The Lean Job Shop

There is a misconception that Lean Thinking only applies to highly repetitive production environments. This misconception is perpetuated by the fact that most examples provided in books on the subject typically involve such companies. However, this is not the case. Manufacturers involved in high mixed model production can realize greater benefits from the application of Lean concepts than their repetitive counterparts. The very nature of Job Shops makes this statement true. It is a Job Shop that can reap the maximum benefits from the flexibility that is characteristic of a truly Lean Enterprise.
Now, it is also true that the application of Lean concepts is more difficult in a non-repetitive production environment. However, this fact should not discourage organizations from pursuing Lean. The potential benefits are just too great to ignore. It does require a deeper understanding of the concepts in order to determine the best implementation approach. Organizations must fully understand the concepts of flow, pull, and visual organization - just to name a few - so that they can overcome the circumstances unique to Job Shops, and successfully implement the concepts while maximizing the results.
So let's identify the challenges facing Job Shops. These include, but are not limited to: variable work content between products, variable product routings through the production process, frequent changeover of equipment. In addition, Job Shops typically have to cope with a high degree of demand variability (e.g. different order quantities) which translates to variable capacity loading. Further, the amount of information required in a Job Shop tends to be greater as well. Therefore, Job Shops need a high degree of flexibility, excellent information quality, short lead times, and outstanding workplace organization. Just the benefits that Lean provides!
Lean Note: It should be stated that while we use the term "Job Shops", there is usually some amount of repetitiveness to these businesses. There are very few truly "prototype" shops where a product is made once, never to be made again, and the product is significantly different than all other products made. There is often more similarity between products than people often recognize. Unfortunately people too often focus on and become overwhelmed by the differences. Therefore, it is often a starting point to analyze and identify the differences between products that are truly significant.
Now let's discuss how Lean provides these benefits - first addressing flexibility. In the lean "toolbox" there exists a key technique called "Single Minute Exchange of Die (SMED)" - being able to change over from one job to the next in nine minutes or less (i.e. single digits). SMED allows for diversified small lot production. The term SMED is now a generic term encompassing all types of changeover or set-up processes even those that don't involve a "die" at all. Think of the impact on the organization, if it could change over all equipment in very short time frames. Reductions in set-up times of 50-90% are typical by the application of SMED concepts [1].
Flexibility is also required with a company's human resources. Defining standard work practices and cross training people in them is an important part of the Lean Enterprise. However, few organizations adequately cross train its people. The reason most often provided for this is a lack of available time as training takes too long to complete. However, this occurs because work practices are poorly defined, and too often an organization depends on individuals who are ill equipped to teach others. The person who has been employed the longest doesn't always make for the best trainer.
One of the foundation concepts of Lean is something called "Training Within Industries (TWI)". As with many of the lean concepts, TWI dates back over sixty years. During WWII, the U.S. War Department developed techniques to define standard work elements, and to teach them to others. Reductions of 75-95% in the time to develop an individual's proficiency are well documented. By application of these techniques, known as the "J's", cross training can become a reality, and flexibility of the workforce greatly increased [2].
Next the flow and quality of information from the customer through the various pre-production processes and into production must be outstanding. Too often valuable time is lost in the "office", and information quality problems are not discovered until production is underway. In the lean "toolbox" is a concept called "Quality at the Source". The ultimate in Quality at the Source is Poka Yoke or Mistake Proofing. It is not always possible to achieve this level of control, but at the very least, methods can be put in place to prevent errors from escaping to the next stage of processing.
Further, an assessment of the current flow of information from the customer to production can identify various obstacles that if addressed can reduce lead time by 50-90%. This is accomplished by use of a Lean tool called "Value Stream Mapping". Think of the impact on the organization if the information flow and quality is significantly improved [3].
