Achieving a product that is easily and efficiently produced relies on a seamless integration between product design and process planning. There are hundreds of steps and components to consider as you determine your specifications, parts, materials, and more – all within a cost-effective manner. As you put together plans, creating a group of structured guidelines around both manufacturing (design for manufacturing or DFM), assembly (design for assembly or DFA), and test (design for test or DFT) can help reduce both the cost and the difficulty of production down the line.
The High Cost of Poor Planning
The design decisions you make, such as materials, processes, and assembly, can account for up to 70% of your manufacturing costs while the production decisions, including components such as machine and tool selection, typically only account for 20% of your overall expenses.
How to Design for Manufacturing
There are just a few common themes to consider when designing for manufacturing and assembly. Of course the design needs to function, but where possible, consider the following:
- Make parts easy to buy
- Make it easy to assembly
- Make it easy to test
- Make it easy to rework
Modular designs help to streamline the steps in manufacturing such as inspection, testing, assembly, purchasing, redesign, and maintenance. With a modular approach, each component can be built and tested individually, prior to final assembly, so if there is an issue, it is identified early in an isolated piece.
Making Electronics Parts Easy to Buy
Where possible, use standard components and when you can, use as few as possible. Standard components are both less expensive and easier and faster to source.
As an example for PCB circuit design, several 1kΩ resistors may be required. Some parts of the circuit may need higher precision and higher voltage requirements than others. It is possible to select 3+ different 1kΩ resistors. These resistors are all very inexpensive when purchased in reels. By combining all of these into the resistor type that meets the higher standard while still at a reasonable cost allows minimal inventory while meeting the design needs. This also helps if the part becomes unavailable. If a particular resistor increases in price too much, that one can stay unique and cost and process savings would still be realized. This same concept can be applied to capacitors, diodes, ICs (through hole vs. SMT, and others).
An example for higher level assemblies or box builds, use the same size screws when possible. This minimizes inventory requirements, as well as keeping the assembly simple by not needing several different size screws when they could have been the same. It may also prevent damage if an assembler accidentally installed the wrong size screw.
Making It Easy to Assemble
For PCB assembly, the position of the components can make the SMT placement reflow process easier. ACDi takes this into account when doing layouts and can review existing layouts for best practices. Using SMT instead of through-hole components when possible minimizes labor required to populate boards. Keeping all SMT components on the top side also makes assembly easier. All of these can be overcome but requires extra steps, tools, and thus cost.
For higher level assemblies, using common fasteners, making sure everything is easily accessible, and providing clear concise assembly instructions will help to minimize labor needs. Similarly, keep torque requirements the same when possible.
Making it Easy to Test
Testing can cover a wide range of time, resulting in a wide range of cost. If the PCB is to be tested using a flying probe or bed of nails, leaving some key pads exposed will provide test points. Consideration also needs to be made with respect to placement of components – if some key test points are too close to tall components such as through-hole capacitors or connectors, they may not be accessible. Ensuring as many key test points are available increases the PCB test coverage.
For functional testing, available test points or signals on test connectors are absolutely needed. Some tests may be able to be created by a special test software. In this case, it is important to make this load, whether it is a separate memory card or reprogrammed.
Making it Easy to Rework
Assess if the product will need to be reworked. Some products are designed intentionally to be throwaways, in which case this section can be ignored. If the product will need to be mechanically reworked, many of the assembly requirements will apply. It is also critically important to consider software updates. If software updates will be required, make sure there is some mechanism to update it externally to the entire system. This may be through a connector or wirelessly. Too often, there are circuit boards within an assembly with the only update mechanism is a connector on the board. If disassembly of a unit is required to update software, this virtually eliminates the possibility of updating in the field as well as significantly increases the cost due to disassembly, re-assembly, and possible damage in the process. It also creates unnecessary delays while getting the product updated.
Checklist Questions When Designing for Manufacturing
As you design for manufacturing, here are some recommended checklist questions you should consider that can help decrease your manufacturing efforts, cost, level of complexity, and time:
- Can you reduce the quantity of off-board components or assemblies?
- Can you utilize standard components or more cost-effective components?
- Can you reduce the amount of manual operations – for example, soldering?
- Can you use snap fits or tabs instead of separate fasteners?
- Can you automate, simplify, or reduce testing operations?
- Can software be updated externally?
Working for Your Best Interest
ACDi works with you every step of the way, with integrated turnkey solutions to make this process as stress-free as possible. We work with you to create a design for manufacturing, assembly, and test so you don’t need to source parts for yourself, work with separate manufacturers and assemblers, or lose time and money with complex and unnecessary parts and processes.