Less is more, part 7

Maximum flexibility with minimum impact

This will be the last in the less is more series and is "tech heavy" again.

In the last posting we described the concept of an error budget as used in design of precision machines and then proposed to apply a parallel concept as a "sustainability budget" for including the environmental/resource impacts in the design process. We hoped with this to design a machine that met both the requirements for machine performance as well as a more sustainable (or at least greener) machine.

We ended with a description of the construction of a sustainability budget following the three basic steps:

Step 1: determine an energy, material and resources (consumables, etc.) model of the machine and its principal components in the form of a series of relationships defining the energy consumption, materials use as a function of machine design or operation. (This might be referred to as energy or materials mapping.)

Step 2:  analyze systematically each type of energy and material use in the system and determine the relative performance-energy/material impact (for example, from Ashby charts).

Step 3: combine the energy/materials impacts to yield upper and lower bound estimates of the total energy/material impact of the machine.

We noted that it was important that the embedded energy and materials must be counted.

So, now an example of constructing a sustainability budget.

The critical part of building these budgets (error or sustainability) is accumulating the data needed to populate the budget. Material data sources are very helpful in determining the basic material-performance characteristics (like modulus of elasticity, thermal properties, density) that are of use in machine design as we have seen. But, these need to be “connected” to embedded energy and operating energy consumption for use in a sustainability budget. Although there are many materials texts available, one excellent source of such “connections” is the text book “Materials: Engineering, Science, Processing and Design” by Ashby, Shercliff and Cebon, Elsevier, 2010.

Ashby uses an approach (or strategy) for materials selection which is comprised of four steps:
- translation of design requirements in terms of function, objectives, etc.
- screening to select most usable materials meeting the requirements
- ranking with respect to some set of criteria, and
- documentation on background and history of the material in this or related uses

This strategy attempts to get the best match between the characteristics of materials (or processes if the four steps are used for process selection) and those required by the design (functionality and constraints). We would add, as one of the screening elements, the need to assess environmental compatibility, energy use and embedded energy, global warming gas emission impacts, etc.  Embedded energy is that energy that has gone into the mining, conversion, processing, and transportation of the material up to the point it enters our control or manufacturing facility for use in our product.

This would work as follows. The machine designer first determines the specifications required for the precision device as usual as inputs to the left side of figure below (from Dornfeld Precision Engineering, Springer, 2010). A parallel discussion could be had for a process design or system of devices of processes but to simplify the discussion we stay with one device here - a precision machine.

Figure  Design to sustainability selection chart, thermal stability example

The designer determines that a  critical requirement is that the device should be insensitive to variations in temperature where it operates and, since the device is heavily constrained (meaning the device cannot change size due to temperature variations without experiencing bending - picture a simple beam that is being heated and it is held at each end in a vise. When it heats up it will expand along the length and, if heated enough, eventually bend up or down) the variable set of interest includes the modulus of elasticity, E, the coefficient of thermal expansion, α, and the conduction coefficient, k. This defines how much the material can be deformed with out permanent "plastic" deformation or damage (that is, spring constant), how much the material expands per degree of temperature rise and how readily the material conducts heat.

For this situation, it is known that the combination of Eα/k (or elasticity times thermal expansion divided by the conductivity) should be as low as possible to minimize thermal distortion and that will define a set of suitable materials. We can find a wide range of materials with differing expansion and conduction coefficients. Depending on which of these materials we choose, we can determine the energy or sustainability impact by noting the embedded energy (for example) as a function of the weight or volume of the material (or materials) chosen and the amount needed for the design. For example, the figure below, from Ashby shows the relationship between embedded energy for a range of materials and the embodied energy/m3, or production energy per unit volume. We see that more “exotic” materials, often

Figure  Production energy per volume for a range of materials, from Ashby 

used for thermal stability have higher embedded energy due to production requirements. This gets us through Step 2 of the sustainability budget creation.

However, it must be noted that there are usually other issues that need to be considered besides embedded energy (such as societal impacts if the material is toxic or hazardous or comes from a region where damage is done in mining or extraction) for a complete assessment of sustainability. Also, it is clear that we could create a set of charts as in the design figure shown first above for other constraints in machine design (chatter or vibration for example, in a milling machine, where the key parameter might include stiffness of the component and the tradeoff could be between cross-sectional area/geometry and stiffness; alternate material choices could be conventional carbon steel, a composite material with high stiffness to weight ratio, or a ceramic (which would also have beneficial thermal properties).

Step 3 of the sustainability budget construction requires combining the energy/materials impacts to yield upper and lower bound estimates of the total energy/material impact of the machine. Summing these for a series of machines in a system would give us a system budget. The most challenging part of this step is determining the “sensitivity” of sustainability to device specifications.

We need to make the same type of analysis relative to the sensitive directions that we are designing our device to protect for error sources and the materials in their configurations we are  using to accomplish that. Ideally, following our procedure in the design figure above, we could determine a range of material properties that can be varied to affect the design requirement of concern, for example thermal stability in the above example, but which would have no or minimal effect on embedded energy. This would be a sort of sensitivity analysis to energy or environmental impact similar to that seen in machine stiffness evaluation.

