Electronic Parts/Guidelines - infoHouse

Plastic Container Manufacturing: The above plastics are some of the more commonly used plastics for
reusable containers. in many applications, these materials can be designed and manufactured into
very rugged and durable containers. Although this guide does give general descriptions of manufac-
turino techniques, the package designer should work with plastic container suppliers to identify and
select the most environmentally-sound, cost effective and durable container design and manufacturing
technique. The following are general descriptions of some of the more common manufacturing tech-
niques:
Injection molding: This is the most common method or process for manufacturing plastic con-
tainers. It provides design flexibility and can produce fine details and uniform wall thickness's
Injection molding tooling is often very expensive. A variation of injection molding, structural foam
molding, requires less expensive tooling. The process involves blowing nitrogen gas through
plastic In a mold. This produces a container wall that has bubbles or voids, but still very stiff. This
technique offers stiffness with less material.
Rotational molding: In this process, liquid (melted) plastic is formed into a container within a
female mold, while the mold is rotated around two axes and heat is applied. Rotational molding is
often used for larger containers that require lots of material. Tooling is moderately to very ekpen-
slve.
Vacuum forming. There are three types of vacuum forming: straight, pressure molding and stretch
forming. Vacuum forming is generally used for containers that have simple configurations and for
lower container volumes (number of units), where higher priced tooling and techniques can not be
justified. Vacuum forming is also generally limited to smaller containers and containers where
dimensional tolerance and consistency is not critical. Tooling for vacuum forming is relatively
inexpensive.
Blow molding. This process is used to form bottles or containers from plastic by expanding a
blank in a hollow mold. The blank is ordinarily a tube. The molds for this process are generally
inexpensive. The most common application of this process is the manufacture of cases for tools.
High Density Cushions: To provide durability and adequate shock protection over a long reuse life,
reusable cushions are usually made of high density foams. The most common high density foam
material used is expanded-polyethylene. Densities of 32 kPa (4 Ibs/cubic R) or greater are often used.
This materlal can be molded and hand or machine fabricated. It is also commonly available and
recyclable. Other high density foams sometimes used are polypropylenes and some polyurethanes.
Corrugated Fiberboards: One of the biggest concerns with reusing Corrugated flberboard containers is
with top-to-bottom compression strength. The compression strength, after repeated uses and exposure
to changing temperature and humidity conditions, quickly weakens. A few alternatives to maintaining
or increasing compression strength include:
adding more flber thru thicker linerboards and mediums or by using a multi-wall construction (Le.,
double or triple wall) ... this adds to material cost and increases the container weight and size,
adding to transportation costs:
using cross-linked fibers ... this paper production technique redirects some wood fibers to run 90
degrees to the paper's machine direction, resulting in more fibers running vertically up and down
on the linerboard of containers;
using high-pressure forming ... this paper production technique involves extending the point of pres-
sure on paper fibers. to more tightly compress them, resulting in a denser sheet of material:
using multiple or bonded mediums ... this paper making technique is based on laminating (usually
with corn-starch adhesives) two or more layers of medium together and then sandwiching the
material between cross-linked or pressure formed liner boards; and
using chemically treated fibers ... this paper making process involves the bonding of fibers with corn
starch, glues, adhesives, PCB's, heavy-metals, and plastic or urea-formaldehyde resins: the use of