11 November 2017, Oded Cohen
Last Thursday (9th November, 2017), I gave a presentation in the 35th TOPA Conference in Vilnius, Lithuania on TOC Buffers.
Discussions that followed the presentation have brought me to realize that there is some misunderstanding of the TOC Buffers.
The word/term Buffer is commonly used today as reserve, on top of, etc. – generally to indicate a mechanism for protection for the unknown, mishaps and unexpected.
Some TOC practitioners have the perception that Buffers in TOC are there just to absorb variability. This is partially true but it is not the full picture, and this does not explain the difference between the meaning of the ‘TOC buffers’ and the conventional ‘buffers’.
The TOCICO dictionary states that: “buffer – Protection against uncertainty. The protection is aggregated and may take the form of time, stock (inventory), capacity, space or money. Buffers are strategically located to protect the system from disruption.”
Actually, the above definition is true for any protection mechanism that was inserted into major conventional managerial systems as early as the 1950s and onward.
As the manager of the computer department in a large Israeli company in 1977-1980 I can state that:
- Safety Stocks were added to the inventory management systems to protect from fluctuations in the consumption and variability of the supply (falls under the definition of the ‘buffer as protection against uncertainty’).
- The mrp – material requirement planning used the Lead Time as the mechanism to provide production with protection from fluctuations and unknown disruptions. One of the formulas to calculate Lead Time was the summation of: process time + setup time + queue time + wait time. That meant adding extra time to what was actually needed for producing the product (falls under the definition of the ‘buffer as protection against uncertainty’).
- Adding extra time when determining production times for processes. Industrial Engineering methods – such as MTM instructed to add extra time for some allowances (falls under the definition of the ‘buffer as protection against uncertainty’) when time and motion study was performed.
- Additional capacity (falls under the definition of the ‘buffer as protection against uncertainty’) was incorporated in the scheduling systems by manipulating the calendars for certain machines – a known mechanism used by production planners.
- Space – debugging of new flow lines also included adding additional space for accumulating WIP in front of machines that are subject to too high level of breakdowns (falls under the definition of the ‘buffer as protection against uncertainty’).
- Money – the general practice while budgeting for new projects was to add time and money contingencies to cover for the unexpected (falls under the definition of the ‘buffer as protection against uncertainty’).
All the above was used by my company and other companies I knew before I met Eli Goldratt and used the OPT.
I think we can agree that using buffers as the protection against uncertainty – in not a TOC invention.
The TOC Buffers are MORE than just the protection against uncertainty. TOC Buffers play a significant role in managing systems and flows, by:
- Providing signals during the execution phase. These signals indicate to management the status of the flow and detect deviations from the planned flow – especially when in cases of slowdown.
- Through the Buffer status, the management is prompted to intervene and take recovery actions to restore the commitments to the outcomes of the flow.
- The buffer status prompts the recording of the causes for delays and stoppages to the flow. These causes are analyzed for system failures and provide input for improvement initiatives.
- Buffers are continuously checked for their purpose – to provide expected level of protection without exaggeration by overprotecting.
Therefore, for at least the TOC practitioners, it should be very clear that the TOC Buffers are a unique feature of TOC. Given that the buffers have been established in the early days of TOC, they should be considered as part of the TOC Pivot in the U-shape.
The TOC Pivot is the Core of TOC that includes the Constraint, the 5 Focusing Steps, the 3 basic assumptions of TOC, T-I-OE, the 6 questions of technology (as minimum set of entities that defines TOC).
A question for further thought:
If TOC buffer is the solution (new concept) – then we have to ask ourselves “what is the problem that lead to the development of this special entity of TOC?”
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Published by Oded Cohen, 11 November 2017