That is, a design/material which allows us to meet design requirements with the maximum of flexibility while having minimal impact on environmental damage would allow the application of the conventional error budget without much additional constraint. It would, in effect, decouple the design and material choice from the sustainability impact for a defined range of conditions.

Let’s look at an example. In the Ashby figure above we can see that, at an embodied energy of  about 105 Mj/m3  a wide range of materials exist spanning cast irons and some carbon steels to metal foams. Depending on the density of metal foams their modulus of elasticity can be as far from or as close to their parent material. This is not the case for carbon steels and cast irons. Similarly, thermal properties will vary tremendously between metal foams and cast iron, as will damping characteristics (important in machine tool structures). But, from an embodied energy perspective they are all quite similar. So there is an insensitivity we can take advantage of.

Tradeoffs in energy/materials sustainability (depending on what part of the life cycle it is used in) also need to be considered. Some “static” structures such as heavy machine tool bases which support but do not move with the machine axes can be made of heavier materials as their impact on energy of the machine during the “use” phase will not be large. Components making up the moving portions of the machine will logically expend more energy during their life with than stationary components as with each motion, energy will be expended in moving the component proportional to mass (among other things.)

This was a rather straightforward example discussed above. More detailed examples are suitable for a graduate course discussion but one can get the idea.

The key "takeaway" here is the concept of a selecting a design/material which allows us to meet the design requirements with the maximum of flexibility while having minimal impact on environmental damage. Maximum flexibility with minimum impact! This would, in effect, decouple the design and material choice from the sustainability impact for a defined range of conditions.

Next time we are going to dig into leveraging a bit further with some examples.

Finally, a couple of "plugs" for conferences you may be interested in. We are hosting, at Berkeley, the 19th CIRP Conference on Life Cycle Engineering - "Leveraging technology for a sustainable world" - website is http://lce2012.berkeley.edu/home.html. There is also a "regional meeting" in achieving low CO2 industrial plants - California France Forum on Energy Efficient Technologies - website is http://caffeet.org/. Look forward to meeting some of you at one or both of these!

Less is more, part 6

Budgeting for sustainability

This will be the second to last in the series and, probably, these will be the most complicated since we are talking about some subtle aspects in the design of machines. But, interesting never-the-less!

In the last posting we looked at Ashby's approach to linking material properties to environmental impacts/resource requirements. This time we'll like to apply this to the an example - the design of a precision machine tool. The material here is adapted from Chapter 12 of my book Precision Manufacturing (Springer, 2010; it's on Amazon if you are interested!). We'll set up the discussion in this posting and complete the story in the next, and final, one.

First, we need a formalism for addressing sustainable design of precision machines. This follows from the formalism used for basic machine design. This is referred to as the "sustainability budget." Let me explain.

In the design of machines, specially precision ones (that is, machines that can operate reliably and repeatably positioning workpieces or tooling to great accuracy and with very high resolution - for example, repeatably positioning something within a couple of microns (or nanometers).) This is often accomplished using a technique called "error mapping" and developing an "error budget." These are methods for accounting for the magnitude and eventual impact of the numerous potential sources of error in a machine’s performance – relative to dimensional accuracy, form error, or surface finish.

One does this by determining the likelihood of errors due, for example, to thermal distortion (remember, things expand when heated and contract when cooled so if a machine component is subjected to either of these due to operation or environment) the component will change shape and that will affect the accuracy of the machine. Seems small but, over long machine components, it adds up. Or, for high accuracy, small temperature changes can have a big effect. Steel, for example, has a coefficient of thermal expansion of 11.7 microns/meter/degree C. So, a steel component 10 cm (or about 4 inches; one tenth of a meter) long that experiences a temperature rise of 5 degrees C during operation will "grow" almost 6 microns due to the thermal expansion. That's a lot in the precision manufacturing community! Larger structures can grow more. And, 5 degrees C is easy to experience in most conventional manufacturing facilities.

We can put the machine in a conditioned environment where the temperature is maintained constant but that cost money and, importantly, uses a lot of energy. Or we can put circulating oil systems on machines with temperature controlled oil to maintain a constant temperature but that adds to the machine's energy footprint also. And, since the circulating system usually runs even when the machine is not producing work, this makes the idle state of the machine almost as bad as the production state.

There are materials with almost zero coefficients of thermal expansion - but they are costly in terms of money and energy to create. So, we'd like to design the machine to have as little sensitivity to thermal distortion while using materials that have lower environmental impact.

One of the concepts in precision machine design relates to identifying, first, the  “sensitive direction” in the machine. This is the direction in which an error impacts the part quality: dimension, form, roughness. For example, if you are trying to create a surface with a certain dimension by machining, then you want to control the position of the cutting tool relative to that surface with great accuracy. Any error in the position of the tool relative to the surface will result in an error. So, for this operation, the axis of tool motion towards and away from the surface during machining would be the sensitive direction.

The way we can keep track of all the contributions to the errors in the machine can be referrer to as an "error budget." This budget allowed us to include all sources of error and an estimate of their relative magnitudes and then determine which of these sources actually impacted a sensitive direction resulting in a part error. The term budget is chosen exactly to represent what, like a budget for household expenditures, is available to be distributed over all the requirements for operation. Just as in a household budget where some of the monthly funds must cover groceries, insurance, transportation, etc., in an error budget, we allocate the elements making up the total error in such a way that, when we are done with designing the machine, the cumulative error, in the sensitive direction, do not exceed our requirements.

