Thursday, November 12, 2009

Is green lean? (Part I of a III part series)

And ... is lean green?

Last time the topic was "stylish longevity" and  the role of style in people's choices for purchase and use of products. I introduced a scale of manufactured goods with function (over style or form) on one end and style (over function) on the other end. The concern was how to encourage longevity of a product (from auto to machine tool) for products that might be rendered obsolete by changes in style. In the middle of the scale I had listed a category  of "function and style".

Today in my graduate class on sustainable manufacturing I  had a guest lecture from someone working at "methodhome", a home care and personal care products company that makes and sells environmentally-friendly cleaning products that really are. And they are safe to use in the home and on yourself (see I think I found another example of a product that is both stylish and functional (I had referred to my MacBook in the blog last time as one example). In fact, according to Drummond Lawson, the speaker in my class, the company found a real niche in the market for these types of cleaning products that can compliment the home environment, and make people feel good and/or associate with the product, as a user. Take a look at their bathroom cleaning products to see what I mean. This is a great strategy ... and addresses the tension between style and function. Now, we need to get this kind of innovation into manufacturing (but more on that in weeks to come!)

Now ... back to the topic of today.

We will focus on lean and green for the next three blogs (this one and next two weeks). And, just in case you don't have a lot of time - the short answer is pretty much "yes" to the first question! But there are conditions and tradeoffs to consider when answering the second question.

First, some more background on manufacturing - specially close to the factory floor with the individual processes of production. You may recall the posting of July 27th (part of the "why green manufacturing" series) that spoke about the next great leap forward. This was not the next "five year plan" from some central government office but the movement to sustainable (or at least green) production. The argument was that this will follow the prior big leaps that accompanied the introduction of the assemble line, flexible production and the Toyota Production System or lean manufacturing.

Each of these changes or leaps occurred because of a realization that an improved system of manufacturing could be attained if the system was “designed and optimized” based on an understanding of some new criteria.  And, they all had a monetary value that could be assigned so that the required "cost-benefit" analysis could be done.

The discussion here is on how lean manufacturing lays the groundwork (or one might say offers a convenient platform or structure for) green manufacturing.

But first we need to define some of the terms and details about how the shop floor works. Let's start with a simple representation of a manufacturing line comprised of individual processes. We'll connect the process boxes to make a system.

First, we'll define a process (see the figure below).

This represents all the elements of a production process (such as a machine tool, or assembly robot, injection molding press, punch or forging press, cookie dough mixer, etc.) and includes:

- Process energy
- Machine/process “tare” energy
- Process chemicals
- Other process consumables
- Machine/process operation consumables
- Machine/process operation environment
- Operator consumables
- Operator operation environment

Not included in the box are the other "expenses" associated with utilization of the process, like
- Building
- Process input supply (water, compressed air, etc) infrastructure,
- Process output exhaust infrastructure

You can probably think of a few more.

Typical manufacturing involves a sequence of individual steps, machines, processes all with, often, distinct input and output requirements. We can illustrate this as in the figure below comprised of a string of the process boxes introduced above with inputs and outputs but, in this case, connected to the up-stream and down-stream processes.

This system of interconnected processes usually operates in either a synchronous or asynchronous fashion (meaning, all the parts advance from process to process at the same time in sync or they can advance to the next process when an individual process is complete, respectively). In the case of asynchronous production there is usually some requirement for a buffer or inventory storage/accumulator between stages to accommodate the different cycle times from process to process.

Between these processes there is some transport mechanism for moving the evolving part along.

Each process step takes time. The transport takes time. The accumulated process step times and transport times from the input to the system to the output of the system constitutes the production time (the inverse of which is the cycle time) and defines throughput, lead time, work in process, etc.

Of the time spent in production, there is productive time and non-productive time or, as I like to call it, value added time and non-value added time. If the resources being used are going to increasing the value of the component being processed in each "box" then we might call this productive time. This would be shape changes, added components, painting or coating, etc. If the resources are not adding value (for the customer) then this is non-productive time. This could include transport from process to process, tooling setup time, inspection, time spent in buffer storage, etc. They all add up to comprise the cycle time but don't all add to the product's value as it moves through the system.

The cycle time should be used as "productively as possible." That is the objective of manufacturing engineers. Our capacity in the manufacturing line should be used as completely as possible, be sufficient to handle our production requirements (throughput and batch or lot size). That is - as little or no waste as possible.

Now we get to the lean part! Lean is defined (see Wikipedia for starters, as a production practice that "considers the expenditure of resources for any goal other than the creation of value for the end customer to be wasteful, and thus a target for elimination."

There is a lot of information available on lean manufacturing and I don't intend to offer a detailed review here. Suffice it to say that "waste reduction thinking", on which the principles of lean production are built, goes back some distance (recall earlier blog references to Henry Ford in his factories and my father after the depression). Since this aligns itself extremely well with  green manufacturing objectives there should be, and I believe is, a natural linkage here.

That is, the practice of lean manufacturing or lean production, if properly applied at a sufficiently detailed level with necessary additional information and data available is to me, inherently, green manufacturing.

And it is to a number of others as well as we shall see next time.

Stay tuned for part 2!


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