and hinge points in place.
In a project we did for Alcon Surgical,
we replaced 120 metal housing, hardware, and assembly parts with a single
housing made of plastic. The weight savings was over 60 pounds, and no
painting was required afterwards.
According to Gordon Sanden, now general
manager of Meese Orbitron Dunne Company, California (MOD Custom
Rotomolding), finished rotomolded parts cost between
50% and 80% less than similar structural foam parts.
Omnica can offer our customer choices
that weren't possible even a few years ago.
Plastics can offer
lighter weight, lower cost, and consistent availability. They can be more
easily manufactured and produced than traditional materials, and part
production costs can be substantially lower. If you have an
existing product or one that is ready to be redesigned, let's talk about
it. The Omnica team may be able to offer you some options.
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