So, errors in the machine due to thermal effects, loads due to moving workpieces or forces generated in machining (which cause another type of distortion, elastic distortion, due to the elasticity of the material the component is made of), gravity loads, or vibrational excitation due to rotating spindles or tooling, are estimated. From these estimates it is determined by modeling the machine structure kinematically, in what way these errors affect the machine tool operation and accuracy and, then, to what extent they affect the sensitive direction.

Now, an important concept in this method is that an error that exists but does not affect the sensitive direction is not of concern. Meaning, something could be going on in the machine but as long as it does not affect the location of the tool relative to the workpiece in the example we've been discussing, we don't need to worry about it.

This would be like going to a restaurant which serves a fixed price buffet. You could eat a lot, or a little, and, from the point of view of your budget, it wouldn't matter. With graduate students, that means you can eat a lot!

So, in the case of an error source not impacting the sensitive direction, we have a lot more design freedom with no apparent penalty in terms of performance.

So by now you are asking what the heck this has to do with the subject of the blog!

Consider if we would add constraints on the environmental performance of a machine while insisting that the other quality metrics are met as well as the manufacturing performance (throughput, lead time, cost/piece to operate, etc.) This could be included in our budget analysis but, in this case, we’d call it a "sustainability budget". A sustainability budget would operate similarly to an error budget except we would be looking for the impact, from environmental metric point of view, of the design and operation of the precision machine, process or system.

Then, using the idea of sensitive directions (and the complementary concept of non-sensitive directions – that is, those directions for which any error from a specific source has no effect) we can imagine an analysis which measures the impact of  materials, designs, or operating conditions on the overall environmental behavior. Then we look for instances of materials, design features or operating conditions that give the largest range of variability, from the point of view of design, with the least environmental impact. That is, those instances for which little  or no sensitivity is displayed.

Following a methodology based on this would allow us to design the machine, or system of machines, in such a way that the basic performance, precision and accuracy, would meet the core error budget constraints but, in addition, we could do so in a way that was more sustainable.

Great idea but how do we do this?! Let's get started.

In the design of a precision machine the first requirement is to derive an error budget. Now it gets a bit complicated. Creating an error budget relies on two sets of rules — connectivity and combinational. Connectivity rules define the behavior of machine components and interfaces in the presence of errors. That is, how does the error in one component affect the position (for example) of another component. This is sort of like trying to level a table in a restaurant by sticking little bags of sugar under one of the legs. Sometimes you are lucky and it works the first time. Other times changing one leg makes another lose contact with the floor and the table still wobbles. That's is a simple example but that is connectivity.

Then, the combinational rules define how the errors are to be combined to determine the impact on the accuracy of the workpiece. That means, how all these connected components, experiencing the various sources of error, combine to affect the sensitive direction. Not surprisingly, this is done with mathematics.

The procedure is comprised of the following three steps:

Step 1 — make the model of connectivity. This is called the error map. We do this by determining a kinematic model of the machine and its principal components in the form of a series of matrices,

Step 2 — analyze systematically each type of error in the system and use the mold to determine the relative tool-work errors. This is determining a relationship defining how the errors affect the sensitive direction, and finally

Step 3 — combine the errors to yield maximum and minimum estimates of the total error of the machine. Sort of like specifying tolerances on a part length - the error of importance will likely be within this range.

If we revise this approach for a sustainability budget, we’d follow the same three basic steps but with some different objectives. For example, we would add some elements to the three steps, or, actually, develop a parallel set of “models” and analysis.

Parallel to Step 1 would be:

- determine an energy, material and resources (consumables, etc.) model of the machine and its principal components in the form of a series of relationships defining the energy consumption, materials use as a function of machine design or operation. (This might be referred to as energy or materials mapping.)

Parallel to Step 2 would be:

- analyze systematically each type of energy and material use in the system and determine the relative performance-energy/material impact (for example, from Ashby charts).

Parallel to Step 3 would be:

-  combine the energy/materials impacts to yield upper and lower bound estimates of the total energy/material impact of the machine.

Importantly, in this parallel analysis, the embedded energy and materials must be counted. That is, we cannot only look at the energy to move an axis of the machine (for example in a precision machine tool) but we’d need to consider also the energy associated with the earlier material processing and conversion, any subcomponents or subsystems, etc. Also, some measure of global warming gas generation and any other environmental impact effects must be included.

We are, essentially, estimating the footprint of this device we are designing. This makes the analysis rather complex and, unfortunately, not as analytical as the construction of the conventional error budget first described.

But, it makes sense. And, next time, we'll add details and apply this to an example.

Less is more, part 5

Designing for small

In the last posting we stated that one of the challenges is linking product performance to material shape and properties. And then making the next link to environmental impacts/resource requirements.
An example of some helpful software that connects material properties to potential environmental impacts/burdens was given. By linking the potential burdens to material properties, and then to the design or production requirements, we can try to choose the least impactful material.

