Design For Manufacturing (DFM)

Design for Manufacturing, as the name suggests, means to design a product with the least complications so that it is easy for a manufacturer to produce it.

A complex part is never good, for two reasons, viz. its difficult as well as costly to manufacture. Hence its always a big challenge in front of an Engineer to keep the geometry of the part as simple as possible.

We all have studied various manufacturing methods during Engineering. Mostly by seeing the part, one can guess the manufacturing process used to make it. But on the same time, one should note that for manufacturing the same part, one can opt for various options. In such scenarios, the deciding factor is the application of the product. For instance, an alloy wheel rim can be made out of Casting as well as Forging. By seeing it, it would be difficult to tell how was it manufactured. But keeping in mind the application, one can tell the process used to be forging as the application requires the part to be strengthened for which forging would be any day a better option to go for when compared to casting.

Each manufacturing process has its own DFM Considerations. But as my domain is Sheet Metal & Plastics, I will be giving a brief idea of the DFM considerations with respect to these processes:

For Sheet Metal:

• Bending Allowance: It is very important to give bending allowance in the sheet else, we will fall short of length while manufacturing the part and will not be able to obtain the desired dimensions.

• Spring Back Allowance: When a sheet is bent, it tends to revert a little from the bent angle towards its original shape. For compensating that, the sheet is bent a little more than the desired angle, so that the sheet reverts to the desired angle after the bend due to the spring back phenomenon. Hence for a designer, it is very important to make sure that there are no flanges interfering with each other.

 For Plastics:

• Draft Allowance: It is the most critical factor that has to be taken care of when it comes to Design of Plastic parts. The value of the draft angel to be given depends on the depth of the part. A part if designed without considering draft cannot be ejected out of the mould, hence the design fails.

• Parting Line: It is important that the designer tries to designs a part as symmetric as possible, making it easier for the Mould Designer to identify the parting line and hence for manufacturer to mould it. Generally, it is considered to be the job of the Mould Designer to decide the parting line for a part. But on the same time, it is also important for the Product Designer to mention if there are any areas where he wants/do not wants the parting line to be seen from the application or aesthetics point of view.  

There are  many other factors which are taken care of by the designer while he designs a Sheet Metal or Plastic part. The same can be found on the Sheet Metal Design & Plastic Design pages respectively.