Wednesday, December 16, 2009

Green Balancing

Knowledge is useful. This may not sound surprising coming from an academic. Or, if not knowledge, then at least start with data.  As we have been discussing in the last few postings, data and knowledge are critical to decision making on the shop floor. The more information you have the easier it is to understand what is going on and what you should do next. And, this simple statement lays out the basic strategy to green manufacturing - at any level.

The webinar just held on December 14th (see Future State Solutions website for archived material) covered some of the tradeoffs between lean strategies of reducing cost, lead time and waste and natural resource and energy use and carbon emissions while at the same time insuring that process capability is maintained (and product quality insured) as well as safety and profit margins. We also spoke about the need to include all the Scope 1 through 3 effects to insure that a full picture of your process or product impact is reflected in your analysis and decision making. For a refresher on that see August 25th posting - which discusses the three scopes of ISO 14064 (1- direct emissions from on-site/company owned assets, 2- indirect emissions  from energy generation or supply, 3- all others resulting from your business operation including business travel, shipping of goods, resource extraction and product disposal).

So - the data requirements can be over a broad range of your operations.

At a deeper level, reflecting our discussions in the last two postings, with data we can look at optimization of performance. Here we discuss this from the perspective of "balancing" resource use. I would like to go into two examples: balancing the operation of multiple machines in a production line and multi capability vs single use machines. In the December 9th posting I went into some detail about the operational peculiarities of a machine tool for illustrating how variations in process parameters could affect energy and resource consumption. The previous posting, December 3rd, defines some of the "in the box" inputs in a process, like a machine tool.

Being good engineers, we often try to coordinate (or synchronize) the actions in a production system so that all processes are operating at the same time completing their tasks. At the end of the cycle time the product, in whatever state of completion along the line is, is advanced to the next station for the next operation. Except for the bottleneck station (the one which, due to complexity or number of operations on the station, uses all the cycle time) there is usually some idle time at each station. Lean techniques try to eliminate this as much as possible but, usually, some still exists.

One solution is to adjust the start/stop time of each process at a station so that, when the line is humming along, all the process steps do not exactly occur at the same time. When all synchronized the energy usage of the line will be at a maximum. If they are staggered a bit, but not so much as to lengthen cycle time, decrease throughput or affect quality, we might be able to shave a bit off the "peak power consumption" of the line. The illustration below shows how this might work (and you might need to click on the illustration for a larger view).

This can have a significant impact on the line and, if applied to other aspects of the factory operations, the overall factory energy use. And it is free. But, you need to be able to see the energy variation within the process cycle so that you know how to stagger the process start/stops.

Another strategy, not so much balancing as compounding, is to look at the potential for multi-function machines. You might recall the discussion in the November 18th posting ( on "smart assembly" and the new multipurpose machine introduced for automotive production. The vendors of this smart machine touted a smaller footprint and faster changeover to each product variation (lean!). This strategy also can save energy and embedded resources (green!). There are a number of machinery builders who are introducing multipurpose machines...specially for machining processes.

If one takes a hypothetical production system with a number of separate conventional machine tools - say for drilling, turning, horizontal and vertical milling applications - and replaces them with one machine that is able to do all these processes, in one set up, with cycle time reductions thanks to reduced part handling, fixturing, etc., it can be argued that, in addition to time, we'll save energy and resources. Then, each process energy input, embedded energy and resources for each machine, embedded energy and resources and operational energy in the handling machinery are all collapsed into one machine. Granted, the machine is more complex - but, one machine never-the-less. The figure below shows this hypothetical comparison (and you'll need to enlarge this one for sure!).

The red line tracks the individual process machines in a sequence. The line goes up to the right to reflect the process energy and the "jump" is the handling machinery impact. The green line shows the operation of the multi-machine. And the hashed green box illustrates the energy savings. Likely cycle time savings are seen as well. Granted this is a simplified illustration but the potential savings are real. And this is an excellent example of one of those "technology" wedges that's been referred to before.

These two examples, one that is for existing machinery and requires little additional cost, and the second when machinery is replaced, are both enabled thanks to data on the process operation at the lowest level. And we can build other efficiencies on top of this.

In the next blog  we'll talk a bit more about Scopes 1, 2, 3 (and 4?).

And happy holidays!

No comments:

Post a Comment