We updated the BOM table as we learned more information about our product. We added more specific manufacturing processes, the material grade, whether or not we could combine or eliminate parts of the toy, and a set of notes detailing the cost implications:
We read through all the DFA or design for assembly methodology rules and selected those relevant to our product. Our comments on each of them are bellow:
Minimize part count by incorporating multiple functions into single parts:
There are two types of gears in our mechanism, simple gears followed by spacers and gears which have attached spacers. If we were to follow DFA rules we would only use the complete gears.
Modularize multiple parts into single sub-assemblies:
As previously mentioned in the report, the legs of our toy have several superfluous components, including joints, screws and sockets. We intend to fix this part, designing one single piece to replace the mechanism.
Standardize to reduce part variety:
Our product has many gears, which have different widths and sizes. We could try to reduce the variety while maintaining the desired gear ratio.
Color code parts that are different but shaped similarly:
As there are a lot of gears that should be fitted in both left and right parts of the body, marking with the same color each gear axis and the area where it has to be fitted would facilitate the assembly process and also make the product more colorful, which is an important aspect for a toy.
Design in geometric properties:
The design on our toy is extremely symmetric, which is essential for balance. No improvements are needed.
Eliminate fasteners:
The left and right parts of the body are joined by very small fasteners and tabs, as well as really small screws. This system could be improved.
Provide flats for uniform fastening:
The body parts were the fastening joints are located are very flat and smooth surfaces, which simplifies the assembly process.
Insert new parts from above:
The antennas in our toy can be placed from above, which is a good manufacturing choice according to DFA. It doesn't apply to any other pieces.
After analyzing each rule, we arrived at the following number of parts:
(a) Number of Parts in the assembly: 70 (obtained from the bill of materials in table #)
(b) Theoretical Minimum Number of Parts: 24. Obtain as follows:
-We can reg the leg components from 18 leg shafts, 18 socks and 6 joints to 6 complete leg pieces.
-We can use complete gears, which are attached to their axis and spacers. This would cut down the number of mechanism pieces from 20 to 10.