Polyurethane can be hard or soft, flexible or rigid, light or heavy,
all depending on its chemical formulation. There are many specific
off-the-shelf systems on the market. But by custom formulating
in-house, we are able to think in terms of a spectrum of properties,
infinitely variable within certain boundaries. Here are some of the
things you can do or have, depending on how we formulate your
DURABLE & ABRASION-RESISTANT
Even though polyurethane doesn't have as much tensile strength as a
high-performance thermoplastic, like nylon, it can usually be made to
accommodate harsh physical demands because of its extreme versatility.
Strategic design utilizing sound structural geometry, thicker
sections, and/or ribbing can produce dramatic results. Plus, there's a
whole realm of encapsulated reinforcing inserts, including metal forms
WIDE RANGE OF DENSITIES
Parts can be molded as light as 2 pcf, as heavy as 70 pcf, or anywhere
between, just by controlling blow. But we can go quite a bit heavier
yet. By adding high density fillers we can mold parts in excess of 150
pcf. And, of course, there's always the option of embedding a chunk of
metal for even greater weight.
EASY TO ALTER WITH TOOLS
Cut with ordinary saws
Grind / sand
Machine with mill or lathe
Screw, nail, staple into
Polyurethane foam has more R value per inch than almost any other
substance. This property is commonly put to use in the construction
industry, with sprayed-on foam and cast sheets. But it can also be
advantageous in certain molded parts.
(Polyurethane is also electrically insulative, as are most other
polymers. But that usually goes without saying. What is worth saying
is that, for some applications, it can be made mildly conductive.)
Won't rot or rust (good replacement for wood or metal)
Won't get waterlogged
Some polymers dissolve in common solvents (like lacquer thinner,
gasoline, acetone, etc.), some don't. Polyurethane is extremely
resistant to most solvents, so applications involving exposure to,
containment of, or immersion in a volatile solvent are no problem.
Polyurethane is a design engineer's dream-come-true. No matter how
creative, artistic, exotic, or downright bizarre the thing you're
trying to do is, our answer is almost always, "Can do!" Here are some
of the basics:
THREADED INSERTS & STUDS
Threaded inserts and studs can be applied as a post-molding operation
(which is pretty good when you consider that urethane is not a
thermoplastic). But these things can also be molded right into the
part, providing the ultimate in strength, and many, many more choices
CAST THREADS, INTERNAL & EXTERNAL
PILOT HOLES & SPECIALTY POCKETS/SOCKETS
Metal forms, stampings, weldments
Fiberglass and other fibrous materials
Custom cast parts
Since STAPP molding is done at relatively low temperatures and
pressures, there is almost no limit on what can be safely
encapsulated. And parts can be fully encapsulated, or stick out in one
or more places. Seal and protect delicate electronic & mechanical
equipment and components while simultaneously molding finished surface
features. Make another product, fitting, or material integral with
your molded part.
THICK & THIN WALL SECTIONS
This is one of the really big advantages of STAPP molding over
injection molding-- you never have to worry about slink marks or
warping when combining thick and thin sections. Mold a big thick boss
behind an 1/8th inch panel if you want. There won't be any dip in the
front to give it away.
ZERO DRAFT AND UNDERCUTS
This is another major advantage. Our tooling utilizes both rigid and
flexible materials, often combined within the same mold. Even severe
undercuts can often be molded seamlessly in a part without special
CLOSE DIMENSIONAL TOLERANCES
On critical dimensions we can typically hold +/-.001"/inch.
PRECISION MATING PARTS
The natural color of polyurethane varies from off-white to dark brown.
A molded part can end up almost any desired color through the use of
one or more of these three principle coloration techniques:
Pigmentation--coloring the urethane compound itself
In-mold coating--a film sprayed into the empty mold that becomes
integral with the surface of the molded part.
Post-painting--conventional painting of the finished molded part.
Polyurethane can be pigmented with almost any color, including
fluorescent (Day-Glo®) colors, and even be made to glow in the dark
with phosphorescent pigments.
Uniform color, various texture techniques
Masked patterns, designs
Hand artistic painting
Staining / antiquing
Decals / transfers
Virtually any kind of texture can be molded in. The mold surface is
cast against a pattern, so any texture we can put on a pattern can end
up on a molded part. Splatter textures and leather textures are the
most common, but the possibilities are only limited by creativity.
Molds cast from a wood pattern can produce amazingly realistic
imitation wood. Stone & masonry surfaces can be use to create
interesting decorative effects. Even body contours and skin textures
LOGOS / SIGNAGE
Lettering and designs can be raised or recessed.
As versatile as STAPP molding may be, there are still some things
it is not well suited for:
LARGE, SIMPLE PARTS
Polyurethane raw material isn't as expensive as some plastics, but
that doesn't mean it's cheap. If a large part can be made out of a
less expensive material, chances are it should be. The advantage of
STAPP molding is in being able to make detailed or complex shapes
without all the labor that would be involved in fabricating or
machining, and without a huge financial investment in tooling. Things
like broomsticks, table tops, plastic 2x4's, etc. don't involve any
exorbitant efforts to get them into those shapes, so there is usually
no reason not to make them out of something cheaper, like wood.
WHEELS & ROLLERS
There are some types of polyurethane with special physical properties
that can't be processed at low temperatures and pressures, and
consequently require special machinery and handling. Wheels and
rollers are usually made of such materials. Consequently, we leave
that production to the manufacturers who have chosen to specialize in
HIGH PERFORMANCE PHYSICALS
A properly designed polyurethane part can offer outstanding
performance in many high physical applications. But you can't squeeze
blood from a turnip, and you can't get 12,000 psi tensile strength
from a molded urethane part. If you need something as strong as nylon,
and you have no room for reinforcements or geometry modifications,
you're pretty much stuck with thermoplastics, and either fabrication
or high tooling costs.
How much heat a material can withstand varies depending on how the
heat is applied, for how long, and what you want from the material at
elevated temperature. Urethanes usually have no problem at 1200F, and
are often used in applications that may intermittently see
temperatures of 1500F or more. But if you need a part that has to
function in an environment that is usually over 1800F, you probably
shouldn't be using urethane.
It's not that clear urethanes don't exist. But they tend to be very
pricey. And if the application involves UV exposure, there's an added
challenge, since the methods normally used to protect urethane from UV
degradation-- high pigment loading or opaque coatings--obviously
defeat the purpose of letting light through. And if you want optical
clarity, you're talking about highly polished mold surfaces that
aren't compromised by uneven films of release agent. Everything
considered, we've chosen to avoid clear urethane molding.
WELD, THERMAL OR SOLVENT
There are numerous ways to attach two or more molded urethane parts
together, but welding is not one of them. Urethane isn't a
thermoplastic. It doesn't melt and resolidify, so you can't thermal
weld it. And it is impervious to virtually all solvents, so you can't
solvent weld it. There are several good adhesive choices, though.