Design for Manufacture and Assembly:
DMFA is any aspect of the product that is designed specifically to make manufacturing and putting the final product together easier. This allows the product to be produced much more quickly, and also allows for easy repairs and replacement if necessary.
One way that Black & Decker does that with this screwdriver is in making all six planetary gears that make up the stacked epicyclic gear box the same. While it is true that all of the gears have to be the same for each gear train, they do not have to be the same for both of them. The fact that they are makes the six gears completely interchangeable, making it less likely for mistakes to be made in assembly of that part.
Because the gear trains are the same, they need to have a sun with the same pitch diameter. Black & Decker uses a planetary carrier that is directly attached to the sun gear in this design. This in itself is an example of DFMA, as it reduces the number of parts, but it is also another example of making it easier to assemble in general. Making more parts the same is just another way they make it easier to produce.
One final example of this is in the screws used in assembling the product. Throughout the screwdriver, the same screw are used almost everywhere. This is one of the most basic uses of DMFA, as it reduces almost any confusion about what screw is meant to be used where on the product.