DFMA: Assembly Mistake-Proofing
#1
A very common thing to observe by the image is that all the 6 planetary gears are totally similar in shape with absolutely no differences. Therefore, this makes it a great example of DFMA. As these planetary gears go into the planetary carrier pins, there are no chances of mixing them up as all the six gears are the same. Secondly, the pins on the planetary carriers are located at equal distances on the circle which makes it further simple to assemble the planetary gears on the pins as there is no sequence that needs to be followed. Hence, symmetry is brought into effect.
#2
This example of DFMA involves the body and the handle. There are specific gears on the handle which can only assemble and blend with the gears on the plastic body in a certain way making it another example of DFMA used by B&D. Therefore, it is not possible to join the handle with the body in any other way as the gears wont allow you to. Also, the plastic body has a unique shape with certain dents and openings here and there which leaves zero sources of errors for assembling the plastic body as well with the handle.
#3
It is very important to make sure that the motor is connected to the head in the right way with all the connections in place as the head has the epicyclic gear train which needs to work properly in order for the screwdriver to function. B&D takes care of this mechanism by using yet another example of DFMA. There are protuberances on the head and the motor which make sure that the motor can enter the head in only a specific way with its alignment in place. The pin which is connected towards the end of the motor enters a hole in the head which also helps the motor and the head to remain connected and compact. The pin wont enter the hole in the head properly unless you makes sure that the motor and the head are aligned properly.
MECHANICAL ELEMENTS
Forward/Reverse Switch
The forward/reverse switch works on the principle of changing the direction of the current through the system. The direction of the rotation of the motor (clockwise or anti-clockwise) depends on what side of the battery (positive or negative) is in contact with which terminal. If you observe the image, there is a piece which can be rotated by the user. Whenever this piece is rotated in a particular direction and pushed by the user, the circuit is completed with the positive side touching one terminal of the motor and the negative side touching the other. The direction of the motor can be changed by rotating the piece so that the positive side of the battery touches the terminal it was not touching before and vise versa for the negative side of the battery. This will result in the change of the direction of the current and the motor spins accordingly. From the circuit diagram it can be concluded that as the piece that can be rotated by the user makes contact with the terminals of the battery, current runs accordingly through the system in a particular direction which makes the motor spin clockwise or anti-clockwise.
Tool handle pivot lock
The mechanical design of the tool handle pivot lock involves the use of the orange outside covering which is the head, the black pin and the hole on the handle. The black pin is inserted into the orange covering as well as the metal hole on the handle at the same time. In the image, the pin has gears which do not line up with the gears on the orange plastic covering only when the pin is pushed inwards by the user making the orange piece connected to the body free to rotate, thereby unlocking it. When the pin is not pushed inwards by the user, the gears on the pin are lined up with the gears on the orange covering thereby forcing it into an automatic lock mechanism which restricts the orange piece from rotating when it is not in use.
Power/Manual Option
This feature involves translating the white ring gear (in the image behind the gold planetary carrier) upward and downward when switching modes between power and manual. When the feature is in 'power' mode, the white ring gear remains down and the gear chain and motor inside keep rotating unless the power is turned back off. Whereas in 'manual' mode, the white ring gear translates upward, locks itself with the gold planetary carrier which prevents the output of the head to rotate as the gears are locked up inside and the user can therefore use the screwdriver in manual mode.