Another foundation concept is visual workplace organization - a place for everything, and everything in its place. Who can argue about having an extremely high level of workplace organization? Why do most companies seriously fall short in this area? Most often we hear, "we don't have the time to get organized". But we seem to find the time to work around our lack of organization. In the lean "toolbox" is a methodology to achieve and maintain organization in the workplace, often referred to as "5S". Think of the impact on the organization if everything can be located in 30 seconds or less. This is the standard that is pursued as part of 5S [4].
Lean Note: The 5 Pillars of Workplace Organization:
Sort: identify all items that are not in the correct place. Relocate necessary items, discard items that are no longer needed.
Set-in-Order: identify a location for every item. The location should be easily accessible by the user.
Shine: not just cleaning, but "inspect through cleaning" to identify equipment problems before they become significant. Also involves "countermeasures" to prevent contamination from being created in the first place.
Standardize: standardize work practices and establish standards for the first three S's. For example, establish a "red tag" program to promote continuous sorting. Implement cleaning and inspection checklists.
Sustain: develop a model to sustain the benefits achieved in the first four S's. Involves periodic audits, recognition programs, ongoing education and practice in 5S concepts.
There are other techniques that are important to the Job Shop including, but not limited to: Flow, Plant and Office Layout, Pull Systems, Management Timeframe or "pitch" and Total Productive Maintenance (TPM). Again, a deeper understanding of these concepts is required for their successful application. However, the techniques previously described should be considered foundation concepts and serve as excellent starting points.
Lean Note:
An example of flow concepts in a sheet metal operation involves making full use of the capabilities of a turret punch or laser system. Let's say an assembly consists of five different parts (each with a quantity of one per assembly) of the same gauge material, and the order quantity for assemblies from the customer is 10. Therefore, 10 of each part will need to be fabricated. Often companies will make the same part in multiple quantities out of the same sheet. The parts will be "nested" in order to reduce material waste. They will repeat this for each of the 5 different parts. Assembly will have to wait until all five parts are available from the turret punch or laser.
An alternative is to "nest" the different parts on the same sheet. Ideally, one would have a nest of all five parts with a quantity of one each on the same sheet. Assembly can then begin after one cycle of the turret punch or laser. Lead Time can be significantly reduced, thereby improving flow through the production process. Quality issues can be more quickly identified as they are often discovered during assembly. Issues of quality can then be more immediately communicated to the turret punch or laser. The benefits of flow and quality often offset any increase in material waste that may arise by this form of nesting.
It may also allow for the purchasing and stocking of fewer different sized sheets. Often, companies will purchase specific sheet sizes for specific jobs, or complete a shear operation at the beginning of the process. For the example provided, one sheet size would be needed (for the one "nest") instead of possibly five (for the five different "nests").
The same concept can be applied to forming processes (e.g. brake presses). Perhaps multiple parts can be processed in the same set-up.
In summary, to say that Lean Thinking does not apply to non-repetitive production environments is to say that common sense does not apply to these organizations. While common sense is not so common, it most certainly always applies.
Typical approach to Lean Enterprise in Job Shops:
Identify product "families"
Complete Enterprise Value Stream Map(s)
Begin to address information flow and quality issues immediately
Begin with 5S
Achieve quick changeover (including TPM if required)
Revise layouts, as necessary, to support flow
Establish capacity planning tools & appropriate management timeframe
Install basic Pull Systems to control flow
Establish Sales & Operations planning mechanism
Continuously strive to improve key metrics (e.g. OTD, Inventory Turns, Order to Cash Lead Time)
References:
[1]: "Single Minute Exchange of Die: A Revolution in Manufacturing" , Shigeo Shingo, Productivity Press (1985).
[2]: "Training Within Industries - The Foundation of Lean", Donald A. Dinero, Productivity Press (2005).
[3]: "The Complete Lean Enterprise - Value Stream Mapping for Administrative and Office Processes", Beau Keyte & Drew Locher, Productivity Press (2004)
[4]: "5S for Operators - 5 Pillars of the Visual Workplace", Shop Floor Series, Productivity Press.