Sheet metal shops differ widely in size, number of employees and types of products. In preparing this introduction to lean production, we have tried to account for the fact that no two sheet metal shops are alike and to present the information in a way that is useful to almost everyone.
To do that, we have chosen to use lightweight, rectangular ductwork fittings as our example throughout. We believe it makes use of a process that any shop engaged in repetitive work can relate to. The process of creating fitting is generally the same in any shop. We cut the pieces, stiffen the large pieces, form corners, form the connecting edges, cut and glue insulation, and finally, assemble the piece.
Shapes vary. Dimensions vary. Job sizes vary. Nevertheless, the process for creating a fitting is the same everywhere. Most shops have competent workers and adequate equipment to perform the steps routinely and with good quality.
It is rare that cutting, stiffening and the other steps in the process present significant challenges. Nor does the process itself present much challenge. The sequence of steps is the same in every shop.
So why do we have problems? We have a fairly straightforward production sequence, competent workers and adequate machinery. Yet, we all harbor the feeling that we aren't doing as well as we could, that we could be more efficient, more profitable. We are right to think so. ...
A different approachLean production is a very different approach to how we do our work. Lean is focused on continuous improvement through the elimination of waste. As we eliminate waste, we reduce costs and improve customer and employee satisfaction. Understanding the lean approach starts with understanding the difference between a process and an operation.
An operation is a step that occurs in the production sequence. Cutting, for example, is an operation. Braking is an operation. ?
A process, or production process, on the other hand, is the whole sequence of events and everything that happens to the metal from the beginning as a flat sheet to the end as a completed fitting. The process includes the travel and waiting time that the fitting goes through as well as the operation where value is added. In the lean view, whatever occurs in the process that doesn't add value is waste.
Generally our efforts to improve efficiency in the shop focus on improving operations. We invest in more machines and faster machines, and try to improve the workers' skill and motivation. Often we are disappointed by the payback. The breakthrough thinking of lean production is the understanding that the greatest opportunities for improving efficiency and productivity can be found in the production process itself, not in the operations. In other words, the greatest opportunity for improving shop performance is in managing the work differently.
Time is key indicator how well a process performs. When we study most production processes, we find that the time when operations are being performed and value is added is only a small percentage of the time the product spends in process. We also find that there is not much variation in the value-added time in operations. There is, however, great variation in the time products are in the process.
the production cycle is waste. Second, that if we can eliminate the waste of non-value-added time, we can schedule work and predict completion times with much greater accuracy. We can also lower production and management cost substantially.
Identifying wasted opportunitiesLean identifies opportunities for process improvement by defining seven kinds of waste. They are:
1. The waste of defects (poor quality) - scrap, re-work, late deliveries.
2. The waste of overproduction - making more than is needed, making product that exceeds customer requirements, over-specification.
3. The waste of inventory - cash tied up in raw material, work in process or unsold finished goods.
4. The waste of waiting - product not being worked on, waiting in a queue, people or machinery waiting for work to do.
5. The waste of transport - the movement of product between value-added steps.
6. The waste of motion - unnecessary worker activity, such as looking for things, unnecessary bending, stooping, walking.
7. Waste in processing - waste hidden within value-added activity. ?
The first challenge in converting a shop to lean production is to organize the shop and put things in order. The lean approach to shop organization and orderliness is called the "Five-S." Five-S will reduce waste in inventory, waiting, motion and the waste hidden in processing. If you only do one thing discussed in this book, do the Five-S. The time you invest will be paid back many times over. Besides improving efficiency, you will have higher morale and a safer place to work. Doing the Five-S shows that you are serious about improvement. Everyone can understand the value, and everyone can (and should) participate.
The 'Five-S'These are the Five-S's:
- Sort. Start by getting rid of unnecessary things. Go into every nook and cranny, every storage area and cabinet. You will find things no one threw out because everyone thought someone else used them. Make sure to involve all shifts. Be sure if you dispose of capital equipment to make the appropriate changes in your accounting system. Be prepared to be amazed by the amount of stuff you throw out.
- Stabilize. Organize what is left, tidy and ready for use when needed. This is the time to determine where things should be. Make it easy to find things. Make shadow boards for hand tools. Put up signs to show where things are kept. Designate aisles and equipment locations with floor tape. Color-code areas and the things that belong in the areas with paint or tape. Make it easy to see if something is missing or out of place.
- Shine. As you put things on order, do a thorough cleaning of the shop and everything in it. Establish routines for regular cleaning. Designate locations for brooms, rags and other cleaning supplies. You may also want to encourage friendly competition between areas and rotate inspection duties among the workers.
- Sweep. Get in the habit of repeating the first three steps over and over. Visually sweep the shop for things that are out of place or need to be cleaned. Develop short, three-minute routines for wiping down machines and sweeping particular areas.
- Self-discipline. If everyone in the shop participates in the initial organizing, ordering and cleanup, and helps to write the rules for keeping the shop orderly and clan, then the group itself will be the most powerful force to keep it that way. Peer pressure and some encouragement from management should be all that is needed. Take the time to make Five-S a habit.
(For information on ordering Sheet Metal Made Lean and Clean, write the Sheet Metal and Air Conditioning Contractors' National Association, 4201 Lafayette Center Drive, Chantilly, VA 20151, or call (703) 803-2980; fax (703) 803-3732; see www.smacna.org on the Internet.)