Stability of Supply Chains

Recently I had some interesting discussions with executives from numerous companies who are at different stages of moving forward in their Lean journey. The business drivers for most of these clients are how to reduce cost and the manufacturing lead times.

After meeting with several clients and doing a bit of research it seems that if there is one metric that companies should focus on is the lead time reduction. Lead time is the core metric that influences the health of the operations. People familiar with “Little’s Law” would quickly grasp that there is a direct correlation between Lead time and WIP in the system. As the WIP is steadily increased in the system the Lead time does not change. This indicates that some level of WIP is good for the supply chain, and the operations can keep running with the same level of operational performance. But at the inflexion point, any increase in WIP will adversely affect the Lead time. What it indicates that some level of WIP is definitely good but in excess it is the cause of the increase in the cost of operation. Excess WIP, requires more handling cost, loss of material, increased material movement, more quality problems due to handling and an overall increase in the complex decision making for scheduling.

Where is your operation with respect to the inflexion point? A typical company never reaches the efficiency as dictated by Little’s Law. It is a theoretical limit and gives perspective for companies to compare their operations to the theoretical limit. The typical reasons for a company to deviate from the limits are a) Increase in product mix, b) batching requirement are each operation, c) volatility of the supply and demand, d) setups and e) not producing parts/components based on customer requirement.

In this highly variable environment, what can companies do to run effectively? Notice – I mention effective and not efficient. Companies can run their operations efficiently by producing material at the resource capacity. This does not mean that the products they are producing are based on customer needs. The end customer can be the next operation, distribution centers, channel customers or end customers. Running effective operations indicate good business practice and produce the right mix of material that can run their operations efficiently as well as meet the customer demand.

The main crux of the manufacturing effectiveness is the 3rd principle of Lean as defined by “James Womach” in his book “Lean Thinking,” which is making the material flow through the system. These concepts are not new, we see this in real life with fluids dynamics. The only way to reduce the residence time of the fluid is to make it flow, thus reducing the stagnation points as defined as “Sinks”. The same thought process can be applied in Manufacturing – we want to avoid “Sink” or material stagnation points. I am not preaching that the sinks should not be there, it is necessary to have these sinks to manage product portfolio, variability in supply and demand, or the manufacturing scheduling constraints e.g. calendar mismatch, rate of production, required mix of production etc. It is however a good process to determine the size of these “sinks” and manage them so that we do not loose control.

This gets us to a new point – how do you compensate or measure the operations managers to run “effective” operations. Do you measure them based on the deviation from the predicted “sinks” or inventory buffer target or do you measure them on resource utilization?