Tuesday, September 1, 2009
Little things matter - precision manufacturing and green
Last time we discussed metrics and spoke about payback time or return on investment among others for assessing the best value for the money from implementing process improvements. We also introduced the idea of a "design space" where we needed to balance manufacturing capability, design and environmental impacts along with cost to achieve an ideal solution.
In preparation for my class on Tuesday I found an interesting discussion about the impact of the CARS program (aka "cash for clunkers").The motivation for this program was to stimulate the economy and to encourage the replacement of autos with poor fuel economy by those having improved fuel economy. We had discussed the need to measure, or at least estimate, the improvement from any plan for greening a process or product.
An article on an Automotive World website (http://www.automotiveworld.com/news/environment/77989--cash-for-clunkers-and-lifetime-co2-emissions) offers some insight into measuring the impact of a change. They compare data on the CO2 emitted during the manufacture of an auto (from Ford for small and mid size and Toyota for an "average" size). The figures range from 8.4% of lifetime emissions for a mid-size car that returns 17 mpg (US gallons) and 10.3% for a small car that returns 25 mpg for the Ford data and 18% for Toyota (which also takes into account the production of materials going into the vehicle). Then, considering scenarios of improvement due to replacing trade-ins with higher mileage vehicles (and an assumption for the amount of CO2 per volume of gas) they calculate the number of miles of driving needed (at the newer efficiency) to save the equivalent of the CO2 from manufacturing of the new vehicle.
Many assumptions needed of course but, bottom line, one of the best case scenarios yields payback in 20,000 miles (or about 1.4 years) if your average annual travel is 14,000 miles. A worst case scenario (either higher manufacturing emissions or smaller improvement in mileage when you swap cars) shows a break even at closer to 75,000 miles (or almost 11 years of operation). Depending on the specifics of your swap - this analysis suggests that the change may have accomplished the first motivation but falls short on the second. Read the article. This is an excellent example of using metrics in a tradeoff analysis.
Fuel economy in automobiles is a convenient transition to our discussion today - precision manufacturing and green. Time to "wax technical" a bit.
A well worn relationship for predicting the impact (in terms of environmental damage, consumption, etc.) is as follows:
Impact = Population x (GDP/person) x (Impact/GDP)
Population grows with time. Most countries strive to improve GDP/capita since that drives living standards, etc. The rate of consumption or environmental impact per unit of GDP is the "rate of damage" done as a result of the technology driving the growth in GDP.
Engineers are most effective at changing technology that affects Impact/GDP. To the extent we can reduce that impact we are, effectively, greening the process.
Now, back to precision. The fuel economy discussion earlier points out one area that engineers, manufacturing in particular, have had tremendous effect. If you are familiar with the recent improvements in the internal combustion engine (yes...our old friend the IC engine) you can see how effective design and manufacturing changes can be in creating technology wedges to address the gap between business as usual and a more sustainable rate of impact.
Some examples. A major German auto manufacturer has been working to improve the "power density" of some of its diesel engines over the past years and has seen an improvement of almost a factor of 3 in power per unit of displacement. That means, for the same engine size (displacement) they have managed to squeeze three times as much power out. Coupled with advanced fuel injector systems operating at very high pressures (once thought absurd) they see enhanced performance in a small engine - increased fuel economy, improved acceleration (due to reduced mass), and reduced emissions.
If you add to that the recent improvements in "hybrid" valves (see, http://www.jobs.mahle.com/C125705E004FDAF9/CurrentBaseLink/W276TH5G611STULEN), which are composed of a laser welded hollow structure made from cold formed sheet steel parts, the valve train performance is substantially improved due to lower mass and higher resistance to combustion pressure and temperatures.
Another enhancement is assembled (rather than forged) camshafts formed of hollow rings friction welded together and shaped by hydroforming. This results in a reduction of part weight of 50% (and manufacturing cost of 15%).
In engines like these - reduced mass means higher acceleration and greater power per unit of displacement. And, improved fuel economy and lower emissions.
This is all due to the improvements in precision manufacturing - the ability to create incredibly small features, dimensions and shapes repeatably and reliably for low cost. The German engine relies on precision machining to create bearing surfaces and interacting parts with tight clearances, low friction and smooth operation. These are dimensions more typical of the semiconductor industry - not automotive. Ditto for the fuel injectors where micron sized injector holes with intricate patterns insure efficient combustion for maximum conversion of fuel to power and minimum emissions.
Don't write off the IC engine yet as part of the drive to reduced automotive energy consumption.
And we can see the impact of manufacturing technology on other products as well - not only for automobiles. The new Airbus 380 boasts better fuel economy and CO2 emissions (gCO2/passenger mile) than most European automobiles must achieve to meet regulations (this is a complex comparison - but humor me on this! and see http://www.enviro.aero/A380casestudy.aspx).
I also teach a graduate class on precision manufacturing and one of my favorite slides to motivate the students shows how improved machining tolerances on an aircraft airframe (a big one like a B747 or the A380) saves weight and, hence, fuel. If the machining process is under control and precision manufacturing principles applied, a reduction in machining tolerances from +/- 0.006 inches to +/- 0.004 inches on the features of the airframe can account for a weight reduction of 10,000 pounds/aircraft and substantial fuel savings (8%). This allows an increase of 10% in passengers (engines don't need to carry as much plane), and substantial reduction in manufacturing cost of the aircraft (less material and improved assembly). And less fuel consumption means reduced CO2 impact from operation. Think of the accumulated savings over the life of the aircraft - incredible.
All because of precision manufacturing technology. In all these above cases - metal cutting and forming!
Green manufacturing derives from an attention to detail and employment of the best engineering and process technology we can master. The examples above are not "rocket science". But they are achievable by precision manufacturing engineers, technicians and machine operators using state of the art precision machine tools and metrology.
We need to be able to confidently evaluate the impact of tradeoffs in design and production and the environment (as we saw in the figure in the last posting), and implement those by first class manufacturing practice.
The need to "green the process" will make many approaches thought to be unfeasible or too expensive very natural and cost effective. And make the manufacturer more competitive in the process.
Last word - for more info on precision manufacturing, I've written a book on the subject, see http://www.amazon.com/Precision-Manufacturing-David-Dornfeld/dp/0387324674/ref=sr_1_1?ie=UTF8&s=books&qid=1251867831&sr=1-1 or contact me if questions!