ICA02_Introduction Toothbrush design has gone through few substantial changes in its long history. Until the early 1900s, toothbrush bristles were generally made of Siberian hog hair. But in 1938, the soft-bristled Miracle Tuft Toothbrush was invented. Within a decade, Oral-B was mass-producing soft-bristled toothbrushes. In 1961, the electric toothbrush was introduced. Beginning in the late 1970s, the toothbrush industry started churning out a variety of new designs. They included variations in bristle shape, size, and texture, as well as unconventional handle styles.

The Manufacturing Process: Injection molding is one of the most common methods of shaping plastic resin into useful objects. The process involves heating pellets of plastic resin to melting point then injecting the molten resin into a mold. Molding the handles and head.

The first step in manufacturing a toothbrush is to create the toothbrush handle. Simple, manual toothbrushes and more complex electric toothbrushes require a plastic handle, though the molds used to shape these different types of brushes are quite different. The injection-molding machine deposits liquid plastic into the mold and then pushes the handle out of the mold once the handle is solidified.
Multi Injection. For multicolored brushes, there will be two-stage injection process as described below: When the pre-injection is completed, the mold slides open with the handles still attached to it. Then the mold rotates 180° and closes so that the brush handles now face another die / cavity which can inject different shape and different color on to the handles.

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Bristling.

After the handles are formed, a filling machine is used to attach the bristles. In modern toothbrushes, these are made from nylon or plastic. The filling machine pushes the bristles into holes in the head of the handle and then staples them into place.
Trimming.

A trimming machine trims off the ends of the nylon bristles so that they are all the proper length. In toothbrushes with specialized bristles, this machine will also trim the bristles to the required shape and angle.
Packaging.

At this point, the toothbrushes are finished, but they still need to be properly packaged so that they remain sterile until they are ready to be used. Packaging machines will form the container to the correct size and seal it around the toothbrush so that dirt and germs cannot get into the packaging.
Justification and Conclusion Injection plastic molding process has many advantages over other plastic molding processes as listed below: Ø Once a job is set up, injection molding can produce very high production output rates with parts coming off the machine every ‘x’ seconds all day and night. Ø It is possible to use more than one material at the same time when utilizing coinjection molding. Ø Inserts can be used in the mold to adapt the product slightly. This means it is not always required to use a new mold for product adaptation. Ø Fillers can be used for added strength to the components.
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Ø There is usually very little “post production” work required to finish each part because the parts usually have a very ‘finished’ look upon ejection from the machine. Ø All scrap plastic may be re-ground to be re-used (unless specified not to); therefore there is very little waste, which adds to the environmentally friendly nature of the process. Injection molding is a method of creating plastic products. Most plastic products are made using injection molding. This process is attractive to manufacturers because of multiple advantages it provides over other plastic molding methods. Overall, injection molding is simpler, more reliable, more versatile and more efficient than most other types of injection molding.

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