Lean manufacturing in the mill room--improve efficiencies, decrease costs and improve quality.

Change, as we often hear, is inevitable. It is sometimes nice, though, when a change actually provides new techniques or methods that will positively help our various manufacturing processes. The current "change" that is entering the rubber industry is lean manufacturing. If one actually looks at several of the "tools" of lean, one can see that they help in the millroom by improving productivity, cost and quality. In this article, I will give an overview of the history of the lean enterprise system, and then I will discuss some of the lean methods that can positively impact a rubber mixing operation, and mention where six sigma can fit into a lean millroom. Also, I will mention some techniques and tips for using dispersion technologies to assist a mill room in getting to a lean enterprise.

A brief history/discussion of lean

If one truly traces the history of lean, one has to start with W. Edwards Deming and his manufacturing missionary trip to Japan after World War II. Deming totally changed the manufacturing philosophy of Japanese management by having them look at the method and constantly improve their processes. Deming introduced the PDCA Shewhart cycle to them, and the Japanese took it to the next level.

Several Japanese corporations took Deming's teaching and revolutionized their manufacturing operations. Toyota really took to his teachings. One of their lead industrial engineers, Taiichi Ohno, added to Deming's teachings and created a revolutionary system, the Toyota Production System, which incorporated the just in time (JIT) delivery system to drastically reduce the cost of inventory in their operations. He added the concept of kaizen, or continuous improvement, to improve the quality of the Toyota car. One of his contemporaries, Masaaki Imai, put these and other ideas into a system that he called gemba kaizen or workplace improvement. This leads us to the early 1980s, when most of U.S. manufacturing noticed that they were losing to the Japanese, not just in cost, but in quality of goods. This caused U.S. manufacturers to go to Japan and observe these companies. Most U.S. companies brought back good ideas but neglected the philosophy of change, and they made teams just for the sake of making teams. For example, the Japanese had teams, so we had to have them, but they did not bring the "why" of teams.

By the 1990s, in a kaizen type of process, slow improvement, most U.S. management had bought in to the concept of lean methodologies and, as we are apt to do, changed it from the Japanese names, called it lean manufacturing and made it ours.

What is lean?

If one breaks lean down to its basics, it is the elimination of muda, or waste. Muda is any non-value-adding step in a process that does not change a product's form, fit or function. Moving raw materials from a warehouse to a compounding room, in-process testing, long changeovers/ cleanouts at a mill, finished goods inventory or nonconforming compounds are all examples of muda. Lean tries to eliminate this muda because of the excess cost of the waste. There is no end to the information available on lean, both through literature and consultants. I will not go into all aspects of the lean enterprise system in this article.

Lean in the millroom

As I have seen and worked in many different types of rubber mixing operations, from custom mixers to end product manufacturers, I have observed many instances of muda. I am sure most rubber technologists have done the same. I have seen hour waits for clean outs and changeovers because the mixer operators had no idea how to do the change out. I have seen white sulfur added to compounds which caused no cure non-conforming batches. I have seen a variety of metal, wood, plastic, candy wrappers, etc., in compound. I am sure that if I took a survey of compounders, most would have seen these instances, and perhaps worse. Lean has tools that can address these and other problems.

To begin a program of lean in a rubber mixing operation, I would recommend that management first educate itself about this philosophy (and it is a philosophy or a way of life, it is not just a manufacturing program), by reading the literature in this field. After this self-education, a consultant would accelerate the process, and the benefits of the implementation will be more readily apparent. A small company could also implement this philosophy in its manufacturing process, it would just take longer.

The lean start and its toolkit

The first step in any implementation would have to be a process audit/flow map or value stream mapping. This is a multi-functional team employing several members of the manufacturing team, production workers, management, first line supervision and technicians. In this exercise, the team maps how a product is made, measuring distances and times it takes for the process of making your product. For example, a mill room flow map exercise would measure and map how a batch/unit of SBR compound was made. A map would be drawn from when the raw materials would arrive at the plant, how long they were warehoused, where they were moved, etc. By having this map, a company can see where they first need to employ their resources. Are their lowest hanging fruit non-conforming batches? Then they employ a method sheet or mistake-proofing program. If contamination is an issue, institute a 5S program. In other words, from this map, one learns what tool to pull out first.

The clean tool 5S

The one tool that is usually the most useful in any rubber operation, or for that matter, any operation, is 5S. 5S is a technique for cleaning and organizing the work place. The S stands for the steps, both in Japanese and English, that a system uses to get the process clean and sorted. The steps are as follows:

* Seiri-sort: In this step, every member of a work group meets, from mixer operator to supervisor to plant manager. A part of the plant is marked off. This is called the red tag area. Then every piece of equipment is tagged and placed in this area, and it is left there until needed. If something in this area is not used within 30 days, it is discarded, as it is muda and is taking up space. If something (mill knives, etc.) is used daily, a place is found for it (selton), and it is left there when not in use.

* Selton-straighten: Now what we want to do is have a place for essential things and put everything in its place. Some useful tools for this would be shadow boards for change out tools, broom closets for cleaning equipment, and any other gadget to keep things out of the way but accessible.

