Have you ever tried to loosen or remove a screw from an assembly but found that your screwdriver could not make a proper vertical alignment with the slot in the fastener head? Perhaps the access space above the screw did not allow for the length of the screwdriver handle so you could not even begin to insert the blade of the tool into the fastener slot.
Not only is this maddening if you do not own an offset screwdriver, but it is also a poor design if the assembly beneath the fastened-downed plate was meant to be accessed as a requirement for field setup or option selections. You have just become a victim of poor design-for-assembly (DFA) planning.
When products are being designed, the engineers must also consider product characteristics beyond functions, user interfaces, appearances, or operating conditions. If DFA considerations are not included in product concept or design review meetings, a perfectly functioning product delivered from engineering to manufacturing may not be producible. Let me give an example that gave one manufacturing team fits trying to create a work-around solution until a new printed circuit board could be fabricated and stuffed.
Without DFA, a product may not be producible.
Thru-hole challenge
In direct-to-enclosure mounted printed circuit cards, there are thru-holes in the PCB material designed to accommodate mounting hardware such as screws and stand-offs. The idea being that the fasteners will hold the printed circuit card securely to the enclosure and will not flex during use or transport. With surface mount components, there is very little tolerance for board flexure as the added stress of bending the board near the components may damage solder connections and or cause micro cracks in the components themselves.
So the placement of these holes and their proximity to components is critical for both short- and long-term reliability. The assembly operation of fastening these boards without over-tightening the fasteners may require a torque screwdriver so torsion parameters of the fastener are not exceeded. These special screwdrivers are bulky and require some operating space in order to get the vertical entry into the slots of the fasteners. If the designer of the enclosure did not confer with the designer of the printed circuit card as to how the card would be mounted and where the fastening holes would be drilled, then there is a high likelihood that there will be assembly issues.
Here is the rub: Often, a design engineer may give the mechanical engineer a board outline with dimensions including the height for the tallest component, but neglects to specify where mounting holes will be in the circuit card. The mechanical cad people will ask how the board will be mounted and may prepare the enclosure with fastening positions in mind, but may not necessarily appreciate the tools required for the fastening operations. The axiom here is that too much information is better than too little.
Access problem
In our real-life snafu example above, the enclosure designer selected a clamshell type 1RU (Rack Unit) and strengthened the top edges by adding ¼" flanged bends. The added bends were not a problem for the prototype assemblers in engineering who did not care about fastener torque requirements. The product was passed onto manufacturing where it was discovered that the torque screwdrivers could not access the fasteners because of the top bends in the enclosure.
This is just one simple example that is meant to highlight the need for thorough communications during the design process that is inclusive of design for assembly issues. In that light, it is best to have manufacturing people involved in concurrent engineering design reviews. Chances are the production floor representative would have mentioned the tools clearance requirements as part of the design considerations.
The work-around turned out to be a procedure where the enclosure bend had to be manually notched to allow for the required production tool access. Unfortunately, there was a PEM nut on the bend that was placed in the same location to help secure the front panel to the enclosure. The front panel had to be redesigned with a new PEM location. The original panels had to be scrapped, and the enclosure design had to be modified, also reflecting the new PEM location to match the front panel changes.
DFA is no less essential for a good design than the design of the hardware or the software. Get your factory people, including contract manufacturers, involved as early in the design cycle as possible. In doing so, you will avoid many issues that can hinder your company's progress.
