The ultimate guide to DFA (Design For Assembly)

The Concept of Assembly Assembly refers to the assembly of components into a product that can achieve the quality of a variety of products. The concept of assembly can be derived from the meaning of assembly: a) Put the components together; b) Realize the corresponding functions; c) Achieve great quality of the product. The most …

The Concept of Assembly

Assembly refers to the assembly of components into a product that can achieve the quality of a variety of products. The concept of assembly can be derived from the meaning of assembly:

a) Put the components together;

b) Realize the corresponding functions;

c) Achieve great quality of the product.

The most important thing in assembly is to achieve the product functions requirement and product quality requirement, not simply locking the screw or putting together the components. Therefore, assembly is a way to realize product function and product quality.

A product needs to go through the process of assembly before it can be manufactured and become a product. Products contain anywhere from a few to millions of parts. A stapler has dozens of parts, a cell phone has hundreds of parts, a car has tens of thousands of parts, and an airplane has more than a few million parts. Assembly is an important part of the product manufacturing process, and the assembly process has a great impact on product quality, product cost, product development cycle, and so on.

There are seven steps in the typical assembly process: 

Step-1  Place the base; The base of a part does not necessarily refer to the fixture bench, it could also be a part. For example, in the winding of the stator, relative to the enameled wire, the stator rack is a part serving as a base.
Step-2 Identify the parts; Identifying parts is also important in the assembly design process. For example, if the color of the O-ring and the parts are all black, it is difficult to recognize different parts in terms of the vision system.
3) Grab the parts; The difference between manual assembly and automated assembly needs to be considered. If the part is too soft, or too slippery, it’s difficult to grasp it for assembly.
4) Move the part to the assembly position; Parts are best assembled once in place with no interference along the way.
5) Adjust the parts to the correct position; Sometimes we need to consider adding guide features to assist the adjustment. 
6) The parts are fixed; The parts of each process are preferably fully constrained, and then proceed to the next process.
7) Inspection; This is the end of a process.

The process of manual assembly and automated assembly will be slightly different. But all assembly design requirements stem from these seven basic steps, so it’s important to remember.

Mechanical designers can generally understand the assembly process based on these seven steps, but assembly process engineers need to know more, such as the location of incoming materials, the arrangement and efficiency of fixture benches, and the specific assembly methods of production line workers. Therefore, after the mechanical engineer completes the DFA (Design for Assembly), it is necessary to discuss it with the assembly engineer.

The Difference Between A Good Assembly Design And A Bad Assembly Design

Good Assembly Process Bad Assembly Process
Parts are easy to recognize Parts are difficult to recognize
Parts are easy to grab and placed in the right position Parts are difficult to grab and easy to fall
Parts can be easily adjusted to the right position Parts need workers to keep adjusting in order to find the right position 
Parts have a single right assembly point Parts can be assembled at multiple assembly points and it’s difficult to tell which point is right. Parts can be even assembled at the wrong point. 
Very few screws. Parts can be assembled quickly. Many screws and many types of screws.
No tool or fixture is needed in the assembly process Tools or fixture is needed in the assembly process
Very few adjustment is needed in the assembly process Consistent adjustments are needed in the assembly process
The assembly process is easy to study execute The assembly process is difficult to study and execute

Design For Assembly (DFA)

Design for assembly (DFA) refers to making the product have good assembly ability in the product design stage, ensuring a simple assembly process, high assembly efficiency, high assembly quality, low assembly defect rate, and low assembly cost. The purpose of doing Design for assembly (DFA) is to figure out the best assembly process of every single component or part by optimizing the product design. 
 
Design for Assembly (DFA) should be considered at all stages of the design process, especially in the early stages of design. As the design team considers multiple options, the ease of assembly of the product or part needs to be carefully considered. Design teams need a DFA tool to efficiently analyze the ease of assembly of a product or part. Design tools should provide results quickly, and be simple and easy to operate. It shall ensure the coherence and completeness of the product assembly feasibility assessment. It should also eliminate subjective judgment in assembly design, allow free association, allow easy comparison of different designs, ensure scientific evaluation of the final solution, determine the scope of assembly problems, and be able to provide multiple alternatives to simplify product mechanical design, thereby reducing the cost of manufacturing and assembly. Through the application of DFA, the communication between manufacturing and design can be improved, and the ideas, reasoning, and decisions made during the product design process can be well documented for future reference.
 
The DFA approach attempts to achieve these goals in the following ways:
① Provide a tool for those designers or teams to ensure that their consideration of product complexity and assembly occurs only at the initial design stage. This can avoid the risk that the designer only focuses on the function of the product at the initial stage of design without sufficient consideration of the cost and competitiveness of the product.
② Guide designers or design teams to simplify products, thereby reducing assembly costs and parts costs.
③ Collect the experience data usually owned by experienced design engineers, organize these data, and provide them to inexperienced design engineers to study.

