Tempered Lean, Inputs/Outputs (also Inventory)

When looking at any interdependent process it's vitally important to see what's going into and out of it. Some call making the map of this a VSM or Value Stream Map. Value Stream mapping is a method of looking at the whole system and identifying where improvements can be made. Zooming in to the macro level shows you the flow, or stream of work within that system.

In order to carry out value stream mapping, it is necessary to gather information and data about a number of different elements such as, the process itself, the people involved and the customers of the product or service. This information and data can then be used to identify the inputs and outputs of the process.

Inputs and outputs

An input is a resource which is being used to achieve a desired end result. For example, a flow meter is used to measure out water. The metered water is an input into the water system. The output is the measured amount of water.

An output is a result which is achieved as a result of the input. For example, a pump is used to create water pressure. The pumped water is an output of the water system.

A good value stream map will identify the inputs and outputs of the process as well as how they are connected. Connections are important; or maybe they are not. Challenge assumptions of where things flow in a system and you may find steps in the process that are not needed, or perhaps they are currently "needed" but have no end value to the customer. Maybe they have intrinsic value in the current process (for example current thinking is that you must do x in order to not pass on a defect).

A simple video series explains some of the VSM process in more detail: https://youtu.be/fkk0hkunfcE

One key observation on this video series; improving the flow in the complete system can often be done at the bottleneck, since by definition, the non-bottlenecks should have an excess of capacity. If at any point a constraint is "broken", you can look at the new constraint within the system and improve flow there. Be sure to look at the VSM again.

Process with simple example

A process is anything that is necessary for one outcome to occur. The process can be broken down into a number of different stages. Each stage has a number of necessary inputs and there are a number of necessary outputs.

The different stages of a process can be identified using the previously mentioned value stream mapping method. Each of these stages have a necessary input. The pump in the water system is an input for the fourth stage. The pump is the means by which the water is used to grow plants, or form or clean the desired plant, the rose. In the first stage, the water is required. In the second stage, the roses are washed. In the final stage, the roses are delivered. In this example it's actually used in several stages.

Inputs form outputs

Where an input becomes an output, it is because the inputs and outputs of the process are connected. In the example of the rose making process, the water is used to make the roses. This is why we refer to it as an interdependent process where one process feeds into another. The goal is not to lose flow or lose flow to wastes.

A connection can be made between inputs and outputs by identifying where the inputs and outputs are connected. This can be done using a funnel. A funnel is a simple diagram which shows the flow of inputs and outputs. The purpose of the funnel is to identify how inputs and outputs are connected. This is why they are used for many other processes like projects, sales, and more. Everyone instinctively knows what happens when water is poured into a funnel.

I actually don't have/know of a good video that shows a funnel where each stage has a separate process loop but you can imagine a funnel like what you might use in replacing oil in your vehicle where which stage in the funnel can take what it needs and process it, and put it back into the funnel. This is an oversimplified way to look at an interdependent process with multiple steps, where each step may or may not need to be done based on the product going through the funnel.

Data and information

In order to identify inputs and outputs, it is necessary to gather information and data. This information and data can then be used to identify the inputs and outputs of the process. This information and data will fall into 4 different categories.

1.) Data about the process

Data about the process includes information about the process itself. For example, the rose making process involves a number of stages. Each stage has a number of necessary inputs and there are a number of necessary outputs.

2.) Data about the people

Data about the people includes information about the people involved in the process. For example, the rose making process involves a number of stages. Each stage has a number of necessary inputs and there are a number of necessary outputs.

3.) Data about the customers

Data about the customers includes information about the customers of the product or service. For example you may know rose preference by customer as well as quantities typically ordered.

4.) Data about interactions between data, and what is of value

This is an often overlooked area, how the process, people, and end customers interact. If there is not good flow here, or low value, or high value, you don't want to ignore this.

A prime example might be sales selling something to a customer, when the data and the current process clearly shows it cannot be completed in that timeframe. In the rose example, it may be that Valentines' day is coming up and the customer wants 10 dozen roses on that day. The Sales department should know if that's possible or not and suggest an alternate, perhaps sending 3-4 dozen two days before, 3-4 dozen one day before, and 3-4 dozen as needed on Valentines' day. In this way, the customer has control over whether they get 9 or 12 dozen (so as to not have waste) and the process is not taxed to the point where you may lose other customers if you try to fulfill this demand. Ignore the transport waste (for now), assume there is a truck leaving each day and it's no trouble stopping as it goes to a central location every day. Or assume that as part of the service replenishment stocking is actually done by the Rose supplier as part of the added value of the service.

What information do you know about your process? Do you know the inputs/outputs? Are they necessary? Are they optimized? Is the funnel you are looking at the slowest part of your process (bottleneck)? Do you have good flow (or does your funnel "overflow" sometimes)? Do you have good utilization with a buffer in case Murphy strikes? These are all important questions to ask yourself with your process. How could we make this simpler?