Understanding Design For Assembly

Design for Assembly (DFA) Guidelines for Product and Prototype Development

Design for assembly (DFA) is the umbrella term for the set of rules that govern part and product design. Design for assembly guidelines work along with design for manufacturing (DFM) rules to ensure that each part is manufactured to specifications, avoid material waste, optimizes machining and even save cost. So, how can you make your part design more functional, aesthetic and production friendly? Below is a quick rundown of the best DFA guides for product and prototype manufacturing. 

Design for Assembly Guidelines 
•    Simplify your design 
First and foremost, ensure that your design has been processed to the simplest form possible. This is because the more complex a design is, the higher the likelihood of an error. Products with higher number of parts also stand lesser chance of attaining perfection. Simpler designs also place less burdens on operators and drives down the cost associated with automation. 

As much as possible, each part should serve a secondary function, reducing the need to introduce another part for that purpose. Multifunctional part will help lower the total number of parts in the design, delivering on both their principal function and secondary objectives.
The designer should make the part in such a way that the number of assemblies required post manufacture is significantly reduced. For each part you decide on incorporating into the design, ask yourself: 

i.    If the part is crucial to functionality or is purely aesthetic 
ii.    If the part must be made from a different material from the other parts 
iii.    If the part moves in relation to other moving components in the design
iv.    If the design can be less complex and simpler without any loss in functionality
If any of the parts in your design fail one or more of these questions, consider taking it out as it means the design will fly if such part were absent.

•    Reduce fastening or joining parts 
Do away with parts that require screws, nuts, washers and bolts to assemble and fastening. These efforts are time consuming and slow down automation. Wherever possible, opt for snapfit joints, composite machined parts, use of bonds and adhesives instead. 
If you must use threaded fasteners, ensure that you use the same type through the design to ensure that postproduction assembly is faster. 

•    Consider efficient handling 
Ensure that product handling during assembly is as seamless as possible by designing your parts such that they can only be assembled in one way. Eliminate the use of flexible components like gaskets, rubbers and cables as they are usually more challenging to handle and assemble. 
Designing your parts with the right orientation will also reduce the wasted efforts that can arise from part ambiguity. In order to ensure that your parts are appropriately oriented, do the following: 

i.    Design your parts with consistent orientations avoiding features that may become tangled, curled or disoriented when fed into the manufacturing process
ii.    Where possible, do not use holes and tabs in the design as they can prevent automation in parts and assemblies of certain types of products 
iii.    Avoid the design of thin, flat parts that cannot easily be picked by the machine or handlers. All parts should be easily placeable and fixtured. 
iv.    Part symmetry is a must. Where it is impossible, ensure that the asymmetry is highlighted to allow proper insertions.  
v.    Ensure that your parts are designed within the tolerance capabilities of the manufacturing technique and machines. 

•    Factor in automation 
Unlike manual operations, automated production does not leave room for a lot of variations. This is why you must design your part in a way that they can be seamlessly handled in automated production. For highspeed automated assemblies, ensure that your design consist of more standard parts than custom parts, avoid tangling by using closed parts (no slots, holes or projections), use pre-oriented parts and design your components to equip a standard gripper. 
Also, avoid the use of parts that need to be secured or camped and use self-locating parts in your design. 

•    Design parts to make unique connections 
Avoid assembly confusions by ensuring that each component in your part has a unique type of port or faucet for accurate fitting and unique connections. This will help to prevent assembly errors where wrong fixtures are attached to each other simply because every component fit into one another. 

•    Use standard parts 
Go for standard, commercial off-the-shelf parts over custom made parts to help save costs and avoid complications during assembly. Another benefits of using standard parts is the wide array of experience and assembly skills that your labour force already has with them. These parts are also widely available, so you do not have to worry about shortage, skill gap or probabilities in their efficacy when they are used with other parts. 

Why DFA?
The advantages of DFA are numerous. Here’s a quick list of some of the benefits of taking a DFA approach in your product design: 
•    Speed
•    Cost of assembly 
•    Assembly time 
•    Material savings 
•    Safety 
•    Operational reliability 
•    Higher quality 
•    Quicker prototyping 

FirstPart Rapid Prototyping Services in China 
FirstPart is one of China’s leading manufacturing hub for Additive, CNC and Conventional manufacturing techniques. We boast of excellent in-house capacity, labor force and logistics while delivering exceptional value for money. We adhere to the best manufacturing practices, incorporating Design for assembly (DFA) and Design for manufacturing (DFM) into every aspect of product development and part production. Our array of services include CNC machining, 3D printing, Rapid Tooling, Die casting, Rapid prototyping, Plastic Injection Molding, Urethane Casting, Aluminum Extrusion, Post-machining/Finishing services and much more. 

Firstpart provides expert services in a series of rapid prototyping options. From 3D printing to vacuum casting, rapid tooling, CNC machining and even urethane casting, we can help you deliver on all your low-volume manufacturing and rapid prototyping solutions. Contact us now and receive a free quote on your next project.