④ Establish a database that contains assembly time and cost elements under various design states and production conditions.

Through design for assembly (DFA), product development can achieve the following goals:

① Simplify the product assembly process.
②Reduce product assembly time.
③Reduce product assembly errors.
④Reduce product design modifications.
⑤Reduce product assembly costs.
⑥Reduce product assembly defect rate.
⑦Improve product assembly quality.
⑧Improve product assembly efficiency.
⑨Increase the utilization of existing equipment.

Supply chain is the last draw for a crowdfunding project

A lot of crowdfunding projects fail to deliver the product. Some inventors hold strong responsibility to deliver the product, but it usually still takes a long time. Unlike movie or art crowdfunding projects, the industrial product campaign comment area often appears a lot of impatience and complaints about the delay, refund requests, or even accusations …

A lot of crowdfunding projects fail to deliver the product. Some inventors hold strong responsibility to deliver the product, but it usually still takes a long time. Unlike movie or art crowdfunding projects, the industrial product campaign comment area often appears a lot of impatience and complaints about the delay, refund requests, or even accusations of liars.

As an inventor, the fantastic side of Indiegogo is that you don’t have to get an MVP (minimum viable product) to be qualified to launch a campaign. As long as you state the development stage of your product (concept idea stage, prototype stage, production stage, or shipping stage), you are good to go ahead with your idea, video, or drawing. In this way, you don’t have to figure out the product’s engineering mechanism about how to operate and supply chain knowledge about how to integrate and make. 

Most often, the inventor is still able to show a fully or partially functional demo prototype to convince the backers of its capabilities of shipping. However, most inventors either unfortunately run out of money targeted for production along the way of development or run out of schedule-timeline in the struggles of solving the manufacturing bottlenecks created in the design. Is it truly inevitable to cause delays or failures in product delivery?

For example, a crowdfunding project called Drumi, which is the world’s first foot-powered washing machine, experienced 7 times improvements after the crowdfunding campaign closed. Whenever they update the design, new problems are to be fixed, and thus the team keeps posted on shipping delays. Drumi team spent 3 years developing multiple prototypes to validate the design before it launched crowdfunding in Nov 2015 and they assume they can finish the production in 6 months after crowdfunding. It turns out that they only delivered by the end of 2018. The reason why Drumi, or many other crowdfunding campaigns, faced this situation is that no manufacturers have the existing experience to produce this kind of new product. So the team has to put efforts into solving the design manufacturability issues so that it can proceed to tooling for production, as well as confirm the specification of every component so that it can pass function reliability test and build fixtures for production.

Indiegogo has been working hard to help the campaign keep its shipping promise. Indiegogo launched Indiegogo for Entrepreneurs Expert Directory, on the prototyping and production sector, LKKER SCM is one of the Indiegogo recommended experts who help transfer new products to high-volume manufacturing. 

From the development side, LKKER SCM helps with the selection of components, especially avoiding components with shortage inventory and discontinuation plans. It’s very common to see some inexperienced inventors’ heads ached for the hyped component prices or long lead time of components because they pick up components with unstable stock or lack of securable sourcing channels. For startups with weak buy power in the electronics components market, the choice is more important than efforts. Located in Shenzhen Huaqiangbei, and familiar with multiple electronics products across industries, LKKER SCM can design PCBA at a fair price, advise cheaper component alternatives and provide a one-stop sourcing solution.

From the tooling side, LKKER SCM helps the inventor with DFM (design for manufacturing) analysis to ensure the design can be made by various tooling technology properly and the design can achieve a good yield rate without assembly interference. As a member company of LKKdesign Group (China’s largest industrial design house), LKKER SCM has been trained for 12 years to carefully consider the product design details and grind the production process to guarantee the design product quality and user experience.

Nowadays, more and more backers show attention to the supply chain validation of crowdfunding projects. Especially for those projects with a high amount of raised funds, there’s high pressure on the order delivery. Therefore, the supply chain has become the last draw for a crowdfunding project. For example, in the campaign OCTO Versatile Titanium 18-in-1 Carabiner w. Window Breaker, the campaign owner, who is a designer, lists LKKER SCM there as an endorsement of supply chain experience. In the campaign GPods: The World’s First Earbuds With Light Control, LKKER SCM, as the designer, completely share the design, development, and pilot run process documentation to help increase the confidence in shipping. 

Good products deserve waiting. But good business can’t wait. Avoid the design traps. implement design for manufacturing, and complete your product today!