So, with respect to either a process/machine for manufacturing (manufacturing phase) or product (use phase), the challenge is to find the design/material/structure combination that:
i. gives the desired performance/meets specifications
ii. can be economically manufactured/operated at sufficient scale with required production rate, quality, and cost,
iii. while minimizing the environmental impact or, better, reducing the impact enough compared to the present performance to offer a "return on investment" that moves the operation of the process or product towards a more sustainable situation.

One of Ashby's techniques to start his analysis (see last posting for more info on Ashby!) is the "use matrix." This matrix arrays, vertically, energy intensive to material intensive products and, vertically, different product "load factors" from high impact to low impact. For example, the categories of energy to material intensity are from primary power consuming to non-power consuming. The primary power consuming products are energy intensive in their use phase and the non-power consuming are, then, material intensive. The figure below is reproduced from Ashby's CES Eco-selector white paper from February 2005.

In this matrix you can see examples of entries in the various categories with an automobile being a primary power consuming high load factor product (meaning the use phase impact is power related) while on the other end of the scale a tent or canoe is low load factor and material intensive since the tent requires no energy to operate so the material consumption in the manufacturing phase is the most significant.

Now, if we looked at manufacturing in the same manner, what could be a “use matrix of manufacturing classes”? Here is my attempt to fill in such a matrix for manufacturing.

You can follow the logic I think. An example of a high load factor energy intensive manufacturing process is something like a furnace for heat treating or a semiconductor manufacturing etch tool. A low load factor manufacturing process or element could be a warehouse or office for a factory which is midway between energy and material intensive depending on the exact activity in that warehouse or office.

Ashby's process uses such a matrix to help determine which phase of the "product" (here a consumer product but in our discussion a piece of manufacturing hardware for a process or factory component),  that is material production, product manufacture, product use or product disposal/end of lied, should be focussed on for the largest improvement.

If one is designing or producing high or modest load factor primary power consuming machines for production, such as rolling mills, forming presses or machine tools, etc. as in the manufacturing matrix above, then we would want to consider these four phases relative to those machines.

Let's consider the example of the design of a deep draw press. We'd like to come up with a press that meets the constraints posed at the beginning of this posting - gives the desired performance/meets specifications, can be economically manufactured/operated at sufficient scale with required production rate, quality, and cost, and minimizes the environmental impact.

If you are not sure what these are there is an excellent on-line video on the operation of one made in Taiwan and its manufacture. Note: this is a sales video but informative! The process performed on such a press is more objectively detailed on Wikipedia under deep drawing.

The elements to be considered in the design of a deep drawing press would include:

- Material production: steel mostly (several tons)
- Manufacture: welding (mostly), machining (some), electronics (not many)
- Use: electricity, hydraulic fluid, compressed air and other consumables
- Disposal: scrap (likely sold for re-use)

The design criteria would include:
- tonnage (pressure/power) which determines the size of the part to be made or thickness of the metal formed
- stiffness
- speed/strokes per minute
- ease of load/unload
- die changing/handling/setup

The press capacity is determined by the tonnage it provides for deep drawing while maintaining the necessary stiffness for the accuracy of the forming process. The speed is dependent on the efficiency of the energy to move the press given the weight of its components. A press that move rapidly (up/down strokes) either must be light (and hence low tonnage) or require a lot of energy to move.

Ashby data provides a measure of the relative "cost" in embedded energy of different materials per unit bending stiffness (affecting precision) and mass per unit of bending stiffness (for the speed vs precision tradeoff).

The curve below, from Ashby's software, shows the "trade-off surface" for this energy-mass for a stiffness limited design. The curve shows the range of reasonable candidate materials for achieving the required mass (for speed) and stiffness (for accuracy) normalized by embedded energy. Ideally, following along this curve gives the designer a set of material that will meet these constraints.

We see that one of the materials lying near the curve is cast iron and another is mild steel in the lower right part of the curve- both reasonable cost alternatives. Others on the curve, but with higher cost, are beryllium alloys in the upper left part of the curve- not likely to be used. Also not likely to be used is chipboard which is a bit below the curve. Another material not traditional used but worth considering is carbon fiber reinforced plastic - one the curve near the bend. These fiber-based materials offer very high strength/stiffness and very low mass so could be a new design for presses for high speed but high stiffness with similar embedded energy, for the amount needed, as steel.

These materials (the steel and cast iron at least) are also easily recovered at the end of life and, in fact, lend themselves to re-manufacturing (another good topic we'll delve into sometime) as well.

Next time we'll apply this to the manufacture of a precision machine tool.

Less is more, part 4

How much less is less?

The last several postings have been discussing the elements of reducing consumption in manufacturing. Not just cutting but making better use of the resources available. This stretched from reviewing the "buy-to-fly" ratio concept to yield issues in metal production and use. We discovered that there is a lot more potential in the material that is left on the floor in production than we might think. In fact, improving material processing yield may actually offer more potential for impact reduction than many other strategies.

But these are technically complex issues. Manufacturers don't waste material on purpose. The swarf from machining is due to material removed to achieve the desired shape. The farther the input workpiece is from the final shape the more material must be removed and shows up as chips on the floor. These chips are routinely recycled of course. But that is a far cry from not using it in the first place.