@Freebird, you are correct. We did our own manufacturing, but at the system levels only. The PCB stuffing and machining and sheet metal fab all were outsourced. So, we had not so much of a vertical integration thing going as much as a hybrid manufacturing operation. We did not have a Turnkey Assembly House because our product line was more characterized as a low volume, high mix. The end product was almost custom for each delivery. Our internal BOM management was based upon configurable BOMs. I liken this to a Restaraunt model, where all the food stores are in the kitchen, but the customer can pick and choose from a menu to suit his or her particular tastes. Our storehouse had sub assemblies that could be mixed and matched depending upon frequency, bit rate, modulation, power, antenna size, cable or wave guide interfaces, single or redundant circuitry, software options for alerts and alarms, mobile vs. stationary...etc. So, the sales people would sit down with the customer and fill in a sales order check list reflecting all of the options above. A data entry clears would plug in all the selections and the BOM configurator would spit out the resultant materials requirements. The order would be included in a master schedule for MRP, and we're off to the races. Our procurement people would order components, modules, and assemblies accordingly. The various qualified suppliers would handle their respective parts of the order and ship the goods to our factory for final assembly and test. As you can imagine, the BOM configuration software was critical to the whole operation and saved us tons of time over having to enter each new Top Level Product into the Item Master with unique part numbers. We cross referenced the Sales Order to the Customer's specifications and serial numbers and that is how we tracked field units and created reorders quickly. Pretty nifty, Huh?
Douglas: it sounds like the example above happened within an organization that still did its own manufacturing. If that is the case, better communication is the solution. But what about outsourcing? I've had the impression for awhile that the DFX function belongs to the EMS. Does that work any better or worse than in-house?
@William, I was sent by our company to scope out the Philips (Phone division) in Scotland as a possible remote factory site for a project we were building for the U.K. The plan was to set up a factory within Philip's factory and staff it with Quality Assurance people from our US Based company. So, you are right about trying to maintain harmony between an engineering operation in one country and a factory in another. As concerns DFM, DFA, and DFT our plan was to equip the factory with the product's manufacturing needs in mind. That way DFA, DFT, and DFM as built into the entire operation. It was a short run, single customer operation so newer product introductions were not a factor in this particular equation. When working with remote CMs, we always asked for an equipment facility list and process and procedure standards before selecting the factory. We also did site visits and surveys to check for calibration compliance and ESD safeguards. There is never an initial 100% compatibility as unique fixtures and training always seem to be part of the manufacturing process. We also had the factory hire local labor that reported to our operations people so there would be no conflict of interest on quality or yield reports. But there is no doubt about it, when the cat is away, the mouse will play.
@Doug, it is more difficult to watch a manufacturing process on the other side of the world. That 15 hour plane ride each way is a bit of a deterrent, as well. Not to mention the language barrier.
I would say that it is important to ensure collaboration amongst the departments. If they continue working in silos the issues will continue to exist. They must learn how to function as a single unit with a broader goal.
Designers must be familiar with the limitations and the capabilities of the manufacturing departments. Any designs must only be approved after a careful scrutiny from the production. Communication is the key here and must be done effectively.
This is a great thread, folks. I'd be interested in hearing some real-world company examples. What companies do you consider to be doing DFA well? Success here is not easy because it requires technological support (obviously) but cultural acceptance, and the latter is always tricky.
This is one of the important reason why it is important to have engineers who have system level thinking. It is very important to have the manufacturing team as part of all product concept discussions.
Machine-to-machine technology is growing so rapidly that one report says there could be 10 billion connected devices by 2016. That's a big market opportunity.
RFID makes it possible not only to increase the quantity and types of products streaming through the supply chain, but also to build higher-level products and services.
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Join EBN contributor Jennifer Baljko on Thursday August 23, 2012, at 11:00 a.m. EST for a live chat on how electronic manufacturers in Thailand have shored up their supply chain to reduce the impact of future natural disasters.
Peter Drucker famously said "Trying to predict the future is like trying to drive down a country road at night with no lights while looking out the back window." Yet in the razor's-edge world of electronics—with a lean supply chain and just-in-time demands—the need to know the future is vital.
While no one really can accurately predict the future, we can take guidance from another Drucker saying which is the best way to predict the future is to create it.
You've heard the saying "the No. 1 supply chain risk is your people." That hasn't always been the case. But today's complex global supply chain requires a new type of multitalented employee. It's one who understands, finance, marketing, economics, is savvy with technology, graceful with relationships and can think analytically.
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