Tuesday, November 24, 2009

Is green lean? (Last of a III part series)


(Or ... is lean green?)

We have been discussing the connection between lean and green. Lean has as its objectives removing everything and anything from the production process that does not add value (in the eyes of the customer) to the product.

If we recall Ohno's "seven wastes" to be avoided (see http://en.wikipedia.org/wiki/Muda_(Japanese_term)#The_seven_wastes) -

1. Overproduction and early production – producing over customer requirements, producing unnecessary materials / products
2. Waiting – time delays, idle time (time during which value is not added to the product)
3. Transportation – multiple handling, delay in materials handling, unnecessary handling
4. Inventory – holding or purchasing unnecessary raw materials, work in process, and finished goods
5. Motion – actions of people or equipment that do not add value to the product
6. Over-processing – unnecessary steps or work elements / procedures (non added value work)
7. Defective units – production of a part that is scrapped or requires rework

and, to extend the thinking, we can add in some of Deming's 14 points (see http://en.wikipedia.org/wiki/W._Edwards_Deming; and excluding for the moment the ones dealing mostly with management practice, work standards, and barriers). These include the need for constant improvement in production and service and less reliance on inspection as a means to insure quality - all for delivering more value to the customer (or the next downstream link in the supply chain).

Reviewing the list, and realizing that it was developed and promoted before the current concern about the environment and green manufacturing was so commonly of interest, we see many that map directly onto green manufacturing practice. Head of the list is producing more than is needed, or storing/inventorying more than needed, unnecessary transportation, unnecessary work steps or processes - all can be "converted" into wasted resources, energy, and other consumables or the indirect of these wastes (such as floor space and HVAC costs, additional tooling and the manufacture and operation of it, unneeded raw materials and the associated imbedded energy, transport, storage and recycling.)

It was on the basis of Ohno's and Deming's work that lean production was established.

In the last posting we introduced the value stream map (VSM) methodology commonly employed as a tool in lean production analysis. The procedures for VSM are well established and they are beginning to be introduced through a number of good starts in the market.  In this process a very detailed assessment of the present state of a production system is determined by identifying all the process boxes with all the inputs/outputs along with  critical process data for each box (cycle time, changeover time, uptime, production batch sizes, scrap rate etc.) This information would be used to assess the ratio of lead time to value added time (basically summation of productive to non-productive time using the definitions of a few blogs ago) to ascertain the efficiency of operation. This is represented in the figure below.

This information, on a process by process (or stage by stage) basis, can be used to identify points in the process or system for improvement.

There is much more to it but this forms the basis of the idea.

Now, recall the string of boxes used to represent a process in the first of this series on November 11. These were referred to as a "process box" similar to the ones to be analyzed in value stream mapping. For each of these boxes, the VSM analysis determines a number of specifics about the operation - the ones we mentioned above - and represents them with the process as shown in the figure below (except here we've added a box to represent energy, consumable consumption and waste - not usually tracked in conventional VSM.)



With this information (the "big picture of what is happening in the box) we are set for the analysis. But, we also know some important information that allows us to assess the impact of that process. With the motor power consumption on a per unit time basis during processing we can estimate the energy used in the process. And from the energy  (and the local conversion factor between energy and green house gases based on the energy supply, i.e. coal, hydro, solar, etc.) we can estimate green house gas generation.

We also know whether or not other consumables are used (water, lubricants, cutting fluid, cleaning solvents, towels/wipes, etc.) during the process. And, on a piece by piece basis, we know how much waste is generated either during processing or during changeover from one part type to another part type. (Remember, one of the key elements of lean production is balancing the flexibility of a production line with the required minimum lot size to meet "pull" demands of the customer or downstream supply chain - at some point changeover time exceeds the cycle time and we reach a point of diminishing return).

This approach is being proposed by, among others, Future State Solutions, Inc. (see http://futurestatesolutions.com/default.aspx) who have developed an integrated lean and green analysis tool called value stream enterprise management for assessing the "triple bottom line". They have a more detailed description of their approach to the lean and green tool on their site. (And, I will mention that I have no relationship with Future State Solutions but I found their information helpful in understanding the potential linkage between lean and green.)

But we can go deeper in this "lean and green" analysis. Inside the process box, tied to the peculiarities of the process (for example, the individual motions of a machine, or steps in an assembly, or actions of a complex process) there is more gold to be mined. Remember, Ohno and Deming were looking for wasted effort and resources at all levels.

Next time we will be boring deeper into the process box. But, for the moment, the linkage between lean methodology and green and sustainable production analysis is a promising collaboration that will offer valuable insight to process improvement that is both economically and environmentally sound - and would likely make the early proponents of lean production quite pleased.

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