The term "net-shape processing" (defined as making things to a final or near final shape without removing material - such as forging) is one approach to reducing the amount of material that needs to be removed to achieve the final shape. This cannot address the requirements of surface conditions (like very low roughness) or some form requirements but it goes a long way. This does not work for all materials. But, for example, plastic injection molding is a classic example of net shape forming (except for the runners, sprue, etc. unless done with hot runner systems as in high production.)

The challenge is linking performance to shape and properties. And then making the next link to environmental impacts/resource requirements.

Engineers like to use "tools" for assisting in making these links. By tools we mean software or other analysis methodologies that assist in presenting data or alternatives to the designer, or manufacturing engineer, to be used in decision making. These tools often help the engineer answer questions like

- what is the function of the device or piece of hardware or component that is being designed?
- what are the objectives that need to be optimized?
- what constraints must be satisfied?

These questions are common to all engineering design problems but are part of the concept behind a wonderful tool from Granta Design called the CES (for Cambridge Engineering Selector) methodology developed by Professor Mike Ashby and his colleagues at Cambridge University in England. This was first developed to help engineers and designers to select materials for use in products and components.

They give the example of a design relative to these questions as "For instance, a car body panel (function) needs to be as light as possible (objective) for a specified stiffness and cost (constraint). Other constraints on the design might be acceptable resistance to mechanical impact and to contact with various environments." This is described in great detail on the Granta website.

I need to mention here that I am in no way associated with Granta Design or Mike Ashby and am not being paid to pitch his product or company! We are, in my lab, using this software (and we paid for a license) and I am only a big supporter because it is one of those products that is very useful and enables us to do things we otherwise would not be able to do. I also use Granta software in my class on sustainable manufacturing.

Ashby developed the concept of selection charts that show one type of material property as a function of another - for example elasticity as a function of thermal distortion. So if you are designing a component, say of a machine tool, and you need a material that has a certain stiffness but is less sensitive to temperature variations (and the accompanying distortion, growth with increase in temperature and shrinkage with reduced temperature) then you could see where different material groups fall and choose a material that is in the range desired.

The data is the same data you'd get from a handbook, or tests, or another expert but the method of presenting it offers additional insight to the designer.

For example, the figure below, from the CES EduPack Manual from Granta (this is available on the Granta's website for teaching tools) shows a typical "Ashby chart" plotting Young's modulus (this is the "elastic limit" for materials in load per unit area which serves as a measure of the stiffness of an elastic material) as a function of density (mass/volume).

This would be the kind of information that an auto designer would use to pick a material that has the required stiffness but with the least possible weight (since lighter vehicles require less fuel to move and lighter frames to support them).

Ashby fits the use of this data in assessing material selection impacts over the life cycle of a product. The figure below, also from Ashby and available at the link above, shows the stages of material usage in a product lifecycle. Ashby data makes it easier for an engineer to see

the magnitude of these impacts. And, of course, it gets back to our "make vs use" impact discussion some time ago (for example as part of the material diet discussion). The take away from this figure is that there are materials issues at all stages of product life.

The one limiting element of Ashby is that he looks at product design through the lens of materials and there are, of course, other concerns. But, this is a small issue compared to the benefit of his approach.

So, where does the "green-stuff" come in?

One of the axes of information that Ashby provides is embodied energy (and its equivalent in CO2 emissions). The figure below, also from Ashby, shows embodied energy (GJ/volume) for a wide array of materials. This data, specially when plotted as a function of material parameters, opens up

the possibility of connecting design parameters to environmental impact. The embodied energy data Ashby relies on is generally reliable. In a number of cases the data may reflect a specific region of the world or particular means for processing the material but it is an excellent base to work from. The red dotted line is only for comparison of materials and embodied energy.

As you can see in the figure above, the potential for looking at energy (and thus CO2) impact for materials is wide open. Within a materials group, like polymers, there is a factor of 10 range of embodied energy. Within the ceramics group this range grows to a factor of 1000 (three orders of magnitude.)

Clearly, all these materials in each group do not have the same properties are, hence, are not interchangeable. But, linking them to material properties, then to the design or production requirements, lets chose the best, least impactful, material.

That's where we start next time and we'll include an example.

Less is more, part 3

Where does the material go?

California is used to the concept of getting more from less. We only have to recall now Governor Jerry Brown's comments when he was governor the first time from 1975 to 1983 and declared that University employees shouldn’t complain about low pay because, as academics, they were getting “psychic rewards.” As a UC faculty member we are now seeing dramatic reductions on state support of education as the campuses, specially Berkeley, charge forward to keep our programs strong. Psychic indeed!

We are not talking about psychic rewards here or starving critical institutions!

We've been talking about making better use of what we start out with (the yield or "buy to fly ratio" approach) as well as process and product design for better results with lower impact.

I have been making good use of Professor Julian Allwood's research at Cambridge University to make the first point. His WellMet 2050 study is inspirational. We'll see more from that below.

Others, like the Air Force SAMI as well as corporate programs are making inroads on this as we discussed in the last posting. TMS (The Minerals, Metals and Materials Society) has produced, with support from the DOE and a host of others, a report in January 2011 titled "Linking Transformational Materials and Processing for an Energy-Efficient and Low-Carbon Economy: Creating the Vision and Accelerating Realization." You can download this report from TMS.

