Posts Tagged ‘product liability’

Cheap, Fast, Good – The Engineering Project Triangle

Sunday, October 31st, 2010

     Suppose it’s lunch time and you’re really starving.  All day your boss has been dumping work on your desk and you’re really busy.  You checked your wallet and you only have a couple of bucks.  Your favorite deli sells inexpensive sandwiches that are really good, but it’s over four blocks away and the lines are long. The only thing that’s going to work for you is to find something to eat that’s both fast and cheap, so you head for the lunchroom and get one of those nasty looking sandwiches out of the vending machine.  As expected, it’s not very good.  It’s downright disgusting.  You toss it in the trash and end up feeling angry and disappointed as you head back to the stack of work on your desk.

     So what does a disgusting vending machine sandwich have to do with engineering projects?  Well, engineers are often called upon to feed a very strong appetite for the design of consumer products, industrial products, and manufacturing systems.  What few people outside of the engineering profession realize is that engineering design projects operate according to three constraints:  cheap, fast, and good.  These constraints have been around for a very long time but they have become more critical in recent times in large part due to globalization.  They are shown in the engineering project triangle in Figure 1 below.

Figure 1 – The Engineering Project Triangle

     Here’s how the triangle works.  Pick any two of the constraints but exclude the remaining third.  For example, in our lunchtime scenario above you chose fast and cheap, and you ended up with food that wasn’t good.  It works the same way in engineering design projects.

     A number of years ago I was working as a project manager at a small engineering firm. One of our customers wanted us to design a consumer electronic product chocked full of really cool features.  He wanted the design completed on a fast track schedule.  As I worked up a quotation, I determined that if we were to design all of the features into the product on the desired tight schedule, I would have to buy expensive design tools and put a large number of engineers to work on the project.  Kind of like having the whole family pitch in to clean house versus you doing it alone.  The bottom line was that although it was possible to give the customer what he wanted when he wanted it, it would cost a lot of money to pull off.  This meant we could only fill two of the proscribed parameters for production, fast and good, but not cheap.

     In today’s fast paced, highly competitive, and minimally staffed business environment, engineers are often under a lot of pressure to somehow beat the project engineering triangle.  No one wants to give up cheap, because budgets are slim and it’s extremely difficult to get more funding.  No one wants to give up fast, because the marketing folks are always looking for ways to get a jump on the competition.  So where does that leave “good?”  Well, unless someone is going to let go of either cheap or fast, good isn’t going to happen.  The end result is most often that sales and marketing end up very disappointed, dissatisfied customers proliferate, sales go down the drain, service costs go through the roof, and potential liability issues start popping up.

     Moral our story?  Don’t fight the engineering project triangle, work with it.  Start by carefully considering the project scope and all the requirements the design must satisfy. Involve engineers in the consideration process, since they’re going to be the ones who are responsible for producing the design. They know their own capabilities and what it takes to meet your expectations.  Based on engineering input, set up your budget and/or schedule to ensure that you get a good result.

     Turns out that with engineering design, as with most things in life, effort-in equals result- out.  


Forensic Engineering Focus On Electrical Fires

Sunday, October 4th, 2009

     Property damage and loss of lives, these are often the result of fires.  But did you know that one of the leading causes of fire is electricity?  Residential electrical fires claim the lives of nearly 500 Americans each year and injure another 2300.  Annually, these fires result in over $800 million in property losses.

     Approximately one third of the nearly 70,000 home electrical fires that occur each year are traceable to design and manufacturing defects in electrical products.  The rest are caused by the misuse and poor maintenance of electrical products, overloaded circuits and extension cords, and incorrectly installed wiring.

     The three components that must be present in order for a fire to manifest and sustain itself are well known.  These components make up the “Fire Triangle,” a potentially lethal combination of heat, fuel, and oxygen.  If any one of these three components is missing from the triangle, a fire can’t be started or sustained.  In the case of an electrical fire, it’s electricity that creates the heat component of the Fire Triangle.


The Fire Triangle

     How does electricity contribute to fires?  One example would be an overloaded extension cord.  Homeowners are sometimes unaware that extension cords must be sized appropriately for their ultimate usage.  If not, they can overheat, particularly if they are damaged.  Damage to cords can result from a myriad of factors, from factory production errors to kinking when heavy furniture is carelessly placed on top of them.

     The same principle holds true for electrical products.  If their internal wiring or a component is insufficiently sized or damaged, overheating can result.  If things get hot enough and there is sufficient airflow (oxygen) and combustible material (fuel) in the vicinity, then the fire triangle is complete.  The fire starts internally and can soon spread to other objects in the area.

