Prototype Plastic Mold Making And Molding
The demand for a prototype plastic mold is not as great as it
once was, due primarily to the 3D graphic ability of high end CAD mold design software. Nevertheless, many advances have been made in the past few decades
that make the prototype an attractive process for industrial designers, inventors and custom molders.
Prototype mold making is a special niche
There are many ways to build a prototype plastic mold, but the common theme is quick,
as in very quick. Most markets reward the first one to the marketplace, and plastic molding is no exception.
You can build a prototype out of aluminum, pre-hard steel such as NAK 55, NAK 80, P-20 and PX5, or even heat
treated tool steel such as H-13, 420SS, or S-7. The decision is based mostly on the detail involved in the plastic
part, time constraints, and the expected life cycle of the mold.
Prototypes are great for injection moulding production
Obviously, if you want the prototype mold to make 100 parts you don't need a hardened
tool steel mold, but rather aluminum. On the other hand, many times the short-run tooling seems to just keep on
performing and the next thing you know, it has produced 500,000 parts!
Using prototype molds for injection
moulding production is one of the tricks of the trade. A well built soft tool can last much longer than
most people think.
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Some companies claim the ability to provide an accurate prototype mold in less than a week, even within days. This
means that the part design has to conform to certain standards, such as no slides or lifters to mold the
Plastic molding design is central
If the designer is able to work around these types of constraints, it can be a great
way to be the first one to the marketplace. Otherwise, you can go a more conventional route and have a short run
production tool built.
Since speed and accuracy do not normally get along together very well, consideration
must be made to decide which details are most important and just how critical are those features that are likely
dimensioned with too close tolerances.
Many times designers simply use default tolerances because they are not familiar with
the mold making side of tooling. This is tremendous waste of time and money in some cases. Who needs an ejector pin
plate to be flat within .0002 in.? Or just how good a surface finish is necessary on the bottom of the part, which
is never seen anyway?
Modular tooling to the rescue
The MUD style mold is another common way to get a precision part molded very quickly.
Since it relies on the interchangeability of the core and cavity sets, there is no need to build a complete mold
MUD molds are quite versatile and have been used in the industry for decades. There
are many variations on this theme, but the common denominator is interchangeability. You can also get a similar
product that uses round inserts, which works well for specific applications.
Prototype mold making is here to stay
Despite the decline in prototype mold making in recent decades, the need is still
very much alive. With the integration of CAD and CAM it is possible to produce an accurate, inexpensive prototype
plastic mold very quickly and reliably.
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