The report presents a prioritized set of new products and technologies prepared by TMS working groups focussed on the following themes:

- Functional Surface Technology
- Higher Performance Materials for Extreme Environments
- Multi-Materials Integration in Energy Systems
- Sustainable Manufacturing of Materials

It is a comprehensive forward-looking review of technology.

There are some obvious (to me) gaps however. For example, in the focus on sustainable manufacturing of materials the group highlighted:

- Net-Shape Processing of Structural Metals (that means making things to a final or near final shape without removing material - such as forging)
- Additive Manufacturing of Components and Systems (combining process or materials in reduced number of operations; but not necessarily rapid prototyping - the term usually associated with additive manufacturing)
- Low Cost Processing and Energy Reduction Technology for Metals (reducing the energy requirements for primary processing of metals like titanium, aluminum and magnesium)
- Separation of Materials for Recycling (promoting increased recycling rates), and
- Real-Time Sensor Technology for Gases and Molten Metals (feedback for process optimization and control).

I did not see much reference to increasing yield (except in the net-shape area) but certainly not at the level of importance to address the tremendous losses pointed out by Allwood.

So, let's pick there from the part 2.

The last posting presented a graphical representation of the cumulative yield (output over input) through several process steps and the accompanying cumulative process energy (energy/ton of material input). During the process steps, typically, yield is reduced (meaning material ends up on the shop floor) and, due to processing and material loss, the cumulative energy increases. As noted in the WellMet 2050 report "Going on a Metal Diet" that is the basis of this discussion "…these graphs will show that the (already energy efficient) process of liquid metal production dominates the cumulative energy build-up but yield losses in the downstream supply chain can increase the embodied energy in the final component by a factor of  up to 10." Up to 10x increase due to downstream yield losses!

I mentioned that Allwood's study had looked at four case studies. I don't want to repeat the report here (and encourage you read the whole report) but let's look at the cases for aluminum. The figure below shows the cumulative energy (reference to the original liquid aluminum) as a function of cumulative yield (actual product to input liquid metal) for three of the case study products (and click on the

image for better detail) investigated - car door panel, aircraft wingskin panel and beverage can. The various steps in production, from liquid, are shown by the open circles on the graph.

Lines connecting the circles going vertically (or more vertical) indicate processes that preserve yield (that is, less wasted material). Lines going horizontally, (or more horizontal) indicate processes that reduce yield (that is, waste material). This is not necessarily to imply that the material is wasted gratuitously but that the inherent aspects of the process are not able to make efficient use of the material.

For instance, the door panel example, indicates that from cast ingot to stamped panel there is a tremendous loss of material (yield from 1 down to 0.4 meaning 60% of the material not ending up in the product) The actual "buy to fly ratio" would be better than the 0.4 shown on the graph for door panels since the auto manufacturer is unlikely to by aluminum in liquid form. More likely the material enters production as cold rolled coil (at approximately .7 yield) and then is converted to the panel. So, buy-to-fly is closer to 50% form the auto manufacturers perspective.

But you see how this does not tell the complete story - specially with respect to the cumulative energy - since most of that is in the liquid to cold coil processing.

Beverage cans are a similar story. Most material is "lost" from the ingot to cup stage. The can producer likely gets the stock as cold rolled coil. From there, the losses due to can production take the yield from approximately 0.7 to 0.55. From the perspective of the can maker, perhaps, this is a reasonable buy-to-fly ratio.

The figure below, from Kalpakjian and Schmidt's manufacturing text (presented on line), shows a schematic of can making from the original blank through the drawing process and the addition of the cap.

There are two major sources of process related material loss - the blanking of the disks used to start the forming process (think cutting circles out of square sheets) and the disk to first cup process due to the requirement to be able to hold on to the end of the disk during this first stage. There is some trimming at the end also. A similar process is required for the lid which, although not as deeply "drawn" still starts as a circle from a square sheet.

The least efficient from a materials efficiency point of view is the wing skin panel (and recall our earlier comments about aerospace buy-to-fly ratios). This ends up with an overall yield (from melt) of less than 10%. Assuming the manufacturer gets the material as rectangular plate (at about 45% yield) their part of the process yields a buy-to-fly of around 25%.

Recycling, oft mentioned with aluminum and other metals, will help, some. The problem is that with "low yield products" a lot of the material "going back into the pot" will not be post consumer waste but production waste. In the case of aerospace components most of that waste is in the form of metal chips removed to get the desired shape. Granted, aerospace is a special case due to the requirements of the product but this is a lot of material to leave on the shop floor. Composite materials will try to address this but they have material efficiency issues as well.

Next time we'll start the discussion about getting more from the material and, specifically, analysis tools to help us do that.

Running with the big guys

And now a word from the government!

In honor of the 4th of July celebration here in the US I am taking a break from our discussion about "less is more" to focus on major initiatives to move the cause of green manufacturing forward - these from the government. The discussion on "less is more" will continue with part 3 next time.

We've heard a lot about some of the major corporations and the initiatives they've taken to enhance the sustainability of their organizations and influence their supply chain. One of the first that comes to mind is Walmart and their efforts to insure the products they sell, and their operations delivering them, are "more efficient, last longer and perform better." There are many more players in this field and a simple glance at Environmental Leader or GreenBiz  website will give a great introduction and allow you to track their progress.

