Articles

DNA had the Right Angle for Black & Decker ~ Appliance Magazine - October 2000

B&D and DNA Group DTD switch: Versa Pak Right Angle Screwdriver

The determination to design the right assembly was a commitment made by both Black & Decker and DNA Group. Today DNA supplies more than a million units, doubled from 1999. The growth of the program from the onset of production is proof of the success of the Versa Pak Right Angle Screwdriver.

Black & Decker, Inc. (Towson, MD) had a great vision with the birth of its Versa Pak product line.

Black & Decker’s (Household Products) Versa Pak right angle screw driver, estimated initially at 300,000 units a year, grew to more than a million within the first year of production. DNA Group, Inc. (Raleigh, NC) is no stranger to the Versa Pak product line. As a supplier of switches and custom PCB’s, DNA was involved with other Versa Pak programs including the 1 and 2 port battery chargers, Scum Buster, 7.2V 2-speed drill and the 7.2V cordless circular saw. The right angle screwdriver has been as successful for DNA as it is for Black & Decker.

The screwdriver application required a double-pole, 3-position switch with “Forward/Off/Reverse” functions, provided by momentary actuation for both ON positions. It also had to match the overall look of the Black & Decker Versa Pak product series. DNA offered a few ideas for alternative construction. Working closely with Black & Decker’s Senior Engineer and Project Manager of the screwdriver program, Kevin Covell, three key ideas were outlined, reviewed and thoroughly analyzed before the final selection was made.

One option proposed was a printed circuit board assembly. It was a plated through-hole double-sided board. The switch, buss bars and positive battery terminal would be mounted on the top of the board and the negative battery terminal mounted to the bottom of the board. The board itself, while providing the basic layout and structure for the assembly, would also act as an insulator between the positive and negative battery terminals. Black & Decker chose not to pursue this idea for several reasons. First, the current-carrying capacity (ampacity) was deemed insufficient for the screwdriver application. Second, there would be high number of solder joints required, and Black & Decker determined this could possibly be a source of future quality issues. Finally, the assembly was cost prohibitive.

Another option reviewed was to use insert molding. The plastic would be molded around the top of both battery terminals, and attached to the bottom of the switch. The idea of injection molding was to provide a mechanical process for consistent parallel assembly of the battery terminals, one critical aspect of the assembly process, reducing room for human error. The injection molding would also serve as an insulator between the positive and negative terminals. However, after the analysis process this idea was also not pursued. Once the assembly was molded the accessibility of the lower level buss for soldering would be diminished. The molded plastic would also make it difficult during assembly to get an acceptable connection between the quick connect terminals and the application. Like the PCB assembly, this idea was also cost prohibitive for the program.

The chosen assembly did not include any of the excess materials as the two previously mentioned methods, such as the PCB or plastic molds. The concept was to solder the value added components directly to the switch rather than through additional materials. The result of the design process was a customized switch that was both economical and yet designed specifically for the look Black & Decker needed. By simply adding customized features to a standard miniature toggle switch the overall tooling cost was kept to a minimum and yet provided the exact fit, function and appeal required for the screwdriver program.

The value-added components, produced at Defond Manufacturing Ltd., Hong Kong, included custom-tooled terminals, positive and negative battery terminals, and angled 110-mm quick connect terminals. The battery terminals have many critical dimensions such as thickness and angle measurements that were required with very minimal tolerance due to the unique design of the Versa Pak battery itself. In the absence of a PCB or molded plastic, fish paper made of vulcanized fiber was used as insulation plates to separate the positive and negative battery terminals and the connection terminals.

In meeting the aesthetic appeal of the Versa Pak program, custom features of the assembly included tooling a glamour cap designed by Black & Decker. The glamour cap is a good representation of Defond’s versatility and molding capabilities and it gave the switch the external design to aesthetically match the Versa Pak product line. The cap has both smooth and textured surfaces and is molded in two different custom colors; the well-known Black & Decker orange, and the red used in Black & Decker’s “Sears-Craftsman” product line. To adjust to the fitting of the glamour cap, as well as allow appropriate mounting of the switch within the screwdriver housing, a metal bracket (upper housing plate) was tooled and the switch shaft was lengthened.

Defond’s vertical integration gave DNA and Defond the edge on this product. The soldering of the terminals to the switch adhered to the standards of IPC regulations (ANSI/IPC-A-610 Rev. B). Defond built fixtures to use during the assembly process for consistency and maintenance of critical dimensions and the parallel assembly of the battery terminals. This enhanced the quality construction of the switch. This final assembly chosen by Black & Decker required minimal solder joints reducing potential problems, reduced the overall materials used and reduced the overall size of the assembly, all resulting in a reduction of the final cost.