1) What is DFM?
Definition of DFM
The term DFM stands for Design for Manufacturing. It can also be defined as the process of designing components, parts or products that can be produced at ease with a minimum cost in addition to having all the other attributes it should have such as good utility and function, high quality and long-term reliability. This can be achieved by optimizing and simplifying the product design. It is a highly effective approach that is being used by large companies all over the world.
The Final Goal of DFM
As stated before, the final goal of the design for manufacturing approach is to produce a product or a part with ease and with the minimum cost; however, what is the reason that makes this possible? The answer is very simple, DFM is aimed at eliminating extra parts and features of a design because these extra details or parts will never be tested, detailed, designed or purchased. As a result, the overall cost of manufacturing the product will be a lot less not to mention that the extra time spent on making complex features will be also eliminated, and thus affecting and reducing the overall time of producing the product.
2) Difference between DFM and DFA
what is DFA?
The term DFA stands for design for assembly. It is similar to DFM in a way; however, it is not the same. DFA can be considered or defined as a process or a technique that its goal is to reduce the cost and the time creating an assembly. This goal can be achieved by reducing the number of parts or combining two or more parts together in order to reduce or eliminate adjustments. Once this technique is applied and properly used, it is then possible to reduce the time of making an assembly by up to 85%. Here is an example of implementing the DFA approach:
This part is made up of a piece of plastic with 4 holes in it, and it would be used for assembly with another part.
This is another part with the same dimension and material; however, as you can see the placement of holes is not the same. The second part is easier to assemble, and this was done by implementing the DFA approach. By simply changing the placement of the holes it is possible to reduce the overall time of the assembly of the product.
Similarities between DFA and DFA
DFA and DFM are really similar when it comes to their final goal, as in the end, they both seek to reduce the overall cost of materials, labor, overhead… They are also both concerned with reducing the overall time and difficulty of manufacturing the final product.
It should be mentioned that due to their common goals, DFM and DFA are now integrated into a single phrase as DFMA which means Design for Manufacturing and Assembly.
Difference between DFA and DFM
Even though both techniques have similarities, they still have their own share of differences some of which are as bellows.
- DFM: Design for manufacturing focuses on overall part production cost by
- minimizing the complexities during the manufacturing process.
- eliminating extra or unnecessary features.
- DFA: Design for assembly process is concerned only with reducing the cost and time of the assembly process. DFA leads to
- minimizing the number of assembly operations and processes.
- making more complex individual parts during the design.
It should be mentioned that for a successful DFA analysis of a product, Assemble Engineers are to be involved.
3) How to implement DFM?
Steps for the implementation of DFM
In order to implement the DFM approach, these simple steps are necessary:
- Process: the first step in implementing the DFM technique is to correctly choose the right manufacturing process. For example, if a plastic piece or product can be manufactured using the easy method thermoforming, there is no need to use injection molding or other advanced manufacturing techniques because they require creating mold tools and dies. So it is best to choose the lower capitalized method. Of course, it is not always an easy choice, and these factors should be taken into consideration: the number of parts being made, the material being used, and the complexity of the surfaces.
- Design: the next step after choosing the manufacturing process is the design of the product. Keep in mind that the design should be compatible with the manufacturing process that was chosen in the first step. That’s why for designing a product, the following factors should always be taken into consideration: the thickness of the walls or surfaces of the product, the tolerances required, the features and undercuts required and other factors and elements such as texture.
- Material: the third step in implementing the DFM approach is choosing the right material. In order to do this, it is necessary to take into consideration the following factors and properties: mechanical properties such as the strength of the final product, optical properties such as being reflective or transparent, thermal properties and how resistant the final product is going to be against heat and high temperatures.
- Environment: the product to be designed and manufactured must withstand certain environmental conditions.
- Testing: the final step is to simply test whether the product complies with safety and quality standards.
Example of Implementing DFM
One of the DFM guidelines insists on avoiding having sharp internal corners such as this part for example:
So in order to implement the DFM, in the first place, the engineers and designers must first be educated on why this guideline and rule should be complied with. The second step is to verify if there are any internal sharp corners. There are of course other factors to focus on, such as the environmental factor, the choice of material, and the choice of the right manufacturing process. Correctly choosing and doing all of these parameters will lead to a cheaper and faster manufacturing method of the product.
Ford Motor Company made a study on the most common causes of warranty repairs and the study concluded that threaded fasteners in a motor were the main ones. The study was later confirmed by similar studies. One of the conclusions of this study was that “If more than 1/3 of the components in a product are fasteners, the assembly logic should be questioned” This was a very important result that could be regarded as a guideline for designing of engines and was later used by other corporations to review their engines. Below shows the result of some of such reviews on Cummins Engines. (Data from Munroe & Associates October 2002)
In conclusion, DFM and DFA are extremely important in the manufacturing industry. In fact, the great successes of big American and Japanese companies are not only due to their work ethics but also because of the proper implementation of DFM and DFA techniques. This also shows the importance of making a proper design based on design principles, because up to 80% of the overall time, cost, and quality of the product is influenced by the design.