SHEARING AND FORMING
Many products start as flat metal sheets. Shearing uses cutting blades to make straight cuts into a piece
of metal as shown in Figure 15-7. Also known as die cutting, you’ll often see shearing used on aluminum,
brass, bronze and stainless steel. Another metal-shaping process is forming, which uses compression or
another type of stress to move materials into a desired shape. Although forming is often used with metal, it
also can be used on other materials, including plastic.
EXAMPLES OF TRADITIONAL LOW VOLUME MANUFACTURING
There are many advantages to using low volume manufacturing that include: Producing a bridge run
(more than a few prototypes but less than full-scale production), reducing capital costs by having lower
minimums, lower financial risk exposure in case the product needs to be changed after a small batch is
created, and having shorter production lead times. This bridge run allows you to get to market more quickly,
while allowing the traditional manufacturings slow ramp-up to happen in the background.
URETHANE CASTINGS (CAST URETHANES)
It’s similar to injection molding in that polyurethanes are injected into a tool. But with cast urethanes, the
FIGURE 157: A Guillotine shear machine is shearing a metal sheet.
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tool is a soft tool, typi-
cally made with a type of
silicone mold as shown
in Figure 15-8. Silicone
is much cheaper than
steel or aluminum but
the drawback to using
silicone is that it doesn’t
last as long as injection
molding molds. With
urethane casting, the
mold is created via a
master pattern using
3D printing. Cast ure-
thanes are suited for low
volume production and
prototyping. Because
the cost for soft tooling
is lower, cast urethanes
are an excellent choice
for creators still testing
product design.
SAND CASTING (SAND
MOLDED CASTING)
This metal casting
process is character-
ized by using sand as
the mold material. The
term “sand casting”
can also refer to an
object produced via the
sand-casting process,
which dates back many
centuries. Over 60% of
all metal castings are
produced by the sand
casting process and
molds made of sand are
relatively inexpensive.
FIGURE158: Sets of Handmade Silicone Rubber Molds used in urethane casting
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Sand castings are produced in specialized factories called foundries, as shown in Figure 15-9. In sand casting,
a suitable bonding agent (usually clay) is mixed in with the sand. The mixture is moistened, typically with
water, but sometimes with other substances, to develop the strength and plasticity of the clay and to make
the aggregate suitable for molding. The sand is typically contained in a system of frames or mold boxes.
CNC MACHINING
As we mentioned above, CNC (computer numerical control) is used to make hard tooling for injection
molding. This process starts with a block of material (such as wood or metal), and removes material with
drills, boring tools and lathes, controlled by a computer program that is designed to make that pattern.
The CNC system transforms a block of material into the precise desired model as shown in Figure 15-10.
CNC is a subtractive process which removes material, while 3D printing is an additive process that builds
material up to create the model.
CNC was a major advancement and improvement over non-computer machining by hand. In modern CNC
systems, the design of a mechanical part and its manufacturing program is highly automated. The process
is fascinating to watch in person; bits of materials are flying everywhere within the enclosed machines and
the precision of the remaining design is impressive.
FIGURE 159: A foundry worker pours molten metal into sand based casts.
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CONCLUSION
Bringing a product to market can be exciting, but also expensive and exhausting. Regardless of the
manufacturing method you choose, there will be delays, mistakes and process interruptions. The more
you research the process, the better you will be prepared to make timely decisions, and the better your
results will be. It’s impossible to know everything in the beginning and you should expect a learning curve.
Hopefully this chapter gave you a glimpse of how to go from prototype to production and how to start a con-
versation with a manufacturer once you are ready for production.
In the last chapter of this book we will demonstrate how companies are using 3D printing to make proto-
types and products. Keep reading to learn how 3D printing will affect us in the future and how it will change
our world.
FIGURE 1510: Industrial high precision CNC machine creating an object.
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FIGURE 1510: Industrial high precision CNC machine creating an object.
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