There are five primary necessities that pertain to human survival. They are: Sustenance, clothing, shelter, transportation, and healthcare. Humans must have food and water, protection for the body from the elements, a domicile that is sheltered from the elements, means to move about and gather materials necessary for self preservation, and remedies for healing from illness and injury.

Humans living in communities or cooperative living require two second tier necessities which are means of communication and means of exchange. One additional necessity of varying significance is defense. Education is a third tier requirement to pass knowledge and skills to the younger generations. These nine primaries, second tier, and third tier necessities are the basis of industries that support the evolution of civilization and technological development.

As necessity is the mother of invention, creativity and invention are ongoing human activities related to improvements in the level of comfort and convenience for civilized habitation. Creativity abounds and not just in the world of humans but in all of the lower species as well. There is something natural in all life forms that cause them to seek more optimal means of survival and comfort. This spirit of creativity brings us to a tenth category of necessity, invention. In modern industrial societies we have specialized careers relating to these ten necessities. Most enter the fields best suited to their personal talents.

Three dimensional (3D) CAD (computer-aided-design) models have enabled major productivity gains in product design and engineering. Prior to the advent of economical desktop computers skilled draftsmen spent hours laboring with graphite lead pencils on velum and Mylar to achieve engineering quality documentation for fabrication and production manufacturing. The process required tedious checking to eliminate errors wherein modification required erasures and redrawing over and over on the same sheet. Large projects had many drawing documents linked to one another that required procedural revisions and archiving.

Two dimensional (2D) CAD (computer-aided-design) was a great step forward in moving from the drafting table to the desktop computer. The graphical display capabilities of the desktop computer enabled a user to graphically draft using mouse, keyboard strokes, text line commands, and tablet with stylus. Each CAD system had its own (UI) User Interface. While manual drafting may have actually been faster in the early years, two dimensional (2D) CAD (computer-aided-design) technologies allowed endless changes to be made with sharp clean printed copies printed without limitation. It was easy to export the CAD drawings in PDF format for viewing and printing on any non-licensed computer.

Injection molding of plastics is one of the most cost effective processes for manufacture of parts in volume. While mold costs can be significant, amortization over many parts can make the overall cost of injection molding highly competitive with other manufacturing processes. The wide range of available polymers multiplied by the huge array of specific blends offer a tremendous range of physical, thermal, electrical, and chemical properties. Engineering plastics, classified by mechanical properties such as stiffness, toughness, and low creep, increasingly replace metals on a cost and performance evaluation.

Designing for injection molded plastics requires planning. Too often parts will be presented to a molder or tool designer late in the product development process only to be confronted with feasibility issues. If that happens the developer faces decisions to rework part designs or to face higher tooling and part costs. Leaving design for manufacturing and assembly (DMFA) considerations until late in the development program is a common mistake the misses out on optimization and disrupts the transition to manufacturing.

Planning begins in preliminary design. Some will argue that consideration for manufacturing early in the program will inhibit creativity; the reality is that it does not if perspectives are kept in balance. In fact design committee often err in committing to a design that later reveals feasibility and cost issues. While designers and engineers need to be free to brainstorm potential solutions, taking time to evaluate for manufacturing options is vital to assume a successful program. http://www.cadmodels.biz/3d_cad_design_for_injection_molded_plastics.html

As with all modern scientific and technological endeavors, computers, software and internet tools play an increasingly important role. As well as the typical business application software there are a number of computer aided applications specifically for engineering. Computers can be used to generate models of fundamental physical processes, which can be solved using numerical methods.