Effective Utilization of Resources, Part II
My article in July discussed thinking more seriously about “resource productivity” as a driver for innovation in (sustainable) manufacturing paralleling the focus we have on labor productivity. We all know the examples of more output per worker hour thanks to a wide variety of developments from automation to training and scheduling. But, for getting at the root of “impact per unit of GDP” and setting up a path for reduction of that impact, resource productivity is one very important element – perhaps the most important if we think holistically about the costs of resources.
Turns out, not surprisingly, that there is a lot of information available about resource productivity.
For example, the European Union (EU) defines resource productivity as:
“… a measure of the total amount of materials directly used by an economy (measured as domestic material consumption (DMC)) in relation to economic activity (GDP is typically used). It provides insights into whether decoupling between the use of natural resources and economic growth is taking place. Resource productivity (GDP/DMC) is the European Union (EU) sustainable development indicator for policy evaluation.
“Resource productivity of the EU is expressed by the amount of GDP generated per unit of direct material consumed, i.e. GDP / DMC in euros per kg. When making comparisons over time or between countries it is important to use the correct GDP units so that the figures are comparable and changes are not due to changes from inflation or in prices.”
One needs to be careful that we consider carefully the contribution of services (which one might argue are typically less material intensive than, say, automobile manufacturing) to GDP growth so we are not seeming to be improving the “by to fly ratio” as we’ve discussed in the past but it is really reflecting shift, or growth, in other forms of commerce. But, I am not an economist so that’s sufficient warning for me.
Wikipedia defines resource productivity, and couples it to sustainability, as:
“… the quantity of good or service (outcome) that is obtained through the expenditure of unit resource. “
“Resource productivity and resource intensity are key concepts used in sustainability measurement as they attempt to decouple the direct connection between resource use and environmental degradation. Their strength is that they can be used as a metric for both economic and environmental cost.”
The Wikipedia definition distinguishes between “the efficiency of resource production as outcome per unit of resource use (resource productivity)” and” the efficiency of resource consumption as resource use per unit outcome (resource intensity).”
They note that from the point of view of sustainability, the objective is to maximize resource productivity while minimizing resource intensity.
So, how do we do this?
At the recent International Academy for Production Engineering (called CIRP – but that is an acronym for the French translation of the name – College International pour la Recherche en Productique!) General Assembly in Copenhagen, a working group meeting on Efficient & Effective Resource Utilization (EERU) met to discuss exactly this issue. The group is working through the various stages from design to end of life in production that impact this and a number of researchers presented ideas towards that goal. The focus of this particular EERU meeting was resource efficient production technologies and the presentations included water and material utilization in a range of industries from automotive to semiconductor.
As an example of efficient production technology, Professor Erman Tekkaya of the Technical University of Dortmund gave a number of examples for material utilization in metal forming applications. Professor Tekkaya started with a figure from Professor Kurt Lange of Stuttgart from some 20 years ago based on his work with the German auto industry. The diagram shows the utilization of material (essentially the “buy to fly ratio“) for a range of manufacturing processes. It also shows energy use per mass of finished part.
We see that for processes like cold forging (formation in dies with the material at room temperature – called “net shape processing as the material is reformed with little loss) the material use is very high (85% due to the fact that the process generates little scrap) versus cutting processes which typically have a lot of chips and waste generated as a “subtractive technology.“ (The third type of material processing is “additive“, like welding and 3-D printing – we’ll be talking about this more in a later posting.) As a result, similar to the figures we saw from Allwood in previous postings (see the “less is more“ series), processes such as cold forming have lower energy/mass values. It must be pointed out that the numbers in this figure do not reflect the whole process chain needed for these operations such as manufacturing of the tooling and dies for forging. But, the numbers are indicative of the impact of more efficient material use.
Professor Tekkaya’s presentation covered four examples – including direct material saving during processing (here a clever washer production process that used a technique similar to wire forming for nails to create washers with no waste due to the center hole or remainder from a blanked sheet), and reduced primary energy of initial material.
Let me elaborate on this second one.
The traditional life-cycle of metallic components, say automobiles, is that at end of life the vehicle is crushed (after some components are removed), collected, re-melted and recast as strip or sheet material and then reformed into new components – say a new hood for an automobile. Allwood points out that although this is helpful, the waste from the first production oft the hood (sheet metal forming is not net shape) and the requirement to re-melt, etc. is a tremendous energy burden on the material. Professor Tekkaya showed an example of reusing portions of a recovered automotive sheet metal part and a side panel from a PC with novel forming processes to create “new“ products without going through the traditional material recycling cycle.
The figure below, from Tekkaya, shows the creation of re-formed parts and process sensitivity to controlling the sheet feeding in to the mold/die setup for a sheet trimmed from a used automobile hood panel. The trimmed sheet shown outlined from the engine hood
is formed using a process called “hydroforming“ (in which the metal sheet is deformed against a form using hydraulic pressure – this avoid the problem of the nonuniform shape and flatness of the original trimmed sheet that would prevent normal closed die forming). The sheet is deformed into a mold with the desired finished shape. The reference to sheet feeder control refers to a method to control the flow of material into the mold during forming. In one case the metal is annealed or softened to remove the work hardening from the prior manufacturing operation. But, as seen in the figure, the resulting shape is impressive – even if some of the original paint is still in place!
For the reuse of the PC side panels, Tekkaya experimented with a process called incremental sheet metal forming to create another workpiece for another product.
Consider the potential if the designers of the parts planned a bit to allow easier reuse of panel portions of the metal parts – thus enhancing the possibility of direct reforming for reuse.
There is still some scrap as evidenced by the trimmed pieces in the figure. But, compared to crushing, melting, recasting, rolling and re-forming the sheets, as usually done with recycled automotive metals, this is a tremendous improvement in “resource productivity.“
This is just one example. But, it demonstrates the role process innovation can play in improving manufacturing and promoting efficient and effective resource utilization. Consider other “large flat sheets” used in products – sides of washers and dryers, refrigerator housings, etc. These area ready for re-use.
David Dornfeld is the Will C. Hall Family Chair in Engineering in Mechanical Engineering at University of California Berkeley. He leads the Laboratory for Manufacturing and Sustainability (LMAS), and he writes the Green Manufacturing blog. This article was republished with permission by David Dornfeld.
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