One of the problems with JIT manufacturing is that it is susceptible to supply chain interruptions. Taiichi Ohno, the inventor of JIT/Lean manufacturing, recognized that problem. It is worth quoting in full Goetsch & Davis’s discussion of this issue and Ohno’s solution:
Mass production advocates emphasize that the lines need to keep moving and that the only way to do this is to have lots of parts available for any contingency that might arise. This is the fallacy of just-in-time/Lean according to mass production advocates. JIT/Lean, with no buffer stock of parts, is too precarious. One missing part or a single failure of a machine (because there are no stores of parts) causes the JIT/Lean line to stop. It was this very idea that represented the power of JIT/Lean to Ohno. It meant that there could be no work-arounds for problems that did develop, only solutions to the problems. It focused everyone concerned with the production process on anticipating problems before they happened and on developing and implementing solutions so that they would not cause mischief later on. The fact is that as long as the factory has the security buffer of a warehouse full of parts that might be needed, problems that interrupt the flow of parts to the line do not get solved because they are hidden by the buffer stock. When that buffer is eliminated, the same problems become immediately visible, they take on a new urgency, and solutions emerge—solutions that fix the problem not only for this time but for the future as well. Ohno was absolutely correct. JIT/Lean’s perceived weakness is one of its great strengths. (Goetsch & Davis, 2021, p. 378-379)
According to this, maintaining a buffer stock hides any supply chain issues until the buffer stock is exhausted. This only happens, though, when the buffer stock levels are not monitored. By continually tracking buffer stock – and the rate at which the stock is replenished – any supply chain problems are revealed, and they are revealed at the exact same time that users of JIT manufacturing would notice these shortages. The difference is that the company maintaining buffer stock is not immediately affected, whereas the one using JIT must halt production until the situation is resolved.
The solution Ohno advocates (according to Goetsch & Davis) is that supply chain problems cannot occur (“there could be no work-arounds for problems that did develop, only solutions to the problems”). Problems are avoided simply by having everybody involved working on alternatives to problems that have not yet occurred. Unfortunately, no plan survives contact with reality, and no amount of mental gymnastics will change this, and when there are shortages, Ohno would resolve the issue by having multiple people screaming for a solution. Having multiple people call a supplier pressuring them to resolve a delay does no better than having one person making one call. Phone calls, by themselves, are not sufficient to identify and repair the problem that caused the supplier’s inability to produce needed parts.
One of the workarounds (that Ohno claims is unneeded) to the issue of supplier shortage is to maintain “total visibility – of equipment, people, material, and process” (Kumar, et al, 2013). There are two problems with this: adding such visibility is sure to increase the level of bureaucracy in the supplier, and not all suppliers are willing to allow total visibility. The reason for the latter is that when a company wants visibility into a supplier, it is wanting not only the production rates of a certain part, but also for all the company’s competitors that happen to use the same part.
Akhil Bhargava offers a number of different solutions to the supplier shortage issue. According to him, “The solutions to the traditional mindset of holding Safety stock include Increased data processing involvement in implementation planning efforts in order to upgrade systems to JIT level, statistical process control enhancement to provide timely feedback for engineering and managing tuning, meaningful contingency planning as a response to defects in critical parts, and materials and effective user supply dialogues to support delivery and quality issues.” (Bhargava, 2017). He is basically calling for “better living through IT™”, and none of these solutions actually address supplier shortages, except for the “meaningful contingency planning” option, which is just another phrase for maintaining buffer stock.
The JIT supply chain fragility issue appears to be a problem that has not been resolved and may be unsolvable.
References
Bhargava, A. (2017). A study on the challenges and solutions to just in time manufacturing. International Journal of Business and Management Invention, 6(12), 47-54. https://www.academia.edu/69920210/A_Study_on_The_Challenges_And_Solutions_To_Just_In_Time_Manufacturing
Goetsch, D. L. & Davis, S. B. (2021). Quality management for organizational excellence: Introduction to total quality (9th ed.). Pearson.
Kumar, S., et al. (2013). Difficulties of Just-in-Time implementation. International Journal on Theoretical and Applied Research in Mechanical Engineering, 2(1), 8-11. http://www.irdindia.in/journal_ijtarme/pdf/vol2_iss1/2.pdf
No comments:
Post a Comment