For example, one recent item on GreenBiz refers to Marks and Spencers "carbon neutral bra" program  which complements their "carbon neutral undies." These are, according to GreenBiz, "a way to showcase an energy-efficient  factory in Sri Lanka that was built as part of Plan A. The factory is powered, in part, by solar energy and hydropower." (Plan A = Marks and Spencers sustainability effort;  'because there is no plan B'). It was also an exercise in carbon footprinting since the bra contains some 21 component parts from 12 different suppliers. The article states that M&S are offsetting the CO2 generated by the bra’s manufacturing and shipping by planting 6,000 trees in Sri Lanka. Since some of these trees are lime and mango trees there is the potential to generate income for farmers in the area.

Meanwhile, on the US fashion-eco front, one of our research collaborators Sarah Krasley, alerted me to the fact that Lady Gaga's infamous meat dress will become an exhibit in America's Rock and Roll Hall of Fame Museum. The "dress" from the 2010 MTV Video Music Awards will be part of a display at the museum in the 'Women Who Rock: Vision, Passion, Power' exhibition. Another reason to visit Cleveland this summer.

You will recall that the outfit was made entirely of raw animal flesh and generated an "environmental reaction" which I commented on.  The dress has apparently been preserved to prevent deterioration so is, according to Sarah, likely to be rather like a "jerky dress."

But the story here is on government initiatives. First, one announced by President Obama recently on manufacturing.

Berkeley will be one of the six universities in the US participating in the Advanced Manufacturing Partnership (AMP). The AMP is being developed based on the recommendation of the President’s Council of Advisors on Science and Technology (PCAST), which released a report June 24 entitled “Ensuring Leadership in Advanced Manufacturing.” The PCAST report calls for a partnership between government, industry and academia to identify the most pressing challenges and transformative opportunities to improve the technologies, processes and products across multiple manufacturing industries.

According to the PCAST report, manufacturing has been declining as a share of U.S. GDP and employment, and the loss of U.S. leadership in this domain has not been limited to low-wage jobs in low-tech, conventional industries; the United States is also trailing in high-tech industries that employ highly-skilled workers. The U.S. trade balance in advanced technology manufactured products shifted from surplus to deficit starting in 2001, according to PCAST.

The report lays out three compelling reasons why the US should strive to revitalize its leadership in manufacturing, and in particular advanced manufacturing, as:
1. Jobs: Manufacturing that is based on new technologies, including high-precision tools and advanced materials, can provide high-quality, good-paying jobs for American workers.
2. Innovation: It is not enough to invent in America and manufacture abroad. By keeping manufacturing local, a number of synergies ensue through which the design, engineering, scale-up, and production processes feed back on the conception and innovation sectors to generate new ideas and novel second- and third-generation products.
3. Security: Domestic manufacturing capabilities using advanced technologies and techniques are vital to maintaining national security.

One of the specific program goals is increasing the energy efficiency of manufacturing processes; and developing new technologies that will dramatically reduce the time required to design, build, and test manufactured goods.

First of all, anything that shines a little more light on manufacturing is great. Second, one of the objectives is energy efficiency of manufacturing processes. To me, this includes all of the approaches to green manufacturing we've been discussing here. The "design to production" element is also good for greening manufacturing if we can insure that sustainable design decisions are made early in the process and, to re-iterate Walmart's focus, make sure products are more efficient, last longer and perform better.

For our part at Berkeley we'll make sure that green manufacturing, as part of jobs, innovation and security, is an integral part of the discussion.

But there is more, also from a government organization. This time the Defense Department.

The Air Force has launched a sustainable manufacturing initiative. This in response to the 2010 Department of Defense Strategic Sustainability Performance Plan (SSPP). The SSPP identifies goals for meeting the intent of Executive Order 13514 “Federal Leadership in Environmental Energy and Economic Performance.” An essential component to sustainable acquisition and procurement is sustainable manufacturing.

A white paper on line gives a lot more detail on the Air Force ManTech Sustainable Aerospace Manufacturing Initiative - acronym SAMI. From the white paper, the purpose of SAMI is to "fulfill Department of Defense (DoD), AF, and industry strategic intent for sustainability by maturing sustainable manufacturing practices that will enhance the production capability necessary to process and fabricate DoD weapons systems with optimized energy footprints and environmentally sustainable processes while preserving performance requirements." SAMI operates out of the Wright-Patterson Air Force Base Materials and Manufacturing Directorate.

Specific program goals include:
- Develop assessment tools for identifying manufacturing process step-changes
- Demonstrate sustainable technologies in military unique process
- Design for sustainability
- Produce military systems with less energy
- Minimize environmental impacts
- Reduce environmental footprint associated with manufacturing without compromising capability or end product performance

The Air Force is partnering with a number of organizations on this including the LMAS of UC-Berkeley (my lab), the NCDMM in Pennsylvania, and several organizations in the supply chain such as General Dynamics Ordnance and Tactical Systems, Remmele Engineering, and GKN Aerospace in addition to others.

The importance of all these initiatives, from Walmart and Marks & Spencers to the Air Force, is that they are laying the groundwork for systematically designing, procuring and manufacturing, distributing, selling and, eventually, recovering products covering a wide range of "consumer needs."

