Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2001-09-20
2004-06-22
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S162000, C700S197000, C219S069110
Reexamination Certificate
active
06754557
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to systems and methods for manufacturing mold components. More specifically, the present invention provides an integrated system and method for manufacturing plastic injection mold cavity stack components.
BACKGROUND ART AND TECHNICAL PROBLEMS
Plastics are used to make countless different goods, from pen caps, to coffee makers, to automotive heating and cooling systems. To manufacture such a wide variety of plastic articles in large quantities with precision, many manufacturing processes have been developed. For example, plastic part manufacturers have developed plastic injection molding, compression molding, vacuum forming, casting, extrusion, rotational molding, blow molding and injection stretch-blow molding to make parts. All of these processes have one common feature—the use of a mold.
Generally, a mold is a containment device whose internal cavity replicates the shape of a part to be manufactured. Ideally, a mold allows a manufacturer to produce anywhere from one to millions of a given part, each part being essentially identical to every other part made with that mold. Also ideally, the process used to make a plastic part reduces the amount of labor required to produce the final product and is the most cost effective process available for production of that product When deciding which of the above processes to use, and the type of mold to use, a manufacturer must weigh the often conflicting goals of cost reduction, high output and precision For manufacturers who specialize in the production of “low-precision” parts, such as inexpensive disposable pen caps, low cost and high output may be important considerations. Some plastic parts manufacturers, however, specialize in the production of extremely precise, high-end plastic parts, such as those that might be used in the medical industry. For those manufacturers, a high level of precision is an important requirement. However, even a manufacturer for whom a high level of precision is the ultimate goal hopes to achieve that goal while minimizing production costs and maximizing efficiency and output.
Plastic injection molding is often a desirable technique for making plastic parts because it can typically produce very precise parts at high volumes, for a low cost per item Basically, plastic injection molding involves designing and building a mold, injecting molten plastic into the cavity of the mold, allowing the plastic to harden into the plastic part being made and ejecting the plastic part from the mold. One disadvantage of plastic injection molding is the high front-end cost of making the plastic injection mold required for the process.
FIGS. 4
a-c
, in the accompanying drawing figures, illustrate a simplified representation of a standard mold for plastic injection molding and a simple plastic piece made with the mold. Typically, a plastic injection mold consists of a mold base
430
and a “mold cavity stack assembly”
410
. As described in further detail in the Detailed Description below, a mold base
430
is the unit which retains, aligns and supports the mold cavity stack assembly
410
and is typically a fairly standardized component of a plastic injection mold. A mold cavity stack assembly
410
, however, is almost always customized to at least some extent. It is the part of the mold into which molten plastic is injected and, thus, is the part of the mold that is custom designed and made for the manufacture of a specific part.
The mold cavity stack assembly
410
typically has two halves—an A side
410
a
, which includes one or more cavities
404
, and a B side
410
b
, which includes one or more cores
414
. A cavity
404
defines the outer shape of a feature of a plastic piece, while a core
414
defines the inner shape of the piece In
FIG. 4
a
, the mold base
430
and mold cavity stack assembly
410
are shown spaced apart.
FIG. 4
b
shows the mold base
430
and mold cavity stack assembly
410
in a mated configuration, with the plastic piece
420
formed by injecting molten plastic through an injection channel
412
(such as a heated sprue bushing) into the space created between the cavity
404
and the core
414
.
FIG. 4
c
shows the mold base
430
and mold cavity stack assembly
410
apart again, with the plastic piece
420
separated from the mold.
The mold cavity stack assembly
410
is typically made by designing and manufacturing individual components, usually from metal, ceramic and/or other heat-treated materials, and configuring these components together within the mold base
430
to form the cavity stack assembly
410
. Although the cavity stack assembly
410
in
FIG. 4
is relatively simplistic, other cavity stack assemblies may be very complex, involving multiple component parts to make up the cavity
404
and the core
414
. For example, a cavity stack assembly
410
may be designed to make an intrinsically complex part, multiple copies of the same part, or different parts. In general, and for purposes of this specification, the phrase “cavity stack components” means component parts used to construct a mold cavity stack assembly
410
.
Before a mold cavity stack is actually produced, it must be designed. This process starts when a parts order arrives at a plastic parts manufacturing company. The parts order may include partial or complete drawings of the part to be manufactured and/or a solid model of the part. If appropriate, a parts manufacturer may use drawings and specifications to create a three dimensional model of the part. For example, Unigraphics (Cypress, Calif.) provides software systems for digital solid model data sharing, such as its MoldWizard system, including mechanical computer assisted design (“MCAD”) software for producing three dimensional models for mold making.
After a plastic part to be manufactured has been thoroughly studied and modeled, it is typically the job of a mold designer to design the mold itself The designer may take dozens of hours or more to construct a preliminary mold design, often with the help of a computer assisted design (“CAD”) system. A plastic parts manufacturer may then require that the preliminary mold design be approved by one or more people other than the designer. For example, the preliminary design might require approval by a team of engineers or other mold designers, as well as one or more persons in charge of “tooling” the mold—i.e., machining raw “workpieces” of metal into finished mold cavity components (described further below). A designer may then have to change a design to receive the approval of the other members of the design team. Thus, the preliminary design of a mold typically changes with input from various members of the design team and with subsequent adjustments by the designer.
After the a mold is designed on paper, it must be constructed. The job of creating an actual mold from a design is often the job of a “master mold maker.” A master mold maker typically has many years of experience and training in mold making and is the person, mentioned briefly above, who decides how to best machine raw workpieces into finished mold cavity stack components. Often, a master mold maker begins to make a mold cavity stack assembly from a design and then, as the cavity stack is being assembled, makes adjustments to the design to make the mold configuration more effective. Master mold makers typically understand the intricacies of mold making to such an extent that they can anticipate engineering, manufacturing and performance problems, oftentimes before the mold is even fully constructed
FIG. 5
, in the accompanying drawing figures, shows how one, very simple cavity stack component may be machine-tooled The component resembles the A side of the cavity stack assembly
410
a
pictured in
FIG. 4
, which was used to make a pill bottle.
FIG. 5
a
simply depicts a raw workpiece
320
, which may be a block or piece of metal or other suitable material.
FIG. 5
b
shows the workpiece
320
with a cavity
318
that has been milled, drilled or otherwise machined into its surface.
FIG. 5
c
sh
Garland Steven R.
Picard Leo
Snell & Wilmer L.L.P.
The Tech Group
LandOfFree
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