Metal Spin Casting Applications
Overview
One
of the most exciting modern applications of spin casting technology is
its use in rapid prototyping and product development. It is ideal for
quickly and economically producing numerous fully functional, fragile
parts in high-strength metal or plastic from computer-generated RP
models.
Product designers can then subject multiple parts to
thorough testing and evaluation in their intended applications. With
the new rubber mold materials now available, molds can be made and
prototypes or development parts cast in as little as three hours.
Even
complex parts usually take less than one day. Thus, design changes in
size, function, fit or appearance can be quickly reproduced without
requiring a large investment in tooling or machine time.
Spin Cast Advantages
- Achieve a competitive edge with faster "time to market" capabilities
- No costly metal tooling required
- Same-day results with in-house control
- Simple to use technology
- Increase productivity – provides 30-50% more casting cycles per hour, per operator
- No heavy mold cover plate – to handle each cycle
- No lift-over of molds
- Automatically adjusts for mold height – no manual adjustments needed
- All mold handling done at waist level
Maximum Part Size
The
maximum part size that can be cast using spin cast technology is 100 x
50 x 35mm (L x W x H) with nominal wall thickness ?of 2.5mm (min.) to
6.5mm (max.).
Metals that can be Cast
ZINC: Commercial grade zinc-based alloys,
derived and modified from standard zinc pressure die cast alloys. Zinc
alloys are often used as direct replacements for aluminum, iron, copper
and low grade steel-based alloys to provide similar strength and/or
reduced cost on the same application.
Zinc alloys readily accept a wide variety of decorative and
corrosion-resistant surface finishes. They can be painted to match
adjacent parts, externally dyed in a variety of colors or chrome plated
for a hard, durable finish. They can also be fully electroplated to
take on the appearance of brass, bronze, stainless steel, silver,
chrome or gold, etc.
High tin, white metal & lead alloys Containing no lead or cadmium.
Lightest tin-based alloy for jewelry casting. Highest degree of
strength, whiteness and brightness. Castings do not need to be plated.
Suitable for intricate shapes, filigree, textured surfaces and for
pronging and model making. Normal casting temperatures range from 274 –
330?C.
Special grade, ready to use zinc-aluminum-copper alloy
This
is the most popular spin-casting zinc alloy, ideal for medium-sized
parts up to 1kg each, with wall thickness of 16mm or under. Produces a
very fine-grain, smooth-surfaced finish with excellent detail and very
low porosity. Has high strength and hardness and is fully
electroplatable. Normal casting temperatures range from 400 – 420?C.
Provides a very long mold life, usually 30% longer than other
commercial grade zinc alloys.
Six Easy Steps
Step 1: Preparing The Mold
Parts or models are
laid out on a disc of uncured silicone rubber. Depending upon
model/pattern thickness and shape, cavities may be cut or molded by
hand to accommodate the part. The uncured silicone material is soft and
pliable like clay. The mold parting line is formed at this stage and
can be built up or lowered around any section of the model/pattern.
Parts of any complexity can be handled. Cores and pull-out sections can
also be easily incorporated, if required. Mold parting compound is
sprayed on the mold and "acorn" nuts are arranged around the edge where
(like pins of a die) they precisely position the mold halves in line
with each other.
Step 2: Vulcanizing The Mold
After preparation,
the mold is placed in a vulcanizing frame. This frame is placed in the
heated vulcanizing press for curing. The combination of heat and
pressure forces the silicone into all crevices and around all details
of the model/patterns.
The heat cross-links and cures the silicone. The resulting mold is
tough, resilient, dimensionally accurate, and heat and chemically
resistant.
After vulcanization the mold is easily flexed to release the
patterns (and later, parts) from the cavities. This is true even for
patterns with many undercuts.
Step 3: Gating & Venting
The gates, runner
system and air vents are easily cut into the cured rubber mold with a
sharp knife or scalpel. Air vents may also be drilled into the cavity
to aid in venting of trapped air or gases. Similar gating and venting
systems are used for metals and for plastics, so both materials can be
cast in the exact same mold for evaluation, if desired.
Step 4: Placing The Mold In The Spin-Caster
The
mold is placed into the casting unit – the front-loading unit shown.
The mold is automatically centered and closing the door activates a
pneumatic mold clamp. Spin speed, clamping pressure and cycle time are
fully adjustable with the solid state digital controls.
Step 5: Pouring & Spin-Casting
After the
spin cycle starts, the liquid metal, plastic or wax is poured into the
casting unit. Pressure caused by centrifugal force pushes the liquid
through the mold's runner system, completely filling every section,
corner, detail and surface finish in each mold cavity.
Step 6: Removal Of Spin-Cast Parts
After metals
solidify and plastics set, the parts are quickly removed from the mold.
With metal, 50 to 60 cycles per hour are usually required; with plastic
or wax, 8 to 12 cycles per hour are typical.
The gates, runners and vents are easily broken away by hand.
Castings are ready for assembly, for painting, planting or coating,
with no additional clean-up needed. Spin casting is a precision casting
process producing high-integrity, close-tolerance parts comparable to
die casting or plastic injection techniques.
* Reference: www.nicem.it
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