Big organizations driving big effects. That's worth some fireworks!

Next time we'll continue with  "less is more" part 3.

Less can be more! Part 2

Where did all the material go?

Some time ago (July last year to be specific) we discussed the concept of "buy to fly ratio" used to track the ratio of the amount of material that an aircraft manufacturer starts with to the amount that actually ends up on the airplane. It was part of a discussion on degrees of perfection and was a led in to a series of discussions about how to actually measure the impact of what we are doing in terms of "greening" manufacturing. That is, if we keep track of everything - are we ahead at the end of the day or not?

The buy-to-fly ratio came out of the aerospace industry but has applicability to manufacturing broadly. Unfortunately, numbers for this ratio are not too impressive and I cited some published from aircraft manufacturing that are in the 30's - meaning only a bit over 3% of the material purchased actually ends up on the plane. This waste for machined components is usually in the form of chips - which are recycled of course but discarded never-the-less.

And here is the issue. Even with recycling of "wasted" materials in manufacturing we use energy and resources. So, recycled content is not free!

Recall Henry Ford's comments cited in one of the first postings for this blog on "why green manufacturing" two years ago:  "… we will not so lightly waste material simply because we can reclaim it — for salvage involves labour. The ideal is to have nothing to salvage." This was published in his book "Today and Tomorrow" (1926).

At that time Henry was probably generating his own electricity from "waste" steam from steel or coke making or wood chips from his wooden frame production so he wasn't even thinking about the cost of energy. And, I don't think the concept of global warming/CO2 was a topic of discussion then.

(Note: Today's Ford Motor Company is fully engaged in energy and resource efficiency in both product and manufacturing. You can find their CSR report online)

So, back to the chips (or the "hole").

The International Society of Industrial Ecology just held their annual meeting in Berkeley. One of the attendees was Professor Julian Allwood from Cambridge University and we had a chance to meet up and talk a bit about his work under the banner of "WellMet 2050." I introduced this project in a blog earlier this year on 'resource dieting.' He is a creative thinker about green manufacturing challenges and firmly grounded in processes and analysis.

One of the big 4 themes of their research is "less metal, same service" and Julian was discussing, basically, the "buy to fly ratio" problem. He focusses specially on metals in his research.

The details are documented in the "Going on a metal diet" report from the study and you can download it from their website.

One focus of the study as part of the "less metal, same service" is on reducing the scrap in manufacturing. There is a common misconception (or, at least, benign neglect) that recycling hits the reset button on inefficient use of material. This is a big mistake!

Inefficient use of materials is usually referred to as yield loss. That is, in the course of normal manufacturing (whether you are making airplanes, automobiles, semiconductors or polo shirts) material gets 'left on the foor.' Shapes are cut out of sheets and the bits around the shape that need to be held in the press, or due to standard size sheets larger than the part being produced, etc. are left over.

At best these leftover pieces are large enough to be used for other pieces (a concept called "nesting" in manufacturing). At some point there is not enough material left to be used productively in the operation and it is discarded and, hopefully, recycled.

Recall that recycled can mean anything from remelting and added to virgin material for making new sheets of material (as used here); mixed with other similar materials to produce lower quality metal; or collected and dumped somewhere (recycled to you - waste to the collection organization).

Take a peak at the Ricoh Comet circle from prior blogs to see the various paths of "down cycling" of materials.

The metal diet report states boldly "Going on a metal diet has much greater potential for CO2 emissions abatement than the pursuit of further efficiency measures in an already efficient liquid metals production process." So Professor Allwood's research team is focussed on the data to prove that statement.

First, let's define what we mean by yield. The figure below, from Allwood's "Going on an energy diet" shows how yield is determined based on the ratio of

metal going on to a downstream process over the sum of all process inputs. That which is not part of yield along the process chain is lost.

Now, how about the connection between the yield losses and the embodied energy of the material? Allwood has used a very novel way to display this that pretty clearly points out the challenge.

In the graph below, also from Allwood's "Going on an energy diet" report, the horizontal, x, axis shows the "yield path" of a material amount during processing through several steps. That is, starting with 1 ton of liquid metal, it plots the mass remaining after each step of the process. This, essentially tracks the buy to fly ratio across several process steps. The vertical, y, axis shows the cumulative increase in embedded energy with each process step. Constant embodied energy contours are shown.

Reading this figure, for a specific product, tracks the consumption of energy and the loss of mass of the product (relative to the original raw material input at the start). You'd start with the liquid metal, cast it into billets or other shapes, rolled/formed into finished raw material stock (like sheet or bar) and then further processed by stamping or cutting, then finishing, etc. to yield the final product. These process steps are the "process AB" and "process BC" shown in the individual lines of product manufacture on the chart. You'd use as many process steps as needed to complete the product.

One interesting thing to note is that if you want to maintain constant embodied energy in the manufacture of the product you need to follow the constant energy contours.

We will see that this is the real manufacturing engineering challenge for green manufacturing!

In the next posting we'll show some examples of real products from this study (like a beverage can or a car door panel) to illustrate the use of this energy yield vs material yield chart.

Once we are comfortable with the metrics for measuring our success (or documenting our failure!) we'll talk about engineering tools to overcome this scenario in product design and manufacture.