Various DFM guidelines are:
1. Minimize the parts count. (For example, use integral clips for joining rather than separate nuts and bolts.)
2. Build components as similar as possible; this decreases the variety of manufacturing processes comprised. Similarities may be in material, e.g. all plastic; shape, e.g. all cylindrical or prismatic; or specific procedure, e.g. shapes that can be extruded, and so forth.
3. Avoid redundancy, i.e. do not have two portions performing similar function (unless necessary for safety, e.g. a back up braking system in a bus or a back up computer system in a manned space vehicle)
4. Design for ease of assembly by permitting one component to be assembled to the subsequent by vertical stacking movements, (that is, top down assembly). This also aids automation of the assembly process.
5. Avoid using floppy components in a design as they are difficult to handle, especially if automated manufacturing is to be used.
6. If possible design individual components so that they can be made to a wide tolerance yet still function when assembled together; this greatly reduces manufacturing time and cost.
7. Use standardization and modularization wherever feasible. This is of particular importance to today’s world manufacturing environment.
8. Design parts for ease of fabrication. This requires that the most appropriate fabrication procedure accessible be used to make the parts and the part be designed for that process. When choosing a fabrication method, keep in mind such things as required finish and component strength as well as the volumes that will be produced. For illustration, if only twenty or so metal components are to be made then machining may be acceptable, however if the number is to be 200,000 then the product should be designed to allow a process such as die casting to be used. This process has a higher initial cost than machining due to the special tooling necessary, but where large numbers are required the cost per part produced is much less. Also the labor required to operate the die casting machine is less skilled and hence less expensive than that for machining.
9. Minimize handling. Parts should be designed to make position easy to achieve, and the production process should maintain the position once it is achieved, by the use of fixtures. Avoid repositioning and reorienting. Use self fastening and self locating parts.