The beverage industry offers many challenging problems for engineers, applying the cap to a given container being one of utmost importance. Capping a container is a process that must be carefully balanced. If the cap is applied too tightly, the consumer will be unable to open the container and thus unable to enjoy or use the product. However, if the cap is not applied tightly enough the product will never survive being shipped to the consumer. Therefore, a solution that can successfully apply a cap to its container, such that it doesn't leak or become unable to open is desirable.

The American Society of Mechanical Engineers or ASME has offered the problem of orientating, filling, and capping a plastic beverage container as a part of its spring student design competition. The problem begins with a generic plastic one-Liter bottle lying on its side on a flat table with the mouth of the bottle one-Meter from the target area and five centimeters from any portion of the device. The challenge is to then transport the plastic bottle one meter to the target area where it will be filled with one-Liter of colored water. Once the filling is complete the unmodified cap must be applied such that the bottle will not leak when placed on its side for a time of two minutes.

The already challenging task of orientating, filling, and capping a plastic bottle is made even more difficult by requirements developed by the ASME. The requirements fulfill two purposes. First they serve to help limit the cost of a possible solution, and second they provide a common starting point from which all designs can be evaluated during the competition.

Of the all the limitations developed by the ASME two are most crippling. The first of these is that only 1.5-3.0 Volt DC Radio-Shack motors powered by a single AA battery are allowed to actuate any motion. This requirement is limiting because the motors without substantial gear reduction incapable of significant torque. The second extremely limiting requirement that must be considered during the development of any solution is that eventually all elements of the design must fit within a rigid box measuring 30x30x50 centimeters.

Before undertaking my quest for a solution to the problem of capping the bottle some important assumptions were made. First it was assumed that the bottle would be transported to an upright position and subsequently filled. Second that any design was allotted one-third of the space and time allowed to the entire group to complete any processes. The solution developed works in the following manner. The presence of the bottle is sensed via a photoelectric sensor. This sensor inputs a signal to a PLC which then actuates three Radio-Shack DC motors. Two stacked motors provide the twisting motion while a third motor coupled to a gearbox lowers the tightening device to the mouth of the bottle. Once the cap is tight (determined by timing), the stacked motors stop rotating and the geared motor reverses. The rubber lined cap holder is pulled off the cap as the water heavy bottle stays in place. The system is then ready to accept another bottle and cap.