* Seiso-scrub: This is the step that employees usually like, if only to see their plant manager scraping rubber out of mill stops or off of floors. This is where we clean out the old nasty stuff of neglect, the old rubber cured up in dust stops, the foot or two of carbon black on the floor. This is where you really get a bang for your buck; here we clean out all the potential contamination. Paint is recommended for a reason, because not only are we doing a big cleaning, but also we are preparing this operation to be continuous, an everyday occurrence. This clean environment does more than make us feel good. When we have clean equipment, it is much easier to read gauges, watch for leaks and do daily preventive maintenance. But this is also the most expensive step in a 5S campaign.

* Seiketsu-systematize: Management really comes into play with this step. Here we try to change workplace philosophy. This is when we make daily and weekly upkeep part of our jobs. Often, there is a "not my job" mentality in cleaning and maintenance. Here we set up a system of checks and steps to maintain this clean state, and this is often where tough management decisions are made. But without this program, the system would move to a state of chaos again.

* Shitsuke-standardize/self discipline: This is similar to the above step, but it is the continuous part of the cycle. Here, management continues to challenge the work group to improve in its 5S by many methods. Here is also where celebrations happen and results are noticed.

Each of these steps is essential in allowing the work place to evolve into a clean, orderly operation. The most important step is the last, the self-discipline, and this is usually where an organization fails, or most importantly, where top management fails in maintaining this program. Dispersions, both oiled and polymer bound, can really assist in getting to a 5S state. By eliminating the dust, it will only help a mixing room maintain this environment.

The maintaining tool--TPM

Total preventative/productive maintenance really goes hand in hand with a 5S program. I highly recommend that after a 5S event, a TPM program be initiated. But what is TPM? Often times an operation will run a piece of equipment until it breaks, and they often lose efficiency on the machine, waiting for it to break. TPM is a different outlook. With TPM, the responsibility for daily upkeep falls more on the operator and less on the mechanic. Daily and weekly checks are done to ensure that lubricant levels are correct and the machine is running at optimum levels. Maintenance is involved, but more in the support role than in the fix role, because, with a good TPM program, equipment will not go down until a company wants it to go down.

The quality tool--poke yoke 

This is an extremely important part of lean. Here we try to make bad batches that are due to operator error go away. This again is a team event where a problem or a potential error is identified in the value stream mapping process, and then a team of workers and management finds ways to prevent it from ever happening again. In my career, I have seen many errors in mixing due to an incorrect chemical, either the wrong one or the wrong weighment, causing a non-conforming batch. This is a problem where a company should look at out-sourcing to a dispersion company. Then this relationship can often provide mistake-proofing tools for the millroom. Colored curative masterbatches can be used for specific compounds, or colored bags can be used to identify the right compound mixture. I have used a system of "Garanimal" type tags to ensure the right mixture went into a bag for a compound. The important part of this is to ensure that it is simple to implement and easy to use. Ideally, a temporary employee can then load the mixer line without misinterpreting TAC for TAIC, but will get the red slab instead of the blue slab.

The education tool--method sheets

These, like TPM/5S, are inherently related to poke yoke. In the past, a lot of companies used job certification books or how-to sheets for a job, but these were often a long dissertation on how to do a job. As soon as an employee had read them, they did what they wanted to do anyway. A method sheet is more of a multimedia education tool that does away with these useless sheets. Here, pictures are used to help explain how to do a job. They are kept with the machine assist in the daily operation. It is important that they are set up, so that anyone can move to the equipment and, from looking at the method sheet, have a good idea of how to do the job. An example in a mixing room would be a sheet on how to start up a batch-off machine or a sheet on how to clean out a mixer.

Six sigma/continuous improvement

When talking about lean, one has to talk about six sigma. Several experts think that six sigma and lean are exclusive, but from my reading they are very inclusive. Six sigma can actually be an extension of the continuous improvement process of lean. Six sigma is more project-oriented, using the DMAIC process to get to a better operating level that will hopefully put dollars to the bottom line. Regardless of what one wants to call a continuous improvement program, kaizen, TQM, or six sigma, an organization has to constantly strive to improve itself.

Conclusion

This has been a brief introduction to lean. There is much literature on the subject, and I highly recommend that everyone with an interest read and educate him or herself in this philosophy. The important idea that I would emphasize to anyone in rubber mixing is that there is no official lean program. Adapt the tools and the philosophy to your own individual situation, because everyone's plant is different. The important thing is that we in rubber can get some good savings and efficiencies from this philosophy.

References

Imai, Masaaki, Gemba Kaizen. McGraw Hill, 1997.

Walton, Mary, The Deming Management Method. Dodd Mead, 1986.

Box, George and Draper, Norman, Evolutionary Operation. John Wiley and Sons, 1964.

Smith, Bonnie, Lean and Six Sigma-A one-two Punch. Quality Progress, 2003.

Greenwood, Thomas, Building the Lean Enterprise. University of Tennessee, 1999.

Arthur L. Scott, Flow Polymers