     Electrical arcing can occur when an energized electrical circuit is broken.  For example, suppose a wire carrying current is suddenly broken in two.  If the voltage is high enough, the electricity will want to continue to flow through the air across the break to form an electrical arc.  If the power flowing through the arc is great enough, heat can once again complete the Fire Triangle, resulting in fire.

     Forensic engineering analysis of evidence collected from a fire scene often yields telltale signs of overheating due to overloaded electrical circuits or damaged wiring in components.  Under close examination by an experienced professional, even the smallest strand of wire can point to the cause of an electrical fire.

     CSI skills aren’t only employed at crime scenes.  Forensic engineers also use similar techniques to get to the true story of cause and effect.


Machine Safety, Operator Safety, And Keeping Those Fingers

Sunday, September 27th, 2009

     Crushed fingers, amputations, burns, blindness, these are all too common undesirable occurrences involving moving machinery.  Eliminating the risk of such accidents is an integral part of the engineering design process, where risk assessment goes hand and hand with industry standards in order to provide adequate machine safeguards and protection to operators as well as bystanders.

     Machine safeguards fall into three basic categories: Guards, Devices, and Distance.

     Guards are physical barriers that are added to machines with the goal of keeping body parts, clothing, etc., separated from potentially hazardous areas.  An example would be a metal cage surrounding drive belts and pulleys.  Guards can also serve to keep material fragments and debris from flying out of machines while in operation, such as when an enclosure is built around the grinding wheel of a bench grinder.

     Devices can consist of automatic controllers, often connected to sensors on machine componets.  These controllers use a form of “safety interlock logic” to monitor the operating state of machinery.  They must act quickly and automatically to stop the normal operation of a machine if they sense that an undesirable object, say a person’s forearm, is in danger of entering a hazardous area.

     Controllers can be in the form of hard-wired electromechanical relays, embedded microprocessors, or programmable logic controllers (PLCs).  Their sensors can include electrical switches embedded in floor mats or mounted on movable guards, incorporated into control handle grips, or linked to an access door latch.  Still other sensors are more elaborate, using more sophisticated methods to maintain safety, such as photoelectric devices known as laser curtains.  These act by spreading beams of light across an opening which may be a gateway to a dangerous area.  If the beam is broken by an object, the controller takes appropriate action and renders the machinery inoperable.

     Distance safeguards operate as you would infer them to, by designing machinery so that hazardous areas are kept a great enough distance from body parts, etc., so as to eliminate any danger of them being drawn into an unsafe area.  An example of this factor at work would be when machinery is developed so that moving gears and other potential hazards are kept far out of the reach of someone by virtue of their overall design. 

      Sometimes even the best machine safeguard designs can be rendered ineffective after a piece of machinery is put into actual operation.  The reasons for this are varied, from poor maintenance of equipment, to lack of training for operating personnel, to inadequate supervision of workers, or perhaps the machine has been modified to operate outside the parameters of its design capacity.  Whatever the reason, people can be put at risk for serious injury and even death if machine safeguards are bypassed, eliminated, and defeated.


The Key To Successful Product Development

Sunday, July 12th, 2009
     We’ve all seen instances where someone was making something up as they were going along.  And the end result is usually not very good.      It’s no different in the product development process.  If an engineer designs a product without identifying all requirements, then the product may not meet the expectations of its end user.  Worse yet, it may pose a hazard during use and open up a world of potential liabilities.             There are three basic requirements for successful product development:  functionality, performance, and constraint.  A functional requirement specifies the necessary task, activity, or action that the product must be able to achieve.  A performance requirement specifies how well the product must perform under specific conditions.  A constraint requirement sets out the constraints under which the product must operate.  An example would be compliance with government regulations and industry standards. 

     In every successful product development project the goal is to create requirements that are well defined, well specified, and traceable, meaning each requirement should include the name of its originator and a space for their signature, indicating approval.  This eliminates any spinning-of-the-wheels due to misunderstandings, finger pointing, etc. 

     Well defined requirements are, of course, tied into specific design criteria and form the basis of a detailed design specification.  These criteria guide the way through all stages of the product’s development.  Each requirement should be listed, along with the rationale for its creation and a test method to verify that its objectives have been met. 

     Requirements are only good if they are achievable, verifiable, unambiguous, complete, expressed in terms of a need (not a solution), and consistent.

     Otherwise, what’s the point?